Curious cuckoos

One of the most iconic sounds of spring is the call of the male cuckoo, the two notes heralding the changing seasons.

Cuckoos will have just started to arrive in Britain after their long migration from Africa where they spend the majority of the year. They have a fascinating life cycle and cuckoos and their chicks and eggs are wonderfully adapted to parasitising the nest of other bird species. Just two of the 54 species of Old World cuckoo can be found in Europe and here we will take a closer look at the common cuckoo.

Arrival

In late February cuckoos will slowly begin their 10,000km journey to Britain, leaving the rainforests of central Africa where they have spent our autumn and winter. They will have been feeding up on the insects these forests provide ready for the 50-60 hour Saharan crossing which makes up one of the more perilous legs of their journey. Cuckoos make the crossing in one non-stop night flight and sadly many don’t make it to the other side. Cold temperatures, dust storms and high winds could all put bring their migration to a premature end. There are further obstacles for the cuckoos as they navigate their way through hunters in the Mediterranean and possible wet or cold weather on their passage.

The breeding season

Once the cuckoos arrive at their destination (they breed across Europe) the most familiar part of their life cycle begins. Males can be spotted on open perches making their onomatopoeic call, while females have a less-famous bubbling call which they make as they search for a suitable nest. Each female will be adapted to parasitise the nest of a certain host bird, a trait they pass on to their chicks, forming distinct races. The reed warbler and the meadow pipit are the most common unwitting parents to cuckoos, but over 120 species have been recorded with cuckoo eggs in their nests. Cuckoo eggs have a thick shell so the egg can be quickly laid from above the nest while the parents are gone, and the cuckoo chick has a concave back to help roll other eggs out of the nest. They also have a large gape and loud calls, which trigger the parents to bring food despite the often odd appearance of a giant cuckoo chick squashed into a too-small nest being fed by tiny parents.

But this harbinger of spring is on the decline, on the UK red list of birds. An important factor is the increasingly unpredictable weather, which can play havoc with the cuckoos migration flight and their insect food sources. Cuckoos can be spotted on many of the Trust’s nature reserves but are regularly recorded at Hook Common and Bartley Heath Nature Reserve and Blashford Lakes Nature Reserve.