Sand martin update

I could put a load of mindless trivia in this blog posting like retrapping 9 birds with successive ring numbers or controlling a bird where a reversal of two digits of the ring number would have made it one of ours, or even taking L333271 and L334271 out of successive bags when neither had been ringed at that colony (one moved 2km and the other 4km) however all these are just fairly uninteresting chance events. Of much more significance is the overall pattern of captures.

In 2011 we have caught a total of 1372 individuals so far, of which 1191 are new birds and the remainder are retraps or controls. These 181 birds are of most interest to the project. The tables below show where the birds were ringed in 2010 and where we have recaught them in 2011, with NOR and SOU being two colonies near Whittington, ARK being near Arkholme, NETB being near Tunstall and CDB being deep inside the Bowland fells.

82 were ringed as juveniles in 2010:

NOR SOU ARK CDB Total
NOR 28 9 7 44
SOU 2 2
ARK 1 4 5
CDB 2 2 2 6
NETB 13 4 8 25

Total 44 15 21 2 82
9% of Juveniles ringed in 2010 have been recaught this year.

Adults ringed in 2010:

NOR SOU ARK CDB Total
NOR 45 4 2 51
SOU 1 1
ARK 7 7
CDB 5 5
NETB 1 5 3 9

Total 46 10 12 5 73
10% of adults ringed in 2010 have been recaught this year.

A further bird ringed in 2010 by the group at Gressingham swallow roost has been caught at Tunstall. We have also retrapped 13 birds from 2009 and one from 2007.

Note the adults have been highly site faithful with the exception of those at site SOU. This colony is largely abandoned probably due to predation by rats and stoats last season with only a small part active this year. The adults could have moved 200 metres along the river to the northern colony however it appears like more have gone to Tunstall around 2km away. Last year we did not ring at the Tunstall colony so made two visits this year to find out how many of the birds at our existing RAS sites use it. The answer is clearly a lot (around 10% of adult birds caught were retraps from last year) and as a result we plan to extent our RAS scheme to include this colony.

The totals for 2011 for each site are as follows with the retrap figure excluding within year retraps and controls:

New Adult New Juvenile Retrap Adult % (adult) retraps
NOR 260 318 95 27
SOU 17 6 3 15
ARK 41 0 12 22
CDB 50 39 11 18
NETB 320 140 34 10

Of the 11 controls the most interesting is likely to be L597913 which we caught on 29th June and is a Juvenile. My guess is it is from Scotland however we will have to wait for the ringing unit to get back to us. Juveniles do make rapid movements in late June and July often visiting active colonies in search of sites to breed. Will this one return next year?