Norevik et al. (2020)


- Wow. 

- Expensive, but: wow! 

- Tested in the field and on photographs

Ageing & Sexing of Migratory East Asian Passerines – Gabriel Norevik, Magnus Hellström, Dongping Liu, Bo Petersson. Avium förlag A B, Mörbylånga. 
Price: around € 90,00

Wow! During the autumn of 2020 I was able to test the chapters of several species of Ageing & Sexing of Migratory East Asian Passerines. I was impressed.

The rumours that Lars Svensson has been working on a revised version of his ringers' Bible (Svensson, 1992) are persisting. The question is how urgent that still is - a thought that would have been unthinkable just a few years ago. "The Svensson", even though outdated on some parts, was the best there was on ageing ans sexing passerines in the WP for a long time. But now I hardly ever use it. Ringers and bird watchers interested in the fine art of ageing, sexing, moult and wing formulas have been served by many books in recent years (often, of course, indebted to Svensson). Demongin (2016) wrote the New Testament for ringers, but there is also the spasserine handbook by Shirihai & Svensson (2018) and the revised Jenni & Winkler (2019). And of course there is Javier Blasco Zumeta’s website - who is also in the process of publishing a book! And now the hefty and pricy Ageing and Sexing of Migratory East Asian Passerines is added to the pile.

A number of species in this book are common in Western Europe (though sometimes other subspecies are involved):  Marsh Tit, Bluethroat, Goldcrest, Brambling and Siskin. It also deals with a few species that are not expected to occur here, like the Chinese near-endemic Yellow-bellied Tit. But most interesting are probably the species that occur in Europe as rarities. These vary from very scarce, but annual birds like Pallas’s Leaf Warbler, Richard’s Pipit or Rustic Bunting, to absolute megas like Eastern Crowned Warbler (Figure 2), Siberian Accentor, Blue Nightingale or Taiga Flycatcher.  

With a bilingual book, the authors (three Swedes and a Chinese) have chosen to make a book for both the East Asian and the European market. The text pages are split vertically: in English on the left, in Mandarin on the right. On the photo pages, the Mandarin captions are underneath the English ones. The two-language approach, though understandable, contributes to the large size and heavy weight of the book. The layout is very pleasant. It is regular, predictable and the pages never ‘scream’ which offer a pleasant read. This is a point where, for instance, the 'crammed' Demongin could be improved a bit.  

The species accounts shortly deal with the ID, but the soul of the book treats the ageing and sexing. Moulting schemes are presented in a table that is remarkably spacious and in a very large font. The texts on ageing and sexing are precise and to the point. Much is already known from, for example, the Svensson or Demongin - but not everything. Interesting is the value that is assigned to body feather structure and age identification. In juvenile birds these often have a different, looser structure than in adults. These are usually moulted within the first months after fledging. For example, juvenile Chiffchaffs or Tree Creepers are often easily aged by this feature. But the way in which this book uses feather structure after the post-juvenile moult was new to me: never before had I, for example, searched for unmoulted, juvenile undertail coverts of a Yellow-browed Warbler in late autumn to determine its age. An eye-opener, which does require some practice.

The photo quality is excellent. They are razor sharp and well exposed. Almost all are taken against a grey background to reflect colours as neutral as possible (with a natural background these can be distorted by photographic effects). Perhaps aesthetically less natural, but extremely effective for the purpose. And these grey backgrounds certainly contribute to the ‘calm’ layout of the book. In general there is also quite a bit of empty space on both the photo and text pages. By far most relevant plumages have been photographed, but when one is missing for instance, the space is left empty.


Figure 2. Sample page with Eastern Crowned Warbler

The test


Marsh Tit, Bluethroat, Goldcrest, Brambling, Siskin
These species are superbly photographed here - more extensively and thus more illustrative than in any other book. In many species the shape of the tail feathers can be used for ageing (usually pointed in young birds, rounded in adults). Jenni & Winkler only show wings, Shirihai & Svensson only field photos in which this is more difficult to judge. In Demongin and Svensson, one (though illustrative) figure is usually included, but here we are treated to a fine series of tail photos, which offer a much broader picture of the variation. A nice addition!


Yellow-browed Warbler
This is a notoriously difficult species to age, and ringers sometimes even use wrong "features". The myth that pointed tips to the tail feathers – as if it were a Goldcrest – is difficult to eradicate (in YBW, bot adult and young birds show this feature). The book does hint at a subtle difference in the tail shape, but even with this photo series I couldn’t really figure out what the difference was. I mainly see a lot of variation within and overlap between ages. But here, the feather structure of unmoulted undertail coverts may well provide an answer! An interesting feature to practice with in the future.


Dusky Warbler
In the single bird I handled, this feature seemed to work! The longest undertail covert had a loose structure and was therefore still juvenile (Figure 3), which would make this a 1st cy bird. Birds in the field, will probably never be captured well enough to use this feature.  


Figure 3. Undertail coverts of a Dusky Warbler. The longest appears to be loose in structure, and therefore juvenile. Meijendel, Zuid-Holland, the Netherlands, 5 November 2020

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!

Dwerggors HvH 02102020.JPG

Figure 4-5. Little Bunting, Hoek van Holland, Zuid-Holland, the Netherlands, 2 October 2020. With the book I identified the bird as an adult male. 

Dwerggors HvH 02102020 nr4.JPG

Radde’s Warbler, White’s Thrush and Red-flanked Bluetail
For these three species I used the book for rarity committee assessments. None of these individuals I saw myself, so this was based on photographs only. For Radde’s ageing worked well, but it also would have with other books. With the Bluetails (Figure 6) however, I sometimes got stuck in the past. The descriptions in other books are accurate, but I was sometimes struggling with the interpretation of it on poor photographs. So while this book does not tell anything new, the sheer amount of quality photos really  provided useful insights for a species a never handled myself. In autumn 2020, the first twitchable White’s Thrush in 16 years was only poorly photographed. The best photo however, does show the tail. And it is owed to this book that the committee was able to age it (all visible tail feathers, including the central pair, are tipped whitish – a feature for a 1st cy)!    


Figure 6. Red-flanked Bluetail sample page.  

This book is pricy, but for the those with a passion for ageing, sexing and moult it’s worth flipping the piggy bank. My experience during a part of one autumn only, is that this guide is very useful for all songbird ringers and bird watchers with an interest in Asian passerines. As a bonus, it can also be used for a number of more common species in the Netherlands. Are there any wishes? Well, yes. A paperback in English only (which would make the book about a third thinner), or a PDF at a lower price will be welcomed. But otherwise I’d like to end like I started: wow.