Cuckoo – A Bird in Decline

Have you heard a Cuckoo lately?
The Cuckoo is a migrant RSPB Red List bird and has been in decline for 25 years. The Cuckoo population has dropped by 65% over this period. The cause of decline is not well understood but changing climate and trends in host breeding habits are cited, resulting in a fewer number of host nests for the Cuckoo to invade.

Reasons for decline
It is far from clear which are the major factors influencing the falling population of the Cuckoo. UK nesting host decline (dunnock, robin, reed warbler, meadow pipit, Spotted Flycatcher and Pied Wagtail) is possible. Decreases in moth populations which the Cuckoos eat as caterpillars may also be contributing. Farming methods, pesticides and herbicides, general pollution and reduction in habitat perhaps all take their toll as they do with other species of wildlife.
Other explanations suggested are Africa’s changing habitats, farming production changes and the attrition of bird numbers during migration from Africa to Britain. Current estimates are 10,000 to 20,000 breeding pairs in the UK.

The bird has a blue-grey head, back and tail with a darkly barred white underneath, a yellow eye ring and slightly down curved beak. Some females, though not all, are reddish brown (rufous brown) in color. The bird has a long tail and in flight it distinctively beats its wings below its body. Somewhat similar to the sparrowhawk but the Cuckoo has pointed wings and its beak is not hooked. It is small pigeon or dove sized at 33cm, 110gm (13″, 3.9oz)

Breeding habit
The Cuckoo lays its eggs in another species nest after the host female has laid its own clutch. An individual Cuckoo targets a particular host species. Once the parasitic host is found the Cuckoo lays one egg and may eat a host egg or a chick at that time. The Cuckoo will lay 9 to 15 eggs in total although some sources suggest up to 25 eggs may be placed. The Cuckoo chick will systematically eject the remaining host hatchlings when it is two or so days old so gaining the undivided attention of the host adult. The chick rapidly becomes significantly larger than the host adults who must work very hard foraging food to feed the young Cuckoo.

When and where to see in Britain

The Cuckoo is a migrant from sub-Saharan Africa. They arrive in late April to June and leave late July or August, though they may rarely be seen until September. More numerous in southern and central areas they are (sparsely) spread all over the UK. It returns to west, central and southern Africa for the rest of the year, where its decline is also noticed. In Britain the Cuckoo inhabits moorland, open country, farmland, hedges and the periphery of woodland but also enters our gardens in its quest for a parasitic host to lay its egg.

How can we help?
In our gardens, we can feed the hosting species and incidentally encourage other garden birds, Try to refrain from spraying pesticides so encouraging insects in the breeding season. Cuckoos themselves favor hairy caterpillars and have an adapted digestion to process the poisons these caterpillars can contain. They do eat other caterpillars and other insects as do the host birds. A compost heap would become a helpful source of worms and other insects.

Practical information and guidance on feeding, watering and the nesting of garden birds is available on this website, which may help encourage some host birds targeted by the Cuckoo.
The RSPB is the Royal Society for the Protection of Birds its Red List is the RSPB list of birds in most severe decline (greater than 50% or globally threatened).

by Bridie

6 comments to Cuckoo – A Bird in Decline

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  • admin

    Gilberte, Thanks for your comment and inquiry.
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    Bridie R.

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