Wader ecology:

references, abstracts and comments. Where there is no abstract, an abstract has been written, where abstracts are too long they have been abridged. Abstracts in languages other than English have been translated into English. The comment is personal, it points out errors and possible follow-ups, it is begun: CP:

M, N, O, P, Q, R, S, T, U, V, W, X, Y, Z, Å

Meise, W. (1952): Über Zug und Mauser des Kiebitzregenpfeifers, Squatarola squatarola (L.). Beitr. Vogelk. 2: 137 - 151.

Meissner, W. (1997): Autumn migration and biometrics of the Common Sandpiper Actitis hypoleucos caught in the Gulf of Gdansk during autumn migration. Orn. fenn. 74: 131 - 139.

Autumn migration and biometrics of the Common Sandpiper were studied at the Gulf of Gdansk during twelve seasons: 1983-1994 (from mid-July to the end of september). Based on ringing recoveries, the mean direction of autumn migration of adults was 214° (± 22 °) and juveniles 221° (±14°) - but the difference is not statistically significant. Bird numbers peaked in the first half of August, when juveniles appeared. Adults had a significantly longer bill and shorter tarsus plus toe and wing than juveniles, although those differences were very small. The body mass of the Common Sandpipers varied from 35 to 71 g and, on average, juveniles were significantly heavier than adults. Juveniles of the Common Sandpiper migrating in the second half of July had longer bills than those migrating in the second half of August. Late migrants were heavier than birds arriving in the second half of July and in the first half of August.

Meissner, W. (1999): Biometrics of Redshanks Tringa totanus caught in the region of the Gulf of Gdansk during autumn migration. Vogelwarte 40: 110 - 116.

Biometrics of the Redshank migrating in autumn through the Gulf of Gdansk were studied between 1983 and 1990. A total of 78 adult Redshanks and 775 juveniles was caught and measured. On average all measurements of adults were longer than those of juveniles. Almost all measurements of juveniles differed significantly among half-month periods, but not seasonally (except wing length) /which means: there was a seasonal trend in wl CP/. There was a significant decrease in tarsus plus toe length from the second half of July to the first half of September. Similar trends were shown in total head length and wing length. These facts correspond with dates of arrival of birds from the "southern" and "northern" populations.

Meltofte, H. (2001): Wader Population Censuses in the Arctic: Getting the Timing Right. Arctic 64: 367 - 376.

There is increasing evidence that breeding wader censuses often have significantly underestimated densities in the Arctic and other areas. This evidence includes the recording of many more red knots Calidris canutus in the West Palearctic and African wintering areas than can be accounted for on the Arctic breeding grounds. The main causes of underestimated breeding numbers are that many species behave very inconspicuously during incubation, when most censuses have been performed, and that censuses taken later, during the chick-rearing period, record only successful breeding attempts. Records of four seasons at Zackenberg in central Northeast Greenland suggest that in the Arctic, the best population density data are obtained by mapping pairs and territorial individuals during the pair formation, territory establishment, and egg-laying periods, that is, when all birds are present and easiest to record. Revised summer population estimates for Old World wintering Nearctic waders are 20-200% higher than previous estimates.

Minton C. D. A. & L. Serra (2001): Biometrics and moult of Grey Plovers in Australia. Emu 101: 13-18.

Mitchell, P. I., Scott, I & P. R. Evans (2000): Vulnerability to severe weather and regulation of body mass of Icelandic and British Redshanks Tringa totanus. J. Avian Biol. 31: 511 - 521.

Nebel, S. (2006): Latitudinal clines in sex ratio, bill, and wing length in Least Sandpipers. J. Field Orn. 77: 39 45.

Differential distribution of nonbreeding Least Sandpipers (Calidris minutilla) according to sex, bill, and wing length was documented using capture data from six locations between California and Ecuador. The distribution of age classes did not vary with latitude. Females, which are slightly larger than males, migrated further south. Wing length increased toward the south for both males and females, which is consistent with the notion that longer wings are adaptive for longer migrations. Bill length also increased in both sexes from north to south. A latitudinal cline in prey burying depth may underlie the clines in bill length as well as in sex ratio.

Netterstrøm, B. (1991): Efterårstrækket af Islandsk Ryle Calidris canutus i Vestjylland. DOFT 64: 223 - 228.

Since 1954 observations of bird migration have been made at Blåvandshuk, the western point of Jutland, Denmark. In 1963 the bird station of Blåvand was established, and thorough registration was started, especially of waders. In primo August 1962 a chain of observers along the west coast of Jutland studied the migration and in a similar study 1967 also Jæren, W Norway was included. This publication deals with the autumn migration of the Knot (Calidris canutus).
The results from the bird banding at Jæren and Øland, Sweden, show that both Greenlandic and Russian Knots pass through Norway on their autumn migration and that the birds at Blåvand are from this migration. The Greenlandic birds seem to winter in Great Britain after having spent their autumn in Holland and Northwest Germany. The Russian birds seem to winter further south.
At Blåvand the migration has two peaks. About 1.8 the adult birds migrate, and about 20.8 birds in winter plumage and juvenile birds migrate.
The Knots leave the Norwegian coast south of Jæren, and the approach to the west coast of Jutland takes place along the whole coast line, however, especially in the Blåvand area.
The 30,000 Knots passing Blåvand every year is just a little part of the birds which are seen in the end of August in Holland (ROOTH 1966).
It appears that a north west displacement of the migrants over Scandinavia takes place, and that the west coasts of Norway and Denmark will act as guiding-lines, and cause several species of waders to concentrate at Blåvand.
Anticyclonic weather with south easterly winds over Scandinavia often result in strong migration of Knot, Dunlin (Calidris alpina), Bar-tailed Godwit (Limosa lapponica) and Grey Plover (Squatarola squatarola).

Nicoll, M, Rae, R., Summers, R. W, Strann, K.-B. & K. Brockie (1991): The biometrics of Norwegian and Svalbard Purple Sandpipers Calidris maritima. Ring. & Migr. 12: 67 - 71.

The biometrics of breeding Purple Sandpipers from southern and northern Norway and Svalbard were described from fresh material. There was a slight size difference for the birds in the two areas of Norway, and the Svalbard birds were significantly larger than the Norwegian birds. (...)

Norton, D. W. (1971): Two Soviet recoveries of dunlins banded at Point Barrow, Alaska. Auk 88: 927

OAG Münster (1990): Zur Biometrie des Kampfläufers Philomachus pugnax während beider Zugphasen. Vogelwelt 111: 2 - 18.

In a former sewage-farm near the town of Münster 6,310 Ruffs were caught and measured from 1969 to 1984. The results of the biometric analyses were:
1. In 2,746 Ruffs captured for the first time the sex of all but four individuals could definitely be determined by means of discriminance analysis. All measurements taken show an obvious overlap between male and female birds, except for the wing lengths, where the overlap is only small. There is a significant difference between the wing lengths of first-year, second-year and older birds of both sexes, due to feather abrasion between moulting periods. This is about 2.5 mm in females and 3.2 mm in make-figures, and lies clearly below those found in the Red Knot, which covers partly greater distances in migration than the Ruff. The "Handflügel-Index" (Kipp 1959) as a flight-biological measurement shows an obvious cline from north to south in many long-distance migrants. Apparently, this is not the case in the Ruff. In spite of the different distances covered by the sexes and age groups on migration, the "Handflügel-Index" shows a remarkable stability during spring as well as fall migration periods. First-time birds, however, have significantly larger indices than adults on fall migration.
2. The abrasion of the middle tail feathers between two moulting periods (about 2.8 mm in the male, 2.6 mm in the female) is somewhat greater than that of the outer primaries.
3. For both bill measurements (total bill length and nalospi - distance from bill tip to outer edge of nostril) no differences were indicated between the different age groups within the two sexes. As opposed to wing length and wing index, the bill measurements (of first-year birds, only) show a clear development during the fall migration period. This leads to the conclusion that first those birds hatched in the more southern breeding areas pass through the sewage-farms of Münster, later followed by birds originating further north and north-east. Such a staggered passage could neither be proved for the spring migration periods nor for adult birds in fall; here, the geographic origin of the birds does not seem to influence their arrival in Central Europe.
4. The tarsus measurements, also, show a well-defined development over the fall migration period, and also restricted to the first-year birds. Thus, these two measurements - the only ones that show a clinal progression - indicate a staggered passage of first-year birds according to their geographical origin.
5. (...)
6. Due to relatively high number of recaptures in later migration periods individual measurement comparison has been possible. In most cases the later measurements differ less than 1 % from the original figures; there is a tendency for small first measurements being higher in later years and vice versa, probably influenced by the s.e. Only few birds ringed in their first year could be recaptured; yet the data indicate that they are already fully grown at the time of fall passage.

O'Hara, P. D., Lank, D. B. & F. S. Delgado (2002): Is the timing of moult altered by migration? Evidence from a comparison of age and residency classes of Western Sandpipers Calidris mauri in Panamá. Ardea 90: 61 - 70. Internetversion av denna uppsats.

Resident species typically undergo post-nuptial moult directly following breeding, whereas long-distance migrant species usually do so after arrival at staging or non-breeding ("wintering") grounds. It has been suggested that moult and migration are mutually exclusive activities. If so, one will displace the other in time. We contrasted the moult timing of migrant versus non-migrant Western Sandpipers Calidris mauri, taking advantage of the fact that in Panamá, most yearling birds (11 - 22 months of age), and some adults, were non-migratory summer residents. Yearling birds and other summer residents completed primary moult approximately 3 - 4 weeks earlier than adults returning from the breeding grounds. The same general pattern occurs with contour moult. Some adults of unknown migratory status also have moult patterns similar to summer residents. We interpret these patterns as indicating that earlier moult is advantageous, partially compensating residents for not migrating and breeding that year. We consider potential mechanisms that may favour an earlier moult, and discuss how moult schedules may influence Western Sandpiper migratory and life history strategies.

O'Reilly, K. M. & J. C. Wingfield (1995): Spring and autumn migration in Arctic shorebirds: same distance, different strategies. Amer. Zool. 35: 222 - 233.

The Arctic is an extremely inhospitable region for most of the year, but during the summer months it bursts with life. A major proportion of avian species nesting in the Arctic are shorebirds. They migrate thousands of kilometers from their wintering grounds to take advantage of abundant food resources each summer and display a variety of migratory strategies. In an attempt to classify this variation, not only between spring and autumn migration, but within a migration, we present four categories. These relate to the distance a species generally flies between stopovers: short distance bout, intermediate distance bout, long distance bout, and combinations. We then explore further differences between spring and autumn migration. Spring migrants experience poor weather and decreased food availability as they fly north. Many cope with huge flocks, which serve as protection from predators, but may also reduce foraging efficiency and increase aggression. In contrast, autumn migrants generally encounter favorable weather and ample food. Flock sizes are usually smaller, thus foraging efficiency is higher and aggression lower than during spring migration. Physiologically, spring migrants are preparing for breeding and reproductive hormones are secreted. In the Western Sandpiper (Calidris mauri), luteinizing hormone levels are higher for spring than autumn migrants. Late spring migrants have higher testosterone levels than either early spring migrants or autumn migrants. Corticosterone levels are also higher in spring vs. autumn migrants. Although spring and autumn migrants travel similar distances, their strategies differ behaviorally and physiologically.

Ottvall, R. (2005): Boöverlevnad hos strandängshäckande vadare: den relativa betydelsen av predation och trampskador av betesdjur. Ornis Svecica 15: 89 - 96.

Ottvall, R. & K. Larsson (2005): Uppföljning av häckfåglars förekomst och utbredning på öländska sjömarker. Meddelande 2005:21 från länsstyrelsen i Kalmar län. Download of the report on the Internet.

Pearson, D. J. (1987): The status, migrations and seasonality of the Little Stint in Kenya. Ring. & Migr. 8: 91 - 108.

The Little Stint is the most numerous and widespread Palearctic wader species visiting inland Kenya, where over 50,000 are estimated to winter, mostly on the lakes of the rift valley. A few thousand also occur locally on the coast. Adults arrive mainly between mid August and mid September, and juveniles between mid September and October. Most birds leave the coast in late April, but the main departure from the rift is during mid May. very few birds oversummer. Data are available from some 15.000 birds mist-netted in the rift and about 800 on the coast. Rift birds have been recovered in the USSR (Kazakhstan), Zaire and Zimbabwe, and have included controls from Zambia, Sudan and Zimbabwe. A comparison of monthly retrap frequencies at Lake Magadi indicates that most August adults, many September adults and many September-October juveniles are passage migrants; birds present in April-May are still mainly wintering individuals. Approximately 2.3 % of birds ringed at Magadi were retrapped in a subsequent season. First year birds caught from November onwards we4re as likely to be retrapped in a later season as adults. The annual decline in probability of subsequent season retrapping at Magadi was indicative of a turnover in the population of about 40 %. The longest interval between ringing and recovery was eight seasons. Wing lengths of freshly moulted adults and juveniles were not significantly different. Mean adult winglength decreased by only 0.5 mm during the May-August migration and breeding period. There was little overlap in the bill-length ranges of the two sexes. Weights were almost all within the range 18-26 g from November to March. A few higher weights (up to 38 g) were recorded in the rift in autumn, mainly in adults. In spring, mean weight increased in the rift to above 30 g (highest weights above 40 g), but comparable fattening was not found on the coast. Analysis of carcasses from Magadi showed that most October-March birds contained only 4-10 % lipid (as percentage of total weight). Some August-September birds were fatter (20-30% lipid) and most late April-May birds were very fat (30-40 % lipid). Pectoral muscle total weight and lean dry weight were significantly greater at times of migration August-September and late April-May, than in the wintering period. The status and structure, migrations and flight ranges of the rift valley populations are discussed.

Pearson D. J. & L. Serra (2002): Biometrics, moult and migration of Grey Plovers Pluvialis squatarola at Mida Creek, Kenya. Ostrich 73.

Pienkowski, M. W. (1982): Diet and energy intake of Grey and Ringed Plovers, Pluvialis squatarola and Charadrius hiaticula, in the non-breeding season. J. Zool. Lond. 197: 511 - 549.

Piersma, T. (1987): Hop, skip, or jump? Constraints on migration of arctic waders by feeding, fattening, and flight speed. Limosa 60: 185 - 194.

We develop an analytical model which determines optimal depature fat loads and stopover site use for time-minimizing bird migration with any number of sites, to identify conditions under which birds carry more fat than necessary to reach the next stopover site (overloads) or skip suitable stopover sites. The model is analysed with three sites: the wintering ground, one stopover site (both of which are characterized by their daily fattening rates), and the breeding ground. Overloads and skipping can occur if the sites decrease in quality in the direction of migration. Departure fat loads are usually either at the level necessary to reach the stopover site or at the level for a non-stop flight to the breeding ground; overloads are only deposited under rare circumstances. To model the effects of stochasticity in fat deposition we include explicit functions for the dependence of fitness on arrival time. If overloads are deposited, they are largest when the fitness function is concave, lowest when convex, and intermediate when linear.

Piersma, T., Klaassen M, Bruggemann, J. H., Blomert, A.-M., Gueye, A. Ntiamoa-Badiu, Y. & N. E. Van Brederode (1990): Seasonal timing of the spring departure of waders from the Banc D'Arguin, Mauritania. Ardea 78: 123 - 134.

The northward departure of 13 wader species was studied in the Baie d'Aouatif, Banc d'Arguin, Mauritania, in the springs of 1985, 1986 and 1988. Waders left the area in the late afternoon. Wind speed and direction were registered near ground level (all years) and at altitudes up to 5 km (in 1988). A total of 31 000 waders were observed heading northwards, with those species wintering locally in largest numbers being most common. The majority of wader species showed fairly short periods of departure and unimodal departure peaks. Redshank and Dunlin departed over extended periods. Average departure dates of species correlated positively with the estimated midpoints of ranges in breeding latitude (ca. 2 d per degree latitude). Since winds at ground level did not correlate with winds at higher altitudes, and since it is likely that thedeparting waders traveled at great heights, it was not surprising that there is no correlation between the average afternoon tail wind vector at ground level and the daily departure intensity. We suggest that the timing of departure from the Banc d'Arguin is largely under internal, instead of under direct environmental control.

Piersma, T. & J. Jukema (1990): Budgeting the flight of a long-distance migrant: changes in nutrient reserve levels of Bar-tailed Godwits at successive spring staging sites. Ardea 78: 315 - 338.

A single population of Bar-tailed Godwits Limosa lapponica was studied before departure from their wintering grounds on the Banc d'Arguin in Mauritania, and at a spring staging site in the Dutch Wadden Sea. On the Banc d'Arguin the godwits started gaining body mass in the course of March at rates of about 2.8 g per day in males and 3.2 g per day in females, before leaving north between 25 and 27 April. In the Wadden Sea, body mass increased linearly over the entire staging period (29 April-31 May) at 5.6 g per day in males and 7.5 g per day in females. Half of the mass increase was due to the deposition of fat, the other half to increases in fat-free tissue (mainly muscle protein). If the godwits flew at the heights with most tail wind assistance by varying their flight altitude up to 5.5 km, they gained an average wind assistance of 18 km/h, which would add considerably to their estimated air speed of 57 km/hour. At an average ground speed of 57 + 18 = 75 km/hour the godwits would cover the required 4300 km in 57.3 h.During this flight, males and females were estimated to lose 136 g and 178 g respectively. Since half of these mass losses consisted of fat, they represent energetic equivalents of 3163 kJ and 3857 kJ respectively, leading to estimated flight costs of 55 kJ/hour for males and 67 kJ/hour for females. The energy reserves stored on the Bamc d'Arguin would not enable the Bar-tailed Godwits to cover the distance between W. Africa and the Wadden Sea in one flight without making good use of favourable high-altitude winds.

CP: The estimates of this paper are outdated, look for more recent values.

Piersma, T., Prokosh, P. & D. Bredin (1992): The migrating system of Afro-Siberian Knots Calidris canutus canutus. WSG Bull. 64, suppl.: 52 - 63.

Piersma, T., Gudmundsson, G. A. & K. Lilliendahl (1999): Rapid changes in the size of different functional organ and muscle groups during refueling in a long-distance migrating shorebird. Physiol. Biochem. Zool. 72: 405 - 415.

Pitelka, F. (1959): Numbers, breeding schedules and territoriality in Pectoral Sandpipers in northern Alaska. Condor 61: 233 - 264. Internetversion av denna uppsats

Several population characteristics of the Pectoral Sandpiper on its breeding grounds in northern Alaska are described, especially numbers, breeding schedule, and territoriality. Unlike any other shorebird species occurring on the arctic Alaskan slope, the Pectoral Sandpiper is common in both coastal and foothill zones, but at least near the coast, large year-to-year differences in relative abundance may occur. In the breeding season, the species is dispersed generally over coastal tundra, the males occupying territories where low promontories are available, the females nesting in virtually all habitats providing grassy cover. They are primarily insect predators; in early July, near Barrow, dipterous insects comprised at least 75 per cent of the prey.
From data gathered on census plots for five seasons (1951-53, 1955-56), usual or "average" densities were estimated at 5 to 6 breeding territories of males per 100 acres. The minimal densitu observed was 3 per 100 acres in 1952, the maximum, 10-15 per 100 acres, in 1953. Numbers of breeding males in 1953 was four to five times that for 1952, the densities for the other three years falling in between. Numbers of females were about the same. Nests are placed without direct relation to territories of males and usually away from them. The pair-bond is short, and once nesting is started, females are independent of males.
Eggs may be laid over a period as long as a month, from early June to early July. Near Barrow most eggs are laid in the last ten days of June. In the interior the period is probably of the same length, but the modal interval falls about a week earlier. Testis size is maximal for about five weeks from early June to early July; testes regress over about three weeks in July and early August.
The seasonal trend in numbers in relation to breeding schedule can be divided into six phases: (1) early summer rise in numbers of settled birds; (2) interval of relative stability when territories are occupied annd when most eggs are laid; (3) desertion of territories by males, in late June and early July; (4) completion of incubation by females and care of recently hatched young; (5) departure of females in late July and early August; and (6) departure of juveniles from late July to the first days of September. Flocking is most conspicuous in July when numbers of both breeders and non-breeders moving about in early stages of migratory departure are greatest. A striking amount of flocking in 1952 in conjunction with the low breeding densities of that year indicfates that near the coast, at least, this was not a productive year.
The flight display of territorial males and seven other displays are described briefly. Males isolate themselves on areas used for pairing (and probably mating), feeding, and roosting. These areas support females similarly during their short period of association with the male. Territory size is estimated at 10 to 15 acres. The period of territorial occupation is about a month long, from early June to early July; number of established males reaches a peak in the third week of June. With respect to patterns of space occupation and aggressive behavior as well as other features, the behavior of the male Pectoral Sandpiper is analogous to that of other well-known "classically" territorial species. There is no evidence for territoriality in females.
A model of the seasonal schedule of biomass per unit area for Pectoral Sandpipers shows that the peak is reached in the early part of the summer, in late June. The main populational contraction occurs during July. This appears to be an adaptation which acts to improve the food situation for young and hence for their survival; that is, it is a populational timing mechanism superimposed on any relation between periods of active growth in young and of maximal food supply for them. This interpretation of the midsummer contraction in numbers is preferred over the alternate view that the contraction has been selected evolutionarily because it reduces losses to predation.(...)

CP: Pitelka is one of the American "apostles", and he writes an enjoyable prose. Compare the Tomkovich & Soloviev paper in Ardea 1996, both C. canutus and C. melanotos have a swift migration after breeding.

Portenko, L. A. (1959): Der Sichelstrandläufer Erolia ferruginea. J. Orn.100: 141 - 172.

Prater, A. J. (1972): The ecology of Morecambe Bay. III. The food and feeding habits of Knot (Calidris canutus L.) in Morecambe Bay. J. Appl. Ecol. 9: 179 - 194.

Sánchez, M. I., Green, A. J., & E. M. Castellanos (1998): Seasonal variation in the diet of Redshank Tringa totanus in the Odiel Marshes, southwest Spain: a comparison of faecal and pellet analysis. Bird Study 52: 210 - 216.

Aims To assess seasonal variation in Redshank diet at a major passage site, and to compare data derived from analysing pellets or faeces.
Methods At the Odiel Marshes in 2001, pellets from spring migration (39), autumn migration (121) and midwinter (15) were analysed, together with faecal samples from autumn (84).
Results The abundance of different invertebrate groups in pellets varied between seasons. In spring, Chironomus salinarius pupae and larvae dominated by volume, followed by Ephydridae larvae and the beetle Paracymus aenus. Polychaetes and molluscs dominated in autumn, and isopods in midwinter. In autumn, chironomid larvae, Mesembryanthemum nodiflorum seeds and Artemia cysts were relatively more abundant in faeces, whereas polychaetes, isopods, molluscs and cestode cysticercoids were more abundant in pellets. Harder and/or larger items were thus relatively more abundant in pellets than faeces. Pellet analysis gave more emphasis to mudflat prey, and faeces to saltpan prey.
Conclusion Pellet and faecal analysis give different results for wader diet, and it is useful to combine the two methods. However, they show significant correlations both in diet range and rank abundance of prey items. Redshank diet shows much seasonal and spatial variation in southern Europe.

Sandercock, B. K. (1998): Assortative Mating and Sexual Size Dimorphism in Western and Semipalmated Sandpipers. The Auk 115: 786 - 791. Scannad internetversion av uppsatsen. No abstract.

Sandercock, B. K., Lank, D. B. & F. Cooke (1999): Seasonal declines in the fecundity of arctic-breeding sandpipers: different tactics in two species with an invariant clutch size. J. Avian Biol. 30: 460 - 468. Scannad internetversion av uppsatsen.

The breeding biology of Western and Semipalmated was studied for four years near Nome, Alaska.

Sandercock, B. K., Szekely, T. & A. Kosztolanyi (2005): The effects of age and sex on the apparent survival of Kentish Plovers breeding in southern Turkey. The Condor 107: 583 - 596. Internetversion av uppsatsen.

Accurate estimates of annual survival are necessary for conservation of threatened species of migratory birds. We studied a large, stable population of Kentish Plovers (Charadrius alexandrinus) breeding in southern Turkey (368439N, 358039E) for five breeding seasons (1996-2000). Kentish Plovers of Eurasia and the conspecific Snowy Plover of North America are a species of conservation concern. We captured 2077 birds, and used time since marking models to estimate apparent survival (f) and encounter rates (p) for juvenile and adult plovers. Return rates of young banded in their natal year were low (4%, 52 of 1176) and most philopatric young were recaptured as yearlings (69%, 36 of 52). Low return rates of shorebird young can be attributed to post-hatching mortality if apparent survival rates are ranked: chicks , fledglings 5 adults. We were unable to separate mortality from dispersal because apparent survival was ranked: chicks (S(1y) = 0.08), fledglings (S(1y) = 0.15) f f, adults after banding (S(1y) = 0.59), adults in later intervals (S(2y+) = 0.64). Time since f f marking models gave improved estimates of the apparent survival of adults that were higher than return rates in other populations of Kentish Plovers, but lower than estimates of apparent survival for other Charadrius plovers. Sex-biased mating opportunities in Kentish Plovers were not explained by biased sex ratios at hatching or differential apparent survival among adults. Instead, male-biased adult sex ratios were explained, in part, by differential survival of juveniles and by higher encounter rates among adult males (p = 0.84) than females (p = 0.74). Our baseline estimates of apparent survival will assist assessments of population viability for Kentish and Snowy Plovers throughout their geographic range.

Schekkerman, H., Nehls, G., Hotker, H., Tomkovich, P., Kania, W., Chylarecki, P., Soloviev, M., & M. van Roomen (1998): Growth of Little Stint Calidris minuta chicks on the Taimyr Peninsula, Siberia. Bird Study, 45: 77 - 84.

Growth of mass and linear body dimensions (bill, tarsus and wing length) was studied in the Little Stint Calidris minuta at several locations on the Taimyr Peninsula, Siberia (73-76N) in 1983-94. Little Stints fledged at near-adult body mass, at 15 days of age. Growth followed an S-shaped pattern which was best described mathematically by a logistic curve. Curves of this type showed that growth was similar between study sites and years, although there were differences in mass development during the first days after hatching, perhaps related to weather conditions. When the logistic growth curve was used, KL (the standard measure of maximum growth rate) was 0.285. Conversion of this parameter to another S-shaped curve, the Gompertz curve which has been widely used to describe wader chick growth, yields KG = 0.194. This is higher than predicted from an allometric relationship based on 15 other precocial wader species, and might be related to the Little Stint's high latitude breeding range.

Schekkerman, H., van Roomen, M. W. J. & L. G. Underhill 1998: Growth, behaviour of broods, and breeding productivity of Curlew Sandpipers Calidris ferruginea. Ardea 86: 153 - 168.

Senner, S. E., West, G. C. & D. W. Norton (1981): The spring migration of western sandpipers and dunlins in southcentral Alaska: numbers, timing, and sex ratios. J. Field Ornithol. 52: 271 - 284. Internetversion av denna uppsats.

Little is known about the migration of Dunlins and Western Sandpipers between the Fraser River Delta, British Columbia and the Copper and Bering rivers delta system (C-BRD). Censuses of transects and central population estimates at Hartney Bay, within the C-BRD system, show that these two species constitute about 95 % of all shorebird species using intertidal habitats. The bulk of migration at Hartney Bay occurs between 30 April and 15 May, with peak numbers occurring between 2 and 10 May. Throughout the C-BRD system, male Western Sandpipers predominate early in migration, while this phenomenon was not observed with Dunlins. Sightings of color-marked Western Sandpipers at Kanak Island suggest lengths of stay of 1 to 2 days, while marked individuals sighted at Hartney Bay remained for intervals of 2-6 days.
Large numbers of Western Sandpipers, far outnumbering Dunlins, were recorded at Kachemak Bay in lower Cook Inlet. These data are consistent with the hypothesis that Western Sandpipers, unlike Dunlins, need to stop at intermediary sites such as Kachemak Bay while en route between the C-BRD system and western Alaska breeding grounds (Senner 1979). However, we were unable to confirm this hypothesis because Western Sandpipers collected in Kachemak Bay had body measurements distinct from specimens collected in the C-BRD system. Whether the Western Sandpipers collected at Kachemak Bay and on the Chukchi Sea coast have breeding or wintering areas different from those of individuals which use the C-BRD system needs further investigation. Migrant Dunlins collected on the Chukchi Sea coast probably represent the subspecies which winters in Asia and breeds in Arctic Alaska.
The C-BRD system and Kachemak Bay stand out as "habitat islands" on the North Pacific coast and attract large numbers of migrating shorebirds. Studies considering the ways in which Western Sandpipers and Dunlins exploit these limited wetland habitats are needed fo fully evaluate the significance of the C-BRD system and Kachemak Bay in their annual cycles.

Serra L. & R. Rusticali (1998): Biometrics and moult of Grey Plovers (Pluvialis squatarola) in northeastern Italy. Vogelwarte 39: 281 - 292.

Serra L., Whitelaw D. A., Tree A. J. & L. G. Underhill (1999): Moult, mass and migration of Grey Plovers Pluvialis squatarola wintering in South Africa. Ardea 87: 71 - 81.

Smit, C. J. & T. Piersma (1989): Numbers, mid-winter distributional migration of wader populations using the East Atlantic Flyway. In: Boyd, H. & J.-Y.Pirot eds.: Flyways and reserve networks for water birds, pp. 24 - 63. IWRB Spec. Publ. 9. Slimbridge.

Soloviev, M. Y. & P. S. Tomkovich. (1995): Biometrics of Sanderlings Calidris alba from the Taimyr. Ring. & Migr. 16: 91 - 99. pdf version of this paper on the Internet.

Soloviev M. Y. & P. S. Tomkovich (1997): Body mass changes in waders (Charadrii) at Northern Taimyr, Siberia. J. Orn., 139: 271 - 281. pdf version of this paper on the Internet.

Soloviev M. Y. & P. S. Tomkovich (1998): The phenomenon of brood aggregations and their structure in waders in Northern Taimyr. In: International Wader Studies 10: 201 - 206. pdf version of this paper on the Internet.

Summers, R. W., R. L. Swann & M. Nicoll (1983): The effects of methods on estimates of primary moult duration in the Redshank Tringa totanus. Bird Study 30: 149 - 156.

The duration of primary moult of Redshank was estimated from various methods involving drawing straight and curved lines through a scattergram of points. Estimates ranged from 72 to 109 days. The growth of the primaries was not constant, so linear regression analysis did not fit the best line to the data, even when the curving effect of describing moult in terms of moult scores was corrected for. Linear regression analyses also gave unrealistically early values for the start and completion of moult. More satisfactory methods involved drawing a curved line through the mean dates for each moult score, or each 5 % of feather mass grown. An even spread of records (nonmoulting plus moulting birds) through the moulting season is essential to give a good estimate of duration.

Summers, R. W., Nicoll, M., Underhill, L. G. & A. Petersen (1988): Methods for estimating the proportion of Icelandic and British Redshanks Tringa totanus in mixed populations wintering on British coasts. Bird Study 35: 169 - 180.

Both British and Icelandic Redshanks may be found in Britain in the non-breeding season. They are indistinguishable, though their average measurements differ. Samples of breeding Redshanks were caught in Iceland and Britain to collect biometric information to be used to estimate the proportions of Icelandic and British Redshanks in mixed winter populations. Wing, bill and foot were the only structures whose lengths were significantly different between the two populations and which could be measured wirh reasonable precision. Two methods were used to estimate the proportions in mixed samples: discriminant analysis and a maximum likelihood analysis of mixtures of Normal distributions. A simple graphical method based on the discriminant analysis was devised. The methods resulted in similar estimates of the proportions of Icelandic Redshanks when used on mixed samples. Estimates from captured samples in eastern Scotland indicated that there is an equal mix of Icelandic and British Redshanks in autumn, but that almost the entire winter population is Icelandic. Variability in measurements between and within observers was quantified and is discussed in relation to future work.

Summers, R. W., Underhill, L. G., Clinning, C. F. & M. Nicoll (1989): Populations, migrations, biometrics and moult of the Turnstone Arenaria i. interpres on the East Atlantic coastline, with special reference to the Siberian population. Ardea 77: 145 - 168.

Three populations of Turnstone were studied. Primarily a series of comparisons was made between the Canadian-Greenland population which winters mainly in western Europe and the Siberian population which winters partly in southern Africa. There was no long term change in the size of the latter population over the period 1976 to 1989. There is evidence for site fidelity to winter quarters in South Africa. Spring migration takes place through the Mediterranean and autumn migration through the Black and Caspian Seas. There are only small differences in size between the three populations of Turnstones, but marked differences occurred in patterns of change in mass. The Siberian population has no midwinter fattening in contrast to the Canadian-Greenland population. The annual food consumption by the Siberian birds was slightly less than (that of) the Canadian- Greenland birds. The duration of primary moult of 1y+ Siberian birds was about 45 days longer than that of Canadian-Greenland birds; it started two months later and was less synchronized. Of first-year Siberian birds 32 % of the population undergo partial wing moult whereas no first-year Canadian-Greenland birds moult.

Summers, R. W. & M. Nicoll. (2004): Geographical variation in the breeding biology of the Purple Sandpiper Calidris maritima. Ibis 146: 303 - 313.

Studies in Iceland (66N) and Svalbard (78N), combined with the results of previous work, allowed geographical comparisons of different aspects of the breeding biology of the Purple Sandpiper Calidris maritima, testing predictions that they may be related to latitude and altitude (here taken as surrogates for climatic severity). The breeding density was lowest in the polar deserts of Franz Josef Land (82N) and highest in coastal Arctic Tern Sterna paradisaea colonies in Iceland where the terns perhaps afforded protection from predators. There was no difference in the percentages of 1-year-old (first-year) birds in the breeding populations in Svalbard and Iceland. Time of breeding was related to both latitude and altitude, being later at higher latitudes and altitudes. In Iceland, larger males and males over 1 year old nested earlier than small males and 1-year-old males, respectively. Relaying occurred in Iceland but it was not observed in Svalbard. There were no geographical differences in clutch size. Egg size was related to female size in Svalbard. There were also geographical differences in egg size associated with female size (wing length), with the largest eggs in Iceland and smallest in south Norway. Males usually attended broods and the rates at which females deserted their broods were similar in Iceland and Svalbard. Chick growth rates were similar for Iceland and Franz Josef Land. Thus, in breeding biology, Purple Sandpipers varied geographically only in breeding density, time of nesting and egg size, which was associated with female size.

Summers, R. W., Underhill, L. G., Nicoll, M., Strann, K.-B. & S. Ø. Nielsen (2004): Timing and duration of moult in three populations of Purple Sandpipers Calidris maritima with different moult/migration patterns. Ibis 146: 394 - 403.

Timing and duration of primary moult in three populations of Purple Sandpipers Calidris maritima were described and discussed in relation to the birds' need to complete moult before the onset of winter, when resources are required for survival. We predicted that moult would be completed earlier by birds wintering at higher latitudes. The south Norwegian breeding population, which moults and winters along the coast of east Britain (54-57N) had a mean starting date of 21 July for primary moult (16 July for females and 24 July for males), a mean duration of 61 days, and completed on 20 September. Resident Icelandic (64-65N) birds had a mean starting date of 22 July for primary moult (17 July for females and 25 July for males), a mean duration of 51 days, and completed on 11 September. Birds moulting in north Norway (70N) arrived in north Norway in suspended primary moult or without having started moult, and completed it there. They had a mean completion date of 2 November for primary moult (31 October for females and 3 November for males). Starting date and duration could not be estimated because some suspended moult for an undetermined period, but it was thought that they started in late August. It is likely that most originated from Russia. The onset of moult appears to be set by the end of breeding and there is little overlap in these two events. The earlier start of moult by females in all three populations may be because they abandon the males when the chicks hatch, leaving the males to attend the chicks. Although the duration of primary moult followed the expected trend, being fastest in north Norway and slowest in Britain, the onset of moult was so late in north Norway that they had an unexpectedly late completion date, despite their rapid moult. The late completion of primary moult in north Norway suggests that wintering in the far north may not pose the energetic constraints on Purple Sandpipers that had previously been supposed.

CP: The initial "prediction" isn't very interesting, and the results are in a sense a non sequitur, but a Darwinist treadmill of this kind is what is needed to make a paper palatable to The Ibis, and the authors know it. The really interesting problem concerns how one and the same bird belonging to a particular population adapts to early and late breeding, i.e. the dynamical adaptation to weather events (which is very prominent in the Dunlin and must be so in related species as well). The Darwinist point of departure keeps these authors from asking the really interesting questions - and they are among the few, who might have both asked them, and answered them. I hate to see experienced workers presenting papers of this kind, appearing as a sort of Darwinist swots, but with no real thinking effort in it.

Thelle, T. (1996): Trækket af Strandskade Haematopus ostralegus fra Vestnorge til Vadehavet. DOFT 64: 229 - 247.

(Quote: Investigations in Jutland, Denmark (main site: Blåvand) between 1962 and 1967, in 1967 observations at two sites in SW Norway (main site: Revtangen) as well. Main observation hours: 0400-0900 and 1700-1900.)
The observations in southwest Norway showed a rather large migration at revtangen. Most of the birds followed the coast, but a few of the flocks had a tendency to migrate out towards the sea in directions S-SSW. A comparison between observations at Revtangen and observations near Egernsund showed some irregularities, probably most due to too short comparable periods. At least one day (5 August with NW-wind) the migration probably left the coast between the two localities, since a large migration at Revtangen was not registrated at egernsund. The majority of the birds is believed to leave the coast in the area of Egernsund. The direction of flight over the North Sea is supposed to be SSE. (to be continued)

Tomkovich, P. S. & M. Y. Soloviev (1994): Site fidelity in High Arctic breeding waders. Ostrich 65: 174 - 180.

Tomkovich, P. S. & M. Y. Soloviev (1996): Distribution, migrations and biometrics of Knots Calidris canutus canutus on Taimyr, Siberia. Ardea 84: 85 - 98.

Studies carried out in northern Taimyr in 1982-84 and 1990-92m were combined with data from other sources to describe the breeding distribution and densities and the migration of Knots in Taimyr peninsula, north-central Siberia. Morphometrics, recent ring recoveries, dates and directions of migration all support the idea that Knots breeding at Taimyr pass through western Europe to winter most probably in Africa. They also confirm the suggestion that Taimyr cannot harbour the entire flyway population and that an unknown breeding area is still to be discovered in Siberia. On the basis of discriminant analyses of linear dimensions, formulae to sex Knots were derived; maximum wing length and bill length were the best predictors.

Tomkovich, P. (1997): Breeding distribution, migrations and conservation status of the Great Knot Calidris tenuirostris in Russia. Emu 97: 265 - 282.

All known published and unpublished Great Knot Calidris tenuirostris breeding records, and probable breeding indications, have been reviewed. For 15 sites, breeding is confirmed by nests or unfledged chicks. The available information allows a general delineation of the breeding range to be made, although in some cases this is very approximate. The species occupies alpine and sub-alpine habitats in north-east Siberia and north Far East Russia at, and above, the upper tree line, at altitudes below 1000 m asl in the eastern half and usually above 1000 m asl in the western half of the breeding range. Vegetation mapping is used to assist in defining the probable breeding range. Literature, specimens and unpublished data from several observers are used to characterise the migrations of Great Knot within the Russian part of the East Asian-Australasian Flyway. On northward migration, birds pass non-stop hrough the region for a few days in late May; a limited number of emergency stop-over sites have been identified. In contrast to previous views, only a few non-breeding Great Knots occur on the Russian Far East coast. Post-breeding migration starts in late June and seems to occur in three waves in the northern Sea of Okhotsk up to early September. There are indications that non-breeders, failed breeders and females migrate southward first, followed by males which have bred successfully. The final wave consists of young birds. In the more southern regions, the first migration wave is not pronounced, and migration of young birds lasts through October. Estuaries and bays in the north-eastern and north-western parts of the Sea of Okhotsk and in northern Sakhalin Island are very important staging areas on south-ward migration. These are almost certainly being used for refuelling before long non-stop flights further south towards Australia.

Troy, D. M. (1996): Population dynamics of breeding shorebirds in Arctic Alaska. International Wader Studies 8: 15 - 27.

Underhill, L. G., P. S. Tomkovich & J. A. Harrison (eds) (2006): The annual cycle of the Curlew Sandpiper Calidris ferruginea. International Wader Studies 19: 1 - 211. Cape Town: International Wader Study Group.

Van der Have, T. & V. Van den Berk (1994): De Mediterrane trekroute: een netwerk van wetlands voor watervogels. Limosa 67: 159 - 162.

(...)One of the characteristic wetland types of the Mediterranean Flyway is "windflat", that is, mudflat exposed by wind force. The largest system of windflats is found in the Sivash, a lagoon system in the Crimea near the Sea of Azov, Ukraine. In some brackish lagoons invertebrate densities equal those of tidal wetlands and these wetlands were found to be of international importance for arctic waders in general, and in particular for at least one third of the European population of Broad-billed Sandpipers Limicola falcinellus. A comparison among Mediterranean wetlands showed that larger wetlands have more waterbirds and more species of waterbirds, implying that wetland loss will result in loss of biodiversity. It can be concluded that the network of European wetlands within the Mediterranean Flyway is equally important for waders as is the chain of wetlands along the East Atlantic Flyway.

Verkuil, Y., Van der Have, T. M., Van der Winden, J., Keijl, G. O., Ruiters, P. S., Koolhaas, A., Dekinga, A. & I. I. Chernichko (2006): Fast fuelling but light flight in Broad-billed Sandpipers Limicola falcinellus: stopover ecology at a final take-off site in spring (Sivash, Ukraine). The Ibis 148: 211 - 220.

We studied phenology, staging time and refuelling in Broad-billed Sandpipers Limicola falcinellus stopping over during spring migration in the Sivash (Black Sea, Ukraine) in May 1991-94. In the study area, peak staging numbers of 2000-2500 individuals occurred in the third week of May. In May 1993, 460 birds were marked with a yellow dye and 126 of these were colour-ringed. Before 28 May no departure of birds dyed yellow could be detected; by 3 June all birds had departed. Colour-ringed adults in mid May 1993 staged for a minimum of 8.2 days. After the observed departure of large flocks (24 May and later) the staging time of colour-ringed birds decreased significantly with body mass at the time of capture. Of birds mist-netted in 1991-94, 99.3% were in full summer plumage and 89% were adults. In second-year birds, fuel deposition rate (measured between individuals) was 0.44 g/day. In adults caught from early May to 24 May, overall fuel deposition rate was 1.04 g/day (3.4% of lean body mass). Mean adult body mass in early May was 34.8 g, increasing to 45.5 g after 24 May. Estimated body mass at departure was 51 g. Departure body mass and flight range estimates suggest that although birds refuelled quickly, fuel loads are only just sufficient for an unbroken flight to Scandinavia and the Kola Peninsula. We suggest that Broad-billed Sandpipers use the Sivash as a crucial final take-off stopover site, and that they follow a 'jumping' migration strategy, performed under narrow time constraints.

Vogrin, M. (1998): Occurrence and passage of Wood Sandpiper Tringa glareola and Green Sandpiper Tringa ochropus on the Dravski polje, north-east Slovenia. Wader Study Group Bulletin 87: 55 - 58.

Vogrin, M. (2001): Migration pattern of Common Snipe Gallinago gallinago on Dravski polje, NE Slovenia. Wader Study Group Bulletin 95: 42 - 44.

Waldenström, J. & Å. Lindström (2001): Migration and morphometrics of the Broad-billed Sandpiper Limicola falcinellus at Ottenby, southern Sweden, 1950-2000. Ornis Fennica 78: 184 - 192.

The Broad-billed Sandpiper is a little studied European wader species with unfavourable conservation status. We describe the migration of the Broad-billed Sandpiper at Ottenby, southeast Sweden, from 1950-2000 using data from ringing activities and field observations. Numbers of ringed and observed Broad-billed Sandpipers varied considerably between years. There was no trend in numbers trapped over the study period, but a positive trend in numbers observed (probably explained by improved identification skills and observation possibilities). The populations passing Ottenby during autumn migration have probably been relatively constant in size during the last 50 years. The species was only rarely seen during spring migration (median 29 May). As shown by autumn ringing data, adult birds pass mainly in July (median date 21 July) and juveniles mainly in August (median date 17 August). Adult birds had on average somewhat longer wings and longer total-head than juvenile birds, but there were no significant differences in body mass between age groups. Broad-billed Sandpipers carried an average fuel load proportional to 25 % of lean body mass, which is relatively low for migrating waders, but some individuals may have had fuel stores of up to 50-70 %. In recaptured birds, the highest recorded mass gain rate was 7.1 % of lean body mass per day, which is close to the maximum predicted for a species of this size. Broad-billed Sandpipers seem to prefer migrating with relatively small fuel stores, making use of several stopover sites along the migration route.

Warnock, N. & M. A. Bishop (1998): Spring stopover ecology of migrant Western Sandpipers. Condor 100: 456 - 467.

We describe stopover ecology for 132 migrant radiomarked Western Sandpipers (Calidris mauri) relocated repeatedly along the Pacific Flyway of North America. Eighty-eight percent of radiomarked birds were detected at 1 - 5 sites north of their banding sites, at distances ranging from 240-4,000 km away. We compare length of stay and physical indices of Western Sandpipers banded at coastal sites (San Francisco Bay, California and Grays Harbour, Washington), and an interior, western Great Basin site (Honey Lake, California). Western Sandpipers radiomarked at the interior site had significantly shorter length of stays than birds radiomarked at coastal sites, and they had significantly lower fat scores. The ephemeral nature of Great Basin stopover sites and an increased risk of predation may explain some of this variation. Fat and body condition indexes explained little of the observed variation in length and stay of Western Sandpipers at banding and other stopover sites. Length of stay of birds radiomarked at Grays Harbor were significantly longer compared to birds radiomarked to the south that also stopped at Grays Harbor, suggesting a potential capture effect on length of stay of birds at banding sites. Mean length of stays at seven sites other than banding sites ranged from 1.1-3.3 days and were not significantly affected by sex of bird, year of study, or banding location. Length of stay of male Western Sandpipers at the Copper River Delta, Alaska became significantly shorter later in the migration period, but not for females. Coastal sites along the Pacific Flyway from San Francisco to the breeding grounds generally function as stopovers for Western Sandpipers instead of staging areas.

Whitfield, D. P. (2003): Redshank Tringa totanus flocking behaviour, distance from cover and vulnerability to sparrowhawk Accipiter nisus predation. J. Av. Biol. 34: 163 - 169.

Over 11 winters I examined the interactions between sparrowhawk Accipiter nisus attack behaviour, the gregariousness of redshanks Tringa totanus and local geography to test hypotheses that suggest birds should flock to reduce their risk of predation and that predation risk should decline with the prey's distance from cover. Sparrowhawk attacks on redshanks feeding on beaches around the high tide mark (the strandline zone) were more frequent and more successful than attacks on redshanks feeding seaward of the strandline zone (in the intertidal zone). The results therefore confirmed hypothetical expectations that predation risk should decline with distance from cover. Flocking only appeared to influence the outcome of hawk attacks at shorter distances from cover on the strandline, with attacks on singletons and small flocks being more successful than attacks on larger flocks. Distance from cover had a stronger influence on the likelihood of attack success than did flock size. Mid-range flock sizes (6-45 birds) were attacked more frequently than expected, but singletons and large flocks were attacked less than expected. Despite these differences an individual redshank's likelihood of predation by a sparrowhawk declined with increasing flock size, thereby confirming the 'dilution effect' and 'vigilance' hypotheses for the evolution of flocking in birds. Food intake rates of redshanks declined with increasing flock size, further indicating that redshanks flocked to avoid predation rather than to increase their food intake rates. The strong interaction between two influences on predation risk revealed by the present study suggests other studies should take great care when considering a single influence on predation risk in isolation from others.

Whitfield, D. P., Brade, J. J., Burton, R. W., Hankinson K. W. & S. Young (2004): The abundance of breeding Knot Calidris canutus islandica. Bird Study 43: 290 - 299.

Six sites around Borup Fiord, west central Ellesmere Island, Canada, were surveyed for breeding Knot Calidris canutus islandica. Breeding density at the main study site was estimated using a calculation based on hatching success, brood counts and the probability of broods being resighted: estimates from other sites were based on this assessment. Density at the main study site was 4.6 pairs/km2, varying between 0.4 and 12.7 pairs/km2 in different areas. Density was negatively correlated with spring snow cover. At other sites density estimates ranged from nil to 5.7 pairs/km2. Brood counts and registrations of territorial activity accounted for only 33% and 67% of pairs, respectively. A literature review suggested that within the Knot's breeding range, densities appear to be highest in areas showing a warm regional climate, early snow-melt, and high vegetational diversity and density. The Knot's dependence on such areas may be related to its size and need for an early start to breeding. The total breeding population of C.c.islandica was estimated to be 61 000 pairs, or 304 000 individuals in autumn. Over-optimistic estimates of breeding numbers and productivity, however, may mean that about half of the Knots wintering in Europe may not be C. c. islandica.

Wichmann, G., Barker, J., Zuna-Kratky, T., Donnerbaum, K. & M. Rössler (2004): Age-related stopover strategies in the Wood Sandpiper Tringa glareola. Orn. Fenn. 81: 169 - 179.

Wood Sandpipers have been trapped between the years 2000 and 2003 during their autumn migration at Hohenau, in the north-east of Austria. Birds seem to deposit fat reserves continually throughout a small step migration across Central Europe; hence Wood Sandpipers need a large number of stopover sites to continue migration. Fat score of the birds increases as the season progresses at Hohenau, which may be an insurance against any deterioration of food supply as the time available for migration decreases. /referring to time of season or longer nights? [CP]/ Strong evidence was found that adults and juveniles use different migration strategies: adults possessing higher body mass and thus carrying higher fat loads than juveniles. The juveniles are therefore forced to spend more time feeding and in consequence are more vulnerable both to a deterioration of food supply and to predation. Juveniles seem to avoid competition with each other. Transient juveniles may be adapted to migrate in longer stages than temporary residents. Potential flight ranges were calculated, suggesting that most of the birds, especially the juveniles, need additional staging sites before crossing the Mediterranean Sea and the Sahara.

Wilson, J. R., Czajkowski, M. A. & M. W. Pienkowski (1980): The migration through Europe and wintering in west Africa of Curlew Sandpipers. Wildfowl 31: 107 - 122.

Wood, A. G. (1988): Discriminant and graphical analyses of Norwegian Knot biometrics: the sex and race problem revisited. Wader Study Group Bull. 52: 9 - 11.

Wymenga, E., Engelmoor, M., Smit, C. J. & T. A. van Spanje (1990): Geographical breeding origin and migration of waders wintering in West Africa. Ardea 78: 83 - 112.

This paper discusses the geographical origin and migration routes of 3.5 million waders using the Banc d'Arguin, Mauritania and Guinea-Bissau, based upon morphometrical data and supplementary ringing recoveries. For several species our analyses confirm earlier findings on breeding areas and migration routes. For at least part of the Ringed and Grey Plovers, Redshanks, and to a lesser extent also Bar-tailed Godwits, Whimbrels, Curlews and Turnstones, there are indications that birds wintering in Guinea-Bissau originate from breeding areas further north and east, as compared to birds wintering in Mauritania. The morphological characteristics and measurements do not allow the determination of the exact location of the breeding areas. This is due to clinal gradients in measurements, as a result of which there is much overlap in sizes. During spring migration most wader species wintering in W. African coastal wetlands travel via a route following the W. African and W. European coastline. Little Stint, Curlew Sandpiper and Curlew are exceptions to this rule. There are indications that at least part of these birds migrate through NW Africa, the Mediterranean and the Black Sea area.

Zwarts, L., Ens, B. J., Kersten, M. & T. Piersma (1990): Moult, mass and flight range of waders ready to take off for long-distance migrations. Ardea 78: 339 - 364.

Wader species wintering on the Banc d'Arguin increased their body mass by about 40 % during the 4-6 weeks before their departure in spring. This estimate is based on 1) the empirical fact that most waders which had finished or suspended their body moult into summer plumage were heavy and thus ready to take off, and 2) the assumption that only the heaviest birds in the population left, which allowed the mass of disappearing waders to be estimated from counts and the frequency distribution of body masses in samples of captured birds. The mass gain on the Banc d'Arguin is just over 1 % per day, when expressed as a proportion of winter mass. A review of studies on waders preparing for migration shows that 1) the total migratory reserve adds 20-80 % to winter mass, 2) the rate of mass gain is 0.1-4 % per day and 3) the period of mass increase lasts four weeks on average, but longer if waders prepare for spring migration in the wintering areas. We suggest that all wader species leaving the Banc d'Arguin at the end of April and the beginning of May are able to reach SE and NW Europe without refuelling. This seems only possible if current equations to predict flight range systematically underestimates this range, even when the energetic benefits of favourable winds at high altitude are taken into account.

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