Líffræðifélag Íslands - biologia.is
Líffræðiráðstefnan 2023
Höfundar / Authors: Jón Einar Jónsson 1, Ellen Magnúsdóttir 1, James A. Fletcher 1, Jamie Noreen Carroll 1, Árni Ásgeirsson 1, Jón Jakobsson 1, Elisabeth Knudsen 1, Anna Ejsmond 1.
Starfsvettvangur / Affiliations: 1 University of Iceland’s Research Center at Snæfellsnes
Kynnir / Presenter: Jón Einar Jónsson
Nest initiation dates are important in long-term population studies; they vary among years and individuals and often are related to variation in weather. Common eiders were banded in south Breiðafjörður 2014-2023. We compared nest initiation dates from all nests found, to those of banded females caught 6 times or more often during 2014-2023. Average nest initiation date for these individuals ranged between 13 May and 4 June, which corresponded to the distribution for the whole study population. The standard deviation for Julian nest dates ranged from 1.8 to 12.9 within individuals, indicating some consistent and some flexible individuals. Nesting was late for the whole population in 2015, 2019 and 2021. We used within-individual standard deviation for nest initiation date to examine each individual for any late or early nesting years. Of 22 birds (79 %) present in 2015, 64% showed later nesting. Of 40 birds (83%) present in 2019, 15% showed later nesting. Of 28 birds (58%) present in 2021, 29% showed later nesting. We also found late or earlier nesting in the year first banded (27%) or the last year recovered (22.5%). Lastly, 18 individuals (37.5%) showed early or late nesting in other years. Female eiders thus exhibit individual strategies for nest initiation dates, and older birds seem indifferent to population averages.