About "adult buff" coverts

(dedicated to the grand lady of Dunlin research in the Baltic: Jadwiga Gromadzka)

The literature list contains the following papers referring to "adult buff" coverts: Clark 1984 , Gromadzka & Przystupa 1984 , Gromadzka 1985 , Gromadzka 1986 , Gromadzka 1989 and Engelmoor & Roselaar 1998 . In May, Goede et al. 1990 recorded no "adult buff" medians among Waddensea staging birds, and the level of consciousness related to them seems to be low already from the North Sea area. With growing knowledge of plumages, such birds are gradually being recorded in S. Sweden in spring, however, and the same applies to the Pacific area (subspecies sakhalina and arcticola; Jimmy Choi, pers. comm.). So, in the case of Europe, "adult buff" coverts seem to be a more or less exclusive Baltic Sea affair, possibly because they are easy to discern when medians and tertials are fresh in late summer and early autumn, but not later on and further the the west (Waddensea, Irish Sea), when wear sets in. In her 1986 paper, Jadwiga Gromadzka refers to investigations by Juhani Vuorinen at Ottenby as early as 1977; the main concern here seems to have been how to separate 1c birds from 2c birds with fresh "adult buff" coverts. That is not a major problem, however, since there are three - four characters that will readily separate 1c birds from 2c birds. A more specific reason for Vuorinen's concern might have been the fact that many early August (5 - 10 - 15 August) juveniles in the south Baltic by all likelihood come from the "adult buff" area, the pattern of their medians reminding somewhat of the pattern in 2c+ "adult buff" birds. At least 50 % of these early juveniles have Meissner rankings 2 and 3, they are of obvious eastern provenance in that respect, too. Even in this latter case, separation between 1c and 2c+ birds is fairly straightforward. Most of the majority type (western alpina ) juveniles starting to arrive in the Baltic by September 1st - but occurring from August 10th as well - have more white, grey and true buff on exposed edges, they are less reddish, see left juvenile median of Fig. 1. Also see pictures 4, 7, 8, 45, 46, 47 and 51 of the picture collection. The colour label "buff" always wondered me a little, since a majority of birds is "adult chestnut" or better still: "adult cinnamon"; adult buffs from the Sound area in most cases have a distinct reddish hue.

adult buff/standard alpina

Fig. 1. Three "adult buff" medians and three common median types in alpina juveniles on the Falsterbo peninsula in autumn.

Comment I: wear These feathers are rapidly worn (the first juvenile plumage being extremely soft), the outermost edge of alpina juveniles disappearing already in late October, and many birds belonging to populations with "adult buff" coverts are probably not identifiable as such from unmoulted nuptial plumage in June/early July since their reddish edges have been completely lost. Some "adult buff" coverts will be completely unworn in late July, however, replaced by new feathers by that time. One standard alpina bird had one new grey median on 31.7, one "adult buff" (lower left) all medians fresh on 10.8. Note that true "adult buffs" are lighter grey than "adult"cinnamon" or "adult chestnut"!

Comment II: extent of reddish/buffish edge A juvenile reddish edge to e.g. a tertial covert will in most cases be clearly demarcated from the dark core of the feather, an "adult buff" edge to a median fades into the grey centre. The outer vane of medians is darker than the inner vane, this is also indicated in the picture. Some "abc" birds have 1/3 of the visible median edged and are very rich in colour, they call the American name "Redbacks" into memory, extremes at the other end of the scale have one single, indistinctly "adult buff"-edged feather. I am inclined to appoint the uppermost, left median as normative "abc", but even more common in the Baltic in early August is an inconspicuous dusky brown edging, covering only a few % of the feather edge (look for it in birds with advanced moult, use magnification!).

Comment III: new coverts WARNING The innermost tertial is one of the first "coverts" replaced (often with the first primaries); it will have a broad chestnut edge, fading into the dark center, in an "adult buff" bird in the Baltic area already from 25 July. These birds are easily mistaken for 2nd calendar year by unexperienced workers, but they are not! In such cases: trust the tips/edges of primary coverts instead.

silver-edged medians

Fig. 2. There is another category with fast and early moult: the "silver-edged" median. (A shiny grey-and-white edge, very difficult to reproduce). On August 3rd a 2c male with two fresh silver medians had P1 - 4 fresh, P5 0.9, P6 0.4, this matches the most advanced "adult buff" by the same time. Mantle feathers in summer plumage are yellowish and buffish rather than chestnut; the reddish alpina hue is suppressed. Edges to juvenile feathers in a 2c bird belonging to this category are often not buff or reddish, but just white and grey (with a slight tinge of light buff), and I suspect that juveniles later in the season with very light (whitish) edges to tertial coverts etc. also belong to this group. The pattern of coverts is much the same as in "abc" birds, the moult is advanced, the inner primary ranking may be anything between 0 and 3. There is an overall arctica character to this form, although it is larger and has an early moult, there's no doubt in my mind that its provenance is Russian. (The whole phenomenon of reddish/chestnut and yellowish/buffish edges in Dunlin calls the dualism of colouration in juvenile Sand Martins to mind, here there is one sandy yellow or even whitish variant, one fox red/chestnut). For comparison three versions of standard alpina medians in adults have been added, altogether grey or dark grey with light grey edge is standard, I believe that the white edge connects with "adult buff" (or "silver" medians) in the east. (15.8.03: The three major types may mingle in all populations, but I have the impression that the white distal edge occurs with increasing frequency as we move east through the alpina "landscape").

Finally it could be added that "droplet (primary) coverts" share the "adult buff" pattern of early and fast moult, and they are connected with ranking "3" (see pictures of "droplet" and rankings: to Meissner scale ) as often as "adult buff" medians are. On the other hand there is no automatic connection between "droplets" and "adult buffs"; birds with "droplet" primary coverts have "adult buff" medians as often as not. Inversely, most well-developed "adult buffs" have distinct droplet coverts as well. Droplet coverts occur mainly after the first complete postnuptial moult, they may be used as an "adult" character, too - but there are exceptions, 1c birds with droplets.

droplet coverts

Fig. 3. Droplet coverts; adult type tips to primary coverts restricted laterally. Note that the bird has inner primary ranking "0"; the medians were all grey. Migrant 2c+, male from biometry, in complete winter plumage (moulted on or near breeding-grounds), Falsterbo peninsula, 26.9.07. .

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  • To "Phenology and biometry of Dunlin Calidris alpina migrating by way of the Sound area, S. Sweden"
  • To "Migrating Dunlin Calidris alpina in the Baltic area: the moult issue"
  • To "Risk-prone or risk-averse? Dunlin Calidris alpina migrating with and without moult-gaps in the Baltic area"
  • To "Wintering and spring staging Dunlin Calidris alpina in the south Baltic area"
  • To "Migratory progress of juvenile and adult Dunlin Calidris alpina from two perspectives: the Baltic and the Waddensea"
  • To "Bill-length distributions in Dunlin Calidris alpina "
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  • To the Meissner scale
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    The whole text revised 25.10.08.