Seasonal time-energy budgets of free-living chukars in the Negev Desert

Alectoris chukar seasonal activity patterns were studied in the Negev Desert highlands of Israel, to examine whether their ability to inhabit hot, dry areas is influenced by limitations imposed on their activities by the physical environment. Daily energy expenditure (DEE) of chukars was calculated by converting time-activity budgets to time-energy budgets, and by using the operative environmental temperature (T_e) to estimate the chukar's thermoregulatory requirements. Mean DEE was 630 kJ/(kg.day) in summer when birds foraged mianly on high energy foods in cultivated fields, and 960 kJ/(kg/day) in winter when they ate mainly natural vegetation of lower energy content. Consequently, chukars spent twice as much time foraging in winter than in summer (7-8 hr/day vs. 3-3.5 hr/day). The activity pattern during summer was bimodal, characterized by long periods (7-8 hr/day) of rest in the shade during the hot part of the day. A significant positive correlation was found between time spent resting and mean daily maximum and a significant negative correlation was found between the latter and time spend foraging. The geographical distribution of chukars is limited by a combination of the duration of time that they can remain active without risking their heat balance and the amount of time they need to find and eat enough food to meet their daily energy requirements. -from Authors