A couple of mornings of relatively warm settled weather in the last week resulted in good catches (107 and 120 birds respectively on 30 June and 3 July).

The catches broke down as follows:

The features of the last couple of sessions have been:

• Proving breeding in grasshopper warbler. We captured three birds in juvenile plumage over the two sessions (along with a male with a cloacal protrusion and a female with a brood patch during previous sessions). Two males continue to reel on the marsh.
• Capturing a house martin on 3 July. This was only the second we have caught at the marsh (albeit we don’t target the species). A swallow was in the same net line. The conditions were very still and hirundines were foraging low over the reed bed.
• Juvenile reed warblers starting to appear in number, and our first young blackcaps and Cetti’s warblers.

House martin

Grasshopper warbler (Emma Cole)

We are now going into the busiest few months of the year at Oxwich. Between July and October inclusive we can expect returns of 500-1,100 birds per month as birds begin to disperse and migrate. It is therefore a good time to take stock, and see how numbers and diversity compare to previous years.

The table below provides data on unique birds captured between 1 Jan and 3 July in each of 2014-2016 respectively:

Juvenile reed warbler

There are some interesting differences between years, albeit all conclusions must be qualified (as the amount of net is not constant / effort varies in accordance with availability of personnel and due to weather). These include:

• higher numbers of whitethroat, reed and sedge warbler in 2016 than preceding years. This is likely to simply be the result of a better (and longer) net ride through the reed bed and fringing scrub than we had in previous years.
• lower numbers of blackcap. There appears to have been a genuine fall in the numbers of birds around the marsh during spring passage and in the breeding season over the past two years.
• lower numbers of blue tit and higher numbers of great tit. We are currently catching a lot of young great tits, but relatively few blue tits. This may indicate that productivity in the species has been quite markedly different in 2016.
• variation in numbers of the various finches captured. It appears to be a good year for goldfinch and chaffinch, with large numbers of juvenile of both species swelling the catch at present. Similarly we have done better on siskin than in previous years, but they now appear to have (largely) dispersed, and we have one caught one bird in the past two sessions. It will be interesting to see if there is evidence of a second brood in July. Unfortunately greenfinch numbers trapped in the first half of the year continue to fall, and it is hoped that this is not due to population decline caused by trichomoniasis.

The Top 20 in terms of new birds ringed is as follows:

Finally, the  last few sessions have seen some nice invertebrates, including hairy dragonfly and four-banded longhorn beetle (see below).

Thanks to all those who have attended recent sessions: Heather Coats, Paul Aubrey, Wayne Morris, Emma Cole, Val Wilson, Ben Rees and Lynn Watts.

Owain Gabb
03/07/2016

Four-banded longhorn beetle