Terugkeer van broedende Sperwers Accipiter nisus bij het Koninklijk Instituut voor de Tropen in de binnenstad van Amsterdam in 2012

Sparrowhawks have been breeding in the city of Amsterdam since – at least – the early 1990s. Much information was collected in 1998-2006, when several pairs were closely observed with videocameras and by means of photography. One of these pairs at first occupied a territory in Artis Zoo (2 years) and then switched to the nearby garden of the Royal Tropical Institute (7 years). As nesting trees, the pair used Fagus sylvatica, Taxus spp., Betula spp., Morus nigra and Cedrus libani libani. This territory was deserted in 2007, but in 2012, after an absence of five years, a new pair – consisting of a first-year male and an adult female – took up residence at the same site. The nest was well hidden in a large Cedrus libani libani, but prey transfers took place on one of the ornamental dormers of the Institute’s roof, in full view of observers watching from a balcony of the same Institute. Based on fledging date, c. 19 July, onset of laying is calculated to have been around 16 May, a late start compared to the average start of laying in The Netherlands. Of the presumed brood of five, only three reached the fledgling stage. On average, the male delivered a prey every 142 minutes (based on 26 hours of observation between 8.30 h and 13.00 h summertime on six days throughout the nestling stage). Prey transfer from male to female took place on the roof of the Institute, the female disappearing with the prey to start plucking on a 20 m high flat roof (without any cover but out of sight of observers), the male departing for another hunting foray. Local gulls, mainly Lesser Black-backed Gulls Larus fuscus, and Magpies Pica pica were recorded as potential kleptoparasites. Among 27 identified plucks collected during the nestling stage, House Sparrows Passer domesticus predominated (51.9%), but a total of ten bird species were identified as prey. Twentyone out of 27 prey taken during the nestling stage were in juvenile plumage (77.8%). This diet reflects the local city structure, with parks and gardens providing a habitat for a range of passerines.