A Juvenile but from where?
by Martin and Nils
Swifts are amazing. Just their biology/ life history can be a jaw dropper. The Little Swift at New Brighton was yet another British record of the species which appears to be in fresh, full juvenile plumage. Little Swifts from deeper into Africa breed in our winter and the adults are fresh in our summer, so their juveniles tend to be more worn in our summer. This bird is completely fresh without any moult-signs and looks too extensive pale fringed for a fresh adult. If our assessment that the New Brighton bird is a juvenile is correct, it begs the question as to the bird’s origins. Perhaps like some other mid summer rare birds it is coming, not from the south but from much further east (and a bit south)?
Fresh from the nest. Where’s it from?
juvenile Little Swift, New Brighton 22 June 2012, all photos by Jim Almond (website). A Common Swift with that much white fringing over the upperwing coverts, leading edge of the wing and head pattern would be instantly aged as a juvenile.
The idea that some of the British records of Little Swifts involved fresh juveniles is not new. Here’s the notes on Little Swift in the 2008 BBRC rarity report:
This particular Little Swift (Yorkshire, Spurn – 26th June and Old Moor RSPB – 2nd July 2008) fits in well with the established pattern of the majority of the less-than-annual records of this species, with 17 of the 23 having occurring in May and June. Singles have appeared in late April, mid July and mid August, and there is a cluster of three records in November.
One intriguing aspect of British records, hitherto unaddressed, is that at least two of those in May (Isles of Wight on 5th-6th May 1997 and Nottinghamshire on 26th-29th May 2001) can be aged from photos as juveniles in fresh plumage. This would necessitate the parent birds’ breeding season beginning no later than February of the same year. That would seem to exclude northwest Africa as the origin, as the birds there begin laying only in mid April (BWP). The bird at Cromer, Norfolk, on 12th-13th November 2005 also appears to have been a juvenile, although this is perhaps less surprising.
House Swift versus Little Swift
This raises interesting questions over the geographical origins of Britain’s Little Swifts, which may be travelling farther than generally appreciated. Furthermore, it seems an opportune moment to note that, while less likely to occur, the sister taxon, House Swift A. nipalensis, with its greater tendency to show a shallow tail fork, narrower white rump band and more uniformly dark vent and undertail coverts (fading to paler grey and contrasting more with the black belly in Little Swift) should not be written off as potential vagrant.
white -tipped underwing coverts are also more typical of juvenile swifts and there is no sign of a tail fork (which you might expect in House Swift). We both enjoyed the company of Gerald Driessens (co-author of the ‘Swifts’ monograph) in Hungary recently. So we checked with Gerald on the New Brighton bird. He responded:
” Indeed looks like a fresh juvenile. I don’t think you’d find such sharply fringed greater coverts in adults… Just checked my Kenya sketches and in July, most of them (but still far from all) were halfway through primary moult by then. But in the tropics, there’s a lot of variation in moult timing of course.”
juvenile Little Swift, New Brighton 22 June 2012, all photos by Jim Almond (website). The shape of the outer tail-feather (t5) is a good ageing feature according to Cramp et.al (BWP) and this bird have a quite obvious blunt and rounded tip fitting juvenile.
P.S. It also seems from our correspondence from Gerald that a much debated white-rumped swift sp. in Ireland in December a few years ago may well have been a Horus Swift. And on that bombshell….!