Some of these articles and short notes have been published before, others were made for this site. Some contain (partly) new information, others are to present described features more clearly, e.g. like how to use characters for ringers in field identification.  

Blue Ross's Goose (with Fred Visscher)

Markers for Snow Goose genes in a blue "Ross's" Goose in The Netherlands

Ageing Spotted Crakes

The best markers for ageing, including a (possibly) undescribed feature.

Hybrid redstarts vs. Eastern Black pages (with Nicolas Martinez)

citroenkwik Teylingen nov 2010.jpg

Citrine wagtail calls
Can ssp. be identified based on calls?
by Maarten Wielstra & friends

The Chiffchaff ID files
Iberian and Siberian (looks, calls, genetics)

Blyth's Reed Warbler
How wing structure can be used  for field identification

Crossbill flight calls (by Thijs Fijen)
How to separate Parrot Crossbill calls from several Common Crossbill types

Coues's Arctic and Mealy Redpolls
A note on the undertail coverts

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