Een broedgeval van de Slechtvalk in de stad Groningen in 2016

Breeding of Peregrine Falcon Falco peregrinus in the city of Groningen in 2016 -- Peregrine Falcon Falco peregrinus is an annual breeding bird in the province of Groningen, The Netherlands, since 1998. Breeding in the city of Groningen was recorded for the first time in 2016. This article documents this case. Breeding took place in a nest box on top of the Gasunie headquarters, a building with a height of 89 meter. The nest box was put up in 2008. The breeding site is regularly monitored since that year. It remained unoccupied for several years. Peregrine Falcons were regularly observed since early 2016, territorial behaviour was observed onwards from the beginning of March. The entire breeding cycle was closely monitored. Four young, a male and three females, were colour-ringed on 24 May, photo on page 25, all four fledged. Fledging took place on 14 June. One young was found dead a few days after fledging. The photo's at the upper part of page 24, dated 10 June, depict the young in front of the nest box. The photo at the lower part of page 24 is taken from inside the Gasunie headquarters. The photo, dated 17 June, depicts a fledgling. Calculations based on measurements taken during ringing (Table 1, 'geslacht' = sex; 'vleugel' = wing length, maximum chord, mm; 'gewicht' = body mass (g); 'klauw1' = claw span incl. nails (mm); 'klauw2' = claw span (only pads, mm); 'krop' = crop) indicate that egg-laying commenced around 29 March and that hatching of the first young was around 30 April. Sightings from the ground confirm these dates. Both adults were unringed. Their origin and age are thus unknown. In total 54 prey remnants were collected (Table 2), mainly Feral Pigeons Columba livia (n=20, at least 11 of them racing pigeons) and Starling Sturnus vulgaris (n=10). Table 3 lists the residence of the owners of these racing pigeons. A Redshank Tringa totanus is depicted on page 27 (photographed on 17 May). This prey remnant was situated at a plucking site on an inaccessible site of the building. Peregrine Falcons are regular winter visitors in the city of Groningen since the end of the 1990s. It is estimated that in 2016 just less than 10 breeding pairs were present in the province of Groningen. Their territories are spread over the province and include ground dwelling breeders on uninhabited Wadden Sea islands.