Wildfowl 24 EDITED BY G. V. T. MATTHEWS AND M. A. OGILVIE Published for the Wildfowl Trust, Slimbridge by Blackwell Scientific Publications Oxford London Edinburgh Melbourne 1973 Editorial address: The Wildfowl Trust, Slimbridge, Gloucester, GL2 7BT, England. Cover painting by Peter Scott of Bewick’s Swans flying over the Wildfowl Trust’s Observatory at its Welney Refuge, Line illustrations by Peter Scott, and others Price £2.00 ($6.50). Postage extra Photoset, printed and bound in Malta by St Paul’s Press Ltd Contents 4 International Swan Symposium 88 Waterfowl in north-east Asia by A. A. Kistchinski 5 Environmental stress on the Whistling Swan by William W. H. Gunn 103 A cosmopolitan duck moulting resort; Takslesluk Lake Alaska by Ja m es G. 8 A continental study of Whistling K ing Swans using neck collars by W illiam J. L. Sladen 111 Behaviour and distribution of wild geese in south-east Scotland by I. 15 The use of small airplanes to gather Newton, V. Thom and W. Brotherston swan data in Alaska by Ja m es G. K ing 123 T he m anagem ent o f grassland areas 21 Population structure and productivity for wintering geese byMyrfyn Owen of Whistling Swans on the Yukon Delta, Alaska by Calvin J. Lensink 131 The manurial effect of Cape Barren Goose droppings by R ich a rd W. 27 Trumpeter Swan management by M a rrio tt Henry A. Hansen 135 Studies of shorebirds at Lindisfarne, 33 Hyôko: winter habitat of wild swans at Northumberland. 1. Feeding ecology Suibara by R o se L esser and behaviour of the Bar-tailed God- wit by P. C. S m ith a n d P . R . Evans 43 A moulting population of non-breed­ ing Mute Swans with special reference 141 The systematic status of the Cape to flight-feather moult, feeding ecology Barren Goose as judged by its photo­ and habitat selection by Sven M athias- responses by J. Kear and R. K. Murtón son 144 Proximate and ultimate determinants 54 Mortality of the Black Swan in New of clutch size in Anatidae by P a u l A. Zealand—a progress report by M urray Johnsgard W illiam s 150 Platform-building by male and female 56 Lead shot in Bewick’s Swans by M ary Ruddy Ducks by W. R o y S iegfried E. Evans, N. A. Wood and Janet Kear 154 Icelandic eiders—a few observations by Ralph S. Palmer 61 Leucistic Bewick’s Swans by M a ry E. E vans a n d T om L eb ret 158 M aternal nesting behaviour by male M allards by Charles Dane, Willard 63 Censuses of Anatidae in the central Steffen and Patrick Caldwell delta of the Niger and Senegal delta— January 1972 by Frances R o u x 162 R esearch 81 Fluctuations in the numbers of wild­ 165 C onservation fowl on an equatorial hippo wallow by S. K. Eltringham 176 Publications 3 Wildfowl (1973) 24:4 International Swan Symposium at Slimbridge In association with the annual Executive work on Bewick’s Swans complete the pre­ Board Meeting of the International Water­ sentation in this volume. fowl Research Bureau, which took place O ther papers presented to th e sym posium at Slimbridge, a 2-day symposium on were those of Dr C. D. T. Minton on ‘A swans was organized jointly with the Wild­ study of Mute Swans in Central England’; fowl Trust on 7 and 8 December 1971. It Dr C. M. Perrins and Malcolm Ogilvie on did not prove possible to publish the pro­ ‘A study of colonially breeding Mute Swans ceedings of the symposium in book form, in Dorset’; Dr J. Cadbury on‘Swans on the but a number of the major papers are Ouse Washes, eastern England’; A. Tim- printed in this issue of Wildfowl. These mermann ‘On the occurrence of swans in are the contributions by William W. H. the Netherlands’; P. Andersen-Harild Gunn (Canada); Professor W. J. L. Sladen ‘Swan research in Denmark’; Dr A. Haapa­ (Co-ordinator of the I.W.R.B. Swan Re­ nen on ‘Whooper Swan research in Fin­ search Group), James G. King, Calvin J. land’; and R. F. Ruttledge on‘Distribution Lensink and Henry A. Hansen (all of the of W hooper and Bewick’s Swans in Ireland’. United States); Mrs. Rose Lesser (Japan); Dr Tom W. Barry (Canada) presented a Dr Sven Mathiasson (Sweden); Dr Murray draft ‘Bibliography of the Swan’ and this Williams (New Zealand). A major part of has since been extended, in association with C. M. Reynolds’ (U.K.) contribution was Dr Janet Kear, to cover more than a thou­ published in Wildfowl, 23:111—118, ‘Mute sand annotated entries. It will shortly be Swan weights in relation to breeding per­ published by the Canadian Wildlife Service. formance’. Mary Evans outlined the Other participants were G. L. Atkinson- Bewick’s Swan research being carried out Willes (U.K.), H. Boyd (Canada), Professor by the Wildfowl Trust and Dr Janet Kear P. Grenquist (Finland), Mr K. Honda introduced ‘The Swans’, the monograph by (Japan). P. N. Humphreys, Professor G. V. Peter Scott and the Wildfowl Trust which T. Matthews, Dr M. Owen, B. L. Sage, Sir was published shortly afterwards. Two Peter and Lady Scott, Dafila Scott, N. A. papers on particular aspects of the Trust’s Wood (all U.K.) and Mr S. Yoshikawa (Japan). Figure 1. Feeding time of the wild Bewick’s strated to the symposium participants on a misty Swans Cygnus columbianus bewickii is demon- morning. K. Honda Wildfowl (1973)24:5-7 Environmental stress on the Whistling Swan WILLIAM W. H. GUNN In North America, Whistling Swans Cygnus Lake Erie and Lake St Clair c. columbianus number about 100,000 birds. They breed across the Arctic from When the spring migration from Chesa­ Alaska to Baffin Island; on the winter peake Bay begins in March, the first major range, they are separated into two fairly- stop-over is 400-500 miles (650-800 km) evenly divided populations residing a con­ to the north-west, in the marshes of Lake tinent apart, on the Pacific and Atlantic Erie and Lake St Clair. Some birds carry on coasts. to Shiawassee National Refuge and Sagi­ My comments in this paper refer to the naw Bay in Michigan. Atlantic population because it has been The extensive pollution of Lake Erie is studied in more detail, but there is reason now a matter of international concern. to believe that similar circumstances exist More and more heavy industry continues to for the Pacific population. take up space along its shoreline on both On the Atlantic seaboard, the eastern sides of the border. Many of its marshes population of about 50,000 Whistling have been destroyed or seriously depleted. Swans winters largely in Chesapeake Bay As a haven for migrating swans, it can now but, of late, they have been appearing in support only a few thousand at a time. increasing numbers as far south as Back Lake St Clair still has extensive marshes, Bay, Virginia, and the coastal marshes of particularly along the eastern shore, in North and South Carolina. Canada. The much publicized discharge of Beginning in March, their spring mercury from a chemical plant into the St. migration takes them northwestward across Clair River is probably of less concern to the continent some 3,000-4,000 miles swans than the effluent from oil refineries, (5,000-6,500 km) to the breeding range. As polymer plants, and municipal sources. To one follows them on this long trek, accom­ what extent the quality and quantity of plished in 3 months, it becomes more and swan food has been affected in recent years more evident that they are faced with in­ is not known. creasing stress from actual or potential Within the past 5 years, swans have deve­ ecological damage of a serious nature at loped the habit of flying from the St Clair both ends of their range and at every major marshes daily to glean corn from agricul­ stopping point in between. tural land. Between 5 March and 5 April at least half of the eastern population of Chesapeake Bay Whistling Swans visits a 4-mile by 5-mile (6-5 by 8-0 km) area of corn fields east of The heavy traffic of tankers and other Lake St Clair. Whether this development shipping in the narrow confines of Chesa­ is to exploit a newly found food source or peake Bay make oil pollution of the Bay a whether it has been made necessary by continuous threat. Neighbouring Delaware deterioration of the marsh vegetation in Bay, occasionally visited by swans, recently Lake St Clair is an important matter we suffered a serious oil pollution incident. should hasten to investigate. Oil slicks of a minor nature are probably a chronic condition on Chesapeake Bay but, in addition, massive industrial and muni­ The sloughs of North Dakota cipal pollution pours into the Bay from the Susquehanna and Potomac Rivers and By late March or early April, the swans are from the giant Bethlehem Steel plant on the heading for their next major stop-over, on Bay. the plains of North Dakota, fully 850 miles Whistling Swans frequent the small in­ (1,370 km) to the west-northwest. There, lets and marshy reaches to obtain their the countryside used to be dotted with basic diet of aquatic and sub-aquatic sloughs and potholes. In recent years, the vegetation. How well this vegetation is trend towards increasing mechanization standing up to severe water pollution and and large holdings in wheat-farming oper­ shoreline development is a problem that ations has brought about accelerated drain­ is being actively studied.