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:

A, B, C, D, E, F, G, H, I, J, K, L,

Alerstam, T., Hjort, C., Högstedt, G., Jönsson, P.-E., Karlsson, J. & B. Larsson. (1986): Spring migration of birds across the Greenland inland ice. Monographs on Greenland. Bioscience vol.21.

Radar observations from a long-range surveillance station in SE Greenland (65°31'N, 37°08'W) during the end of May and beginning of June 1980 and 1982, demonstrated regular bird migration across the Inlandice in both E/SE and W/NW directions. according to supplementary field observations from SE and W Greenland 1980, 1982 and 1984, and to available information from the literature, the most probable species to carry out a transglacial E/SE-migration in spring are Gavia immer, Clangula hyemalis, Mergus serrator, Anas platyrhynchos and, possibly, Alle alle and Larus hyperboreus. These birds probably depart from the ice-free coasts in W Greenland towards breeding sites along thee E Greenland coast and, at least in Clangula hyemalis, Iceland and possibly even further to the east. Plectrophenax nivalis and Calcarius lapponicus probably also travel eastwards over the southern Inlandice to SE Greenland breeding sites.
Species involved in the transglacial W/NW-migration comprise geese, Anser albifrons and Branta bernicla, and high arctic waders, Charadrius hiaticula, Arenaria interpres, Calidris canutus and Calidris alba. In addition, it is highly probable that also Oenanthe oenanthe, Sterna paradisaea and Phalaropus lobatus belong to this category. The geese and high arctic waders depart from staging areas in Iceland to undertake a long-distance flight to breeding grounds in W Greenland or NW Greenland and N Canada. The flight route passes the Sermilik fjord region in SE Greenland, where the migrants shift from a W/WNW course over the Denmark Strait to a WNW/NW course across the Inlandice.
The route from Iceland via Sermilik to NW Greenland and N Canada is about 10% longer than the great circle route across the central and northern Inlandice. However, wind conditions for a high altitude transglacial flight are much less favourable along the great circle route. The observed migration patterns involve the crossing of 450-700 km of inlandice, reaching 2500-2800 m asl, with temperatures about -10°C. The total flight distance from Iceland to NW Greenland and N Canada is 2300-3000 km.
Staging areas for ducks and divers along the Greenland west coast, and for geese and waders in Iceland, are probably of crucial importance for the evolution of the observed transglacial migration patterns. The distance from Iceland to the northernmost part of the Nearctic is smaller than from corresponding spring staging sites in North America. Hence, Iceland serves as a spring-board to Nearctic breeding grounds for Old World winter populations of waders and geese. Staging sites probably have a dual effect as spring-boards and bottle-necks, respectively, for the evolution of migration patterns in arctic birds.
Gaps in the circumpolar breeding distribution of arctic species, and a relatively low diversity of species breeding in the sector around Greenland, may be due to competition for limited staging resources in combination with the isolating effects in this sector of sea expanses and the Greenland Inlandice.

Balachandran, S., Hussain, S. A. & L. G. Underhill (2000): Primary moult, biometrics, mass and age composition of Grey Plovers Pluvialis squatarola in southeastern India. Bird Study 47: 82 - 90.

Little is known about the biology of waders wintering in southern Asia; this paper deals with the Grey Plover Pluvialis squatarola, a species extensively studied only in western Europe. Adult Grey Plovers wintering in southeastern India underwent primary moult in autumn; the duration was estimated to be 127 days, with mean starting date 1 September and mean completion date 5 January. Some first-year Grey Plovers initiated primary moult in late winter and spring, and completed this moult the following spring. The average mass of adults on arrival in September was 200 g, fluctuated close to 220 g from October to February, and increased to 280 g near the end of May. The mass variation did not show the January peak observed in western Europe. Breeding productivity, measured as the percentage of first-year birds in winter catches, varied between 5% and 70% over six years, and showed a positive correlation with that of Dark-bellied Brent Geese Branta b. bernicla in western Europe and Curlew Sandpipers Calidris ferruginea in South Africa.

Barter, M., Tomkinson, D., Sixian, T., Xiao, Y. & Q. Fawen (1997): Staging of the Great Knot Calidris tenuirostris, Red Knot C. canutus and Bar-tailed Godwit Limosa lapponica at Chongming Dao, Shanghai: jumpers to hoppers? The Stilt 31: 2 - 11. Internet version of this paper.

Banding and count data obtained for Great Knot, Red Knot and Bar-tailed Godwit on Chongming Dao, Shanghai, from 25 March-16 April 1966, indicate that these three species are moving through quickly after flying non-stop from north-west Australia. It is suggested that they could be using a time-minimisation migration strategy to reach wetlands in the northern Yellow Sea which may be offering better feeding opportunities than those on the east China coastline. These northern wetlands are of critical conservation importance as they would probably be the last used by many migrating waders before flying directly into the breeding areas in the Russian Far East.

Bengtsson, S.-A. (1970): Breeding Behaviour of the Purple Sandpiper Calidris maritima in West Spitsbergen. Orn. Scand. 1: 17 - 25. The Purple Sandpiper was studied in West Spitsbergen in 1967. The majority of sandpipers were in pairs on 23 June, when the coastal tundra was still snowcovered. This prevented the pairs from spacing out. Territorial behaviour was observed in the last week of June. The first eggs were laid about 24 June. Wing-lifting was the most frequently recorded posture. Vocalization was complex. The flight song was often performed at a great altitude. The territories were well spaced out and boundary conflicts rare. Courtship display involved ground and flight chases with frequent wing-lifting. Copulatory behaviour involved wing-lifting, hovering, and a slightly forward posture with cocked tail. Also in the brooding phase wing-lifting occurred frequently. Only the male attended the young.

Boyd H. & T. Piersma (2001): Why do few Afro-Siberian Knots Calidris canutus canutus now visit Britain?. Bird Study 48: 147 - 158.

The nominate (Afro-Siberian) subspecies of the Knot Calidris canutus canutus breeds on the Taimyr Peninsula in Siberia and occurs commonly in the westernmost Wadden Sea during migration to West and South Africa. The recoveries and controls of 2045 Knots ringed in Britain and Ireland provide no evidence for canutus wintering there nor for their regular passage during autumn and spring migration. Five juveniles ringed in the first week of September 1963 were recovered in Africa between eight and 37 days later, and another two birds ringed at the same time (one as an adult) showed up in subsequent years in Spain and Germany at times typical for Afro-Siberian Knots. There have been no comparable bursts of southern recoveries since. The period in 1963 during which the Afro-Siberian juveniles were captured on the Wash was characterized by sustained wind patterns conducive to bringing naive juvenile waders from the Siberian tundra to the southwest. Such conditions have been increasingly rare in later years. The paucity of recent records may additionally reflect a decline in this population. Juveniles leaving Siberia would probably fly a constant compass course to western Europe, a flight of more than 5000 km logically ending in southeastern England. The scarcity of Afro-Siberian type recoveries based on Knots ringed a mere 350 km (five to six hours of flight) west of the Wadden Sea is therefore remarkable.

Branson, N. J. B. A., Ponting, E. D. & C. D. T. Minton. 1978: Turnstone migrations in Britain and Europe. Bird Study 25: 181–187.

Burns, J. G. (2003): Relationship of Calidris sandpiper wing shape with relative fuel load and total migration distance. The Auk 120: 827 - 835. Internet version of this paper

It has proven difficult to support the classic prediction of aerodynamic theory that highly migratory birds should have more pointed wings than less migratory birds. This study extends the search by testing for correlations between wing shape of Calidris sandpipers and a traditional migratory variable (total migration distance) as well as a novel variable (relative fuel load). Using phylogentically independent contrasts, it was determined that relative fuel load is a better predictor of wing shape than total migration distance.

Burton, J. & R. McNeil (1976): Age determination of six species of North American shorebirds. Bird Banding 47: 201 - 209. Internet version of this paper

Working first from the characteristics of the juvenal plumage, mainly primaries and secondaries, it was possible to determine the plumages of the first cycle (retained primaries and secondaries and other juvenal traces, mainly wing coverts). The first cycle remiges were compared to their homologues in order to characterize the second cycle plumages. For the six species studied (Semipalmated Plover, Greater Yellowlegs, Lesser Yellowlegs, White-rumped Sandpiper, Least Sandpiper, and Semipalmated Sandpiper), black-and-white photographs illustrate the diagnostic differences found on the primaries or secondaries between first-year birds and second-year birds (or older ones). The method has been tested in the field through three years of banding activities for four of the six species studied.

Burton, N. H. K., Dodd, S. G., Clark, N. A., & P. N. Ferns (2002): Breeding origins of Redshank Tringa totanus wintering at two neighbouring sites on the severn Estuary: evidence for partial racial segregation. Ring. & Migr. 21: 19 - 24.

The breeding origin and racial composition of Redshank wintering in the Cardiff area of the Severn Estuary were investigated using information from ring-recoveries and biometric data. In total, between 1991 and 2000, we received 56 reports from the breeding season of Redshank ringed at Cardiff. these involved 36 different individuals, 31 reported from Britain and five from Iceland. There was a slight bias in records within Britain towards the north and west of the country. The proportion of adult Redshank of the Icelandic race T. t. robusta present during the non-breeding seasons varied according to the month of capture and, importantly, between two neighbouring sites within the study area: Cardiff Bay and Rhymney. The latter site held a higher proportion of Icelandic birds throughout the winter. Percentages of Icelandic birds were lowest in October and November (2 % and 27 % at Cardiff Bay and Rhymney respectively) and highest in february and March (27 % and 61 % at the two sites respectively). The proportions of British Redshank T. t. brittanica in the populations at Cardiff were higher than in studies in eastern Scotland, Teesmouth, The Wash, Merseyside and north Wales but less than in north Kent. The apparent partial segregation of Icelandic and British Redshank between Cardiff Bay and Rhymney may have been related to differences in the availability of prey species at the two sites and/or a result of differences in the competitive ability of the two races. The segregation of Redshank between the two sites could potentially have increased the impact of the impoundment of Cardiff Bay in 1999 upon British-born birds, though lessened the impact for Icelandic-born birds. The potential for similar segregation occurring elsewhere in other species of migratory birds needs to be considered in determining the impact of any similar environmental change.

Burton, N. H. K. & M. J. S. Armitage (2005): Differences in the diurnal and nocturnal use of intertidal feeding grounds by Redshank Tringa totanus. Bird Study 52: 120 - 128.

Aims To determine whether there were differences in how wintering Redshank used intertidal feeding grounds during the day and night.
Methods The movements of 38 Redshank caught and radiotagged at two neighbouring sites on the Severn Estuary were monitored during four different study periods between January 1997 and October 1999.
Results Individuals used a greater number of sites at night than in the day (on average, two as opposed to one). Kernel home range analyses also indicated that individuals used larger core areas and home ranges at night. In addition, there was a significant difference between the sizes of ranges of birds caught at two neighbouring sites. One foraging site was almost entirely avoided during the day, probably due to disturbance from an adjacent heliport, but was used by the majority of individuals at night when the heliport was unused. This site was rich in invertebrates as a result of the high organic and nutrient input from a sewage outfall pipe. Redshank also used riverine mudflats less during the night, preferring more open mudflats - perhaps to avoid nocturnal predators.
Conclusions Comparison with previous studies suggests that the importance of sites predominantly used at night and the total extent of the areas used by waders may be underestimated by studies that rely on daytime surveys alone. It is important, therefore, that information on nocturnal distributions should be available to inform decisions on site management and protection.

Butler, R. W., Ydenberg, R. C. & D. B. Lank (1991): Wader migration on the changing predator landscape. WSGB 100: 130 - 133.

We suggest that the spatial and temporal patterns of danger arising from the annual migration of birds of prey has important implications for patterns of habitat use and for the evolution of wader annual movement patterns and annual cycles. We discuss how waders might respond to danger by their choice of migration routes, the time of year they choose to migrate, the quantity of fuel they carry, the length of time they spend at staging and stop over sites, the duration of the breeding season and parental care, and the timing and location of feather moult.

Clark, N.A., Gillings, S., Baker, A.J., González, P.M. & R. Porter 2005: The production and use of permanently inscribed leg flags for waders. Wader Study Group Bull. 108: 38 - 41.

Coooper, J. & L. G. Underhill (1991): Breeding, mass and primary moult of European Starlings Sturnus vulgaris at Dassen Island, South Africa. Ostrich 62: 1 - 7.

Davidson, N. C. & P. R. Evans (1982): Mortality of Redshanks and Oystercatchers from starvation during severe weather. Bird Study 29: 183 - 188.

Body condition (fat and protein reserves) was analysed for Redshanks and Oystercatchers that died during severe weather on the Ythan estuary (Grampian) in January and February 1979 and the Montrose Basin (Tayside) in January 1982. All birds died after using almost all their fat and protein reserves, and in very similar condition. Even in the exceptionally low temperatures in January 1982, waders mobilised fat reserves fast enough to supply their energy requirements. In January 1982 death occurred after fat reserves were exhausted, through an inability to mobilise protein reserves rapidly. Small individuals died with larger pectoral muscles and relatively higher lean mass than large conspecifics, probably because of differences in metabolic rate. High first-year mortality may be partly a consequence of small first-year body size, in addition to poorer feeding efficiency.

Delany, S. & D. Scott (2002): Waterbird population estimates - 3rd ed. Wetlands International Global Series No. 12. Wageningen. The Netherlands.

Diadicheva, E. & N. Matsievskaya (2000): Migration routes of waders using stopover sites in the Azov - Black Sea region, Ukraine. Vogelwarte 40: 161 - 178.

Dick, W. J. A, Piersma, T. & P. Prokosch (1987): Spring migration of the Siberian Knots Calidris canutus canutus: results of a co-operative Wader Study Group project. Orn. Scand. 18: 5 - 16.

In spring 1979 the Wader Study Group organised a co-operative project to study the spring migration of Siberian Knots Calidris c. canutus from their west and south African wintering grounds to the breeding grounds in central Siberia. S. African wintering birds migrate via the western seaboards of Africa and Europe. Siberian Knots seem to use only a few staging sites between W. Africa and Siberia. Most birds only use the W. German Wadden Sea. Staging areas of lesser importance are the Tejo Estuary in Portugal, the Vendée coast in France and, probably, the Westerschelde in SW Netherlands. At the latter three sites in early May, birds appear to arrive with lower body weights than in Schleswig-Holstein (W. Germany) at the same time. The migration from W. Germany to central Siberia is most probably made in one flight via the Gulf of Finland. Detailed information on the timing of migration is presented. A model on body weight changes during migration in a fixed time schedule is employed to discuss the energetic constraints on the migration strategy of Siberian Knots.

Dodd, S. L. & M. A. Colwell (1996): Seasonal Variation in Diurnal and Nocturnal Distributions of Nonbreeding Shorebirds at North Humboldt Bay, California. The Condor 98: 196 - 207.

Recent studies of nocturnal foraging by shorebirds (Charadriiformes: Charadrii) suggest that many species feed at night. Much of this research has been qualitative and/or restricted to a small portion of the annual cycle (e.g., a few nights or one season) making it difficult to evaluate the extent to which nocturnal foraging varies seasonally. Consequently, we examined seasonal variation in abundance and distribution of diurnal and nocturnal foraging shorebirds from 10 Jan 1992-10 Jan 1993 at North Humboldt Bay, California. Shorebirds foraged primarily during the day. Overall, day/night frequency of occurrence (percent of censuses with birds) was 87%/48%. In fall, frequency of occurrence of shorebirds differed less between day and night (day/night: 82%/64%) than during spring (day/night: 79%/14%) or winter (day/night: 100%/42%). Moreover, nocturnal abundance of Marbled Godwit (Limosa fedoa), Willet (Catoptrophorus semipalmatus), dowitchers (Limnodromus scolopaceus and L. griseus), and Black-bellied Plover (Pluvialis squatarola) peaked in fall, whereas diurnal abundance of these species peaked in winter (Marbled Godwit, Black-bellied Plover, and dowitchers) or spring (Willet). Taxa varied in day/night patterns. For Scolopacids, diurnal abundance significantly exceeded nocturnal abundance. However, abundance of American Avocet (Recurvirostra americana), Black-bellied Plover, and Semipalmated Plover (Charadrius semipalmatus) did not differ significantly between day and night. Our results suggest that a researcher's choice of season or taxa may influence observed patterns of diurnal and nocturnal distributions of shorebirds considerably.

Dunn, P. O., May, T. A. & M. A McCullough (1988): Length of stay and fat content of migrant semipalmated sandpipers in Eastern Maine. Condor 90: 824 - 835.

Semipalmated Sandpipers (Calidris pusilla) stop at coastal staging areas in the Canadian maritime provinces and northeastern United States to replenish fat reserves before initiating a nonstop transoceanic flight of at least 3,200 km to wintering areas in South America. The relationship between estimated fat content at capture and length of stay (days between marking and last observation) of Semipalmated Sandpipers at one of these staging areas in eastern Maine was used during 1980-1982. Total body mass and wing chord length were used to estimate fat content. When data were analyzed by week of initial capture, mean length of stay of both adults and juveniles decreased with increasing fat content. This supports the assumption that resumption of migration is affected by fat content at staging areas for long-distance nonstop flights. However, fat content at capture was apoor predictor of length of stay, which suggests that other factors are more important in determining length of stay.

Ens, B. J., Duiven, P., Smit, C. J. & T. M. van Spanje (1990): Spring migration of Turnstones from the Banc D'Arguin in Mauritania. Ardea 78: 301 - 314.

Farmer, A. H. & J. A. Wiens (1999): Models and reality: time-energy trade-offs in Pectoral Sandpiper (Calidris melanotos). Ecology 80: 2566 - 2580.

We used a combination ofmodeling and field studies to determine the spring migration strategy of Pectoral Sandpipers (Calidris melanotos). We developed a dynamic programming model to predict patterns that should be detected along the migratory route if Pectoral Sandpipers use a strategy of early arrival at the breeding grounds (time minimization) or arrival at the breeding grounds with excess energy reserves (energy maximization). The predictions were then compared to data collected at stopover sites in the mid-continent of North America and at the breeding grounds in Alaska over a 5-yr period (1992-1996).
During spring migration to their Arctic breeding-grounds, Pectoral Sandpipers stop periodically to feed. The length-of-stay of such stopovers, for both time minimizers and energy maximizers, was predicted to vary inversely with date and body fat, and to vary directly with invertebrate abundance. We observed that: (1) length-of-stay was negatively correlated with capture date in Missouri and Nebraska, but not in Texas; (2) length-of-stay was not correlated with body fat at any site; and (3) length-of-stay was positively related to invertebrate abundance at the Nebraska and Missouri sites. As the population moves northwards in the spring, three regional patterns are diagnostic of migration strategy. Length-of-stay is predicted to be bimodal (energy maximizer) or constant (time minimizer) with respect to latitude, but neither pattern was observed. The migration window, or period of time during which spring migrants occur, was predicted to decrease with increasing latitude for time minimizers, a pattern that was seen for both males and females. Body fat was predicted to increase with latitude for energy maximizers, a pattern that was seen for females but not for males.
The evidence suggests that males and females differ in their spring migration strategies. Both sexes attempt to arrive in the Arctic as early as possible after ice breakup in the spring. Additionally, females gain significantly higher fat loads than males (up to 60 % body fat for females) during migration, and these energy reserves may later enhance female reproductive success. However, females gained large fat loads only during 1993 and 1995, which had above normal spring precipitation along the migration route. We believe that the correlation between female body fat and precipitation reflects an abundance of high-quality stopover habitat during wet springs. This view is supported by model sensitivity analyses showing that the spacing and quality of stopover habitat can strongly influence observed migration patterns. Our results suggest the need to focus additional research on the landscape-level features of the flyway through which shorebirds migrate.

Figuerola, J. & A. Bertolero (1995): The primary moult of Curlew Sandpiper in the Ebro delta, North-East Spain. Ring. & Migr. 16: 168 - 171.

The primary moult of Curlew Sandpiper was studied at a staging area in the south of Europe. The duration of primary moult was estimated at 73 days (9 August to 21 October), a shorter period than those reported in the wintering areas. Birds in moult showed a lower speed of fat accumulation than non moulters. An increase in the proportion of moulting birds was detected at the end of the migratory period, probably as a result of a longer staging time of moulting birds in the study area. The number ans sex-ratio of birds in wing moult showed agreat annual variation. The brooding system of this species, in which only females give parentall care, and the great annual variation in breeding success could be two of the factors that explain the great yearly variation in moult schedule of Curlew Sandpiper.

Figuerola, J. & A. Bertolero (1998): Sex differences in the stopover ecology of Curlew Sandpipers Calidris ferruginea at a refuelling area during autumn migration. Bird Study 45: 313 - 319.

We investigated the stopover patterns of male and female Curlew Sandpipers at a stopover area in northeast Spain. Curlew Sandpipers were trapped and colour-ringed during autumn migration in 1992 and 1993. Stopover length was similar to those reported previously for this and other waders that migrate using a small number of widely separated staging areas, but were greater than stopovers reported for other waders that migrate using a large number of staging areas separated by short distances. The differences in stopover length between the birds using these two strategies could be related to the fuel reserves that have to be accumulated to reach the next staging area. Males stayed longer in the area than females. Seasonal changes in prey availability or sex differences in moulting and migratory patterns do not account for these differences in stopover ecology. Following a time-selected model of optimal migration, sex differences in stopover ecology could be related to a dominance of the larger females over the males or to a higher foraging efficiency or a shorter search and settling time in females. Whether these differences are restricted to the studied area or are widespread in other staging areas used by the species could be important for assessing the possible differences in the migration speed of Curlew Sandpipers. The finding that males leave the breeding grounds 21-35 days before females but arrive at the study area with only a 10-day difference supports the hypothesis that females migrate faster than males at least in the first half of their migration.

Furness, R. W. & S. R. Baillie (1981): Age ratios, wing length and moult as indicators of the population structure of Redshank wintering on British estuaries. Ring. & Migr. 3: 123 - 132.

Ge, Zhen-Ming, Wang, Tian-Hou, Yuan, Xiao, Zhou, Xiao & Wen-Yu Shi (2001): Use of wetlands at the mouth of the Yangtze River by shorebirds during spring and fall migration. J. Field Orn. 77: 347 - 356.

The mouth of the Yangtze River is an important stopover site for migratory shorebirds using the East Asian-Australasian Flyway. From 1984 to 2004, we censused and banded shorebirds and monitored hunting activities at the mouth of the Yangtze River to understand how shorebirds used the study area. Counts and banding data revealed greater numbers of shorebirds at the mouth of the Yangtze River during northward migration (spring) than during southward migration (fall), with ratios varying from 1.5:1 to 7.2:1 at different sites from 1984 to 2005. The most common species observed during spring (northward) migration were Great Knots (Calidris tenuirostris), Red Knots (Calidris canutus), Bar-tailed Godwits (Limosa lapponica), Sharp-tailed Sandpipers (Calidris acuminata), and Red-necked Stints (Calidris ruficollis). During spring 2003–2004, 96.98% of the shorebirds observed were adults (ASY or older) and 3% were after hatching-year and second-year birds (AHY or SY). In contrast, almost all (94.73%) birds counted during the fall were hatching-year (HY) birds. These results indicate that adult shorebirds either use a different migration route during fall migration or use the same route, but do not stop at the mouth of the Yangtze River. HY birds, however, may depend on the coastal stopover sites for feeding during their first southward passage.

CP: The ageing method used in this paper reeks of ignorance, and the results cannot be trusted. The ageing data should have been weeded out in the reviewing process.

Gill, J. A., Clark, J. A., Clark, N .A. & W. J. Sutherland (1995): Sex differences in the migration, moult and wintering areas of British-ringed Ruff. Ringing & Migration 16: 159 - 167.

Gill J. A., Norris, K., Potts, P. M., Gunnarsson, T. G., Atkinson, P. W. & W. J. Sutherland WJ (2001): The buffer effect and large-scale population regulation in migratory birds. Nature 412: 396.

Buffer effects occur when sites vary in quality and fluctuations in population size are mirrored by large changes in animal numbers in poor-quality sites but only small changes in good-quality sites. Hence, the poor sites 'buffer' the good sites, a mechanism that can potentially drive population regulation if there are demographic costs of inhabiting poor sites. Here we show that for a migratory bird this process can apply on a country-wide scale with consequences for both survival and timing of arrival on the breeding grounds (an indicator of reproductive success). The Icelandic population of the black-tailed godwit, Limosa limosa islandica, wintering in Britain has increased fourfold since the 1970s (ref. 5) but rates of change within individual estuaries have varied from zero to sixfold increases. In accordance with the buffer effect, rates of increase are greater on estuaries with low initial numbers, and godwits on these sites have lower prey-intake rates, lower survival rates and arrive later in Iceland than godwits on sites with stable populations. The buffer effect can therefore be a major process influencing large-scale population regulation of migratory species.

Grant, M. C. (1991): Relationships between egg size, chick size at hatching and chick survival in the Whimbrel Numenius phaeopus. Ibis 133:127-133.

Gratto, C. L. & E. Cooke (1983): Nesting success of yearling and older breeders in the Semipalmated Sandpiper Calidris pusilla. Can. J. of Zool. 61: 1133 - 1137.

Gromadzka J. & L. Serra (1998): Differential migration of juvenile and adult Grey Plovers Pluvialis squatarola at the mouth of the Vistula River, Poland. Ornis fennica 75: 193-199.

Gudmundsson, G. A, Lindström, Å. & T. Alerstam (1991): Optimal fat loads and long distance flights by migrating Knots, Sanderlings and Turnstones. Ibis 133: 140 - 152.

Arctic waders often build up large fat loads and complete their migratory journeys by a few long-distance flights between traditional staging sites. Optimal fat loads and choices of staging sites differ depending on whether the birds are adapted to minimize energy or time spent on migration. In the latter case, we predict that the birdswill depart for the next staging site when the instantaneous speed of migration expected after arrival at the next site, exceeds the corresponding speed at the departure site. The instantaneous migration speed is a function of the rate of fat deposition and the current fat load. As a consequence of this, overloading (birds deposit larger fat loads than needed merely for covering the flight distance to the next destination) and by-passing of possible, but low-quality staging sites, are expected under specific conditions in time-selected migration.
Estimates of fat deposition rates and departure fat loads were obtained by captures of Knots Calidris canutus, Sanderlings Calidris alba and Turnstones Arenaria interpres in W. Iceland during spring migration. Further fat deposition data referring to spring migration of these species were compiled from the literature. Fat deposition rates at different sites, as measured by the daily gain in mass relative to lean body-mass, range between 1.0 and 3.6 %/day, and departure fuel loads (in % of lean body-mass) between 27 and 73 %.
Comparison with flight range estimates suggests that overloading may be a regular phenomenon during spring migration of Knots, Sanderlings and Turnstones. Furthermore, fat deposition rates at different staging sites, and the general difference in migration patterns between spring and autumn, indicate that by-passing of possible staging sites may well occur. Hence, it cannot be excluded that the waders' migratory habits primarily serve to maximize the overall speed of migration.

Gudmundsson, G. A. & A. Gardarsson (1993): Numbers, geographic distribution and habitat utilization of waders (Charadrii) in spring on the shores of Iceland. Ecography 16: 82 - 93.

Guillermo, De la Cueva, H., Warnock, N. & D. B. Lank (2003): Apparent survival rates of Western Sandpiper (Calidris mauri) wintering in northwest Baja California, Mexico. The Auk 120: 55 - 61. Internetversion av denna uppsats.

To estimate annual apparent local survival, we collected capture-resighting data on 256 individually marked male Western Sandpipers (Calidris mauri) wintering at Estero de Punta Banda, Mexico, between 1994-1997. A hierarchical modeling approach was used to address the effect of age class and year on survivorship rates. The best-fit model included a constant apparent survival probability ([straight phi] = 0.489; 95% CI = 0.410-0.569), but several models fit nearly as well, and averaging among the top five, to account for model uncertainty, suggested that adults had somewhat higher values than juveniles ([straight phi] = 0.490 + or - 0.051 vs. 0.450 + or - 0.067). Detection probability was substantially higher for adults than for juveniles (p = 0.741 vs. p = 0.537). Those apparent survival estimates are low compared with those from other studies of Western Sandpipers at breeding and other nonbreeding locations, and substantially lower than the true survivorship rates expected for small sandpipers in general. We interpret these results as indicating that this site is of below average quality for nonbreeding male Western Sandpipers.

Hedenström, A. (2004): Migration and morphometrics of Temminck's Stint Calidris temminckii at Ottenby, southern Sweden. Ibis 137: 336 - 404.

Data are reported from 55 years of ringing and observation on the migration of Temminck's Stint Calidris temminckii at Ottenby Bird Observatory, Sweden. Numbers ringed have declined since the 1940s due to high numbers caught in 1948 and 1949. Thereafter there is no clear trend. The overall autumn migration direction of 13 recoveries is south-southwest, with a concentration of recoveries in northeast Italy. Median date of spring passage was 20 May, while median date of autumn passage was 28 July for adults and 20 August for juveniles. Hence, the duration of the breeding season is about two months. On autumn migration, adults carry larger fuel (fat) loads (32 % of lean body mass, LBM) than juveniles (21.2 %), and so adults are capable of a direct flight to the northeast Italian stopover, while the average juvenile cannot do so unless assisted by winds. Over the autumn migration season, fuel loads did not change in adults but late migrant juveniles had higher fuel loads. The maximum rate of fuel accumulation was 7.7 % of LBM, which is near the physiological maximum. The maximum migration speed was estimated to be 150 km/day.

Helseth, A., Lindström, Å. & M. Stervander (2005): Southward migration and fuel deposition of Red Knots Calidris canutus. Ardea 93: 213-224. Internetversion av denna uppsats.

We compared the differences between spring and autumn in migration speed, fuelling rates and fuel loads of migrating Red Knots Calidris canutus. As a basis we used ringing data from Ottenby Bird Observatory, southeastern Sweden, collected 1948-2003, with morphometrical data from 1990-2003. Numbers ringed varied between 0 and 301 per year (average 56). Morphometrics, recoveries and recaptures of ringed birds indicated that most birds belonged to the Afro-Siberian subspecies C. c. canutus, possibly mixed with some Nearctic Red Knots C. c. islandica. Median trapping dates were 5 August (adults) and 31 August (juveniles). Mean body masses were low and almost equal for adults (111.8 g) and juveniles (111.4 g). The mean estimated fuel loads were 13-14% of lean body mass (LBM). In juveniles fuel loads increased with date. Among the few birds stopping over for longer than one day (2% of adults, 14% of juveniles), adult birds stayed on average 2.5 days and juveniles 3.4 days, with an overall average fuel deposition rate of 2.8% of LBM d-1. The autumn migration speed was estimated from ringing recoveries at 86 km d-1, which equals the speed of spring migration calculated from published information. The observed fuelling rate was as high as that of Red Knots at major spring stopover sites. We conclude that migration in autumn is as fast as in spring, although the generally small fuel loads indicate that migration is carried out in much smaller steps.

Hoffmann, L. (1957): Le passage d'automne du Chevalier sylvain (Tringa glareola) en France méditerranéenne. Alauda 25: 30 - 42.

Hötker, H. & A. Segebade (2000): Effects of predation and weather on the breeding success of Avocets Recurvirostra avosetta. Bird Study 47: 91 - 101.

We investigated breeding success of Avocets Recurvirostra avosetta on the Wadden Sea coast of Schleswig-Holstein, Germany, during the years 1988-1997. Annual variations in hatching success were mainly determined by the presence of Red Foxes Vulpes vulpes in an embanked part of the study site and by the occurrence of storm tides on the saltmarshes. Hatching success did not correlate with the population size of avian egg predators. Annual chick survival rates were positively associated with June temperatures. The influence of predators on chick survival rates was not detectable. Annual breeding success (number of fledglings per number of breeding pairs) was significantly correlated with June temperature and chick survival, but not with hatching success.

Insley, H., Peach, W., Swann, B. & B. Etheridge (1997): Survival rates of Redshank Tringa totanus wintering on the Moray Firth. Bird Study 44: 277 - 289.

Long-term mark-recapture data were used to estimate the annual survival rates of Redshank wintering on the Moray Firth in Scotland. Survival modelling required the exclusion of all birds caught during the main passage months (August, March and April), and a highly variable annual catching effort limited the precision of annual survival estimates. Survival rates of juvenile Redshank (between the first and second winters of life) varied markedly from year to year and averaged 43% (se 3.6%). Adult survival rates were less variable between years and were age-dependent, with 67% (se 5.0%) surviving and returning between the second and third winters of life, compared to 74% (se 1.4%) for older birds. Year-to-year variation in adult survival was weakly (and negatively) related to the number of snow days in winter. Year-to-year variation in first-year survival was non-linearly related to winter rainfall, with low survival during dry (and cold) winters, higher survival during winters with average rainfall and lower survival during wet winters. Having accounted for these weather relationships there was no evidence that survival was related to the size of the local wintering Redshank population. Organized annual ringing programmes of wintering waders on British estuaries have the potential to monitor long-term changes in survival rates and productivity. Although constant effort sampling may be difficult to achieve for wintering waders, the utility of mark-recapture data collected on estuaries is likely to depend heavily on careful study design.

Kersten, M. & A. Brenninkmeijer (1995): Growth, fledging success and post-fledging survival of juvenile Oystercatchers Haematopus ostralegus.. Ibis 137: 336 - 404.

We studied the consequences of differences in growth rate on the subsequent survival of Oystercatcher Haematopus ostralegus chicks. Fledging success increased sharply with growth rate, from zero in chicks growing at less than 6 g per day to about 85 % in chicks growing at more than 10 g per day. The age at which chicks fledged varied from 27 to 52 days. Chicks which fledged at an early date displayed a much faster growth rate than later fledging chicks. Although slow growth resulted in a considerable prologation of the period before fledging, slow-growing chicks fledged at a smaller size and with a lower body-weight than fast-growing chicks. After fledging, all chicks remained almost completely dependent on their parents up to an age of 3 months and often longer.
Almost 40 % of the fledglings eventually returned to the breeding area. This figure probably reflects post-fledging survival. Age and size at fledging had no effect on a chick's probability of return. Body-weight at fledging had a small positive correlation with the return probability, but this was not statistically significant. We conclude that although slow growth severely reduces a chick's chance of fledging, it probably does not result in irreversible damage causing an increased risk of mortality during the first years after fledging. Apparently, any possible disadvantage associated with small size or low body-weight could be compensated for after fledging.

Kraaijeveld, K. & E. N. Nieboer (2000): Late Quaternary paleogeography and evolution of arctic breeding waders. Ardea 88: 193 - 205.

This review links published data on mitochondrial DNA phylogeography of three wader species breeding in the Arctic to the availability of suitable breeding habitat during the past 250 000 years. We argue that the breeding ranges of arctic waders were most restricted in size during warm phases in the earth's climate (interglacials), resulting in population bottlenecks in species breeding in the high arctic zone, such as Red Knot Calidris canutus and Ruddy Turnstone Arenaria interpres, and population contraction and the initiation of genetic divergence in low arctic species, such as Dunlin Calidris alpina. When the c limate cooled, all species could spread over larger areas. However, large ice-sheets fragmented tundra habitat, which resulted in more differentiation. Subspecies of Dunlin that became isolated during or before the last glacial period are genetically distinct, while those that originated after the glacial cannot be distinguished using mitochondrial DNA. The sensitivity of waders breeding in the high Arctic to increases in global temperature raises concerns over the effect of possible global warming due to anthropogenic factors on these species.

Lank, D. B., Butler, R. W., Ireland, J. & R. C. Ydenberg (2003): Effects of predation danger on migration strategies of sandpipers. Oikos 103: 303 - 319.

We examine the potential selective importance of predation danger on the evolution of migration strategies of arctic-breeding calidrid sandpipers. Adult calidrids truncate parental care for reasons not obviously related to levels of food abundance on the breeding areas or at migratory stopover sites, suggesting that a different trade-off occurs between providing additional care and adult survivorship. The southward migrations of adult western sandpipers precede those of migratory peregrine falcons by almost a month. By moving early and quickly, adults remain ahead of migrant falcons all the way to their non-breeding areas, where they rapidly moult flight feathers. They complete the moult just as falcons arrive in late September-October. By migrating early, they avoid exposure to falcons when they are unusually vulnerable, due to the requirements for fuelling migratory flight and of wing feather moult. Juvenile western sandpipers migrate south just as falcon numbers start to increase, but do not moult flight feathers in their first winter. Pacific dunlin use an alternative strategy of remaining and moulting in Alaska after falcons depart, and migrating to their overwintering sites after migrants have passed. East of the Rocky Mountains, the southbound migration of falcons begins 4-6 weeks later. Southbound semipalmated sandpipers make extended migratory stopovers, but their lengths of stay shorten prior to falcon migration to the sites in September. Predation danger also may affect the evolution of migration routes. Southbound western sandpipers fly directly from Alaska to southern British Columbia, in contrast to the multi-stage journey northward along the Alaska panhandle. We estimate that a direct flight would be more economical on northward migration, but may be avoided because it would expose sandpipers to higher mass-dependent predation danger from migratory falcons, which travel north with sandpipers. By contrast, few raptors are present in Alaska during preparation for the southward flight. A temporal and spatial window of safety may also permit semipalmated sandpipers to become extremely vulnerable while preparing for trans-Atlantic southward flights. Danger management may account for the these previously enigmatic features of calidrid migration strategies, and aspects of those of other birds.

CP:A paper with terrible, monocausal reasoning, it makes me bristle.

Leuzinger, H. & L. Jenni (1993): Durchzug des Bruchwasserläufers Tringa glareola am Ägelsee bei Frauenfeld. Orn. Beob. 90: 169 - 188.

The Wood Sandpiper belongs to the few wader species with a high proportion crossing the continent on migration. It therefore needs adequate inland stopover sites. This study analyses autumn and spring migration at a small stopover site in NE Switzerland, 1966-1988. The migration through Switzerland is described based on ringing recoveries.
Wood Sandpipers which migrate through Switzerland arrive from Scandinavia with SSW directions and a mean speed of 90-100km/day. This suggests non-stop flights of up to 1000 km. From Switzerland, most birds fly SW to SE France (Camargue), a few to SW France or across the Alps to N Italy, before continuing migration to their winter quarters in W Africa. Three recoveries suggest that birds may occur in S Spain during winter. Two others show that autumn migrants may fly NE out of the Alps.
Regular counts over 22 years at Ägelsee revealed a prominent autumn and a weak spring migration peak, probably due to reduced surface of shallow water in spring. The number of birds and their seasonal patterns varied from year to year. Adults migrate about one month earlier than first-year birds. The number of birds observed decreased markedly over the years due to the reduction of the surface of shallow water, the increase in vegetation and other factors.
The proportion of birds retrapped within the same season were lower, and the duration of their stay shorter, in adults than in first-year birds. This is in contrast to more northern stopover sites and to the Common Sandpiper Actitis hypoleucos at Ägelsee. Only 0.5 % of all first-year birds ringed were caught again in a later year.
Wing-length and bill-length showed no trend with autumn migration season in adults, but decreased significantly in first-year birds. This suggests that different groups of first-year birds migrate through Switzerland at different times of year. This might be a reason for the bimodal seasonal migration pattern of first-year birds.
During the second half of the morning, first-year birds with low body mass were caught; these birds have short wings in relation to their bill-length. Body-mass increased significantly in first-year birds over the autumn migration season, but not in adults. Thus, late migrating first-year birds have more energy reserves than early migrating ones.
First-year birds which stay at Ägelsee for some days (retraps) had higher body mass and longer wings, but not bills, than first-year birds caught only once. Retraps increased their body mass by 0.44 g/day (maximum 30 g in 12 days): Birds with long wings and low body mass at arrival increased their body mass more quickly than birds with short wings and high body mass. The proportion of birds retrapped, their stopover duration and body mass increase showed no trend over the 22 years. This suggests that the decrease of the number of Wood Sandpipers observed at Ägelsee is primarily due to the decrease in the surface of shallow water and not to a reduced quality of the habitat. Hence, not only the present but also the extension of shallow waters are of importance to Wood Sandpipers during their migration.

Leyrer, J. Spaans, B., Camara, M. & T. Piersma (2006): Small home ranges and high site fidelity in red knots (Calidris c. canutus) wintering on the Banc d'Arguin, Mauritania. J. Orn. 147: 376 - 384.

Using automated and manual radio-telemetry and resightings of individual colour-ringed birds, we assessed the daily use of space of red knots Calidris canutus canutus at a tropical wintering area along the Sahara coast, the Banc d'Arguin in Mauritania. Confirming earlier suggestions, we found that birds were very faithful to their roosts and that the daily foraging range was small; in the course of several winter months birds used an area of only 2-16 km2 of intertidal area. We found no differences between their movements in daylight and at night. Additionally, individuals seem to return to exactly the same locations in subsequent winters. This pattern is very different from red knots wintering in the temperate Wadden Sea. Here, they readily change roost sites and easily cover areas of about 800 km2 in the course of weeks but, just as in Mauritania, no differences between day and night are apparent. In northern Patagonia and north-western Australia, red knots have range sizes closer to those on the Banc d'Arguin, but here they do show differences in space use between day and night. Ecological explanations for these contrasting patterns require further comparative data based on in-depth studies on the predictability of the food base and the presence of diurnal and nocturnal predators.

Lopes, R. J., Múrias, T., Cabral, J. A. & J. C. Marques (2005): A Ten Year Study of Variation, Trends and Seasonality of a Shorebird Community in the Mondego Estuary, Portugal. BIOONEOnline 28: 8 - 18.

A monthly shorebird census in Mondego estuary, Portugal was made during ten years (1993-2002) and the information adds to the midwinter census carried out at international level. It is shown that higher variability in shorebird community occurred during the breeding and migrating periods, while the winter assemblage was very similar among years. The study provides precise information of the importance of the Mondego estuary, and the trends and phenology of its shorebird community. Six species are responsible for a large proportion of the total abundance throughout the year. Dunlin (Calidris alpina) is the most abundant species, followed by the Avocet (Recurvirostra avosetta). Over the study period, there was a significant increase in the total number of shorebirds that occur in some months. This was mainly due to the increase of the main species, the Dunlin. Only the Avocet showed a significant decrease in abundance. These trends were not explained by changes in overall flyway population or the Portuguese totals. Therefore, local explanations need to be considered (e.g., changes on habitat quality).

Lyons, J. E. & S. M. Haig (1995): Fat content and stopover ecology of spring migrant Semipalmated Sandpipers in South Carolina. Condor 97: 427 - 437.

Semipalmated Sandpipers (Calidris pusilla) stop at staging areas during migration to replenish fat reserves that fuel long distance flights. We hypothesize that if sandpipers are minimizing time spent en route between wintering areas and breeding grounds, a negative correlation should exist between fat content upon arrival at a staging area and length of stay. We examined the relationship between these two variables at a spring staging area in coastal South Carolina using simple and multiple regression models. Length of stay was independent of estimated fat content at capture after controlling for date in the season. Birds with sufficient energy reserves for long distance flights were as likely to remain on the study area as lean birds. Date in the season showed more influence on stopover time than estimated fat mass at capture. Stopover time decreased with later date, suggesting an increase in the speed of migration as the season progressed. These results show that date is a critical variable influencing Semipalmated Sandpiper migration stopover strategy. Migrants appear to shift their migration priorities with respect to fat stores and stopover time as the season progresses.

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