A new book about Common Cuckoo, published in Norwegian, contains the revelation that the birds which parasitise Common Redstart in northern Scandinavia may be a separate species.
Though not morphologically different from Common Cuckoo as far as is yet known, the Scandinavian birds may constitute a cryptic species and preliminary genetics have shown that these particular specialists are more closely related to Indian Cuckoo. This pan-Asian species may be a recent immigrant to the Scandinavian avifauna, the authors speculate, and they plan to institute a radio transmission project similar to the BTO's successful tagging of Africa-bound Common Cuckoos last year, regularly covered by Birdwatch.
Superficially, the book's assertions may be supported by the fact that the birds in question winter in the Indian subcontinent rather than Africa, but no vocal or plumage differences have yet been detected.
The new information is published in Norwegian in the book Gjøkens forunderlige verde by Moksnes, A, Røskaft, E and Stokke, G, and is available from http://butikk.tapirforlag.no/en, but as far as can be told, no English translation is yet planned and the findings have yet to be formally published as a scientific paper.
This tantalising snippet comes on the back of many eye-opening studies of cuckoos and parasitic birds in general. The Sound Approach will be outlining their belief, largely on the basis of sound recording analyses, that Common Cuckoo may represent two 'eco-species' in Europe, one specialising in reedbed hosts and the other in woodland hosts. Previously several researchers have suggested that each Common Cuckoo host specialist can be viewed as a different 'race', defined as different from the taxonomic term subspecies, as each female cuckoo is only able to mimic the eggs of one particular host species, indicating a complex differentiation within the species as it is currently understood.