Gareth Huw Davies

Environment

Exit cuckoo, pursued by climate change?

 

Cuculus canorus, RSPB

‘The cuckoo then, on every tree, 

Mocks married men; for thus sings he, 

                                                    “Cuckoo; 

Cuckoo, cuckoo!” O, word of fear, 

Unpleasing to a married ear!’ 

(When Daisies Pied and Violets Blue, by

William Shakespeare)

 

We have had a long association with the cuckoo. I live on the edge of a village in rural Southern England. For 25 years, in the third or the fourth week of April, we would first hear a cuckoo in the countryside to the north of our house.

From then on, we would hear it, or another, or others (I once saw two together flying over my garden) almost without fail, daily, for the next four or five weeks.

Some years the bird arrived a week or so late, after its  prodigious travels from south of the Sahara. Rarely was it earlier than about April 20th. The call of the cuckoo was so predictable, I grew complacent about it. I felt sorry for friends in London who rarely if ever heard the cuckoo in spring. Weren’t we the fortunate ones?

Then, about seven years ago, things changed. In 2011 or 2012 the cuckoo arrived, very late, and called a few desultory times. In 2013 I heard it only once. It was in 2014 when I didn’t hear it at all from our garden. In 2015, there was one call. And nothing since then.

Cuckoos return to the area where they were born, so it is likely that several, and possibly multiple, generations in the same lineage come back to this same jumble of uncultivated fields and hedges and woodland around the nearby canal.

There are no physical changes to explain its absence, no new housing estate built, no switch to intensive agriculture –  although fields close by in another direction are treated with the usual cocktail of chemicals. And have been since we lived here.

The British Trust for Ornithology (BTO) says the UK has lost over half its cuckoos over the past 20 years. For a bird that advertises itself so unmistakably, the cuckoo and its movements are clouded in mystery. Elucidation may come from on-going work the BTO is carrying out. Trackers that the trust fitted, from 2011, to about 50 cuckoos in the UK could help us to better understand their movements. Already it has gathered useful data about migratory routes.

One interesting emerging theory is that the cuckoos, and their progeny over many years, are not returning here because the birds whose nests they use, the meadow pipits, dunnocks and reed warblers, are in decline, or because their breeding season no longer coincides with that of the cuckoo, due to a changing climate. One theory is that they have finished feeding their offspring before the cuckoos arrive to eject them from the nest. Finding no nests in which to lay their eggs, did the cuckoos move on?

So could a delayed spring in 2018, with migrating reed warblers for instance arriving late from the deep south, together with the resident (and also breeding late in 2018) dunnocks and other birds actually restore some order to the cuckoo’s disrupted breeding clock? If only for one year? But surly that would require cuckoos that were raised in the fields around our home before 2011 to have sufficient recall to return here. Is that too long a gap? Or will new cuckoos call in on a speculative search for those now available nests?

Cuckoo calls, or their absence, over the next month or so will provide the answer.