Seasonal Time-Energy Budgets of Free-Living Chukars in the Negev Desert

Chukars (Alectoris chukar) have a broad Palearctic distribution which includes mesic and semi-arid, but not very hot, arid areas. We studied the seasonal activity patterns of Chukars in the Negev desert highlands of Israel, and examined 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 (350 to 550 g body mass) was calculated by converting time-activity budgets to time-energy budgets, and by using the operative environmental temperature (Te) to estimate the Chukar's thermoregulatory requirements. Mean DEE of Chukars was 630 kJ/(kg·day) in summer when they foraged mainly 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 to 8 hr/day vs. 3 to 3.5 hr/day). The Chukars' activity pattern during summer was bimodal, characterized by long periods (7 to 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 Te|Te,max| and a significant negative correlation was found between time spent foraging and |Te,max|. We concluded that the geographical distribution of Chukars is limited by a combination of two key factors: the duration of time that Chukars 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.