Earlier colony arrival but no trend in hatching timing in two congeneric seabirds ( Uria spp.) across the North Atlantic

• Published in: Biology Letters
• Main Authors: Merkel, Benjamin, Descamps, Sébastien, Yoccoz, Nigel G., Danielsen, Jóhannis, Daunt, Francis, Erikstad, Kjell E., Ezhov, Aleksey V., Grémillet, David, Gavrilo, Maria, Lorentsen, Svein-Håkon, Reiertsen, Tone K., Steen, Harald, Systad, Geir H., Þórarinsson, Þorkell Lindberg, Wanless, Sarah, Strøm, Hallvard
• Other Authors: Norwegian Oil and Gas Association, Norwegian Ministry of Foreign Affairs, Norwegian Ministry for Climate and the Environment, Natural Environment Research Council, TOTAL E&P Norway and the TOTAL Foundation, Norges Forskningsråd
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 2019
• Subjects: General Agricultural and Biological Sciences; Agricultural and Biological Sciences (miscellaneous); North Atlantic; uria
• Online Access: http://dx.doi.org/10.1098/rsbl.2019.0634; https://royalsocietypublishing.org/doi/pdf/10.1098/rsbl.2019.0634; https://royalsocietypublishing.org/doi/full-xml/10.1098/rsbl.2019.0634

A global analysis recently showed that seabird breeding phenology (as the timing of egg-laying and hatching) does not, on average, respond to temperature changes or advance with time (Keogan et al. 2018 Nat. Clim. Change 8 , 313–318). This group, the most threatened of all birds, is therefore prone to spatio-temporal mismatches with their food resources. Yet, other aspects of the breeding phenology may also have a marked influence on breeding success, such as the arrival date of adults at the breeding site following winter migration. Here, we used a large tracking dataset of two congeneric seabirds breeding in 14 colonies across 18° latitudes, to show that arrival date at the colony was highly variable between colonies and species (ranging 80 days) and advanced 1.4 days/year while timing of egg-laying remained unchanged, resulting in an increasing pre-laying duration between 2009 and 2018. Thus, we demonstrate that potentially not all components of seabird breeding phenology are insensitive to changing environmental conditions.