The effect of thermal microclimate on foraging site selection by wintering Mountain Chickadees

The relationship between the thermal microclimate and foraging site selection by Mountain Chickadees (Parus gambeli) was investigated during February and March 1992 in south central Wyoming. Air temperature, wind speed, and solar radiation were measured at 465 actual foraging sites and 525 available sites using battery powered dataloggers and sensors mounted on extendable poles. Mountain Chickadees selected sites that had higher air temperatures and lower wind speeds than available foraging sites. Solar radiation at actual foraging sites did not differ from available foraging sites. Standard operative temperatures at actual foraging sites were closer to idealized warm sites than were available foraging sites. The thermal environment, in addition to food availability, may contribute to foraging site choice by Mountain Chickadees in winter.