rains

Rain bird

A few days back we have started hearing the by now familiar ‘wip-wip-weeu’ that the rain bird or red-chested cuckoo (Cuculus solitarius) make endlessly at the time the rains should start in Zimbabwe. But, where have they been since their appearance last year?

 

Before I knew much about bird movement and migration, I often asked myself this question. I recall watching in awe widowbirds displaying in Northern Kenya and asking my friend Paul about their whereabouts during the rest of the year. His reply, was that they would go to the Sudd[1], a huge swampy area located in Sudan.

Sudd_swamp Credit NASA (Public domain)

Sudd Swamp -a Flooded grasslands and savannas ecoregion in South Sudan. To the left the river/wetland Bahr al-Ghazal connecting to Lake No (top). This photograph was taken during the driest time of year—summer rains generally extend from July through September. Taken from space, May 1993. Credit: NASA (Public domain).

So, every time that someone asks me now where a particular bird is when it is not seen, I say that it is in the Sudd, a very convenient reply!

The truth about the rain bird is that they are intra-African migrants that breed in southern Africa between September and March, although most arrive in mid-October and the majority are gone by the end of April.

The rest of the year they reside in Sub-Saharan Africa, in countries of Central, East and West Africa, including the Sudd wetlands in South Sudan!

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Rainbird distribution map. Attribution: BirdLife International (2019) Species factsheet: Cuculus solitarius. Downloaded from http://www.birdlife.org on 02/11/2019.

Their preferred habitats are woodlands where they perch high up in the trees. The red-chested cuckoo is usually solitary and it takes on more than a single mate so it is polygamous. Every year they visit our garden where they are occasionally seen while they feed on caterpillars and other insects in the tall msasa trees.

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While in Southern Africa -including Zimbabwe- the rain birds practice brood parasitism by breeding through egg-laying in other bird species nests, some twenty-seven of them! The most common hosts are thrushes and robin-chats and the Cape robin-chat (Cossypha caffra), the Cape wagtail (Motacilla capensis) and the white-throated robin-chat (Cossypha humeralis) are the most popular hosts.

The cuckoo’s resemblance with a small bird of prey (like a sparrow hawk for example) scares the future parents from their nests and the cuckoo female lays the egg that, not always, resembles their hosts’. It is estimated that they lay about twenty eggs scattered in various nests every season. Then it is up to the surrogate family to raise the chick.

Piet-my-vrou_&_cape_robin

A cape robin feeding an almost fully-grown rain bird. Attribution: Alandmanson [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)%5D. https://upload.wikimedia.org/wikipedia/commons/f/f4/Piet-my-vrou_%26_cape_robin.jpg. Downloaded from Creative Commons on 2/11/19

A very interesting biological phenomenon helps the cuckoo chick to have a head start from the other chicks in the nest: the female cuckoo literally incubates the egg inside her for 24 hours before laying it! [1] This ensures that the chick will hatch first and eliminate the competition at the nest.

Cuckoos are great travellers, capable of flying enormous distances during their migration and, although the red-chested cuckoo covers less distances than others, it uses the same mechanisms to do so. These navigation skills are genetically passed on to their young. The latter stay behind to complete their development while their parents depart but the new generation are able to fly back north on their own to join their parents!

Now we only need good rains while we watch the cuckoos until they depart and then we wait for them to announce the rains in 2020.

 

[1] See: https://www.bbc.com/news/science-environment-11401254

A dozen eggs

Luckily it is raining well in Harare. More than we expected so our pool -turned into a water reservoir for a few years now- spilled over and the area became a true wetland! Water was also running from the top of the garden in large rivulets that avoided our dikes and continued unstoppably to the bottom of the garden washing our scarce topsoil. The consequence was that we needed to perform some emergency repairs to our contention dikes.

While digging from the sand the pile that we keep for this kind of work we found a cluster of twelve small eggs! Their shells were flexible so they clearly belonged to a reptile, probably a chameleon.

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Stephen (our caretaker) and I were very excited to find them and went to communicate the good news to my wife as we were sure she would also be happy as I was quite sure them to be chameleon eggs. The news was received only with lukewarm enthusiasm and I was both disappointed and surprised!

It was after a few minutes of thinking that the penny finally dropped so I declared: “I am sure that they are not snake eggs”, trying to convince myself that there were not! “Why not?” was her immediate and rather expected reply. I could not argue so I decided to find out what they were!

I performed a rather thorough check in the Internet and could almost confirm that they were in fact what I thought. However, to keep the peace I agreed to leave them where they were found so that they will continue with their normal development.

Further reading educated me that it takes up to 300 days for chameleon eggs to hatch and the breeders of these animals in captivity start checking for hatching from day 220! So, if you had any hope of learning what came out of the eggs, you will need to wait until next year, if we are lucky to see the newly born emerging from the sand!