Primary moult in non-breeding second-calendar-year Swifts Apus apus during summer in Europe

• Published in: Ringing & Migration
• Main Authors: Jukema, Joop, van de Wetering, Henk, Klaassen, Raymond H G
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2015
• Subjects: Apus apus
• Online Access: https://hdl.handle.net/11370/50190ee3-8ce7-4082-8589-d8166b066ee5; https://research.rug.nl/en/publications/50190ee3-8ce7-4082-8589-d8166b066ee5; https://doi.org/10.1080/03078698.2015.1059632; https://pure.rug.nl/ws/files/84972786/Primary_moult_in_non_breeding_second_calendar_year_Swifts_Apus_apus_during.pdf; http://www.scopus.com/inward/record.url?scp=84936883075&partnerID=8YFLogxK

Little is known about the extent of primary moult in non-breeding second-calendar-year Swifts during summer in Europe. A sample of 352 Swifts of this age group was captured during May–July in a village in the Netherlands. Primary moult was almost completely restricted to July. During the first and second halves of July, respectively, 20% and 60% of the second-calendar-year Swifts were moulting. Moult was restricted to the first four inner primaries, but 62% of individuals moulted the innermost primary only. Surprisingly, in 63% of moulting birds, primary moult was asymmetric.