TURNSTONES
turning stones to see what's underneath
AGEING SPOTTED CRAKES
Ageing Spotted Crakes in summer/ autumn
There are quite a few good sources (see end of this web article) to age Spotted Crakes (Porzana porzana), yet ageing them in summer and early autumn seems to be difficult at times. In this article I summarize my favourite markers to separate first-winters from adults. This includes an under discussed – perhaps undescribed – feature that’s helpful. It's based on 21 birds I trapped in Meijendel, The Netherlands between 2008 and 2017, and photos on the internet. There are more features, but these should be useful both in the hand and in the field.
Ageing juveniles, first-winters and adults
I always check several features to be certain. Juveniles are a piece of cake. These birds are mainly brown: no grey on the breast, no grey on the head. The supercilium is heavily speckled white and they sometimes have greenish brown bills. But after the partial post-juvenile moult (head and body feathers) young birds start to look more like adults. They moult between July (but mostly August) and October. My favourite features mentioned below help to separate the first winters and the transitional plumages from the adults. Note that the descriptions for the throat and iris are also useful for juveniles.
Step 1: forget about the bill!
First of all, let’s stop focusing on the bill colour as an important feature! I’ve noticed that quite some people refer to the bill first when ageing Spotted Crakes. IMHO it can be helpful in the most obvious young birds (as they have greenish brown bills), but in many others it can be confusing. A bird with a (nearly) complete yellow bill and orange red on a large part of the lower mandible should be an adult, but I’ve seen young birds with mostly yellow bills with a red base, and adults with quite a lot of greenish on the upper mandible. So ignore the bill when it’s not greenish brown. There are much better ageing features.
The chin and throat
One of the best features is the colour of the throat and chin: slate grey in all adult males and in summer plumaged females, white in young birds that have not yet moulted these feathers. First winters that have moulted their chins and throats are harder to separate from winter plumaged females (note: males keep their grey throats year-round). In first-winters it’s “white with grey speckling” whereas in adult winter females it's “grey with white speckling [sic]... but with centre of chin still grey" (Demongin 2016).
But a general rule is: white = young bird, slate-grey = adult. This allows most birds to be aged (Figure 1)!
Figure 1: chins and throats, Meijendel, Wassenaar, The Netherlands, 7 August 2013
Left: first calendar-year with mainly white chin and throat, with some grey speckling
Right: adult with plain slate grey chin and throat
Supercilium
Juveniles have a brownish supercilum with many speckles. In adults this is slate grey, and speckling – if any – is reduced to back of the head. Moulted first calendar year birds also have a grey supercilium, with less speckling, but usually still more than in adults (figure 2).
Iris colour: a general rule
In both young birds and adults iris colour is variable, but a green or olive iris = young bird, a reddish one = adult. This ‘general rule’ should be a helpful feature (figure 2). There are also several intermediate colours that IMHO are susceptible to interpretation, even more so when handling a bird in the dark (take “brownish” for young birds vs. “yellow-brown in adults”, Demongin 2016), so let’s forget about these other colours .
Figure 2. Supercilium, iris and throat. Left: juvenile, Meijendel, The Netherlands, 7 August 2013. Right: adult, Bloemendaal, The Netherlands, 23 August 2013 (Lars Buckx)
Left: speckled supercilium, green iris and white throat of a young bird
Right: grey, unspeckled supercilium, reddish iris and grey chin and throat of an adult
Wear of wing and tail feathers
I cannot find this feature in the books of my shelf. Though perhaps it can be deducted from the described moult strategies, it’s something I first noticed in the field. Young birds in summer and early autumn are of course very fresh: their feathers are brand new. Adults however, have very worn wings and tails (Figure 3-4). This image is confirmed by pictures of trapped birds on the internet from The Netherlands and Belgium (www.trektellen.nl). Perhaps not surprising given the moult strategy of adults: complete between July and October, and partial (body feathers) in winter (Baker 2016, Demongin 2016). But none of the references I have actually mention that feather wear is a useful ageing criterion. It takes adults only three weeks to renew all of their flight feathers. All but one adult birds I ever trapped (n=7) showed (very) abraded wing feathers, and had not already moulted. The only exception is the latest adult I ever trapped: at the end of September (all others between the end of July and through August). I checked the tails less often, but it’s a feature I see in several of my pics. I never trapped one in active wing moult, but with all flight feathers moulted in such a short time they probably do not migrate then.
So fresh wings in summer and early autumn do not exclude an adult since it’s possible that they’ve already moulted . The reverse however seems to be true: obviously worn wings and tails are diagnostic for adults in this time of year.
Figure 3-4: state of the wing feathers. Upper: first-calendar year, Meijendel, The Netherlands, 7 August 2013. Lower: adult, Meijendel, The Netherlands, 23 August 2013
Upper: first calendar-year with fresh remiges and coverts
Lower: adult with worn (and bleached) remiges, tertials and coverts; also note worn tail
In the field
So does it work in the field? With reasonable to good photographs (Figure 5-6): yes! Also see the summary (Table 1).
Figure 5. Spotted Crake, 20 July 2009, Groene Joncker, The Netherlands (Fred Visscher)
A= worn primaries
B= slate grey supercilium with speckling restricted to back of head
C= slate grey chin and throat
So this is an adult!
Figure 6. Spotted Crake, 30 August 2016, Valkenburgse Meer, Zuid-Holland, The Netherlands (René van Rossum)
A= speckled supercilium
B= whitish throat
C= fresh primaries
So this is a first calendar-year!
Table 1 Summary of ageing features
Additional photographs can be found in the 'appendix' below
Acknowledgements
I would like to thank Lars Buckx, René van Rossum and Fred Visscher for their great and instructive photographs.
References
Birds of Aragon website by Javier Blasco Zumeta: Spotted Crake
Baker, J. 2016. Identification of European non-passerines. British Trust for Ornithology, Thetford
Demongin, L. 2006. Identification guide to birds in the hand. Beauregard-Vendon.
Appendix: additional photographs
Figure 7. Spotted Craje, juvenile, Meijendel, The Netherlands, 11 August 2012
Note that this bird is brown: juveniles are easy to age.
Figure 8. Spotted Crake, juvenile, Meijendel, The Netherlands, 22 August 2017
A= green iris
B= speckled supercilium, no obvious grey on the head
C= white throat
Hence, this bird is easily identified as a juvenile
Figure 8. Spotted Crake, first winter, Meijendel, The Netherlands, 18 August 2012
A= fresh primaries and tail (not diagnostic, but indicative)
B= note moulted, grey supercilium, with few white speckles
C= The pure white throat is the best ageing feature in this bird!
Hence, this bird is a first winter
Figure 9. See below
Figure 10. See below
Figure 9-11. Spotted Crake, adult, Meijendel 15 August 2015. See reddish iris, grey chin and throat, and, in this case only moderately, worn primaries. With some white speckling on the throat and white mottled ear coverts, my guess is that this is a female. Same bird as the picture of the flank on top of this web article.
Figure 12. Spotted Crake, adult, Bloemendaal, The Netherlands, 23 August 2013 (Lars Buckx). Same bird as in figure 2.
A= worn wing
B= reddish irish
C= slate grey and largely unspeckled supercilium
D= plain, slate gray chin and throat
So this clearly is an adult
Figure 13. Spotted Crake, adult (left) and juvenile (right), Meijendel, the Netherlands, 21 August 2018. Note slate grey throat of adult vs. white throat of young bird. Also note much greyer breast of adult.