The effect of temperature and other factors on roosting times of Szechenyi Monal Partridges Tetraophasis szechenyii during the breeding season

Abstract

In response to low temperatures, birds can choose between reducing their activity to minimize heat loss and increasing it in the hope of higher heat production. In this study, these aspects were evaluated in the rare Szechenyi Monal PartridgesTetraophasisszechenyii by examining the timing of breeding-season roosting. The partridges arrived at roost sites 54.7 3.0 min before sunset (n = 78), perched on branches 22.9 1.8 min before sunset (n = 78), and departed 7.3 0.1 min after sunrise (n = 91). Generalized linear mixed modelling with temperature and several other environmental variables (e.g. day length, cloud cover and precipitation) included as factors, showed that - all other things being equal - the par- tridges perched earlier and departed later on cold days. This result suggests that Szechenyi Monal Partridges reduce their activity to minimize heat loss in low temperatures. How- ever, the partridges did not arrive early at roost sites on cold days, and the effects of low temperature on departure times were less than those on perching times: temperature had a partial coefficient of -0.89 for departure times versus -1.29 for perching times. Thus, we argue that the amplitude of these temperature effects may depend on food availability, or the birds level of hunger.