Sand martin pulli
Sand martins in front of the wall
This year we have carried out mist netting sessions in front of the sand Martin wall once a fortnight on Sundays. Our first session was on 24/05 and subsequently we made catches on 07/06, 21/06, 05/07 and 19/07, with a final catch on 03/08.
On our first session we used the technique we used last year, with two nets in front of the entire wall, with one team of ringers and another of extractors. This year we videoed the front of the wall as we caught to try and identify the holes from which individual birds emerged to fly into the nets, and used individually numbered bird bags to keep track of each extracted bird. This proved a challenge as tracking the birds and linking them to the numbered bags was difficult using this method.
The first session was very successful with a total catch of 130 birds, one of which was a blackbird which was caught once the nets had been set up, but before they were moved in front of the wall, so it was extracted before the nets were moved into position.
Of the sand martins caught 86 birds were retraps, with both birds which were adults and pulli ringed in the wall in 2025. 42 birds were unringed so must be birds which had found their way to the site either late in the season in 2025, before making their way south, or on their way back this spring. Because sand martins complete a pre-breeding moult of all their feathers it is not possible to tell in spring whether the birds were hatched in the previous year or not. One bird was a French ringed control, and was a bird we had caught previously last summer, returning again to breed.
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| White clothing shows up birds in the net better. |
On the second session, on 07/06, we continued to try to identify the holes the birds were coming from. Again this was challenging despite some improvements of the technique we used. We caught 149 birds, of which 86 were retraps. 14 of the birds were birds hatched this year, with 2 of these unringed and therefore not hatched at the Wetlands. We identified the holes of 36 of the birds.
Session 3 on 21/06 saw us adapt our technique to improve our identification of the holes the birds were using. We used only one net and moved the net in to position, recording the process using video, then, when a suitable number of birds were caught, we brought the net back out before extracting the birds. This led to fewer birds caught in total as birds leave the holes while the net is not in place, but a much better data set. We caught 118 birds, identifying the origin of all bar 10 of these. 17 birds were from this year's hatching.
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| Buff edges on Greater Coverts indicate this is a young bird |
Subsequent sessions on the 05/07 and 19/07 used the same method. Again we managed to identify the majority of the holes the birds were from. Numbers gradually diminished as the breeding activity in the wall slowed down and birds started to leave to head south. 77 birds were caught on the 5th, with only 4 first year birds, and all birds allocated to holes except for 4.
The proportion of first year birds in the catch increased in the final two sessions, with 73 birds caught on 19/07, 13 of which were first year's which (as good adolescents!) tended to appear later in the morning. 22 of the birds could not be allocated to holes in part due to the sun making seeing the video difficult. On the 3rd August we caught only 69 birds of which just 15 were adults the remainder being juveniles with only 3 unringed birds. We allocated 41 of the total birds for the day to holes.
Overall the sand martin bank has been very successful. We are in the process of writing more detailed reports for this which will published in due course.
