Controversial age assessment of White-fronted Goose

Found by Dave Warner on 17th January, a White-fronted Goose was present with a mixed Greylag and Canada Goose flock at Sywell Country Park and remains there today. Initially aged as a first-winter, it has since sparked some controversy over how old it actually is.

Shortly after Dave had seen it, I found it still with the local geese, in a field on the north-east side of the reservoir and managed to grab a few photos through the park’s rather thick boundary hedge before it walked off over the rise of the field. It initially appeared rather plain-looking but was also sporting a noticeable white forehead.

First-winter White-fronted Goose, Sywell CP, 17th January 2022 (Mike Alibone)

Appearing to lack the black belly bars of a ‘standard’ adult – at least when viewed from its left – I was happy enough that it was indeed a first-winter, albeit with a fairly well-developed white blaze. When viewed from the front, however, it displayed some less conspicuous, thin dark lower belly bars and some on its right side, these normally being associated with more adult plumage.

First-winter White-fronted Goose, Sywell CP, 17th January 2022 (Mike Alibone)

Having tweeted an image out, Tom Lowe made the comment: Pale nail, white blaze, belly bars and squared flank feathers make it an adult, surely? That was based on the image above and it’s difficult to disagree but there are a number of conflicting ID criteria out there.

First-winter White-fronted Goose, Sywell CP, 17th January 2022 (Mike Alibone)

For example, Stoddart (2020) states: Adult Russian White-fronts have a small white ‘front’ (actually the forehead) and highly variable black belly barring. Juveniles and early first-winter birds (the white ‘front’ and black belly markings are acquired during the first winter) lack these features. The keyword here is early. This suggests that first-winters, later in the season, can have black belly bars.

Cramp & Simmons (BWP 1977) states: White forehead appears during first winter but black bars of underparts lacking or incomplete until second autumn. Again this suggests that some black bars may be present during the first winter. Relating specifically to first-winter (and first-summer) birds, it further states: Virtually no black feathers on belly but those of sides of body with contrasting edges like adult.

Relating to first-winters, Reeber (2015) states: Black ventral bars are absent or reduced to a few spots. And furthermore: Second winter identical to adult but adult type birds in autumn/winter lacking black ventral bars (black over less than 10%) could be in their second winter.

So it would seem, from the above references, that it is possible for some (minimal) black to be present on the bellies of some first-winters.

However, this does not explain other features on the Sywell bird being at odds with what is generally accepted as being consistent with first-winter birds.

Looking at the nail of the bill which, despite being illustrated as black by Cramp & Simmons, they state: Bill nail (of juvenile) dark horn becoming white during first winter. This conflicts with Reeber, who states, of juveniles, that the bill has a dark nail but subsequently goes on to say that the bill gains adult colours between mid-winter and spring.

The bill nail of the Sywell bird appears to be pale horn to whitish. Interestingly, Dave Irons’ photo ID gallery shows images of immature Whitefronts taken in November with a pale bill nail, and some in October with extensively dark nails. It is well known that blackish bill nails can remain well into the winter, too. Images of some November birds illustrate a white facial blaze to the same extent as the Sywell individual.

Apart from the extent of black on the underparts, extent of white facial blaze and bill pattern, the stage of moult also plays an important role in ageing.

According to Cramp & Simmons, adults post-breeding undergo a complete moult which is mostly finished before reaching winter quarters. Post juvenile moult, however, is partial. Some moult mantle, scapulars, chest, and longer flank feathers November – January and all body feathers are renewed by February. Also, first-winter/first-summer take on some adult-like feathers. Shape of moulted feathers of mantle and breast square but not as broad as adult. Sometimes medium coverts also moulted but usually many juvenile wing coverts are retained.

Reeber, too, makes similar comments regarding moult. In winter one should expect both adult-type birds and others with an obvious mixture of two generations of feathers among young birds. He goes on to say: until the second pre-basic moult (first summer), the wing feathers are juvenile, often obviously worn, as well as the retrices. And with regard to feather detail: (Adult) feathers of the mantle and scapulars are square-tipped, medium brown with white fringes and black subterminal bars.

Looking again at the first of the above images, it appears (to me, at least) that there is a contrast between what appears to be fresh, second-generation mantle/scapular feathers, with an adult-type pattern described above by Reeber, and the wing coverts, which appear to be faded and worn with abraded tips, indicating retention of first-generation juvenile feathers. The tail feathers also appear pointed and possibly worn, too.

If that’s the case, then the bird is what I would describe as an ‘advanced’ first-winter. If that’s not the case then, taking into account a statement from Reeber that second-winters are generally identical to adults but adult type birds in autumn/winter lacking black ventral bars (black over less than 10%) could be in their second winter, then the Sywell bird might be of that age.

Let’s face it, most birders scanning through a flock of Whitefronts would simply be appreciating the beauty of the flock or looking for other species which might be in the mix, cursorily differentiating between obvious adults and obvious juveniles. It’s only when a lone individual turns up with a local gaggle that it comes under scrutiny …

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