Distribution and numbers of moulting non-breeding Whooper Swans Cygnus cygnus in the Baltic States and South Sweden

Hakon Kampe-Persson,Dmitrijs Boiko,Julius Morkūnas

doi:10.34080/os.v22.22588

Abstract

Non-breeding Whooper Swans Cygnus cygnus were recorded moulting for the first time in Latvia in 1989, in Estonia in 1993 and in Lithuania in 1997. Moulting has been recorded at 13 sites, three in Estonia and five each in Latvia and Lithuania, but not at all in South Sweden. The total number of moulting non-breeders increased from at least 83 birds in 2003 to at least 187 birds in 2012. The majority of the marked birds found moulting as non-breeders in the Baltic States usually originated from moulting sites within 25 km, the others from countries, including Germany and Poland, situated to the south of the moulting site. Distances between sites of hatching or breeding and moulting for these two groups ranged 0–81 km and 191–836 km, respectively. When caught for ringing, 40% were 2nd calendar year birds, the others older. Life-histories of Whooper Swans marked as moulters, or found moulting, in the Baltic States were used to discuss the lack of known moulting sites in South Sweden.

Highlights

Feathers wear out through constant use so birds have to replace them
Of birds undertaking a moult-migration to Russia, the last individuals usually leave in the middle of June (Boiko & Kampe-Persson 2012)
The majority migrate to traditional moulting grounds in Russia

Summary

Introduction

Feathers wear out through constant use so birds have to replace them. Most birds replace their primary and secondary wing feathers one or two at a time so that their power of flight is not drastically impaired. The Whooper Swan matures slowly and first breeding is usually at the age of 4–6 years (Einarsson 1996). A high proportion of the population consists of non-breeding birds. About two thirds of the population does not attempt to breed in each year (Garðarsson & Skarphéðinsson 1984, Haapanen 1991, Rees et al 1991, Einarsson 1996, Schadilov et al 2002, Brazil 2003)

Objectives

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Results

Conclusion