Small patches of broadleaf trees influence nest-site selection and reproductive performance of two tit species (Paridae) in a Japanese cedar plantation

Abstract

ABSTRACTConifer plantations generally provide less food for woodland birds such as tit species than do broadleaf or mixed forests. We examined whether small patches of broadleaf (thus, caterpillar-rich) trees in a Japanese cedar (Cryptomeria japonica) plantation could improve the breeding success of coal tits (Periparus ater) and varied tits (Poecile varius) using nest boxes in the plantation. We evaluated the relationships between the distribution of the broadleaf trees (the minimum distance from each nest box to the nearest patch and the total area of broadleaf patches within 25, 50, 100, and 200 m from each nest box) and breeding performance (clutch size, number, and body mass of fledglings, fledging success, fledge rate, and nestling period). Coal tits selected nest boxes regardless of the distribution of broadleaf patches. By contrast, varied tits nested preferentially within 50 m of broadleaf patches and, within 50 m, favored boxes near a larger total area of broadleaf patches than coal tits. The breeding performance of both species was not affected by the distribution of patches; however, the clutch size of varied tits (but not coal tits) tended to decline in nests ≥50 m from broadleaf patches, and there were no large clutches in such positions. The broadleaf trees might have improved the habitat quality, particularly for varied tits, by providing food resources. Thus, broadleaf patches as foraging sites and nest boxes as breeding sites could both be critical to the breeding success of woodland birds in conifer plantations.