大象传媒

New Series - The Living World: A Home In The Reeds

The elusive reed warbler weaves its cup-like nest among the swaying stems of reeds which makes it hard to study. For The Living World Joanna Pinnock joins Dave Leech from the British Trust for Ornithology in his study area in an East Anglian reed-bed.

Dave Leech is researching why reed warblers are bucking the trend of decline in long-distance migrants by counting nests and ringing chicks. Unlike turtle doves, nightingales and other birds which winter in south of the Sahara and which are disappearing from any areas of the UK, reed warblers are increasing in numbers and in their range. Part of their success could be in their amazing productivity, with some pairs producing two broods a year. They can also nest over open water which makes the nests less vulnerable than those of ground-nesting birds, and could be benefitting from reed-bed creation by conservationists.

But as Joanna discovers, the warblers can't escape from one of their parasites. Reed warblers are a main host of the cuckoo, a bird which is declining even as the reed warbler is increasing. The discovery of a cuckoo's egg in an unsuspecting warbler's nest is no surprise to Dave Leech who has been observing cuckoos and their relationship with their hosts at this site and others. Here cuckoos parasitize around 5-8% of the reed warbler's nests and seem to be thriving, so in the face of huge decreases in the numbers of British cuckoos, could the reed warbler present them with a lifeline?