Wildfowl 25 EDITED BY G. V. T. MATTHEWS AND M. A. OGILVIE Published for the Wildfowl Trust, Slimbridge by Blackwell Scientific Publications Oxford London Edinburgh Melbourne 1974 Editorial address: The Wildfowl Trust, Slimbridge, Gloucester GL2 7BT, England. Cover painting by Peter Scott of Dark-bellied Brent Geese flighting over the sea wall at Horsey Island. Back cover: Negative Maplin. Line illustrations by Peter Scott, Paul Johnsgard and others Price £2.00 ($6.50). Postage extra Photoset, printed and bound in Great Britain by Butler and Tanner Ltd, Frome and London Contents 5 On the biology of the Spectacled Eider 89 The number of adult Eiders in the Baltic by A. A. Kistchinski and V. E. Flint Sea by B. Almkvist, A. Andersson, A. Jogi, M. K. Pirkola, M. Soikkeli and J. 16 The Shelduck population of the Ythan V irtanen estuary, Aberdeenshire by I. J. Patter­ son, C. M. Young and F. S. Tompa 95 Range expansion and population in­ crease of the Gadwall in eastern North 29 Criteria for ageing embryos of the Eider America by Charles J. Henny and Nor­ by Manyn L. Gorman man E. Holger sen 33 Brood care, pair bonds and plumage in 102 The Wildfowl T rust expedition to Spits­ southern African Anatini by W . Roy bergen, 1973 by E. E. Jackson, M. A. Siegfried Ogilvie and M. Owen 117 Preliminary observations on waterfowl 41 The survival of broods of the Egyptian ofWestern Madagascar by Dafila Scott Goose in Uganda by S. K. Eltringham and Joanna Lubbock 49 Territorial behaviour of wild Shovelers 123 Etho-ecological studies of Teal winter­ at Delta, Manitoba by Norman R. ing in the Camargue (Rhone Delta, Seymour France) by Alain Tamisier 134 An ecological outline of a moulting area 56 On the behaviour of the White-headed of Teal, Vejlerne, Denmark by Leo Duck with especial reference to breed­ Kortegaard ing by G. V. T. M atthews and M ary E. Evans 143 The ecology of the invertebrate com­ munity of Borough Fen Decoy Pond by 67 The development of rank order and Margaret Palmer aggressiveness in a group of juvenile G reylag Geese by Britt-Marie Stahlberg 149 Ten years of intensive late-winter sur­ veys for waterfowl corpses on the north­ 74 Climbing ability of ducklings of some west shore of the Wash, England by cavity-nesting waterfowl by W. Roy R. E. M. Pilcher, J. V. Beer and W. A. Siegfried Cook 155 The taxonomy and relationships of the 81 Foot adaptations in four species of northern swans by Paul A. Johnsgard Whistling Duck Dendrocygna by Eric G. Bolen and M . K ent Rylander 163 Research, Education, C onservation and Publications 84 The behaviour of wintering Smew in southern Sweden by Leif Nilsson 176 N otice to C ontributors , On the biology of the Spectacled Eider A. A. KISTCHINSKI a n d V. E. FLINT The range of the Spectacled Eider Somateria underwater beds of Hippurus sp., and with fischeri is rather restricted, and its biology is small islets. The so-called 'laydas’ vast poorly known. Some biological observa­ depressions (2-5 km in diameter) that are tions have been made in the Siberian tundras flooded in June, after snow-melting, and between the Yana and Kolyma rivers (Birula, overgrown by A. fulva and sedges are 1907; Mikhel, 1935; Uspenski et al., 1962; especially characteristic as a habitat of Spec­ Vorobyev, 1963) and inAlaska(Nelson, 1887; tacled Eider. Usually, in the middle of a Conover, 1926; Brandt, 1943; Bailey, 1948; ‘layda’ there are deeper patches of open Johnsgard, 1964a). In the sum m er of 1971, water, and among grass-sedge thickets and we obtained new ecological information in these patches, small islets and the dry tus­ the delta of the Indigirka (c. 71°N, 150°E) socks are scattered. By the end of the summer where this eider is the most common duck the water level falls and most of the area of species. Our work proceeded from 3 June to ‘laydas’ dries; nevertheless, they remain 6 August, and we were able to visit both hardly passable. On such lakes Spectacled inner and maritime parts of the delta where Eider is the most numerous duck (besides, life conditions for Spectacled Eider are there live a few Long-tailed Duck, Clangula different. hyemaIis). Spectacled Eider needs large areas of coastal shallows (0-10 cm deep) for summer Breeding habitats and numbers living, most of which is a temporarily flooded moss-sedge bog. This bog is inhabited by The Spectacled Eider is the most common great numbers of hydrophilous larvae of duck in the delta of the Indigirka river; the crane-flies Prionocera spp. (Tipulidae) and fact having been recorded by Mikhel (1935). those of various caddisflies which make to­ It is most numerous in the maritime half of gether the bulk of the summer diet of this thedelta, up to 40-50 km from the sea. Eiders eider. live here in the moist low tundra with numer­ Farther from the sea, in the inner parts ous shallow ponds bordered by coastal of the delta, favourite eider habitats are less flooded growth of Arctophila fulva, with extensive, and accordingly, eider numbers Table 1. Population density and total numbers of the Spectacled Eider in the delta of the Indigirka river Number Total Pairs (June) or Total Total Territory of area of females (July) area spring within the delta census census per 10 km 2 of the numbers plots territory (pairs) Limits Mean Maritime parts, 5 66 33-60 47 3.100 14,570 south-westwards to the settlements Yar and Tabor Central parts from 3 39 8-12-5 10 1.800 1.800 Yar and Tabor south-westwards to the settlement Polyarni and mouth of the Keremesit river Innermost parts 4 41 0-5 2-5 4,300 1,075 and the tundras southwards of the Kolymskaya channel Total 12 146 9.200 17.445 5 6 A. A. Kistchinski and V. E. Flint are lower. Southwards of the Kolymski common here. In 1971, the numbers were channel, near the Keremesit river, Spec­ said to be slightly lower than usual. tacled Eiders were rare; they lived there near shallow lakes 10-200 m in diameter bordered by polygonal bogs flooded by Arrival melt-wat er in June. In July, a good number of females were Eiders arrive at the breeding grounds at the also observed in the narrow strip of maritime beginning of June. In 1971, they appeared meadows dominated by Dupontia psilo- on 8 June; an intensive passage took place santha, sedges and cotton-grass, rich in on 9—10 June and ended on 13 June. Eiders brackish potholes devoid of Arctophila and flew directly from the east, in flocks of seven dotted with small islets. to thirty birds, very low—usually 2-3 m We have determined the numbers of above the ground. Probably eiders flew great Spectacled Eiders on census plots 6-30 km2 distances without landing—from the resting by surveying all the lakes and ponds on grounds on marine bays to the breeding them during one or more days. At court­ lake. ship time, pairs on lakes are easily visible. The sex ratio in the arriving flocks was In July, males are nearly absent in the near to 1:1. From 9 to 13 June 1971, tundra; non-breeding females and those seventy-two males and sixty-nine females which have lost their clutches gather in were counted. Pairs were easily visible in flocks and sit for hours on the favourite the flocks. resting spots situated on dry lakeside tus­ socks or islets where they can easily be counted. Incubating females in July could be Breeding either identified by their behaviour when feeding on channels and lakes or frightened Spectacled Eiders arrive in pairs. We were from the nests. Of course, some females were not able to see courtship behaviour at the missed. Nevertheless, we consider our esti­ breeding grounds; only on 19 June were mates to be reliable enough—especially residual displays of this type observed. because in July of 1971 successful females Males performed a display close to ‘Head- made up quite a small part of the popula­ forward-lifting’, and females—‘Chin-lifting’ tion (see below). When calculating we (in terms of Johnsgard, 1964b) (Figure 1). equated the number of females in July to the Eiders were in pairs up to 24 June. On number of pairs in June (the spring sex 25,29 June and 4 July we saw and collected ratio being 1:1). females which had just finished egg-laying. In order to estimate total numbers, we (In 1960, in the mouth of the river have divided the delta into three zones with Bogdashkina, north of the delta, a nest with different population densities of Spectacled two eggs was found on 15 June, and a full Eider (Table 1). Calculations have shown clutch with five eggs on 24 June (Uspenski that, in sprin'g, the numbers of the eider in et al., 1962).) At the end of June, pairs were the delta and tundras adjacent to it in the broken, and the males disappeared. In 1960, south are close to 17,000 — 18,000 pairs, of an eastward passage of males along the sea which 15,000 are in the maritime half of the shore north of the delta was observed at delta. the end of June (Uspenski et al., 1962). H ow ­ According to local people, the numbers of ever, we saw single drakes from time to Spectacled Eider in the delta fluctuate in time in the flocks of non-breeding females different years, but the species is always up to 15 July.