Tuesday, 28 April 2015

Crawford 24th & 27th April 2015

Keeping the feeders going has paid off and resulted in a couple of interesting sessions over the past few days. The natural seed bank is at its lowest at this time of year and seed eating birds can still struggle to find enough food even though the weather is warming up. The number of Goldfinches using the feeders at this site is much greater now than it was earlier in the winter although this has not been reflected by the Goldfinches visiting the feeders in my garden. Lesser Redpolls only started coming to the feeders fairly recently and none had been caught before the 7 yesterday (27th). One of the Redpolls was a control (ringed elsewhere) but I suspect it was ringed at Kings Moss, just a couple of km away, as the ring number is similar to other birds that have come from that site. In addition there were 4 other controls, 2 Goldfinch and 2 Greenfinch, with these birds also likely to have been ringed at Kings Moss.

Ringing totals (retraps and controls in brackets) for 24th April 2015: Goldfinch 18 (3); Greenfinch 4 (1); Chaffinch (3); Yellowhammer (1); Coal Tit 1; Dunnock (1);  Blackbird (1); Blackcap 1; Jay 1. Total 35.

Ringing totals (retraps and controls in brackets) for 27th April 2015: Lesser Redpoll 6 (1); Goldfinch 7 (4); Greenfinch 4 (1); Chaffinch 3; Tree Sparrow 2; Dunnock 1. Total 29

Now the breeding season is getting underway the sex of some birds can be confirmed by checking for the presence of a brood patch and or the shape of the cloaca. In many species the female develops a large and distinctive brood patch with the cloaca not being very prominent and generally pointing back towards the tail while the male doesn't develop much of a brood patch, if any, and the cloaca is usually prominent (sometimes bulbous) and sits at a right angle to the body or points slightly forward. It was interesting that 2 of the 3 female Lesser Redpolls had brood patches as I initially thought they would all be birds that were still on passage rather than breeding somewhere nearby.

A well developed brood patch confirms this Lesser Redpoll is a female. A good blood supply to the bare skin keeps the eggs warm. The presence of a brood patch also indicates that the bird is probably breeding nearby and the condition of the brood patch suggests it already has a clutch of eggs.
A Lesser Redpoll with a protruding and slightly bulbous cloaca confirming it is a male.
Regular readers of this blog will know my interest in sexing Goldfinches from plumage features, that interest must be shared be a lot of people as my posts on this subject have and continue to attract the most page views by some margin. Not all Goldfinches are breeding yet but I checked each bird for a brood patch or cloacal protuberance to see if it confirmed the sex that was indicated by the plumage. This revealed a couple of interesting individuals that wouldn't have been easy to sex outside the breeding season although the majority were fairly straightforward.

Z414875 had a fairly extensive red mask for a female Goldfinch and no obvious white or grey nasal hairs. It is the sort of bird that is probably best left unsexed outside the breeding season. The lesser coverts were somewhat intermediate being less brown than some females and almost showing as much black as some less well marked males. Strong sunlight doesn't always help when looking at such features and doesn't help with the photography either. The sex was confirmed by the developing brood patch and shape of the cloaca. The bird is still in the process of losing feathers from the belly and lower breast so is only at the early stages of breeding.

Z414877 had a mask and lesser coverts that are not that dissimilar from the bird above although the black parts of the lesser coverts are much glossier and the brown fringes are more distinct. The thing that made me look twice at this bird was the short wing length of 76mm which is at the bottom end of the range for males and is fairly short for a female. It had a well developed cloacal protuberance which I didn't manage to photograph but confirmed it as a male. There is a difference in the intensity of the red of the mask but that can vary from orange-red to crimson in both sexes and shouldn't be used as a supporting criteria. Again this is a bird that may be better left unsexed outside the breeding season.

......and now for images of a couple of birds that show how different males and females can look and shouldn't pose a problem for sexing at any time of year.

Z414709 is a text book female with a restricted red mask and greyish nasal hairs. Unfortunately Goldfinches don't read text books and many females don't look like this. On the other hand the lesser coverts are broadly tipped brown and form a brown shoulder patch which is fairly common feature of female Goldfinches.

Z414876 is a well marked male with an extensive red mask and black nasal hairs. The lesser coverts are glossy black although it is not uncommon for them to have well defined narrow brown fringes. Note there are a couple of stray brown mantle feathers overlapping a few of the inner lesser coverts.

Among the other birds caught a Jay did what Jays do well and bit me. I got off fairly lightly at first but it flew back into one of the nets on release, despite having been let go in the opposite direction. On being taken out of a net for a second time it really let me have it.

About to take a good beak full.
I went back to check the feeders this evening and several were almost empty so I topped them all up and added another. With the feed going down so fast I will try and fit in another visit later in the week.

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