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20 August 2021 Temporal Changes in Wing Length, Fat Reserves and Body Mass of Migrating Eurasian Blackcaps Sylvia atricapilla at a West Hungarian Stopover Site
József Gyurácz, Péter Bánhidi, József Góczán, Péter Illés, Sándor Kalmár, Zoltán Lukács, Péter Molnár, Csaba Németh, László Varga
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Abstract

Changes in biometric characteristics of a migrating bird population at a given capture site could reflect that the migration strategies of the species may be changing. A robust data set (15,520 records) was used to analyse the changes in biometric characteristics of the Eurasian Blackcap Sylvia atricapilla in western Hungary between August and October during the study period (2001–2019). All age and sex classes displayed similar phenology of monthly captures and biometric change: the average wing length, fat score and body mass increased in the migrating population from August to October. This could be explained by changes in the morphometric distribution of different migrating populations, in later months more birds might arrive from a larger distance, primarily from the Baltic regions and the Czech Republic. The biometrics of juvenile birds captured in August did not change significantly from 2001 to 2019, while the wing lengths decreased and fat scores increased significantly between 2001 and 2019 in September and October in both sex classes. This could be explained by a change in the migration distance or different morphology of individuals from the north which stopped over at the study area. Due to the global warming and habitat changes in the last decade, the shorter migration route and favourable conditions at overwintering areas north of the Sahara or around the Mediterranean could favour Blackcaps which migrate a shorter distance.

József Gyurácz, Péter Bánhidi, József Góczán, Péter Illés, Sándor Kalmár, Zoltán Lukács, Péter Molnár, Csaba Németh, and László Varga "Temporal Changes in Wing Length, Fat Reserves and Body Mass of Migrating Eurasian Blackcaps Sylvia atricapilla at a West Hungarian Stopover Site," Acta Ornithologica 56(1), 51-58, (20 August 2021). https://doi.org/10.3161/00016454AO2021.56.1.005
Received: 1 April 2020; Accepted: 1 April 2021; Published: 20 August 2021
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KEYWORDS
body mass
Eurasian Blackcap
fat
long-term dynamics
migrants
temporal change
wing
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