Monday, 25 April 2011

Two birds in the bush

There was a certain amount of relief the other morning when I finally found out what was going on with our nesting Robins. The saga began six weeks ago; a spot of nesting in the grounds at work revealed a Robin’s nest, complete and fully lined, just waiting for eggs. This was clearly the nest belonging to the pair that spent a lot of time around the entrance gate, the male singing from the avenue of trees and, occasionally, the nearby gate post.

A week later and the nest still sat empty. Curious to see what was going on I used the car as a hide and watched for signs of activity. I soon saw a hen collecting nesting material but, to my surprise, instead of carrying it to the nest, she took it to an ivy-covered tree less than 20 foot distant. I watched her for a while to be certain of what she was doing. Several more loads of nesting material followed, each time the bird was cautious in her approach to the new site, spending a short while in the ivy and leaving empty-beaked. I figured that the building work that was going on next door, and within a few feet of the original nest, had prompted her to give up and to try elsewhere.

Another week later and it was time to locate the second nest. I had a pretty good idea where it was and soon found it, complete with three eggs. ‘Great’ I thought, ‘we are up and running’. As a matter of course, I went to check the original nest and was stunned to find it contained six eggs. Was the female using both nests or were there two females nesting in the territory of the one male ­– a case of simultaneous bigamy. My most recent weekly visit has, finally, revealed that it is indeed two females, since both were sitting on their eggs upon my last visit. The female in the tree popped off the nest and took refuge in the ivy while I checked her nest contents (four warm eggs), while the other female simply peered over her nest cup and looked down at me. I left her alone but will return in a few days to see how she is doing.

Robins are essentially monogamous and are renowned for their territorial aggression so it is unusual to see two females with a single male. It does happen though, as it has done here, the two females maintaining their own territories within the larger territory of the male. It will be interesting to see how the birds fare once there are hungry mouths to feed.

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