Sunday May 28 2017

An encounter with a brood parasite

The Klaass Cuckoo is a parasitic bird that

The Klaass Cuckoo is a parasitic bird that depends on other birds to brood and feed during its pre-flight stage. Photo by Matthias Mugisha.  

By Matthias Mugisha & Pearl Eyes

I have been photographing birds for a couple of years without a surprise until recently, when nature unveiled a sight to behold.
While on one of my birding expeditions in Kasangati, I was attracted by an unusually noisy bird. It took me long to comprehend what I saw.
Two different bird species sharing a meal. One big, one tiny. The tiny bird was feeding the giant that could have easily swallowed.
A closer look revealed a male Variable Sunbird feeding an oversized young noisy and hapless immature bird.
The young bird was a Klaass Cuckoo (Chrysococcyx Klaas) from the Cuculiformes Order of the Cuculidae family.
The sun bird flew away before I could take a picture but the cuckoo remained. It was clear this was a classic case of brood parasitism.

Some cuckoo species like the Common Cuckoo and the Klaass Cuckoo are known as obligate brood parasites which cannot complete their life circle without exploiting a suitable host.
Was the male sunbird the host? It seemed so.
The story starts when a female cuckoo stealthily lays eggs in nests of other species leaving the host bird to incubate the egg, thinking that the egg is its own and also care for the chick.
What happens is that the female cuckoo removes the host’s egg from the nest and replaces it with its own.

To avoid the eggs being detected, brood parasites lay ‘mimetic eggs’ that resemble the host’s eggs as closely as possible.
A female cuckoo lays about 24 eggs in one breeding season distributing the eggs in different nests.
This kind of parasitism negatively affects the reproduction of the host birds. Consequently, many host species have developed defences against brood parasites.
In reaction, brood parasites have also invented techniques to counter these defences resulting in sort of an arms race.
When the host birds learn how to recognise parasite eggs and eject them from the nests, the parasite birds, especially the Cuckoos, counter this by evolving eggs that resemble the eggs of the host bird.

Other defences developed by different birds include, warning calls, attacking the parasite, concealing the nest, shifting the breeding season not to coincide with that of the parasite and ejecting the parasitic egg or the young parasite.
Sometimes, ejecting the egg carries a heavy price. Some brood parasites like the Brown-headed Cowbird (Molothrus ater) a North American bird exhibits mafia- like- behaviour when its eggs are ejected from a nest.
It retaliates by destroying all the eggs in the host nest. As a result, the victim birds may know the presence of a parasite egg but leave it in the nest fearing the consequences of ejecting it.

Memorable moments
As I stood there trying to understand what was going on, the young cuckoo started making noise, and opening its mouth wide. Within seconds, the male sunbird came back. Its head almost entered the cuckoos mouth as it fed it. The whole drama took a few seconds and the sunbird flew way.
Cuckoo chicks hatch after an incubation period of 11-12 days. Their survival depends on their ability to exploit the hosts parental care, at the expense of the unrelated nest mates.
In this case, the cuckoo chick destroys the host eggs or kills the host nestlings and starts loudly begging for food while mimicking the host young to avoid being deserted by the mother whose chicks it has killed.

The parasite chick remains in the nest for up to about 21 days and stays with the host bird for up to 25 days. When the chick starts flying, you cannot miss it.
It loudly begs for attention from the host bird by flapping its wings and making loud noises.
I stood there watching, the young cuckoo again employing the attention- seeking techniques.
I knew the host bird was coming. This time, it was the female sunbird.

Feeding time
For two hours, both male and female sunbirds took turns to feed the monster chick. It was so huge that it would have swallowed its ‘foster parents’ with ease had it wanted to.
Eventually I lost the birds as the cuckoo chick flew from one place to another after each feeding session. Nevertheless, for the next four days, it was easy to locate and photograph this natures phenomenon.
Thanks to the noisy chick. It was clear that the sunbirds were overworking themselves by feeding mostly nectar to a giant chick with an insatiable appetite. Cuckoos usually eat insects and butterflies.
When the parasite chicks grow up, they fly away without warning and ‘thanking’ their hosts. The female parasite chick might probably return to its birthplace to do what their mothers did- place their eggs in other birds’ nests.
And on day five, the chick disappeared for good.
Additional Sources: National Academy of Sciences of the USA, Mark E. Hauber and Kevin M. Pilz- Museum of Vertebrate Zoology, University of California and Nature Uganda.

Cuckoo species

Common Cuckoo
It is a member of the cuckoo order of birds, Cuculiformes, which includes the roadrunners, the anis and the coucals.

Cuculus
It is a genus of cuckoos which has representatives in most of the Old World, although the greatest diversity is in tropical southern and southeastern Asia.

Coucal
It is one of about 30 species of birds in the cuckoo family. All of them belong in the subfamily Centropodinae and the genus Centropus.

Couas
They are large, mostly terrestrial birds of the cuckoo family, endemic to the island of Madagascar.

About the cuckoo

The cuckoos are generally medium-sized slender birds. Most species live in trees, though a sizeable minority are ground-dwelling. The family has a cosmopolitan distribution, with the majority of species being tropical. Some species are migratory. The cuckoos feed on insects, insect larvae and a variety of other animals, as well as fruit. Some species are brood parasites, laying their eggs in the nests of other species, but the majority of species raise their own young.

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