Being at the right place interpreting the annual life cycle of Afro Siberian red knots

PhD ceremony : Ms. J. Leyrer, 11.00 uur, Aula Academiegebouw, Broerstraat 5, Groningen

Dissertation: Being at the right place interpreting the annual life cycle of Afro Siberian red knots

Promotor(s): prof. Th. Piersma, prof. D.W. Winkler

Faculty: Mathematics and Natural Sciences

In her thesis, potentially fitness-affecting aspects of the annual cycle in a long-distance migrating shorebird, the Afro-Siberian red knot have been studied by Jutta Leyrer. An important period within the annual cycle is the timing of arrival in the breeding grounds in such way that the offspring’s growth period matches the peak in food supply. This can be challenged by adverse winds during northward migration, which might influence both the timing of arrival but also survival during migration. Yet, the by Leyrer studied population has shown to make use of emergency staging sites when winds are unfavourable en route to potentially avoid a higher mortality. They further have been observed to depart at “non-traditional” times from subsequent staging sites when (again) weather conditions were adverse, probably to escape a local high predation risk, but also to potentially avoid further delays, or to make up for delays carried over from (additional) emergency stops. Although migration has been regarded as a potentially dangerous period, the observed red knot population did not show a higher mortality during migration. Contrarily, they experienced lowest survival shortly after arriving back at their wintering grounds, discovered Leyer. This might be due to an amalgamation of physiological and 'social' challenges: They moult after arrival, when climatic conditions are hot and humid; they might experience carry-over effects from the preceding seasons; settling in a good foraging habitat incurs survival costs. A good foraging site during winter though increases survival and might permit a better start into the subsequent migration and breeding seasons.