The house martins at their colony on Exbury Water Tower have been busy since their return in early May. The numbers have built up gradually, with nest reconstruction their first job. In the photograph (left) taken by volunteer David Marsh, you can see a group of four birds collecting mud, while one is flying off and another about to land.
Some of their nests remain intact from previous years, but a lot of patching and repairing is necessary to others. Some birds head for nests which are pretty dilapidated, in spite of there being seemingly intact nests nearby. Maybe it is their old nest from last year? In the photograph (right) you can see the pale old mud of last year's nest contrasting with darker-looking newly-collected mud with which they are currently building up the nest.
The nests are clustered under the eaves of the tower between the protruding beams of the roof. In some spaces there is only one nest, in others, two. On the south side of the tower, which is the most fully occupied, there are 25 active nests. The birds are flying in and out, inspecting, re-building or already sitting. From the ground it is hard to see exactly what goes on in the nest, but sometimes two birds are there together, heads poking out of the hole. At other times they appear to be mating, with a lot of fluttering and wing flapping. Some are industriously building up the structure; at others the birds swoop in and out without even landing. The martins are most active on warm sunny days without much wind when the whole water tower is a scene of excited activity.
The martins do not have sole occupancy of the nests, however. At least three of them have been taken over by House Sparrows, which are also colonial nesters. They perch on the roof, peer over, and then flutter down to their chosen nest.
As the season goes on it will be interesting to watch the young birds being fed and taking their first flights.