Of great tits and fleas: sleep baby sleep . .

Many bird parasites reduce their hosts’ fitness and, as a consequence, anti-parasite behaviour such as preening and nest sanitation has evolved. These activities are time consuming and, during the day, compete directly with time devoted to foraging and food provisioning to nestlings. Moreover, infested hosts may have to allocate extra time to foraging in order to compensate for the energy loss that ectoparasites impose on the nestlings and parents. Alternatively, brooding females could, at the expense of sleeping, allocate more time to preening and nest sanitation at night. If sleeping has a short-term restoring function, one may then expect a reduction in feeding efficiency of sleep-deprived females. In this study, the effect of a haematophagous ectoparasite, the hen flea, on the activity budgets of breeding female great tits during the day and at night was investigated experimentally. Time allocated to nest sanitation increased only slightly from 0.6 % of daytime in ectoparasite-free nests to 2.8% of daytime in infested nests, thus demonstrating the higher priority given to food provisioning than parasite control. Females in infested nests reduced their sleeping time significantly (73.5% of night-time in parasite-free nests versus 48.1% in infested nests). The time freed from the reduction of sleeping time was mainly used for nest sanitation (8.3% of night-time in parasite-free nests versus 27.1% in infested nests). Despite this strong decrease in sleeping time, there was no effect of ectoparasites on the females’ rate of food provisioning to nestlings. ? 1996 The Association for the Study of Animal Behaviour By definition, parasites reduce the fitness of their hosts (Price 1980). Ectoparasites impair nestling growth and survival (e.g. Møller 1990; Møller et al. 1990; Richner et al. 1993), and anti-parasite behaviour that reduces the parasites’ impact must therefore be favoured by natural selection (Keymer & Read 1991; Hart 1992). Clayton (1991) has demonstrated experimentally that feather preening significantly reduces the load of feather lice on non-breeding adult rock doves, Columba livia. For nesting birds, parents might be expected to allocate time to nest sanitation in order to control the load of harmful ectoparasites of the nest and the nestlings. Such anti-parasite behaviour is time-consuming (e.g. Cotgreave & Clayton 1995) and will therefore reduce the time that a parent bird can devote to foraging. In nidicolous birds food provisioning is the most time-consuming activity during the rearing period (Winkler & Wilkinson 1988). Alternatively, since females commonly brood their young at night until they can fully thermoregulate (O’Connor 1984), they could, at the expense of sleeping, postpone nest sanitation until the night hours. Great tits, Parus major, for example, brood their offspring for at least 2 weeks after hatching (Berndt & Winkel 1972). Sleep deprivation of females that engage in nocturnal sanitation activities, however, may carry short-term costs such as a reduced foraging efficiency during the day, or longer-term costs such as reduced survival. These potential costs will largely depend on the function of sleep in birds, a subject that is poorly understood. In this study, we controlled experimentally the load of a common haematophagous ectoparasite, the hen flea, Ceratophyllus gallinae, in nests of the great tit, and measured the females’ pattern of time allocation to foraging behaviour, and to anti-parasite behaviour in the nest both during the Correspondence: H. Richner, Zoology Department, University of Bern, CH-3032 Hinterkappelen, Switzerland (email: [email protected]). P. Christe and A. Oppliger are at the Institut de Zoologie et d’Ecologie Animale, Université de Lausanne, CH-1015 Lausanne, Switzerland. 0003–3472/96/121087+06 $25.00/0 ? 1996 The Association for the Study of Animal Behaviour