Saturday, 26 October 2013

Oxwich Marsh 26 October 2013

A break in the weather, with the south-westerly winds dropping slightly and the rain holding off, allowed a relatively short session at Oxwich this morning.  The wind did pick up after a couple of hours, and the catch was limited by both the duration of the session and the fact that the nets were seldom particularly still.  After the nets were taken down we did some much needed net ride maintenance and planning for the winter.  This included cutting out a couple of new rides using a brushcutter, and trimming the vegetation around the winter feeding station.  The main target for the winter will be reed buntings, for which there is a long data set for the site.
 
In total 30 birds were caught this morning.  The catch was as follows: blackcap (1); goldcrest (2); Cetti's warbler (1); reed bunting (1); robin (2); (winter) wren (4); blue tit (10), long-tailed tit (5); blackbird (2); dunnock (1); song thrush (1).  Three of the five long-tailed tits, a blackbird, a robin and two of the blue tits were recaptures from previous sessions.  The highlights were the Cetti's warbler and the blackcap, which may have been an immigrant or a late passage migrant.  It was not carrying any fat, so the logical conclusion might be that the bird is likely to stay for the winter.  A picture of one of the goldcrests is below.


As it seems likely that we have recorded the last of our summer visitors, a summary of captures of these species ('new birds' as opposed to retraps) is included below:
Barn swallow - 23
Grasshopper warbler - 2
Sedge warbler - 61
Reed warbler - 112
Whitethroat - 17
Blackcap - 51
Chiffchaff - 41
Willow warbler - 22

The timing of the captures of the reed and sedge warblers seems to bear out conclusions drawn in the field i.e. that the number of reed warbler territories in the marsh was relatively low (individual birds could be clearly heard singing around the reedbed - there was no wall of sound) and that very few sedge warblers bred locally.  Only 2 sedge warblers and 5 reed warblers were caught prior to July, and most birds of both species were trapped in August and September, when they are likely to have occurred in the marsh while on passage. Notwithstanding this, fledged birds caught in July did clearly indicate that both species bred on site.  The two grasshopper warblers were both young of the year, but there was no indication from field observations that breeding occurred in the marsh (and one of the records was relatively late in local terms). 
 
Totals of resident species will be reported at the end of the year.  However 9 new Cetti's warblers have been trapped to date in 2013, which is of local interest.  It is hoped that the current tally of 25 new reed buntings will be substantially increased by Christmas, and that there is a similar increase in goldcrest numbers.  Recent captures of roving tit flocks have resulted in blue tit overtaking reed warbler as the most regularly trapped species in 2013 (the tally of new blue tits currently stands at 121). 
 
By the end of the session 669 new birds had been trapped at the marsh in 2013, and 789 birds if retraps are included.
 
Thanks to Cedwyn Davies and Charlie Sargent for company this morning, and to Charlie for the loan of his brushcutter.

Owain Gabb
26/10/2013

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