Heysham Oystercatchers

On Saturday we had a catch of Oystercatchers at Heysham Helipad. A total of 217 were caught and ringed. This is a lower total than on the previous two Oystercatcher catches (see here and here) however gave us significant amounts of biometric data.

Last year I commented on the lack of juvenile birds in the catch (just 1 out of 569) suggesting a complete wipe out of juveniles in the bay last winter. In the catch over the weekend we caught 10 birds that hatched in 2009 suggesting that rather than being wiped out in the bay the juveniles were actually feeding in land while the birds in better condition roosted. This year we caught 19 juvenile birds which is higher than I expected given the recent cold weather.

With over 1,000 Oystercatchers ringed at Heysham over the last 2 winters I had hoped for some more retraps to help create a reasonable survival estimate. With just 9 retraps this is difficult. Perhaps it is more an indication of the number of birds roosting at Heysham and the surrounding area (a simple lincoln index gives us a figure of 20,000 birds using the site). Last winter we noted ingress of east coast Oystercatchers so it is possible many of last winters birds have moved back to their traditional wintering grounds.

One bird retrapped at Heysham was ringed on 27/3/2010 near Tarland, Grampian at a spring inland roost site. This gives me a great deal of encouragement as our ringing of inland Oystercatchers at spring roosts have so far generated no movements away from ringing sites!

Most recent recoveries from Heysham of Oystercatchers show the birds roosting at Heysham breed on the west coast of Scotland, Orkney, Shetland, Faeroes and Iceland.

Finally I have managed to do a quick bit of analysis of the data and produced a graph which is below. It shows the cumulative distribution of weights for adult Oystercatchers caught on 12/12/2008, 01/02/2010 and 22/01/2011 at Heysham. The 2008 weights are lowest which is no surprise as the birds will have just completed their moult. The 2010 weights are on average about 15 grams less than the 2011 weights for catches essentially at the same part of the winter. In both 2010 and 2011 the catches were made after severe weather, in 2010 about a week after the cold spell ended, in 2011 about 2 weeks after.



Thanks to:
Raymond Duncan (Grampian Waxwing Group) and everyone who helped with this catch. If you want to see some photos visit Fleetwood birder's blog

Richard