Feeding specialisation is a common cause of individual variation. Fitness payoffs of specialisation vary with environmental conditions, but the underlying behavioural mechanisms are poorly understood. Such mechanistic knowledge, however, is crucial to reliably predict responses of heterogeneous populations to environmental change. We quantified spatiotemporal allocation of foraging behaviour in wintering Eurasian oystercatchers (Haematopus ostralegus), a species in which feeding specialisation can be inferred from bill shape. We combined GPS and accelerometer data to quantify foraging time of 64 individuals for every tidal period in one or two winter seasons. Individuals varied widely in foraging time (3.7-6.5 hours per tidal period) and individuals that spend more time foraging had lower inferred survival. Feeding specialisation appeared a major determinant of individual variation in foraging time and its spatiotemporal allocation. Visually-hunting worm specialists foraged more during day-time and complemented intertidal foraging with grassland foraging when the exposure of intertidal flats was limited and nights were well-illuminated. Shellfish specialists increased total foraging time in cold weather, whereas foraging time of worm specialists decreased as frosty grasslands became inaccessible. Our results imply that worm specialists may be most sensitive to cold snaps and day-time disturbance, while shellfish specialists are most sensitive to high water levels. These behavioural responses can be implemented in population models to predict the vulnerability of heterogeneous populations to environmental change, and thereby provide a shortcut to long-term population studies that require fitness data across many years and conditions to make similar projections.
|Date made available||14 Oct 2019|
van der Kolk, H. (Creator), Ens, B. J. (Creator), Oosterbeek, K. (Creator), Bouten, W. (Creator), Allen, A. M. (Creator), Frauendorf, M. (Creator), Lameris, T. (Creator), Oosterbeek, T. (Creator), Deuzeman, S. (Creator), de Vries, K. (Creator), Jongejans, E. (Creator), Van de Pol, M. (Creator) (14 Oct 2019). Shorebird feeding specialists differ in how environmental conditions alter their foraging time. Dryad. 10.5061/dryad.73n5tb2sb