Sedge Warbler

Not only have sedge warblers been late in arrival recently, but even as the longest day approaches the numbers in parts of the upper Thurne have been below normal. However, populations of summer migrants wintering in Africa vary here from summer to summer. And the sedge remains the most widespread of our marsh haunting warblers.

Their breeding season range, covering the greater part of Europe, extends as far as northern Scandinavia.

Sedge warblers advertise their presence by a chattering and varied song, but are often invisible due to the dense herbage they haunt. The birds occupy a range of wetland habitats: lakes, rivers, reedbeds, sedge fens, marsh dykes, ponds, flooded gravel pits and meres.

The song is highly varied — musical passages are freely interspersed with harsh grating ones. Sedge warblers often mimic other species. I recorded an individual which included alarm notes of blackbird, flight notes of chaffinch and linnet, and calls of pied wagtail and great tit in its repertoire.

Sedge warblers devote most time to singing — either from the depths of cover or from such vantage points as alders and birches in full view. When in song the whole bird pulses with effort, turning from side to side with the throat conspicuously puffed-out. Each performance continues for a minute or more without a break.

Impressive song flights separate perched performances at regular intervals. The bird rises almost perpendicularly in the air with fluttering wingbeats before turning rapidly and making a slow spiral descent with wings and tail outspread.

Singing is frequently heard at night. The nest is usually near water, but at other times in tangled overgrown dykes quite dry in summer. It is seldom more than two or three feet above the ground. A neat construction of grass and moss, the nest is lined with horsehair or willowdown.

Song period continues into early August at which time emigration is under way. Autumn passage usually ends by the beginning of October.

The entire breeding population of sedge warblers winters in Africa south of the Sahara. Large fat reserves are needed prior to departure permitting unbroken flight for a small proportion of the heaviest birds to sub-Sahara from southern Britain. This is a remarkable achievement, entailing a flight of some 2400 miles. In the most favourable conditions, including tail winds, such a journey suggests a flight time of between 75 and 95 hours.

By Michael J. Seago

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Illustrations by Dave Nurney from - The Pocket Guide to the Birds Of Britain and North-West Europe By Chris Kightley and Steve Madge © Pica Press and reproduced with kind permission.