Wednesday, 22 May 2013

Three birds in the bush

A few distant but instantly recognisable phrases were enough to reveal the presence of a male nightingale at the bottom end of the local nature reserve. It was early in the season, however, and this could easily have been a passage bird, just passing through. Fortunately, subsequent visits to the site have found the bird still present and seemingly holding territory in a piece of scrubby woodland that looks ideal for a future nesting attempt.

There is no mistaking the territorial claim of a nightingale; a richly varied and explosively loud song that has its own delicate rhythm and a confidence in its timing that echoes the very best of our jazz musicians. At times I have heard nightingales burst into song at the approach of a human observer who has, perhaps, strayed too close to the breeding site. The singing bird will often remain hidden from view, the song post buried deep within a tangle of bramble and other thick cover. On occasion, particularly ahead of dusk and early in the breeding season, the male may sing from more obvious perches and be more accessible to the would-be watcher. Once the eggs hatch, male song virtually ceases and the woods again fall silent, the pair becoming more skulking in habits and harder to locate.

The nightingale is not the only bird singing from the brambles at the moment, as both blackcap and garden warbler are busy delivering their rich, melodic warblings. The two species can be difficult to separate on the basis of their song and it always takes me a while to get my ear attuned once the first of these birds return to favoured breeding haunts. To my ear, blackcap song sounds as if it has been scripted, the bird clear in what it is going to sing and for how long; in contrast, the garden warbler seems more hurried, less organised and has the character of a songster who is making it up as he goes along.

Knowing the songs of all three birds is important to me as someone who surveys and monitors birds. All three species tend to make the most of the cover available and so are heard more often than they are seen. Repeated visits to study sites allows me to build up a picture of where the territories of these species are located and I can also use their calls to inform me of the likely stage of the breeding cycle. For example, blackcaps tend to alarm most readily just ahead of egg laying, then they go quiet until the eggs hatch, after which the harsh ‘tacc’ alarm returns, together with a rasping squeak. Such subtleties in behaviour are useful when working with these birds in the bush.

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