By Colin Jackson
Anyone visiting Kenyan coastal towns or hotels cannot avoid noticing the large number of noisy black birds frequenting piles of rubbish, congregating on telephone wires, chasing chickens and also very likely stealing food off your plate in the restaurant.
Welcome to our most abundant resident, the House Crow or Corvus splendens (formerly the ‘Indian House Crow’) which is a member of the family Corvidae, but an alien species of crow to Africa.
In Kenya we have six species of indigenous crow, but only one on the coast, the black-and-white Pied Crow (Corvus albus), which is also commonly found alongside the House Crow but in far fewer numbers.
The House Crow is indigenous to the Indian sub-continent and was introduced to East Africa first in Zanzibar in 1891, initially as a form of ‘pollution control for rubbish dumps, but by 1917 was rated as a pest with a bounty awarded for any dead crow or egg brought in.
The crow later spread to mainland Africa and up to Mombasa where it was first recorded in 1947. From there it spread north and south becoming ‘common’ in Malindi in the late 1980s and is now in all the coastal towns and inland as far as Voi.
There is now even a small population recently established in Makindu, some 280 kilometres inland, and unconfirmed reports of it being in Machakos. It has become a serious pest in many places in Africa from Cape Town to Djibouti.
Like so many introduced alien animals and plants worldwide, it has been extremely successful, proliferating into the large numbers of birds that can be seen today — counts as much as five years ago in Malindi reached 5,000 birds; Mombasa probably has a population of several hundred thousand and in 2009 the population in Tanzania was estimated at over one million.
Voracious predators
As with most alien, introduced species, the House Crow has created a number of problems both in the natural ecosystems and for human communities. One can argue that the crows feed on the organic rubbish discarded by people and therefore perform an important cleaning job without which the trash problem would be far worse. This is of course true within limits, but in fact the problems far outweigh the advantages of this:
* The House Crow is an extremely voracious bird predating other small (indigenous) birds’ nests, eating the eggs and young and destroying the nest. As well as direct predation, they will also specifically harass and mob a wide variety of birds for no apparent reason other than to cause distress. I have personally seen a House Crow chase a Crab-plover off the beach in Watamu and continue to mob it for 2-300 metres across the water. This behaviour has led to a decline in the diversity of indigenous bird species where crows occur.
* House Crows predate on small reptiles and mammals thus reducing the wider biodiversity in areas where they are found.
* House Crows cause direct and severe losses to agriculture and animal husbandry, taking eggs and chicks of free-range poultry, attacking new-born kids and calves, and feeding on germinating maize, sorghum and other crops. Crows are extremely effective predators and will even work in teams — one to distract the adult chicken while another will snatch one of the now unguarded chicks. People along the Kenya coast have lost significant sums of money investing in chicken farming only to have them annihilated by House Crows. Villagers have also said that they are afraid to leave their small children unattended outside for fear of attack by aggressive House Crows.
* Being a natural scavenger and ‘thief’, House Crows are particularly effective at stealing food from stalls and even from customers’ plates in restaurants and hotels.
* A significant proportion of House Crows diet is human-generated rubbish, which is often carried some distance from the rubbish dump to eat. This spreading of decomposing rubbish clearly increases the risk of spreading disease. Furthermore, below the regular roosting and breeding sites considerable ‘guano’ can build up from the droppings — which if in an urban area can also cause pollution and risk of disease for humans. House Crows have in fact been shown to be carriers of up to eight human parasites. Crows also make a lot of noise — which for many can be significant ‘noise pollution’.
Over the last 25 years considerable experience has been gained from House Crow control programmes in Djibouti, Malindi, Mombasa and Zanzibar. In Zanzibar, trapping and a carefully supervised poisoning using a specialised avicide, a poison specifically designed for birds, reduced the House Crow population in Zanzibar town by 95 per cent, and over the whole island by 75-80 per cent in five years.
Crow traps can indeed be very effective (between 2011 and 2013 some 1,580 crows were caught and killed in traps in Watamu), however they are very labour intensive, require constant supervision and maintenance and also regularly trap birds of prey such as African Goshawks (Accipiter tachiro) attracted into the trap by the ready feast of crows.
Effective poisoning
Other methods have also been employed with varying success — pricking (and therefore killing) eggs, paying a bounty for every crow or egg brought in by members of the public, and even direct shooting of crows. While these all can work to a certain extent, really only the poisoning has been proved to be at effective on a large scale.
Poisons, quite rightly, raise a lot of concern for anyone aware of conservation issues in that they are directly to blame for the extreme crash of many raptor populations and in particular our vultures. However, the poison used, Starlicide, was first produced in the United States specifically to control European Starlings (Sturnus vulgaris) where they are a major introduced alien pest. As poisons go, it is particularly ‘safe’ as it only affects the bird eating it directly (anything eating the dead bird is unaffected as the poison metabolises very fast).
Furthermore, the way in which it is used means that extreme care is taken to ensure that only House Crows take the poisoned bait through careful observation and monitoring of poisoned bait by a trained poisoner. Any other species of bird or animal such as dogs et cetera that
might look interested in eating it are immediately chased off — but in fact, House Crows are so voracious anyway that they effectively out-compete anything else from taking the bait.
The same poison was used in a poisoning programme in Watamu and Malindi between 1999 and 2005 coordinated locally by A Rocha Kenya, a conservation organisation based in Watamu, with support from Turtle Bay Beach Club and the Driftwood Club together with the Malindi Green Town Movement, Malindi Museum Society and other local hotels. It was a very low-level programme, but which within a year had reduced crow populations to a mere five or six birds in Watamu and 30-40 in Malindi.
North and south of Mombasa, by contrast, successful initial control work carried out in the 1990s was not followed up and the pest has re-established itself.
Crow eradication makes economic sense
In 2005, however, the Pest Control Products Board disallowed further importation of the poison due to the correct procedures not having been carried out to register it officially in the country, which, to be fair does make sense. However, there has been little obvious will from the government to support and facilitate any attempt to regularise the importation of the poison and careful monitoring of its use.
Reducing House Crow populations provides great economic and conservation benefits, and control techniques are now well understood and highly effective. In Tanzania a full on crow eradication programme has been in operation since 2010 and well over half a million House Crows have successfully been killed.
However, a concerted and well-coordinated push is required using all means possible in all locations where House Crows occur in order to eradicate them. Indeed, poison is really only effective for large numbers of crows — when you get down to only a handful remaining, probably putting a handsome bounty on the head of each crow and spreading the word among the local vijana (youth) would be the most effective way of eliminating the last few.
House Crows are a voracious and aggressive pest that directly and significantly impact both local indigenous biodiversity and humans. One thing is certain, that if the menace is not rapidly met head on and dealt with very soon in Kenya, House Crows will be found in Nairobi where, with the prolific levels of organic waste left open in a multitude of locations, they will rapidly increase in number and will be effectively be impossible to control, let along get rid of.
A focussed, concerted effort should immediately be made, led by Kenya Wildlife Service whose remit is to protect our indigenous biodiversity, to eliminate crows from all inland sites using direct control methods while pushing the process of getting Starlicide registered with the Pest Control Products Board. Thereafter a tightly controlled programme of poisoning should take place at all major urban centres along the Kenyan coast.
Only in this way do we have any hope of seeing a return of our local wildlife and of protecting the livelihoods of hundreds (and likely thousands) of Kenyans who currently are struggling under the ‘curse of the black crow’.
Colin Jackson works with A Rocha Kenya in Watamu
