Cooperative attacks by urban Peregrines on Common Buzzards Nick Dixon and Andrew Gibbs Abstract Observations of the Peregrine Falcons Falco peregrinus that nest on a church in Exeter city centre have revealed levels of interspecific aggression previously unrecorded in Britain. This paper summarises the frequency and timing of coordinated attacks on Common Buzzards Buteo buteo, several of which proved fatal. The strategy employed by the Peregrines during a typical attack is described and illustrated.
eregrine Falcons Falco peregrinus have nested in Exeter city centre, on St Michael and All Angels Church, Mount Dinham, since 1997, initially on a ledge at the base of the spire and then, from 2008, in a nestbox inside the spire. The resident pair at this site has bred successfully every year, fledging 51 young between 1997 and 2014 (mean 2.8 chicks per year). The Peregrines’ tolerance of human activity at street level allows a year-round, weekly collection of fallen prey remains; data from these, together with detailed observations of behaviour, have provided a valuable opportunity for long-term study of prey selection and diet, as well as other aspects of breeding biology (Drewitt & Dixon 2008; Dixon & Drewitt 2012). In recent years, particular attention has been given to observed interactions with other bird species in the area, most notably the Common Buzzard Buteo buteo, which is regularly seen passing high over the city. Peregrines and Buzzards are often found in the same traditional habitats, such as sea cliffs and upland crags, where aerial encounters and skirmishes can be frequent (Tubbs 1974; Ratcliffe 1993). There are records of Peregrines killing Buzzards in Britain, and Buzzard remains have been recovered at Peregrine eyries, although this is rare (Ratcliffe 1993). Yet in Exeter, the city-centre Peregrines have shown extreme levels of © British Birds 108 • May 2015 • 253 –263
territorial aggression towards Buzzards over the city, something which first came to light during the 2012 breeding season, when ten attacks were recorded and at least three Buzzards were killed. Subsequent observations have revealed a dramatic increase in attacks by the resident Peregrines on passing Buzzards. Such extreme levels of aggression by breeding Peregrines appear not to have been recorded before in Britain. The Exeter Peregrines have also shown intense aggression towards intruders of their own species in defence of the nest site, dependent young or breeding partner. Since 1997, ND has recorded many territorial disputes with intruding falcons of both sexes. It is interesting to note that the most longlasting and ferocious fights, between the resident and an intruding female, occurred during 21st–29th March 2009; and the outcome of these disputes was the arrival of the current female. The male Peregrine is believed to have been at the church nest site since March 2005. Neither of the adult Peregrines is ringed, and we therefore cannot prove that the same individuals have been paired since 2009, although we strongly believe that this is the case. This is based on almost daily observations of familiar behaviour of both birds at the church, by a variety of experienced watchers. There have been no gaps in occupation by either bird, and since they hold territory all year they can both be 253
British Birds May 2015 Sample Publication