Collared Flycatcher Conundrum
Deep in-take of breath. These are never simple!
Beware: you are entering a zone of feather minutiae and funny measurement formulae.
This bird originally drew attention in the ringing lab at Spurn due to a wing length on first measuring of 84+ mm . A quick check of the pattern of white at the primary bases and especially the tail pattern and adrenalin began to kick in – key players in the Spurn ringing lab – Mike Pilsworth (again!) Adam Hutt and Spurn warden, Paul Collins. I got a slightly cryptic radio call to “come to the Warren”. On first viewing the bird clearly had ‘characters of Collared Flycatcher’. Aware of the enormity and complexity of such a claim, birders on sight were then alerted and news of probable Collared Flycatcher was broadcast.
Having been viewed by assembled crowd the bird was released – but just wouldn’t call, and was lost to view. About 25 minutes later Nathan Pickering called me over to a ‘ringed Pied Flycatcher ‘ he had glimpsed near the Warren Gate, and wondered if this was ‘the bird’. One brief view confirmed the same wing pattern as seen in the ringing lab and news was broadcast the bird was on show in the field. First impression was while similar to many 1st winter Pied Flycatchers, it also had a subtle but clearly evident greyish wash to the nape and ‘shoulders’ giving slightly colder feel compared to many Pied Flycatchers.
Back to first steps. Age and if possible sex the bird:
The bird was aged as a first winter, probably a female (an essentially start as critical characters differ with age and sex) by ‘stepped’ tertials (also pattern on white on greater coverts) see here: http://birdingfrontiers.com/2010/08/18/pied-flycatcher/
The brownish tone to the tail feathers and uppertail coverts indicates likely to be a female. The obvious pale tips to the longest uppertail converts seemed rather unusual. Having established age and probable sex…
Three Characters put this bird into Collared Flycatcher territory:
1) Wing length. Double checked by 2 Spurn ringers: 85 and 86mm (max wing chord). A long wing! 1st cy Pied Flycatcher reaches max. wing length of 82 mm (Mild, 1994) and BWP). The wing length best fits Collared Flycatcher and appears to be outside of known range of Pied and also Atlas Flycatcher and Iberian Pied Flycatcher (in case you were wondering!).
2) Tail pattern. White present in 4 outer tail feathers with long clear white lozenge on inner webs of outer 3 tail feathers. Normally white only on outer webs on Pied Flycatcher, or only weakly present on 1+ inner webs. The tail pattern best fits Collared Flycatcher.
3) Wing pattern. White extends to p5 (tiny spot on p4) and quiet substantial, forming rectangular block at base of primaries. 50% of 1st cy female Collared Flycatcher show white only to p5 (Mild 1994) – so that’s OK!. Importantly, white clearly extends the beyond tip of longest primary coverts on closed wing. The depth of white best fits Collared Flycatcher.
Normally a set of definitive plumage characters and biometrics would be enough to sort most passerine identification with room to spare – not Collared Flycatcher!
Stumbling blocks are the nape feathers which had darker tip and base and broad silvery white) central area – but not the anchor shape or cross-bar considered diagnostic.
To illustrate here are the nape feather photos which helped secure the ID of Britain’s only accepted 1st winter (probably female Collared Flycatcher) – thanks to those who pointed out there was one other such record!
p2= p5/6 – meaning the second primary is equal in length to between the 5th and 6th primaries – a wing formula very infrequent in Collared (3%) but very common in Pied (75%). Unfortunately length of p1 relative to the wing point was not measured. Rump feathers were not examined.
There we are. Conclusive ID or stale mate? (and if stalemate – what the heck?!)
Mild, K. (1994) Field identification of Pied, Collared and Semi-collared Flycatchers. Birding World 7: 139-151, 231-240 & 325-334.