Thursday, 31 March 2016

Oxwich Marsh 31 March 2016: interesting recaptures

An overnight frost made for a cold start at the marsh. We put out 340 feet of net, most of which was across the open reed bed. The catch was very modest and is detailed in the table below:

Species
Ringed
Recaptured
Total
Sparrowhawk
0
1
1
Great Spotted Woodpecker
0
1
1
Wren
0
1
1
Dunnock
0
2
2
Chiffchaff
0
1
1
Goldcrest
1
0
1
Blue Tit
1
2
3
Great Tit
0
2
2
Chaffinch
1
0
1
Goldfinch
4
0
4
Siskin
3
2
5
Reed Bunting
1
4
5
Total:
11
16
27

Despite the low numbers there were several interesting features, however. The first was a chiffchaff initially ringed on the marsh in early April 2015, recaptured later the same month (by which time it could be sexed as a male), and then recaptured again this morning. Nice to see a returning bird, and hopefully we can recapture it again later in the season to prove local breeding.

The second was evidence that we are getting a lot better at ageing reed buntings. At this time of year the degree of feather wear in both adult and first winter reed buntings is considerable, but the breadth and shape of the tail feathers and tertials can still give a good indication of age. We tend to enter all but the most extreme birds as being of unknown age from early in the new year onward, but also record our assessment of what age each bird is likely to be based on our experience. Due to the number of reed buntings we have been recapturing from previous years (we have ringed 326 at the marsh since February 2013), we are now able to regularly truth our judgements through corss-referencing IPMR, and are becoming gradually more confident in our ageing of birds later into the winter.  We correctly identified three birds as adults and one as a first winter this morning, which was pleasing.

Sparrowhawk (Keith Vaughton)
The highlight of the day, however, was a male sparrowhawk. This bird has now been captured four times at the marsh. It was initially ringed as a juvenile male in August 2014, recaptured twice in the autumn of the same year, and is now in its third calendar year.

It is interesting to note the deeper, more orange-yellow iris that the bird has developed with age. The bird had some retained secondaries, lesser coverts and rump feathers, allowing it to be aged as a 7 (second winter  male).

Thanks to this morning's team of Paul Aubrey, Keith Vaughton and Emma Cole.

Further pictures of the sparrowhawk from when it was captured this morning and on initial capture in 2014 are below.

Owain Gabb
31/03/2016

Sparrowhawk (Keith Vaughton)

The same bird in 2014 (when juvenile)

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