How did you do?
by Martin G and Paul Leader
Thanks to all who were bold enough to have a go at the 3 ‘Mystery Bird’ photos. Winners at the bottom- scroll down. I bet the folk who engaged with this the most (and had even 2-3 attempts) will have learnt the most. Hope you had fun, whether watching from afar or having a go online. You can thank Paul Leader for testing me (MG) with the snipe and undertail first! Here are the answers:
There were 3 birds and 6 questions:
BIRD ONE: juvenile Long-tailed Skua
Not an easy one! Not surprised that many thought of a dark 1st or 2nd cy Pomarine Skua. The lack of apparent pale tips and fringes in the photo and double pale marks in under primaries and primary coverts didn’t help! Suggestion: lets get rid of pale and dark morph, as descriptive terms for juvenile Long-tails. It’s so passé. Instead I call this plumage ‘MOCHA’ juvenile Long-tailed. Then, of course, we can have latte, vanilla latte and cappucino Long-taileds?!
above: 2 photos are of the same individual: Mystery Bird one– an extreme dark juvenile Long-tailed Skua. Below is another dark juvenile taken, same place, same day but a slightly lighter and perhaps more typical dark juvenile Long-tailed.
BIRD TWO: Adult Swinhoe’s Snipe
I (MG got this wrong) but learned some good things! Pintail Snipe and Swinhoe’s Snipes are virtually indistinguishable in plumage in the field. So it’s critical to see the outer tail feathers and if you can, hear and record the calls. Roughly speaking Pintail Snipe has more same -width thin’pins’ in the outer tail feathers. On Swinhoe’s the outermost tail feathers are pin-like, but there are less pin-like ones and they become thicker towards central tail feathers.
Ageing is based on partial wing moult (in this case within both the secondaries and primaries) it is obvious on the open wing shot attached (but can be seen in the mystery picture), also the few retained and very worn scaps (obvious if you zoom in on the mantle) plus retained and very worn central tail feathers.
Adult Swinhoe’s Snipe tail, by Paul Leader. Same bird as Mystery Bird Two. 6 ‘pins’ for outer tail feathers, which broaden noticeably inward. Now have another look at the original profile shot of the ‘Mystery Snipe’.
BIRD THREE: Pallas’s Grasshopper Warbler ssp. rubescens
The undertail coverts belong to an adult Pallas’s Grasshopper Warbler of the subspecies rubescens. Only rubescens regularly has such dark centred, pale tipped under tail coverts. In Hong Kong it seems that in northerly populations of PGW (mainly rubescens) juveniles do not have a post juvenile moult prior to migration, whereas southerly populations (mainly minor and certhiola in HK) often undertake a post juvenile moult prior to migration and this may include all of the tail. So a rubescens in September with a fresh tail is invariably an adult. see below a photo showing the adult that goes with the tail (which if you look carefully shows new primaries but retained secondaries – which only adults show), and a tail of a juvenile rubescens. We have trapped 40 PGTips this week (2nd week of Sept 2012) in two mornings of ringing!!
Very tricky as many came very close. I got he Snipe age right but species wrong (If any consolation!). Closest I think were:
Aron got it right on the 3rd attempt Julian H got it right over his 3 attempts!
Peter A just missed it with the PGTips subspecies
Andy MacKay just fell on age of the Snipe
Dani, Ryan, Timo and ‘Hemsby Birds and Moths’ were very close- understandable thinking the Long-tailed Skua was a few months older
So I put this lot in a hat and Mrs G pulled out the winning bit of paper: … Peter Adriaens.
Many did better than me. Especially hope you enjoyed it and learnt some stuff. I did.