Crop Field Ringing 19th April - Breeding is under way!
We had our first session of the breeding season down in the crop field area. It was a very cold start but developed into a particularly beautiful day weather wise (though a little too bright and sunny for ideal ringing conditions), as you can see from a picture of the busy team for the day (minus myself).
I had cleared some new rides in the Colyford Common reed bed for us to use and we set nets in our usual areas otherwise. The reed beds are still a little quiet as yet, but the new rides did catch us a few birds including a reed warbler, one of our target species, and a swallow. Overall it was quite a productive day for the four of us, with a good mixture of birds including some we don't catch particularly frequently which is nice, especially when they may be locally breeding.
Our total for today, or 41 birds encountered, is given in the table.
New Birds Retraps Total Blackbird 1 1 Blue Tit 1 1 Cetti's Warbler 2 2 4 Chaffinch 2 2 Chiffchaff 4 4 Dunnock 4 4 Great Tit 3 3 6 Greenfinch 2 2 House Sparrow 1 1 Linnet 2 2 Long Tailed Tit 1 1 2 Reed Bunting 1 1 Reed Warbler 1 1 Robin 3 1 4 Sedge Warbler 1 1 Stonechat 2 2 Swallow 1 1 Wren 2 2 Total 30 11 41
As always at this time of year we are looking for signs that the birds are breeding locally. We check the birds for signs of cloacal protuberance and/or brood patches. We can use cloacal protuberance to relatively easily sex some of the birds as male, and we can use the extent of the brood patch to sex some birds as female. We also look for these indicators in birds we can sex by plumage so we have some idea whether they are breeding in the area or are passing through, perhaps still migrating north.
The picture below shows a greenfinch we have sexed as female based on her plumage with a very obvious and clearly defined brood patch.
The unusual birds for us included the two linnets, which we catch one or two of per year. The bird on the right, though with very little pink colouration, is a male, while the bird on the left is female. They were caught side by side in the same net. The female was starting to develop a brood patch, though there was no sign of cloacal protuberance on the male.
Similarly swallow is a bird we might expect one or two a year, though I always think we should perhaps get more as they skim over the reeds.
The sex of a swallow can be determined by the relative lengths of the tail feathers. A male has longer 'streamers' which is effectively the length of the outer most tail feather. We measure the difference in length between the outer feather and the feather next to it and/or the shortest tail feather. This bird has relatively short streamers and was sexed as female.
Stonechat feel as if they are increasing in numbers, and we have a pair or two breeding. The stonechats we caught today were both male, but there was also a female collecting nesting material just by where we were ringing.
House sparrows are very nice to catch, and this area is one where we might expect to catch at least one most sessions. They travel down from the local houses (in the back of the linnet photograph) to feed in the grassy area in the old crop field and are readily caught moving between bramble bushes or in the gateway between two hedges.
Another interesting record was a reed bunting which we caught for a second time, having caught it initially in the reed bed by the Discovery Hut during one of our evening roost catches. This suggests this bird does not move much! It was showing signs of breeding and we also saw a female collecting nesting material.
So overall a very interesting session which gave us some good indications as to what is happening in that area of the reserve. We will be visiting again shortly so will keep you updated!
