The Crow Must Go

The problem of mass colonisation of exotic birds in South Africa has, for many years, been a hot topic of debate. Examples of exotic birds which have successfully colonised various parts of the county are : House Sparrow; European Starling and Indian Myna. For the most part, these birds are gregarious and often the aggressive nature of the bird leads to displacement of indigenous species, especially in cities, where there is competition for space and resources. Other associated problems include decimation of crops, interbreeding with local species, noise and pollution from faeces.

As in all cases, there is a time when the exotic infestation (or colony) can be eradicated or, at the very least, controlled. Failure to carry out this control may result in the birds becoming resident permanently which, in turn, often leads to the problems listed above.
The emergence of the exotic bird Corvus splendens, or Indian House Crow, in Durban has come at a time when most Durbanites are aware of the problems created by the Indian Myna infestations. Although there are relatively large numbers of house crows in the Metro area (and further afield), it is still possible to control their numbers effectively, although at this stage total eradication would be preferred.

It is estimated that there are currently in excess of 2 000 house crows in the greater Durban area. Herewith a precis of the bird in South Africa, its problems and a brief history of the control exercised thus far in an attempt to eradicate / control.

Corvus splendens, the Indian House Crow, is an exotic bird, which is rapidly becoming semi-localised in cities along the east coast of Africa.
It has become a major problem in countries such as Mozambique, Kenya, Tanzania, Malaysia and Mauritius. The first ever report of its presence in South Africa was in 1972, when a flock of 60 birds was situated at Sodwana Bay.

A population of house crows established itself in Southern Durban and in 1989, the total number of birds was estimated at ±1 600. At this stage, some concern was expressed by the Natal Bird Club, over the negative impact the crow may (and does) have on local bird populations. In 1989, the Durban City Council passed a resolution to engage an eradication campaign. The Parks Department, City Health Department and Natural History Museum were tasked with the feat.
The reasons for eradication are :-

• 1.HEALTH THREAT - Corvus splendens is a vector for diseases and human pathogens, such as cholera and the spread of salmonella and enteroamoeba.
• 2.It constitutes a major threat to urban and suburban wildlife, killing or displacing indigenous fauna as well as domestic pets and small livestock, for example, poultry.
• 3.The nests are constructed almost entirely of wire and this poses the threat of short-circuiting electrical installations.
• 4.The flocking nature of the bird could create an air strike hazard, as the populations are concentrated in the Merebank area, near Durban International Airport.
• 5.The droppings at the roosts and feeding areas, together with the noise generated, also pose environmental problems. The droppings have been known to strip paint off walls and deface statues.
• 6.The bird is an aggressive and opportunistic feeder, that will snatch food from an unsuspecting child and attack the orchards of subsistence farmers, stripping fruit trees and decimating crops.

The initial campaign was a success and, over a four year period, the crow population was whittled down to an estimated 100 - 200 birds. Techniques such as shooting, trapping, anaesthetising and nest destruction were employed. However, in 1994 a lack of staff and a subsequent shortage of the prescribed drug used, saw the increase of the crow population.
In April 1999, the Durban City Council again resolved to implement a control programme. This was based on the increasing number of complaints concerning the house crow, the problems listed above and the fact that the population was breeding so rapidly. Durban would be facing an infestation of over a million birds in probably less than ten years.

Whereas the original 1989 programme involved the Health and Parks Departments, it was found that the lack of dedicated staff, on a daily basis, was one reason for the lack of success. It was proposed and agreed that a conservationist from the Parks Department would be involved with guiding the program and a consultant was contracted to do the day-to-day implementation work. The consultant is a specialist in the field of Indian House Crow control, as he was involved with the 1989 eradication campaign, at the time working in the Vector Control Department of City Health.

The barbiturate / immobilising agent, Alpha-Chloralose, has been used with limited success for the past 10 years. This is due mainly to the fact that the compound is slowly metabolised and birds, having ingested the agent, start to feel and display the effects within 5 - 15 minutes. This results in "spooking" and birds become permanently bait shy.

Alpha-Chloralose has been applied in the following manner :-

Infested areas (usually in the south Durban industrial basin) are pre-baited for 3 - 5 days, to establish a feeding pattern. The drug is then mixed in with the same amount of pre-bait and presented in the same area. Pre-baiting and baiting is usually done just before dawn, before the birds move off the scavenge. It was found that using chicken or tuna worked best, for two reasons :

• 1. The birds, which are carrion eaters, feed readily.
• 2. It eliminated many other non-target species of birds
• 3. Birds feeding (or not) are monitored from a distance and once the crows have moved off, excess bait is removed and kept for later use.

In mid 1999, a visiting vermin control consultant, involved in house crow eradication in East Africa, introduced the Durban team to a whole new approach to invasive bird destruction. A new design of bird cage was subsequently built and is yet to be tested; a change in techniques of bait distribution; type of baits used and, of utmost importance, an introduction to an alternative avicide. This drug is species specific, with no secondary poisoning and, unlike the drug currently used, takes effect some 18 - 20 hours later. Although the product has no secondary poisoning and is species specific, its application and use must be carefully monitored at all times. The Parks Department made application and was recently given authority to import a limited amount of the new drug, which is to be used on an experimental basis. Authorisation was granted by the National Department of Agriculture, Registrar of Act 36 of 1947.

The threat of public outcry is a serious issue that has had to be addressed. To date, no negative press has been given, probably due to the fact that the house crow is such a pest in the industrial, business and particularly residential areas where it occurs, that residents welcome any action to rid them of this pest. The Ethekwini Parks Department also has the full support of the KwaZulu-Natal Conservation Services, the Natal Bird Club, the Wildlife Society, the SPCA and Birdlife Africa. It is hoped that the next phase will continue to receive the help and support which the eradication team has experienced over the past 10 years.

People with complaints regarding the Indian House Crow, or knowledge of possible roosts or active nests, should contact Mr Ross Crouch of the Ethekwini Parks Department on 031-3124466. Only complaints pertaining to the Durban Metro region would receive attention.