ORIGINAL PAPER G. Dewasmes á S.D. CoÃte á Y. Le Maho á R. Groscolas J.P. Robin á G. Vardon á J.P. Libert Effects of weather on activity and sleep in brooding king penguins Aptenodytes patagonicus) Accepted: 6 March 2001 / Published online: 21 April 2001 Ó Springer-Verlag 2001 Abstract Avian sleep is sensitive to thermal challenges. Brooding king penguins Aptenodytes patagonicus) de- fending a territory are exposed to wide daily ¯uctuations in ambient temperature and wind conditions. We stud- ied the daytime behavioural time budget of 89 groups of territorial adults brooding a 1- to 5-week-old chick on Crozet Island during summer 1998. Scans were per- formed every 10 min and each bird was categorized as either active, resting or sleeping. Three ranges of ambi- ent temperatures T1=5±9°C, T2=10±13°C, T3= 14±19°C) and wind conditions calm-light, moderate, strong) were distinguished. Wind conditions did not aect the behavioural time budget of king penguins during summer. Resting, which represented about half of the daytime behavioural time budget, increased by 17% when ambient temperature increased from T1 to T3, mostly at the expense of active behaviours. The percentage of time spent sleeping was low, but was re- duced by 66% when ambient temperature increased over 10°C. Thus, behavioural sleep was mainly observed in a range of temperatures within which resting metabolic rate of adult king penguins is minimal, i.e. between ±1 and 11°C. It is also interesting to note that the range of ambient temperatures in which sleeping was high coincides with the most common microclimatology prevailing at the colony during summer, i.e. ambient temperatures between 5 and 10°C. Introduction Avian sleep is sensitive to thermal challenges. Domestic and wild birds in captivity reduce time spent sleeping when exposed to unusually warm or cold air tempera- tures Stahel et al. 1984; Graf et al. 1987; Szymczak 1987, 1989). The eects of natural thermal conditions on the sleep of free-living birds have also been assessed, but only in behavioural studies. Glaucous-winged gulls Larus glaucescens) and teals Anas crecca) sleep less when facing natural thermal stress Tamisier 1972a, b; Opp et al. 1987). Many birds live and breed under severe climatic conditions where the thermoregulatory demand is intense. This is the case with the king penguin Apte- nodytes patagonicus), a subantarctic species which must endure both cold up to ±5°C) winter temperatures and heat during summer 15±20°C). Resting Metabolic Rates RMR) in king penguins are minimal between ±1 and 11°C Barre 1980). In addition, the subantarctic climate is very windy Barrat 1976), thus signi®cantly increasing the cooling eect of air Birr 1968). The daily time budget of breeding king penguins has recently been studied, and it was found that behavio- ural sleep was profoundly depressed during both the incubation 4±7%) and the brooding 0.3%) periods, when breeders are forced to undertake intense activities of territory and ospring defence day and night Challet et al. 1994; CoÃte 2000). At such times, a single bird may engage in up to 500 interactions/h with ter- ritorial neighbours and spend up to 19% of its time ®ghting CoÃte 2000). However, part of the reduction in behavioural sleep could be generated by climatic instabilities prevailing in the colony. This study is the ®rst attempt to clarify this issue. Polar Biol 2001) 24: 508±511 DOI 10.1007/s003000100249 G. Dewasmes &) á G. Vardon á J.P. Libert Faculte de MeÂdecine et de Pharmacie d'Amiens, URAPC, Universite de Picardie Jules Verne, 80036, Amiens Cedex, France E-mail: Gerard.Dewasmes@sa.u-picardie.fr Fax: +33-3-22827896 S.D. CoÃte á Y. Le Maho á R. Groscolas á J.P. Robin Centre d'E  cologie et Physiologie E  nerge tiques, CNRS, 67087, Strasbourg Cedex 2, France S.D. CoÃte DeÂpartement de Biologie, Universite de Sherbrooke, Sherbrooke, QC, J1K 2R1 Canada S.D. CoÃte Present address: Centre for Ecology & Hydrology, Hill of Brathens, Banchory, Aberdeenshire AB31 4BW, UK