Evening all
I just posted a fairly long email to the UK400 listserver regarding the history and provenance of the Black Kite in order to clarify some misunderstandings there. Much of what is written below is thus likely to be old news for all of you but some feedback on my speculative comments would be useful.
cheers
Alex
ps. if half-way through this email you lose the will to live then have a read about recent Shetland exploits and 'proper birds'
http://www.freewebs.com/punkbirder/
---------------------------------------------------------------
Hi Josh, Lee, all
A few more facts to clarify about this bird, a Black Kite was seen flying north east from Aldeburgh, Suffolk at 6.15am on the 22nd April. Continuing on this NE vector its is a linear distance of 92.32 km to Dead Man's Wood, Sheringham where unquestionably this distinctive bird was first seen at 10.14am the same day. Migrating broadwing raptors can cover about 30 km/h, so this bird could have comfortably made the journey in that time. Its discovery also coincided with conditions favourable for overshooting, and the concurrent arrival of a number of other Mediterranean overshoots including multiple Bee-eaters, Red-rumped Swallows and an Ibe Chiffchaff.
The bird was photographed by Graham Catley over Barton on the 21st May but misidentified as a Red Kite owing to the birds odd plumage and the brevity of the sighting. A number of Lincs birders later reidentified the bird
http://www.lincsbirdclub.co.uk/forum/vi ... c&start=15 as the Norfolk Black Kite which provided some salient lessons in kite identification for all parties involved. The bird was reported again subsequently in Norfolk but the presence of one or more Red Kites around the Burnhams (at least one of which appeared on the net captioned as Black) suggests that the bird remained in Lincs where it was seen as you state on the coast on the 24/25th May.
So these circumstances for the bird's arrival certainly favour a 'wild' origin but do not rule out an
nth generation hybrid. As various people have pointed out in the current thread on this bird
http://www.lincsbirdclub.co.uk/forum/vi ... c&start=30 its plumage is within the range of variation of Black Kite. The progeny of the Scottish mixed Milvus pair were ringed, which this bird is not, so that rules out a Scottish origin for this individual. There have, as Lee states been multiple instances of
milvus/migrans hybrids and one must bear in mind that these pairings may be under-reported in the field because of the difficulty of detectability. I'm not aware whether the F1 hybrids between mixed
Milvus pairings are sterile, if they are then we need not worry about future hybrid back-crosses. If they aren't (and bear in mind that the
Milvus kites are poorly differentiated genetically) then the waters have been well and truly sullied as this may explain the apparently high phenotypic variability in Iberian Black Kites. However, if one weighs up the odds of which is more likely - a vagrant hybrid kite (which are extremely uncommon) or a vagrant Black Kite which is rustier than normal (apparently not that unusual and thus not uncommon) then the former event is far more likely.
This leaves us with the question of length of stay: over six months and counting, remember however that if it wasn't for the digital revolution and then we would not have been able to establish this very fact and track the same kite around the country (as GC pointed out, this would in the past have hyper-inflated totals of this species in the BBRC reports). Now, most Black Kites occur as spring overshoots and presumably subsequently reorientate themselves and return to their traditional breeding range. However if the bird stays beyond the period of its migratory restlessness (
zugunruhe) then its endogenous clock telling it to migrate stops, and so long as it does not experience any major inconveniences - (e.g. food shortages/disturbance) then it will stay where it is (cf. e.g. the Deeping Red-foot). One would expect these same urges to kick in again in autumn and most Black Kites move in the early autumn so its continued presence is unusual. Perhaps the bird suffers from some neurological problems; which could explain its initial vagrancy in the first instance. If it does stay to winter then this fits into a pattern of unusual behaviour for which there are precedents in a number of raptors (which ought to be wintering in tropical Africa) in northern Europe in recent years.
This zugunruhe paradigm brings us full circle to the Black-eared Kite, an arrival in October fits nicely into the established pattern of eastern vagrancy, this bird came from a long way east and after completing a long migration on an incorrect heading its migratory urge 'shuts down' as it should by now be in its winter quarters. This bird wintered in Norfolk and subsequently disappeared in spring, behaviour that is entirely compatible with a far-eastern vagrant (cf the wintering Pallid Harrier).
Thus although this bird (the current Lincs kite) does pose some intriguing questions about the behaviour expected of vagrant Black Kites (and plumage characters) I can see no solid grounds (based on the balance of probability) to call into question either its provenance or genetic integrity.
cheers
Alex
ps I have no conflicting interests, having seen neither this Black Kite nor the Black-eared Kite (despite living in Norfolk...)
_________________
Dr Alexander C. Lees
Lecturer in tropical ecologyManchester Metropolitan University
Lab Associate
Cornell Lab of Ornithology,
Cornell University
http://www.freewebs.com/alexlees/index.htm@Alexander_Lees
Login
FAQ
Search
