The breeding biology of the Willow Tit in Northeastern Siberia

The Magadan region of northeastern Siberia. Clutch size and number of fledglings averaged 7.5 and 6.5, respectively, and both were correlated negatively with the date of the first egg. Nestling growth rate was correlated positively with the date of the first egg, but was not related to brood size. Body mass at fledging was related negatively to brood size. Males fed nestlings significantly more often than did females, while females spent more time attending nestlings. The number of parental visits per young did not change significantly with brood size. During the first 13 days of the nestling period, female feeding rate per young was positively related to brood size while for males this relationship was negative. The nestling diet consisted mostly of Lepidoptera larvae, Arachnoidea, and Diptera.

Vladimir V. Pravosudov and Elena V. Pravosudova, Wilson Bull., 108(l), 1996, pp. 80-93