Wednesday, 27 April 2011

Summer migrants have started to nest

The onomatopoeic song of the male Chiffchaff has been much in evidence over recent weeks, with birds setting up territories in many of the scrubby habitats around the reserve and out in the forest. They are one of the first summer migrants to arrive but their morning chorus has now been joined by Blackcap, Whitethroat and Willow Warbler. While many of the new arrivals are likely to be passing through and not yet settled on a territory, the Chiffchaffs have had time to get themselves sorted and many will now be paired up. This makes it a good time to go out in search of their nests. Later in the season, when the birds are less obvious and the vegetation has grown up, it will be a lot more difficult to pin them down.

I spent a couple of hours this morning watching one of the local Chiffchaff pairs that I thought was settled and likely to have started building. The nest of a Chiffchaff is like a rather untidy and flattened Wren nest, built low down in tangled vegetation but always just off the ground. Many are built where the tangle of the herb layer pushes up into the lowest branches of some shrub.

The male of the pair I was watching was delivering his chiff-chaff song from a number of perches and it took me a little while to pick up the female. She was working her way through the herb layer, swapping between bouts of feeding and pecking at potential nesting material. Her route brought her towards me and, as I watched her flicking from stem to stem, I began to wonder if the position I had chosen to watch her from was a little too close. The hen reinforced this opinion by uttering her off-nest alarm call, a ‘hueeet’ note that rises in pitch at the end, and by picking up nesting material and then dropping it. As soon as it was clear that she was working a semi-circle around me I retreated back up the track to watch from a greater distance.

This seemed to work; the hen stopped calling and began to feed, soon joined by the male who had come to see what was going on. He then flew up to one of his perches and started singing again, prompting the female to pick up some material and carry it to a tangle of dead stems. She repeated this several times, arriving with new material and leaving empty-beaked. I had found the nest but would leave it alone for another week until she was likely to have started laying her eggs. It will be then that another visit to monitor the breeding attempt will be needed.

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