ORIGINAL PAPER Persistent bimodal activity patterns in wild and captive black-tailed godwit Limosa limosa under different environmental conditions A role for circadian rhythm? Francisco Santiago-Quesada & José A. Masero & Sora M. Estrella & Juan M. Sánchez-Guzmán Received: 15 June 2011 /Revised: 29 September 2011 /Accepted: 25 October 2011 /Published online: 12 November 2011 # Springer-Verlag 2011 Abstract There is a large literature dealing with daily foraging routines of wild birds during the non-breeding season. While different laboratory studies have showed that some bird activity patterns are a persistent property of the circadian system, most of field studies preclude the potential role of an endogenous circadian rhythm in controlling bird’ s foraging routines. In this study we compared the patterns of diurnal foraging activity and intake rates of migrating black-tailed godwits, Limosa limosa (radio-tagged and non-tagged individuals) at two stopover sites (habitats) with different environmental characteristics, aiming at identifying proximate factors of bird activity routines. To gain insights into the role of food availability in control of such foraging routines, we also estimated foraging activity patterns in captive godwits subjected to constant food availability. Captive and wild black-tailed godwits showed a persistent bimodal activity pattern through daylight period. Food availability had a significant effect on the intake rates, but had a subtler effect on foraging and intake rate rhythms. Temperature and wind speed (combined in a weather index) showed non- significant effects on both rhythms. Although we could not discard a role for natural diurnal changes in light intensity, an important timing cue, our findings support the idea that an endogenous circadian rhythm could be an important proximate factor regulating foraging activity and food items taken per unit time of wild black-tailed godwits during migration. Keywords Black-tailed godwit . Circadian rhythms . Foraging routines . Migration . Shorebirds Introduction Circadian rhythms are endogenously generated oscillations in biological function that occur over an approximately 24-h period and persist in the absence of environmental cues (Davidson and Menaker 2003). These circadian rhythms enable animals to anticipate and to prepare for predictable changes in their environments (Stelzer et al. 2010). Many daily variations in physiology or behaviour in animals posses a strong endogenous (circadian) component, although these daily variations may be, to a variable extension, modulated by events related to food availability, territory, predation, inter- and intraspecific competition, and temperature (Reebs 2002; Kronfeld-Schor and Dayan 2003; Lazzari and Insausti 2008). There is an extensive literature dealing with daily patterns of foraging activity in wild birds, from seabirds Communicated by W. Wiltschko F. Santiago-Quesada (*) : J. A. Masero : J. M. Sánchez-Guzmán Conservation Biology Research Group, Área de Zoología, Universidad de Extremadura, Avenida de Elvas s/n, 06071 Badajoz, Spain e-mail: fquesada@unex.es F. Santiago-Quesada Unidad Académica Mazatlán, Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Avenida Joel Montes Camarena s/n, Apdo. 811, C.P. 82040 Mazatlán, México S. M. Estrella School of Animal Biology, University of Western Australia, 35 Stirling Hwy, 6009 Crawley, Australia Behav Ecol Sociobiol (2012) 66:397–405 DOI 10.1007/s00265-011-1285-0