Monday, 26 June 2017

Attenborough Sand Martins, Wednesday 21 June

Phil, Pete S and I held another session to catch the adult Sand Martins. The weather was good with a light breeze but this was easterly so the bank protected the net. After the session Phil looked at the results and reported the following:

- 39 birds caught, 22 retraps and 17 new birds

- 4 of the birds were 3Js, one not ringed as a pullus (moved from the natural colony possibly?). So, of the 120+ birds that have fledged so far, it looks as though most of them have already left the area. One of the 3 birds fledged a week ago and the other two must have just fledged (were close to fledging last Friday and are now 23-25 days old).

- Of the 19 adult retraps, only 5 were birds that we also caught on 25 May, when we caught 45 adults. This seems to be a very low proportion. It’s partly explained by the fact that we caught 24 adults on face C last time and only 3 this time and no adults on face A last time and 16 on A today. A better comparison is on face B, where we caught 21 adults on 25 May and only one of these was also caught today (2 birds caught today on B were caught previously on C). It’s interesting to speculate why this might be – might birds have their second brood in a different hole and with the natural colony nearby, might some of the birds have relocated?

- When we then look at A, we caught 16 adults, 10 new birds and 6 retraps. All of the retraps were caught in 2016, 5 as pulli and 1 as an adult. Where were all of these birds on 25 May? Late arrivals or have they also had a brood elsewhere and are now having their second brood on A (as of last Friday, there were 7 nests with eggs on A, 6 of which are new nests where there was not a first brood).

- We had 3 controls of birds that were not originally ringed at Attenborough, none of which have been caught here before.

- For the 2 sessions combined, we have caught a total of 75 adults, 41 males and 34 females. My estimate of the number of breeding pairs is c 41 (based on first brood nests with eggs) and if this is reasonably accurate, we have caught a very high percentage of the adults, which is what we were hoping to achieve with the new net. If the colony is more dynamic, which today’s session would suggest, we’ve probably still achieved this target, albeit with not such a high percentage. We’ve just got to make sure next year, all of the birds breed on the colony!


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