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, a huge swampy area located in Sudan.
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!
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.
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.
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!  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.
It was a rather long trip to Kasanka National Park in Zambia so, departing from Harare on 3 October, we decided to break it in lake Kariba as we anticipated an easier border crossing there. As expected the frontier was quiet and soon we were settled at our hotel in Siavonga in Zambia from where we admired lake Kariba and, later in the evening, saw the Kapenta (Limnothrissa miodon) fishing boats leave from the Siavonga harbour next door.
Our hotel at Siavonga. Pic by Mabel de Castro.
A Kapenta fishing boat slides through the calm waters of lake Karibaat dawn. Pic by Mabel de Castro.
We spent the next day traveling to Lusaka and then getting the car filled not only with fuel but also with all needed food and drinks as the journey to Kasanka would start rather early the following day to beat the morning traffic rush, following friends’ advice. I must say that Lusaka has changed greatly since our stay there in the early 90’s and the traffic today is rather chaotic so it seemed like a good idea.
I am sure that, under normal circumstances, an early departure would have worked. However, on the 5 October 2018 someone decided to transport two large boats to Bangweulu by road, also starting the journey early to beat the traffic! This slowly moving roadblock happened to be in front of us and, added to the on-going road works (it seemed that all the roundabouts of Lusaka were being re-built simultaneously!), created an almost impossible and impassable situation!
Another view of the boat lorries. Lots of wheels mean heavy weight I guess? Pic by Mabel de Castro.
One of the boat lorries being overtaken while breaking a few traffic rules… Pic by Mabel de Castro.
The traffic jam around the boat lorries. Pic by Mabel de Castro.
A view of the two boat cabins being transported. Pic by Mabel de Castro.
Another view of the boat cabins. Pic by Mabel de Castro.
The “Times of Zambia” reporting on the problems caused by abnormal trucks such as the ones we encountered.
There were three enormous lorries, frequent on southern African roads, escorted by the respective pick-ups with flashing lights and red flags warning of the hazardous nature (and ridiculous size!) of the cargo being escorted. The one we met first (the last in the convoy) carried two ferryboat cabins side by side while the other two lorries in front of it transported a hull each!
Overtaking was not in the menu as shown by the amount of traffic around us, so we followed this mad procession for about forty-five minutes. Through our walkie-talkies we discussed the situation and possible options until we agreed that we needed to break a few traffic rules if we were to pass them. The opportunity presented itself at one of the road works and we managed to squeeze through some rough terrain and “No Entry’ signs until, the moving boats overtaken, we returned to the now free road.
Another view of the overtaking manouvre showing the clear road ahead. Pic by Mabel de Castro.
The trip to Kasanka was rather long and uneventful but for our drive next to the interesting “Congo Pedicle” in French la botte du Katanga (Katanga’s boot) that squeezes Zambia into two rather separate areas. The road between Kapiri Mposhi and Serenje touches the southernmost tip of the Pedicle so the Democratic Republic of Congo was in full view. Although we can say that we saw and almost touched the Congo, I am sorry to inform you that it looked just like Zambia…
Of interest, however, is that the Pedicle was the result of colonial negotiations that fought for the control of the mineral wealth of the area. The final word of how long the Pedicle would be was with the King of Italy who drew a north-south line (following a longitude line) where the Luapula River was thought to exit from the Lake Bangweulu swamps!  With that rather random action, he left his mark in Africa.
The map of Zambia showing lake Kariba and Siavonga in the South and Lusaka (large pebble). The kidney shaped seed indicates the Congo Pedicle that divides Zambia into two lobes. The tip of the porcupine quill shows the area where we drove next to the DR Congo. The pear-shaped and red seeds indicate Kasanka NP and the southern part of the Bangweulu swamps, where we were.
We got to Kasanka National Park in the afternoon and camped near the Kasanka River at the Pontoon 2 site. These campsites are very shady and have good ablution facilities. The park is managed jointly by the Zambian Kasanka Trust and the Zambia Department of Parks and Wildlife. The Trust is, in turn, supported by two trusts based in the UK and The Netherlands. Created in 1985 it implements a private-public management model conserving wildlife while supporting the adjacent communities.
Kasanka cellphone docking station!
Cellphone docking station, Kasanka NP style!
Pic by Lola Castro.
A recent map of the Kasanka National Park showing the Pontoon Campsite and the Fibwe hide.
Our camp at Pontoon. Pic by Lola Castro.
Our camp at Pontoon. Pic by Lola Castro.
As the river was next to our tents, every morning we had a good view of Sitatunga (Tragelaphus spekii) and Puku (Kobus vardonii) -both uncommon antelopes- while we also heard hippos in the narrow Kasanka river. All animals were rather shy except for a couple of Bushbuck that daily walked near our camp.
A female sitatunga at the Pontoon swamp.
More Puku at the Pontoon area.
An amphibious antelope, the Sitatunga is restricted to wetlands. Although still classified by the International Union for Conservation of Nature and Natural Resources as of “Least concern”, habitat loss threatens its survival. Loss of wetland areas has isolated populations and the burning of large areas of the Bangweulu and Busanga areas placed them under direct threat and reduces their food supply.
Another female sitatunga.
A female sitatunga and offspring at the Pontoon swamp.
A group of puku antelopes watching the photographer.
A female sitatunga grazing in the Pontoon swamp.
A serious looking hippo found during our walk.
The next two days saw us exploring the park where we observed herds of Puku, more Sitatunga and one hippo during a walk. We also continuously heard (more than saw) the three-note call of the Red Chested Cuckoo (Cuculus solitarius) calling all the time from the canopy above our camp, while the swamp next to our camp offered good sightings of water birds and fish eagles, their haunting calls adding to the beauty of the place.
Although hyenas, buffalo and elephants are present in Kasanka, camp life was peaceful but for the biting flies that were a bit of an issue, particularly for Frank that reacted strongly to their bites. As repellents did not work well, apart from covering himself with appropriate clothing, when the “attacks” were intense, he performed a variation of what I believe was a national Dutch wooden clog dancing to -mechanically- get rid of them!
The vegetation at Kasanka deserves a special mention. Briefly, there are [a?] many different habitats in a relatively small area . Along the extensive floodplains and “dambos” sprinkled by termite mounds there are patches of primary miombo woodland with trees up to 20m in height although the norm is much less as it has suffered by past agriculture and/or fire. Where the woodland has been damaged there is secondary miombo and it is here that we find the “musuku” or Wild loquat (Uapaca kirkiana), the main food for the migratory African Straw-coloured Fruit-bats (Eidolon helvum).
The view from the platform while waiting for the bats to take off. Pic by Mabel de Castro.
One of the large trees at Kasanka. Please note Frank near it. Pic by Lola Castro.
Dusk at a platform. Pic by Lola Castro.
Some spectacular trees are also found in the remnants of different kind of forests. Among them are the shady Red or African mahogany (Khaya nyasica), African locust bean (Parkia filicoidea), Water berry (Syzygium cordatum) and Quinine tree (Rauvolfia caffra) to name a few. We did enjoy great shade provided by Red mahogany trees at our camp at Pontoon.
Since our first visit in the 90’s Kasanka has become world famous because of its bat migration. The park leaflet claims that ten million bats travel to the park in October-December of each year and Richard Attenborough documented the latter for the BBC in one of his well-known videos  and it is truly amazing and well worth watching.
Video credit: BBC.
We climbed the eighteen metres of the Fibwe hide, built on a large African Mahogany tree. From up there we had an uninterrupted view of the Kapabi swamp. Fibwe is best known for offering good sightings of Sitatunga. However, as we had the latter next to our Pontoon campsite, our purpose was different: to check for the arrival of the bats, hoping against hope, as it was too early in October for their arrival!
Although we had great sightings of Schallow’s Turaco and Blue monkeys (Cercopithecus mitis) , no bats were on sight and we were rather crestfallen when we climbed down from Fibwe at sunset on the last day of our stay.
After a couple of minutes drive heading for our camp we saw a large cloud of birds. Amazed by the large numbers we stopped to have a better look through our binoculars. We identified swallows but, together with them, we also saw larger birds. Soon we realized that in fact there were bats! We were one of the first to witness the first arrivals of the 2018 migration! We would not leave Kasanka “bat-less”!
Over dinner we discussed that we could shorten our time at the Bangweulu wetlands and have an extra day at Kasanka on our way back to have a good look at the bats as more were expected to arrive everyday from then on. Agreement was immediately reached and we booked an extra night as well as morning and afternoon guided tours to see the bats.
So, after our Bangweulu wetlands sojourn that I will describe later, we came back to Kasanka on the 11 October to observe the bat migration. While discussing the details of our next morning bat watching, our enthusiasm suffered a setback when Ruston -our guide- casually announced “we would depart for the platform next morning at 04:00hs”! We bravely accepted the challenge agreeing to wake up at 03:30hs and, without further ado, we had an early dinner and were in bed by 21:00hs.
Our early dinner (by Frank) prior to the early morning adventure. Pic by Lola Castro.
The morning started rather tragically for me as I set the alarm clock at 03:00hs rather than 03:30hs to the disapproval of my wife that, unlike me, is not an early bird. Luckily, by the time we reached the BBC platform (similar to the Fibwe and located nearby) things were back to normal.
We already knew that we were all “vertigo-free” people so we climbed to the platform with confidence although it was still dark. We did this with great anticipation and we settled down to wait for the bats while listening to our guide and enjoying a hot cup of coffee. The latter was badly needed as it is amazing how cold you feel in the tropics before sunrise.
We learnt that the bats normally begin to arrive in Kasanka in late October but that this year we were lucky as they were early. Their numbers would build up everyday until, by the last week of November, up to ten million would be crammed into about one hectare of forest (known locally as “mushitu”).
These bats have a wingspan of over one metre and when they roost they look like swarms of honeybees flying in circles until they settle down in a tightly packed mass of bodies hanging from every branch of every tree and even from other bats! Their weight is such that branches break and tragedy ensues as some of the injured get eaten by all sort of predators: crocodiles, monitor lizards, snakes, civet cats and, occasionally, even leopards.
The bats seasonally move hundreds of kilometers, stopping on-route until they reach that relatively small area at Kasanka. Apparently, they congregate here because of the synchronized abundance of fruits, including their favourite: musuku (Wild loquat) but they also feed on the fruits of the Water berry (Syzigium cordatum) and Red milkwood (Mimusops zeyheri).
The millions of bats at Kasanka represent the largest concentration of mammals in Africa with an estimated weight of about three thousand metric tons of fruit bats in one hectare of forest, the greatest concentration of mammalian biomass found on earth.
Everyday the bats leave their roosting area in the evening to find food and they return at dawn to rest in the rather small roosting area. We were about to witness the later while in the afternoon we hoped to see them depart.
While listening to Ruston I could not help feeling sorry for the farmers that dwell near Kasanka and when I made a comment on their difficult situation regarding fruit production, Ruston replied saying that he had never been able to eat a fruit at Kasanka while the bats are there!
Our early morning vigil, waiting for dawn to come and, with it, the bats. Pic by Lola Castro.
After Ruston’s brief we sat silently waiting for the light to increase. During that time I started to ponder how it was known that the bats amounted to 10 million. I concluded that it must have been through a massive release-recapture operation although I doubted that this could be the answer. I was also starting to calculate how much fruit would that bat crowd eat when I was interrupted by Ruston saying that the bats would start arriving to their roosting area below us any time. I made a mental note to find out these facts later .
A few minutes elapsed and then the bats started to appear. Soon they congregated in large numbers over their roosting places resembling a swarm of large bees. Photography was almost impossible so we watched and enjoyed the view. As light increased other animals came to view including White-backed vultures nesting in the trees nearby as well as a Ground hornbill perched very high on a dead tree (the highest hornbill I have seen!).
The perched high above the tree canopy.
Bats about to roost.
Then all bats settled and it was Lola, very observant as usual, that spotted them resembling bunches of grapes well below us in the mushitu trees. As the bats stopped being the centre of attention, we noticed that a number of birds of prey were stalking them. These included Martial, Crowned and Southern Banded Snake eagles. Although we did not see the latter going for the bats, we watched the Martial eagle made a pass, catching one and flying away with it.
The eagle attack disturbed the bats that took off again and, for a while, they circled their roosting area until they settled down again only to be disturbed seconds later when a Crowned eagle (the most beautiful of African eagles for me) flew straight at the roosting area and perched nearby. Ruston told us that the eagle had its nest close by and he pointed out the young eagle calls to its parent.
Bats being disturbed by the Crowned eagle.
The eagle, a resident of the area, was in no hurry and, after a couple of passes that kept the bats unsettled it managed to catch one and perched with it in full view albeit far from us. It fed on its prey for a while until it decided that it was time to bring it to its offspring and flew past us to its nest.
A long distance shot of the Crowned eagle eating a bat.
Time passed really fast and by mid-morning the sun was burning and we were ready to initiate our descent when a group of Crowned hornbills, a trio of Shallow’s and one Ross’ turaco were spotted and intensively watched. Finally, a Blue monkey  appeared on a dead tree and we could admire its beautiful bluish grey coat and its rather long tail. After that final moment, it was time to go.
Coming down from the BBC platform. Pic by Lola Castro.
The BBC hide. Pic by Lola Castro.
Descending from the BBC hide. Pic by Lola Castro.
The bushsnob, accompanied by his wife and armed guard, attempts at explaining something -probably irrelevant- to Lola, the photographer.
The bushsnob and wife back from the BBC hide in the morning, after the arrival of the bats. Pic by Lola Castro.
As planned, we returned for more bat watching in the afternoon as the bats depart in their feeding foray at sunset. We climbed up a new viewing platform recently built near the roosting area and we waited.
The bushsnob waiting for the bats to take off. Pic by Mabel de Castro.
Our companions Lola and Frank getting ready for the bats to leave their roosting area. Pic by Mabel de Castro.
Waiting for the bats in the afternoon.
Nearer to the bat departure during the afternoon. Pic by Lola Castro.
Nothing happened for quite a while and then we started hearing a slight noise as if water started running through the forest: the bats were starting to move. The water noise increased and, suddenly, the bats took to the skies. Although not millions, we watched tens of thousands bats flying around us before moving to their feeding grounds.
Great shot of a bat by Frank Rijnders.
Judging for what we saw during the outings in the morning and afternoon where we saw bats in their thousands, I tried -and failed- to imagine what the sight of ten million bats flying at the same time would be like. I concluded that you must see it to get its real dimension but for that we need to return another time later in the year.
 Dambos are grassy drainage channels and basins with little to no woody vegetation but very palatable grasses. Most woody species grow on exposed termitaria as dambo’s tend to retain water very well. Dambo’s are of a vital importance to grazing mammal species as well as several woodland mammals that choose to graze on the fringes, especially during the dry season (From: https://en.wikipedia.org/wiki/Kasanka_National_Park).
 The rare Blue monkeys live in matrilineal societies as the females stay in their natal groups while males disperse once they reach adulthood.
 Numbers of bats were in fact estimated by counting their numbers through a formula based on numbers of bats per binocular fields, time, distance, etc. by Sorensen UG, Halberg K. (2001). Mammoth roost of nonbreeding straw-coloured fruit bat Eidolon helvum (Kerr, 1792) in Zambia. African Journal of Ecology 39: 213–215 (Abstract seen on 22 October 2018).