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Sexing Goldies


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Sexing Goldfinches: a photographic study (updated 18/02/14) HOPE THIS HELPS MATE

Lets start by stating the obvious - male and female Goldfinches are very similar in appearance. The standard reference that ringers use is the Identification Guide to European Passerines by Lars Svensson although most ringers simply refer to it as Svensson. In the guide males are described as having, on average, more extensive red on the head (or mask as I prefer to call it), black nasal hairs and lesser coverts that are black or brown black, sometimes narrowly tipped brown. While females are described as having, on average, less extensive red on the head (mask), grey or blackish grey nasal hairs and lesser coverts that are broadly tipped brown although occasionally as narrowly as some males. The illustrations give an indication of the differences in the extent of the red mask of males and females and also point out that the nasal hairs in 1Y males can be grey and in 1Y females light grey. Those descriptions and the use of the term 'on average' in particular allude to how slight some of the differences can be and to the fact that there can be a degree of overlap.

Ringers have different opinions on the reliability of the sexing criteria described above or perhaps I should say levels of confidence in them and I have even heard some say that the appearance of the lesser coverts is not a useful feature for sexing. If I had to estimate the general levels of confidence that ringers have for the various features I would expect the extent of the red mask to attract the highest levels, the colour of the nasal hairs would probably attract moderate levels and the appearance of the lesser coverts coming in last and only attracting low levels.

Male+female+GF+collage+rsline.jpg Photo 1. I have tried to show examples of male and female here that match the description in Svensson. If they were all like this they would be easy to sex and I wouldn't be writing this post. Note the red on the male extends well behind the eye and not just past the eye and also ends at a right angle. This differs slightly from the illustration in Svensson but is fairly typical of many males in my experience. The outer row of feathers in the lesser coverts of both birds is almost identical and this is not uncommon but the remaining lesser coverts are very different. One of the problems we have with Goldfinches is that most of us don't get the opportunity to handle known sex birds to get a better understanding of the variation in the plumage features shown by the two sexes. I for one catch very few during the breeding season when the sex can be established from other features such as an incubation patch or cloacal protuberance. If you are lucky enough to catch Goldfinches during the breeding season the sample sizes are not likely to be big enough to get a full appreciation of the variation plus the feathers will be at their most worn which will affect the appearance of the width of any brown fringes to lesser coverts for example. When I asked a very experienced aviculturist for his opinion on sexing Goldfinches using plumage features his only response was 'hens lay eggs and cocks don't'!

Another problem with Goldfinches is that quite a large proportion have what appear to be contradictory and or intermediate sexing features based on the descriptions in Svensson. Of 92 birds I photographed and described in detail (extent of red mask, nasal hairs & lesser coverts) between 23/11/13 and 20/12/13 almost half (45) had one or more sexing features that I considered to be borderline, intermediate or were contradictory to a greater or lesser degree. I didn't sex or only provisionally sexed 16 of these which is around 17% or roughly 1 in 6 of the overall sample. I don't know what proportion of Goldfinches other ringers leave unsexed but I offer these figures to show how difficult I find it is to sex some of my birds using the criteria in Svensson alone. You may be wondering why I didn't leave more birds unsexed if all of the features didn't always fit on around half of the birds and now that I have reviewed all the descriptions and photographs so am I for a few at least. In the other cases the sex was confirmed from their wing length rather than any of the conflicting plumage characters.

So lets look at some of my 'ambiguous' birds. These are not aberrant individuals and are representative of about half of the birds that I caught in late autumn and early winter 2013. In my comments on each bird I may mention the wing length, general appearance and anything else I noted at the time. BWP gives wing lengths for British birds as 76-82 for males and 74-78 for females but I operate off 76 to 84 for males and 74 to 79 for females.

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