The return of the cuckoo to Wicken

Wicken Fen - Cuckoo in flight

The distinctive call of the cuckoo is said to announce the arrival of spring and Wicken Fen Nature Reserve is one of the last strongholds for cuckoos in the country. 

With the arrival of April, Wicken Fen bursts to life. The air is filled with striking birdsong, as residents and summer migrants sing to proclaim their territory and attract a mate.

The European cuckoo

The European cuckoo is about the size of a dove and both sexes have bluey-grey backs and heads, with brownish white barred chests. They spend most of the year in Southern Africa returning to Britain in April to breed. 

The cuckoo population has declined by a worrying 60 percent in the last 30 years, but thankfully Wicken Fen remains one of their strongholds with an average of five or six breeding females returning to the Fen each spring.

A tale of murder, mystery and deceit

Reed warblers will also arrive from over-wintering in Africa during April and will be busy nest building along the lily-lined Wicken Lode. Their tiny intricate nests are a cleverly woven deep cup, threaded between three or four reed stems, hidden deep amongst the reeds. 

Little do they know that they are about to become leading characters in a gripping tale of murder, mystery and deceit to rival any Agatha Christie plot.

Parasitic breeders

Cuckoos are one of a handful of species throughout the world that are parasitic breeders. They lay their eggs in the nests of another species, leaving all the nurturing to the host species. 

Individual female cuckoos can only dupe one host species. At Wicken Fen, the hosts in recent years have been reed warblers, but other host species could include dunnocks, meadow pipits and pied wagtails.

The switching of the eggs

A female, heavy laden with egg, will lie in wait in the tree tops above the Lode bank, staking out unsuspecting warblers nests. 

The moment they leave the nest unguarded she will swoop down, lay her egg and remove one warbler egg, the whole process taking as little as 10 seconds. Her egg will mimick the Warbler’s greenish eggs, albeit somewhat larger.  

" It is one of nature’s mysteries - why do the warblers incubate an egg clearly much larger than their own – or look after a chick so obviously unlike their own?"
- Howard Cooper, Wicken Fen

Murder in the nest

Once hatched the cuckoo chick has one thing on its mind – murder! 

Naked and blind it struggles to remove any un-hatched eggs and young warbler chicks from the nest to eliminate competition for food. In only two weeks, the young cuckoo will have virtually outgrown the nest and will already be about three times the size of the adult warbler with an appetite to match.   

Wicken Fen - Reed Warbler and Cuckoo chick
Wicken Fen - Reed Warbler and Cuckoo chick

The call of the cuckoo

The last calls of the cuckoo are heard in early July as the adult birds depart after their brief stay for their journey to Southern Africa.

Their young fledglings will remain under the care of the warblers and will eventually head south themselves in August or September - hopefully to return to Wicken Fen next spring.

Listen out for them in the East of England

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