Thanks to volunteer Phil for his report and photos
Classical music devotees might recognise this title as a reference to a piece by Frederick Delius called “On Hearing the First Cuckoo in Spring”. Sadly for me locked down in Old Coulsdon there will be no such event at Pulborough this year, so I am reminding myself of this sound by writing about these unusual migrants from Africa, seen and heard on the reserve in spring and early summer.
There is something extraordinarily musical about the simple call of the male cuckoo. It consists of just 2 notes which seem precisely tuned to sound frequencies used in music. It wasn’t just Delius who noticed this. Listen to the 2nd movement of Beethoven’s 6th Symphony (“The Pastoral”) and you can clearly hear the cuckoo calling in various places. Beethoven also incorporated the sounds of nightingale and quail, but neither of these is so recognisable as the cuckoo.
I sometimes compare the cuckoo call with the chiffchaff, which also has a 2 note call but this is not tuned in the same way. We enjoy hearing chiffchaff calls in March as a hopeful sign of Spring arriving, but we soon become bored with its monotonous quality. The musical quality of the cuckoo call is difficult to become bored with.
Cuckoos are not always easy to see because they spend much of the time high up in trees. They look rather like a sparrowhawk, having a barred breast which can be seen clearly in this photo near Little Hanger.
Cuckoo near Little Hanger (Phil Thornton)
Despite its evocative call the cuckoo has a dark secret – it is a “brood parasite”. It has a highly unusual breeding strategy in which it raids the nest of a small bird already with a clutch of eggs, turning out one of the eggs and laying one of its own. The sparrowhawk like appearance may be useful to frighten parent birds away from nests to allow the cuckoo to lay its egg. This photo shows a cuckoo on a fence post close to Nettley’s Hide
Cuckoo outside Nettley's hide (Phil Thornton)
As this is not in the more usual place high up a tree I wonder if it might be a female on the lookout for a suitable nest to raid.
The egg mimics the appearance of the host species’ egg, so female cuckoos usually choose the same species of small bird to ensure the eggs have the right colouration. Several species are targeted but most commonly in the UK these are dunnock, meadow pipit and reed warbler. Sometimes cuckoo eggs will be spotted by the hosts and rejected, and research suggests that some species of small bird may be better than others at recognising these.
The owner of the nest will incubate all the eggs until the cuckoo hatches. Very soon the monster cuckoo chick will turn out all the other eggs or chicks from the nest allowing it to be exclusively fed by the host parents. Astonishingly the urge to feed chicks is so strong that they continue to feed the cuckoo chick until it fledges.
Once fledged the cuckoo then must find its own way to Africa for the winter with no help from its true parents, an extraordinary feat of migration undertaken also by juveniles of several other species.
Despite its appearance the cuckoo is not a bird of prey and feeds mainly on insects and has a liking for hairy caterpillars which are not palatable to most other birds. It will occasionally take eggs or chicks.
Sadly cuckoos are declining in the UK and the population is now about 65% down over the last 25 years with only about 15,000 pairs left. So, while it’s impossible not to feel sorry for host parent birds who lose their eggs, they are providing nature a service as the cuckoo is on the red list of highest conservation concern.
Research is ongoing into the reasons for the decline but problems on their migration routes appear to be indicated as one possible cause. Birds in the spring migration tend to have a strong urge to reach their breeding sites as quickly as possible. Some cuckoos undertake a very hazardous crossing of the Sahara Desert as the most direct route between their winter quarters in the Congo and breeding grounds in the UK. Another route via the coastal countries of West Africa has more refuelling opportunities but has the drawback of being significantly longer and taking more time.
Let’s hope that research can provide enough information to suggest ways that we can help the population of these iconic birds to recover so we can continue to enjoy the evocative and musical call of the Springtime cuckoo.