Sunday, 14 August 2011

Bird Ringing at Titchfield Haven - Mid August 2011 Update

Well it is now the middle of August and the autumn migration appears to be in full swing, and despite some extremely unseasonal weather at times, we have managed five ringing sessions  between the 2nd and 14th August, including a record day on 6th August, when 345 new birds were captured. Sedge and Reed Warblers have been the most numerous species with 555 and 145 respectively, captured, although Grasshopper Warblers continue to break all previous records with 141 new birds captured. The combined total for the July and August total for Grasshopper Warbler now stands at 408 for the year, and it is only mid-August!! 

Willow Warbler numbers peaked on 2nd August with 17 new birds captured; the monthly total  now stands at 50, with 87 in total for the year...a very low total for the species. Locally Garden Warblers did not seem to have a good breeding season, and yet new captures this autumn have also been at record numbers, including a massive 23 new birds on 6th August. 

Garden Warbler - August 2011

During July a majority of birds captured were adult, whereas during August juvenile birds have been the most numerous. Both adult and juvenile birds undergo a partial moult in the summer and a complete moult in the winter. In autumn adult birds can be aged by the presence of slight wear on the tips of the wing and tail feathers and especially the tertials. Juvenile feathers are fresh as in the image below.

Wing of Juvenile Garden Warbler

Garden Warblers can be a difficult species to age on occasions, but the presence of a fault bar on the tail, caused by a deficiency of food in the nest, can make ageing much easier. A total of 57 new birds have been captured to date.

Tail of Juvenile Garden Warbler showing Fault Bar

The Common Whitethroat is a species that appeared to be in steep decline back in the 1980s, but this year the numbers captured have been high, maybe indicating a good breeding season. During July, 25 new birds were captured and a further 41 in August, bringing the total to date to 66. Juvenile birds undergo a partial moult in summer, and are perhaps most easily identified by their dark grey-brown or greyish-olive iris. 

Juvenile Common Whitethroat

The juvenile wing can be recognised by diffusely patterned greater coverts, which have darker centres which grade more diffusely into the rufous edges. In addition there is often a contrast between the outer juvenile coverts and the in moulted adult type feathers.

Wing of Juvenile Common Whitethroat

In juvenile birds the outer tail feathers are uniform light brown, or edged and tipped pure white, but they are obviously fresh and contrast with the rest of the tail.

Tail of Juvenile Common Whitethroat

Overall a total of 1035 birds, of 17 species have been captured to date in August, a total which has already surpassed the 883 birds captured in July.

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