Aerial inter-relationships between four species of raptor at Winchcombe, Gloucestershire (VC33 SP 03 107M O.D.)
P.F. Whitehead
I have previously drawn attention (Whitehead, 2006) to associations of raptorial birds in Worcestershire and provided some discourse, parallels and references for what must have been a more common feature of past times when raptors were more abundant. On a relative's farm in a remote part of west Wales where I have previously been able to study Red Kites (Milvus milvus L.), it's clear that there is a great deal of interplay between individuals of this species, especially during March, which is something one may hopefully look forward to in this area.
March 23rd 2011 was a fine settled day with high levels of insolation and a light easterly air flow. On the low Cotswold foothills at the edge of Winchcombe town in Gloucestershire (VC33 SP 03 107m O.D.), Buzzards (Buteo buteo L.) were conspicuously active once thermals developed. At 1405 hrs GMT four highly vocal Buzzards were persistently falling off the tops of thermals in their highly distinctive 'porpoising' display (Whitehead, 2002). This activity attracted other raptors to the spot and a calling Peregrine (Falco peregrinus Tunstall) along with another more distant unknown falcon, appeared on an adjacent thermal. Less than 100 metres away two Kestrels (Falco tinnunculus L.) commenced vigorous display, the male circling with characteristic 'wing-flicking' before both birds plunge-dived from height into a tall cultivated poplar tree in open country.
In the midst of all of this activity a further more distant call, with a shrill high-pitched cat-like quality that I've heard only rarely, heralded the arrival of a Red Kite, a bird which once "sailed" commonly over parts of the region (Harbird, 1998; Harthan, 1947). This bird behaved differently, flapping steadily through the thermals at a relatively low level on an easterly course presumably acknowledging the presence of the other raptors, or confirming its own presence to them. I was able to demonstrate this 'social networking' to another observer who had never seen some of these birds before and was amazed that they might all occur at one spot. In the warmer parts of Europe, large numbers of some raptors also aggregate on thermals to consume macroinvertebrates caught up in them (Whitehead, 2004).
References
Harbird, R., 1998. The return of the magnificent seven. Worcestershire Record 4:12.
Harthan, A.J., 1947. The birds of Worcestershire. Littlebury & Co. Ltd, Worcester, pp. 1-79.
Whitehead, P.F., 2002. An assemblage of 13 Common Buzzards Buteo buteo (L., 1758). Worcestershire Record 13:13.
Whitehead, P.F., 2004. Omophlus proteus Kirsch, 1869 (Col., Tenebrionidae) heavily predated by Eleonora's Falcon (Falco eleonorae Géné) over Kos, Greece. Entomologist's Monthly Magazine 140:57-58.
Whitehead, P.F., 2006. Aerial inter-relationships between large mostly predatory birds, with particular reference to the Raven. Worcestershire Record 21:19-20.