WITHIN-SEASON TRENDS IN THE FORAGING BEHAVIOR OF THE MOUNTAIN CHICKADEE

We compared foraging behaviors of adult Mountain Chickadees (Parus gam beli) within and among breeding seasons. Foraging behaviors differed l ittle between nestling and fledgling ''feeding'' periods of the breedi ng cycle with the exception of substrate use and foraging distance fro m the bole. During the nestling period birds spent the majority of for aging time searching for prey on the needles in the outer crown wherea s during the fledgling period the birds spent significantly less time in the outer crown yet more time on new shoots. Among year variation w as significant for the majority of foraging variables and data pooled for the entire breeding season masked within season trends. Our result s indicate that within season comparisons of foraging behavior are imp ortant for revealing significant trends in behavior. They also suggest that Mountain Chickadees are opportunistic feeders and may time their breeding season with the growth of white fir so that older nestlings or fledglings are present when new shoots are expanded and thus contai n a greater availability of prey to meet the demands of the older offs pring.