Eurasian Sparrowhawk - Breeding

Breeding

The Eurasian Sparrowhawk breeds in well-grown, extensive areas of woodland, often coniferous or mixed, preferring forest with a structure neither too dense nor too open, to allow a choice of flight paths. The nest can be located in the fork of a tree, often near the trunk and where two or three branches begin, on a horizontal branch in the lower canopy, or near the top of a tall shrub. If available, conifers are preferred. A new nest is built every year, generally close to the nest of the previous year, and sometimes using an old Wood Pigeon (A. n. melaschistos frequently uses the old nests of Jungle Crows) nest as a base; the male does most of the work. The structure, made of loose twigs up to 60 cm (2.0 ft) long, has an average diameter of 60 cm (24 in). When the eggs are laid, a lining of fine twigs or bark chippings is added.

During the breeding season, the adult male Eurasian Sparrowhawk loses a small amount of weight while feeding his mate before she lays eggs, and also when the young are large and require more food. The weight of the adult female is highest in May, when laying eggs, and lowest in August after the breeding cycle is complete. A study suggested that the number of eggs and subsequent breeding success are dependent on the female maintaining a high weight while the male is feeding her.

Sexual maturity is reached at between 1–3 years. Most Eurasian Sparrowhawks stay on the same territory for one breeding season, though others keep the same one for up to eight years. A change of mate usually triggers the change in territory. Older birds tend to stay in the same territory; failed breeding attempts make a move more likely. The birds which kept the same territories had higher nest success, though it did not increase between years; females which moved experienced more success the year after changing territory.