Saturday, 15 October 2016

Oxwich Marsh 15 October 2016: late autumn surprises

A couple of sessions on successive days has resulted in quality as opposed to quantity. 

The wind direction for the last couple of weeks has been easterly / south-easterly, and the weather has been mainly dry, and this was the case for the session on Friday 14 October. This morning the wind had come around to the south-west, bringing with it rain showers, and signalling a period of unsettled weather that looks likely to remain for most of the week. 

The combined capture over the two sessions was as follows:

Species
Ringed
Recaptured
Total
Water Rail
1
0
1
Great Spotted Woodpecker
0
1
1
Grey Wagtail
1
0
1
Wren
1
1
2
Dunnock
0
4
4
Robin
1
4
5
Stonechat
3
0
3
Blackbird
0
1
1
Cetti's Warbler
1
0
1
Reed Warbler
1
0
1
Blackcap
2
0
2
Yellow-browed Warbler
5
0
5
Chiffchaff
8
0
8
Goldcrest
10
0
10
Blue Tit
6
2
8
Great Tit
0
4
4
Chaffinch
1
1
2
Greenfinch
1
0
1
Goldfinch
7
6
13
Reed Bunting
1
0
1
Total:
50
24
74

The features of the combined catch were:
  • The second water rail of the season. 
  • The first grey wagtail captured at the site
  • A few more stonechats
  • A later reed warbler and
  • Five yellow-browed warblers
The water rail was likely to have been a male, as the tarsus measured 46.4 mm (which is outside the zone of overlap between sexes and towards the top of the range of tarsus length recorded in the species). Wing and bill measurements, which can be used to separate sexes, were both within the zone of overlap. Plumage characteristics, including the uniform slate grey on the throat, tentatively suggested an adult (Baker, 1993; Demongin, 2016).

Grey wagtail (Keith Vaughton)
The grey wagtail was a first winter, and was captured in a net set through head high scrub, and seems likely to have roosted close by.

Cetti's warbler (with raised crown feathers)










We have now ringed 21 stonechats on the marsh in 2016, which is likely to be a relatively large proportion of the number ringed in Wales this year (there were 98 stonechats ringed in Wales in 2015). What was interesting was that two of the stonechats and the single Cetti's warbler captured were carrying reasonable levels of fat (scores of 3, 5 and 4 using the British Working Group system). Given that these species don't seem to carry fat at other times of year, this seems likely to indicate these birds have built up fat ahead of dispersal from breeding areas. We also captured Cetti's warblers carrying fat during the preceding ringing session. 

Cetti's warbler
The reed warbler was a typical late first winter bird. It showed very little wear to the flight feathers, was carrying very little fat and had a prominent sternum. It seems unlikely that it will manage a trip to sub-Saharan Africa given its condition, but there is still plenty of food around at present, so hopefully it will make it.

Four of the five yellow-browed warblers were captured on Friday 14 October. Birds had been obvious around the marsh during the week (they were frequently heard calling), but were less so this morning (albeit a bird was heard calling near the ringing station in addition to the bird trapped). Observations of them suggested that some birds were foraging alone, while others were attached to mixed flocks (with blue tit, long-tailed tit and chiffchaffs).

Thanks to Keith Vaughton, who came to both sessions, and to Wayne Morris, Darren Hicks, Val Wilson, Lynn Watts and Ben Rees for company and assistance.

It was also a pleasure to welcome Jeremy Douglas-Jones (of the Gower Ornithological Society) and John Pile on Friday, and to be able to show them a range of species including the water rail and several yellow-browed warblers.

Owain Gabb
15/10/2016

Stonechats (Keith Vaughton)

Grey wagtail (Keith Vaughton)
Water rail (John Pile)
Yellow-browed warbler (John Pile)

Water rail (Keith Vaughton)
Common lizard (male)

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