Some observations of nesting Grasshopper Warblers in west Cumbria, with particular reference to double-brooding
By John Callion
Abstract Most authorities suggest the Grasshopper Warbler is usually double-brooded in the south and generally rears just one brood in the north of Britain. Results from a long-term study show that, after a successful first brood, it is clearly not unusual for Grasshopper Warblers in Cumbria to be double-brooded, and there is a previous record of triple-brooding. Local studies can still add new knowledge about the breeding biology of our familiar species; this paper will hopefully act as encouragement for readers to get out and make discoveries for themselves.
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Source: Bird Watching