The early birds and the rest: do first nesters represent the entire colony?

• Published in: Polar Biology
• Main Authors: Jónsson, Jón Einar, Lúðvíksson, Smári J., Kaller, Michael D.
• Other Authors: Rannsóknasetur á Snæfellsnesi (HÍ), Research Centre at Snæfellsnes (UI), Háskóli Íslands, University of Iceland
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer Nature 2016
• Subjects: First nest date; Arrival date; Nest numbers; Eider; Climate change; Fuglafar; Hreiðurgerð; Loftslagsbreytingar; Örn; Republic of Iceland; Rif; Common Eider; Iceland; Polar Biology; Somateria mollissima
• Online Access: https://hdl.handle.net/20.500.11815/621; https://doi.org/10.1007/s00300-016-1969-z

Climate change studies have detected earlier spring arrival of breeding birds. However, first nest dates (date first nests were found), which commonly provide the metric for earlier arrival, can be biased by population size or sampling effort. Our aims were to determine if: 1) first nest dates and median nest date (date when at least 50 % of all females have nested) were equivalent predictors for the spring arrival and 2) first nest date or median nest date were related to nest numbers. We recorded first and median nest dates and nest numbers at the common eider (Somateria mollissima) colony at Rif, Iceland, during 1992–2013. First nest date was advanced by 11 days during the study, but median nest date was advanced by only 4 days. First nest date and median nest date were correlated, but this relationship was only a small improvement over the null model (Nagelkerke R 2 = 30 %). We found a relationship with nest count for both first and median nest dates once the analysis had accounted for inter-annual variability. First nest date may not represent the colony as a whole but rather the physically fittest or the most determined individuals, which may be more prone to nest early than the general population. Nesting birds must decide how much to advance breeding based on nest numbers and other non-temporal cues which necessitate earlier breeding. We argue that nest numbers affect the birds in a biological sense and that the advancement was not explained solely by increased nest numbers. This study was supported by the University of Iceland. We sincerely thank Auður Alexandersdóttir, Árni Ásgeirsson and Thordur Örn Kristjánsson for their support through the duration of this study. We thank the editor and three anonymous reviewers for helpful comments that greatly improved earlier drafts of this manuscript. Sigmundur H. Brink kindly provided the map for Fig. 1. This study complies with the current laws of the Republic of Iceland and all regulations pertaining to the treatment of study animals, including the banding ...