Thursday, 7 August 2014

Oxwich Marsh 7 August 2014: 3 foreign controls!

The weather at Oxwich was bright and warm with a light westerly breeze.  We put up a total of 560 feet of net in a range of habitats: reed bed, willow and bramble scrub and a new area we are calling 'fen meadow,' which is characterised by tall rushes, common reed, willow scrub and tall herb communities.

The catch was excellent, despite the fact that after a few hours the sun and light breeze were making at least half the nets very visible, and these nets caught very few birds.  A total of 140 birds included 3 foreign controls (two French-ringed reed warblers and a Spanish-ringed sedge warbler).  We will await the details with interest, particularly as French rings are used in some north and west African countries as well as in France (the most likely origin of the birds).  Interestingly, one of the French control reed warblers had previously been trapped on the marsh in late April, but had not been recorded since.  It has possibly bred locally, but perhaps it regularly stages at the site.  We could do with a June capture of this bird in 2015!

The catch of 140 was dominated by new birds.  The total was made up of the following:

Species New Re-trapped Total
Wren 4 0 4
Dunnock 1 0 1
Robin 1 0 1
Blackbird 4 1 5
Sedge Warbler 39 2 41
Reed Warbler 19 3 22
Lesser Whitethroat 1 0 1
Whitethroat 7 0 7
Garden Warbler 5 0 5
Blackcap 8 0 8
Chiffchaff 2 0 2
Willow Warbler 13 0 13
Goldcrest 1 0 1
Marsh Tit 1 0 1
Blue Tit 2 3 5
Great Tit 1 6 7
Chaffinch 0 1 1
Greenfinch 9 3 12
Goldfinch 1 0 1
Reed Bunting 1 1 2
Total: 120 20 140

There were lots of interesting aspects of the catch.  Many of the sedge warblers in particular were carrying significant fat.  In some, this was spread across the breast muscles, indicating that they were either migrating or ready to migrate (fat scores or 5 and 6 were common and one bird had a fat score of 7).  Thirteen of the 41 sedge warblers captured were adults.

Five garden warblers is fairly exceptional.  The species is uncommon, although undoubtedly considerably under recorded, in Gower.  There were no autumn records listed in the 2013 Gower Bird Report.  All the birds we trapped were young of the year.

The catch of thirteen willow warblers was also dominated by young birds.  Only one adult was noted.  The plumage differences between the adult and the young birds was obvious in the hand, and some should be discernible (with good views) in the field.  The adult had far cleaner (whiter) underparts: the juveniles had yellow streaking and more yellow around the face.  The adult bird was finishing its main moult, and the outer two primaries still had waxy sheaths at the base: many of the juveniles had fault bars in the tail, and one had a bar towards the tips of the primaries.  There are more subtle plumage differences in the feathering that can be examined in the hand, and ageing of willow warblers where obvious features are not present, is not always straightforward.

The marsh tit, the second juvenile to be trapped in recent weeks, and the lesser whitethroat were nice features of the catch, as neither species is trapped regularly.  The goldcrest, a juvenile, was unexpected, and the good run of blackcaps continues (125 new blackcaps have now been ringed at the site in 2014).

A really good session.

Many thanks to Charlie Sargent, Cedwyn Davies and Keith Vaughton for assistance and company this morning.

Owain Gabb
07/08/2014


One of the five garden warblers ringed this morning

Paris ring on a reed warbler


Spanish ring marked 'Aranzade San Sebastian' on a sedge warbler (indicating the bird was ringed in northern Spain)

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