Yellow-billed Stork Colony

Yellow-Billed

STORK COLONY

[WRITER: John Coppinger - owner of Remote Africa Safaris ] [ PHOTO: Remote Africa Safaris ]

Each year, beginning in February, a wondrous spectacle unfolds in the Nsefu Sector of the South Luangwa National Park. The largest and most long standing yellow-billed stork colony in Zambia is situated in Chipela lagoon, a short distance from the Nsefu Luangwa Wafwa (oxbow lagoon or literally ‘Luangwa which has died’).

It is not clear exactly how long this colony has been in existence but Norman Carr describes it in his book ‘Valley of the Elephants’ in the 60s. Within the lagoon a dozen or so muchenja trees (Diospyros Mespiliformis) have

colonised various islands and it is in these trees which the storks fabricate their nests. The site is seasonally inundated and this is the fundamental reason that the birds are attracted here as the flooding protects the nests from mammalian predators.

The birds begin congregating in late January, construct their nests early in February and lay their eggs later in the month. According to my observations over the past several decades, the first week of February is critical – should the rains have been sufficiently abundant and the lagoon already flooded, the birds immediately scurry about, excitedly competing for suitable material from the surrounding area and commence nest construction. A boom year is guaranteed. Not only does the flooding provide protection from land-based predators but the inundation of marshes and lagoons triggers an influx of fish, providing plentiful food for the birds.

An estimated thousand nests, each with two to three chicks, will result and several months of fascinating viewing is now assured. As with many storks, hatching of young is not synchronised, resulting in significant differences in body size of the brood occupying a particular nest.

March, however, is traditionally the wettest time of year in the Luangwa Valley and consequently access is very difficult. In our early years of operation, when we offered River Safaris from Tafika, we would access by boat but even that was difficult and hazardous, due to fluctuating water levels. Sometimes we would trudge in through the mud from the main river, but this invariably became rather arduous with boots being swamped with mud and water.

From early May, by which time we have re-constructed our roads, access is possible and comfortable viewing is guaranteed. By then chicks of varying ages may be observed, the youngest of which are still downy white balls of fluff. All are still nest bound. There is a cacophony of rasping bird call, with insatiable nestlings screaming for food. The trees are covered in guano by now and are almost completely white. The adults are flying backwards and forwards, bringing food back to the nests and sometimes materials for nest maintenance. Many come from a great height, folding their wings in a dive and whistle their way down, finally side slipping onto their nests.

In a dry year the nests will be considerably fewer and the colony may be only half the size expected in a good year, but this still results in a truly wonderful spectacle.

Both parents undertake guarding and feeding duties for the newly hatched young. Several nearby lagoons and the Luangwa River itself provide fish stock for this purpose – the birds gorge on small fish, return to the colony and regurgitate the catch for their young… an efficient and safe means of transporting and delivering food.

Several fish eagles and sometimes martial eagles are present, waiting for an opportunity for a free meal. Each time one of them launches into flight the volume of bird call reaches a new frenzied high, alerting all members of the colony that danger is present. Birds of prey are wary of the adult storks, their sharp beaks presenting formidable weapons, but unattended nestlings are easy prey.

Large cats often predate on the storks and in recent years we witnessed a particular leopard regularly hunting the birds, even leaping up and pirouetting in the air in attempts to pluck a bird out of the sky.

By May it is usually dry beneath the colony and several crocodiles, together with numerous undertaker-like marabou storks, lurk, waiting for an opportunity. Sometimes a nestling is shouldered out by a neighbour and sometimes food brought back by the adults is dropped. Sometimes nothing is presented, but they have learnt the art of patience and sooner or later their wait will pay-off.

Once fledglings have taken their first leap of faith, they spend much of the day on the ground beneath the trees. It is a comical sight to observe them resting on their haunches, bowing forward and backward, loudly squawking and begging for food from the adults. Those which do not belong to a particular brood will feign complete disinterest, but will watch keenly from the corner of their eye and dash in to steal some fish should the adult bird regurgitate. This results in much consternation and bickering amongst all concerned.

By the end of July all the birds have reached maturity and the colony is abandoned. Peace returns to the scene, the white guano on the trees remaining testament to the grand event of the previous months.

It is notable that most yellow-billed stork colonies throughout Africa consist of no more than 50 nests, so the Chipela colony is significantly larger than any other recorded in the birds’ range. It is a wonderful spectacle and a big highlight for early season visits to the Nsefu sector of the South Luangwa National Park.