First-year Greenfinches with moulted primaries (12 March 2004)

There has been quite a bit of discussion lately about Greenfinches Carduelis chloris that have renewed one or more primary feathers during their autumn post-juvenile moult.

This winter, from the beginning of November 2003 (when I returned from the USA) to date (12 March 2004) I have caught 109 Greenfinches in my garden or a nearby roost site in north Cheshire. Forty-two of them have been 'adult' birds (Euring age 4 or 6) and I have noted the extent of post-juvenile moult on the other 67 'first-year' (Euring code 3 or 5) birds, as follows:

The proportion (47/ 67 = 70%) having moulted all of their greater coverts is significantly higher than the figures of 43-55% that were found in the early 1980s in north Nottinghamshire by Mike Boddy, quoted in the BTO Moult Guide (H. B. Ginn and D. S. Melville. Moult in Birds. BTO Guide No. 19, 1983), and, based on the greater coverts alone, suggests that British Greenfinches are having a more extended post-juvenile moult than they did 20 years ago. As it happens, my figure of 70% is almost identical to that found by Jenni and Winkler in Switzerland in the early 1990s (Lukas Jenni and Raffael Winkler. Moult and Ageing of European Passerines. Academic Press, 1994).

Out of these 67 'first-year' birds, six (9%) had moulted one or more primary feathers. All of these had moulted all of their greater coverts, five of the six having renewed all three feathers of the alula and the tertials as well. The details of the primaries that had been moulted, using descendant numbering (from the body outwards, as is normal in moult terminology) are: two males p 6 only; a male and a female pp 5 & 6; a male pp 5, 6, 7 & 8; and a female pp 4, 5, 6, 7 on her left wing (pp 5, 6, 7 on her right wing). These six are in addition to the female bird with renewed pp 5 & 6 that I depicted previously from the West Burton ringing course (November 2003).

Again, Jenni and Winkler reported 10% of their Greenfinches in Switzerland moulting one or more primaries. In Fig.32, p.36 of their book, they amalgamate data from 57 Greenfinches at a variety of sites in central and southern Europe that had moulted at least one primary. The most commonly moulted primaries are p 6, p 5 and p7, in descending order of frequency, with a few birds moulting other primaries. For birds that had renewed more than one primary, the moulted feathers were almost always next to each other, although 5 of their sample of 57 Greenfinches had moulted non-adjacent primaries. Jenni and Winkler say that, for all of the finches, primary 6 is renewed most often, and also show data for Siskin Carduelis spinus, Goldfinch Carduelis carduelis and Linnet Carduelis cannabina, but I have not yet noticed any of these species with a renewed primary feather. An illustrated discussion of Siskin moult is the subject of the next 'bird in the hand' essay.

The first photo below shows one of the Greenfinch males that had renewed p6 only:

The next photos show a male and a female with renewed p5 and p6:

Some people find the difference quite subtle, but the renewed primaries - as well as showing more intense yellow edging - have a darker colour, with a blacker vane, and are much less abraded than the other primary feathers, as seen by comparing the feather tips. Note that the yellow tends to reach a little closer to the shaft of the feather than on adjacent remiges. This makes it even more important than usual to look also at the amount of yellow on the proximal part of the tail feathers to be sure of the bird's sex. Chris Mead used to say that there were more changes of sex and inconsistent ages in Greenfinches reported to the BTO than in all other species put together. No doubt there was an element of hyperbole in that statement, but it illustrates the point that we all have to be careful to examine every aspect of Greenfinches.

The bird at the top of the page (shown again below this paragraph) is the male with renewed pp 5, 6, 7 and 8. It seemed to me to be doing a pretty good impression of an adult, which may well be what he intended! The juvenile feathers are structurally weaker, and one can readily imagine how it could be advantageous for birds to replace as many juvenile feathers as possible during their autumn post-juvenile moult. But Dave Okill has questioned why these birds moult p6 (and possibly some adjacent primaries) rather than starting from the innermost primaries, as in a normal full moult. I wonder whether part of the answer, in males at least, is that these feathers, and the yellow on them, are very obvious on the closed wing, and so they look more 'adult'. If this is how other birds see them, they could gain more dominant positions in feeding squabbles - for which Greenfinches are notorious - and they might also win in the competition for experienced mates. One can easily see how such a strategy could rapidly become established through evolution. Of course, this is looking at the birds through human eyes, and mate selection may well depend on criteria other than how bright the bird looks.

The initial 'adult' impression of this bird could apparently be confirmed by looking at his tail as well, with every feather showing the classic 'adult' rounded shape, and in very good condition for late February:
Indeed, I do wonder how many of us might have mis-recorded this bird as an adult. However, close examination of the wing shows quite clearly that it is a first-year bird, hatched in 2003, that has undergone an extremely extensive post-juvenile moult:

This bird was unusual - the first that I have seen - in that it had also renewed two of its primary coverts as well. They are quite visible on the above photo - more rounded, greyer towards the tips and with a greenish outer margin - as well as on this somewhat magnified image:

These are obviously brighter than the juvenile primary coverts, which are normally retained throughout the bird's first year of life, but they are not as bright and clear as the classic adult male alula and primary coverts, which might take several years to achieve:
I have been amazed to find that as many as one-in-ten of my birds have moulted primaries, although this is the first year that I have looked as carefully as this at Greenfinches. I know that some other ringers have been doing so for several years. Extrapolating from this small sample, if there really are 10% of our Greenfinches hatched in 2003 that moulted one or more primary feathers, they could be at the start of a big change in moult strategy. I strongly suggest that it is worthwhile for many ringers to record the extent of post-juvenile moult: now that Greenfinch is the second most-ringed species in the UK, there is ample opportunity to accumulate lots of information. If other ringers would like to join in with a mass collection of systematic data on the extent of post-juvenile moult in Greenfinches, I would be happy to collate the results: if so, please contact me

We can speculate about the reasons for birds to change their moult strategy. There are probably two main causes: climate change, and the extensive provision of supplementary food in Britain, factors which might enable or encourage birds to breed outside their normal periods. There are hints that, as the British climate becomes more Mediterranean, with hotter summers, some species already are starting to show moult patterns more characteristic of southern Europe.