• Vincent

ageing a calling Iberian Chiffchaff

On 14 July I stumbled upon a calling Iberian Chiffchaff (ca 45th record) in my hometown The Hague. Since calling birds are probably overlooked in The Netherlands, I wrote a short note on their calls.

Upper and lower pic by Gerjon Gelling

Quite amazing that I was lucky enough to find two of these birds within 3 months! Ageing this bird turned out to be straightforward. In July juveniles are very fresh, while adults are completely worn and usually in their post-breeding moult - like this bird. So as expected (since a juvenile in July would be sensational), this was an adult bird.

On the 15th, I managed to get some shots, and my friend Gerjon got much better ones. This allowed us to have a better look at its plumage. Well, this bird wasn't very pretty! It was worn and moulting body (there was even bare skin visible on the throat) and wing feathers which, in passerines, are moulted symmetrically in both wings. See pic:

I count 5 visible primaries. The very short P1 cannot be seen in this shot. The shot is just not good enough te be entirely sure, but it seems to be missing 4 primaries. P? is a growing feather and I don't know which one it is (since the inner one is moulted first, this could be P10). There's also a growing inner secondary. So it's hard to judge what's precisely going on, and it's impossible to see if this bird is perhaps in its 2nd cy (see this article), but it's moulting remiges, allright. Hence, this can never be a juvenile!

Btw, here's a typical call of the bird (14 July 2017):

#IberianChiffchaff #calls #ageing #Phyloscopusibericus #moult

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Little Bunting
The most interesting thing about this chapter is the sexing of birds. This could be done on the basis of lateral crown stripe: a new feature for me. Because of overlap between adult females and young males, birds should first be aged. The authors emphasize that this is their vision, and not necessarily the final answer to this matter. I found one in the field in October (Figure 4-5) of which I took reasonable pictures. The very rounded tail feathers look adult, as do the tertials and large coverts. The lateral crown stripe appears to be jet black and is separated from other feathers, such as the greyer back of the head. The orange-red crown stripe really stands out. Conclusion: according to this book this must be an adult male! The deep brown-red cheek - a variable feature according to this book - also fits that. So it works then? Well… how useful this really is, remains the question: based on this book I would label two "females" in Shirihai & Svensson (p546 both top right and bottom right) as males! The caption of one of these even mentions "safely identified as a female" because it has a relatively dull plumage for an adult bird. But is also has a jet black, strongly separated lateral crown stripe! The bird at the bottom right even has a pretty deeply coloured cheek, which I would be happy to call a male. Is this due to different insights, and if so, who should I believe? Or am I not interpreting this correctly? In any case, it is fascinating!

© 2018 by Vincent van der Spek