12 July 2013 Oysterbed update from Chris Cockburn

Hello folks

There are now 64 common tern pairs (plus some wandering male chancers – waving fish at all & sundry in the hope of finding a mate). There are c7 chicks that can lift-off from ground – but are not flying yet. There are also variously aged smaller chicks and there are adults presumed to be on egg. It is looking increasingly likely that common terns will be a feature of the site until late August or even September. Food supplies seem to be OK, with many of the adults seen returning to the site with suitably-sized “silvery” fish prey; but given that winds have frequently been Force 5, these birds may be having difficulties in finding sufficient quantities to feed more than one chick (there have been broods of two chicks in most of the viewable nest sites and all of these broods have rapidly reduced to a single chick – had they reduced to no chicks, predation would have been suspected) . There has been no definite indication of predation of common tern chicks by the gulls – but it is difficult to see what is happening on the eastern (curved) island – and no common tern chicks have been observed being eaten by black-headed gulls, unlike in some previous seasons when the weather has been very bad (long periods of strong winds , rain etc).

The Mediterranean gull nesters are being harassed by increasing numbers of other Meds (presumed to be failed pairs) and there is now a possibility that, given the dry conditions,  adults are having problems in finding earthworms and other terrestrial invertebrate prey to feed their youngsters. I observed only 3 youngsters today (originally there were 10 chicks); but I could easily have missed any that were ‘hunkered down’ trying to avoid the attention of the failed birds.

Black-headed gulls have had an excellent season despite the extremely high density of nests on the two islands and the productivity rate for the site may end up as high as c1.75 fledged birds per nesting pair. Some of the adult gulls are still “sitting” on nests; but it is highly unlikely that any chicks will appear given that they have been “sitting” for well over four weeks.

Oystercatchers and ringed plovers – perhaps a gull/tern colony is not the ideal place for nesting waders. Such waders would normally nest on similar habitats to that at the Oysterbeds’ islands; but, normally, they nest at considerable distances from any neighbouring waders and, if disturbed or threatened, quickly move away from the nest site to distract attention  – they are just not capable of coping with fiercely territorial gulls & terns and to leave a nest unguarded is not the best strategy for success.

Insects are becoming more noticeable (at last!) – it was thrilling for me to see so many Small Tortoisehell butterflies recently after not having seen any (at the Oysterbeds and on my Transect Routes at FM) during the last three years.

PS I hope that you are managing to cope with the current strange phenomenon of summery weather during a summer month.

Regards

Chris C

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