Topic : Land Birds
Article 17 16 January 2007
Oxpeckers – essential partners in the game farming industry
With the proliferation of game farming in southern Africa, it has become essential to protect and expand oxpecker populations as the most effective tool in the biological control of ticks. The main reason for the increase in tick populations on fenced game farms is the lack of fires (controlled hot burns) and absence of oxpecker populations. Game on these farms are fenced in, and cannot migrate to escape the impact of infestations and diseases within these regions. The only effective way to control ticks on game farms is to introduce or protect oxpeckers, and alter the habitat of the parasites (ticks) by burning veld grasses. Strategic placement of breeding boxes (natural or self made) would ease the pressure on natural nest holes in trees, in which oxpeckers normally breed.
Game farms are very often intertwined with cattle farms, so many game farmers have cattle farmers as neighbours. Unlike the management of cattle on farms where dipping programs are undertaken, game cannot be similarly managed for the treated against tick infestations. Game farmers must encourage neighbouring cattle farms to use oxpecker compatible dips (pyrethroyd based dips). Examples of these compounds are Bayticol (Bayers), Curatik (Agricura), Decatix (Coopers), Ectoban (CibaGeigy), Paracide (SmithKline) and Sumitick (Shell). Arsenic and organophosphate based compounds should at all costs be avoided if communities wish to collectively increase oxpecker populations in the neighbourhood.
In natural environments, oxpeckers feed almost exclusively on what they can glean from the skin of large African animals. The bulk of their diet is therefore ectoparasites (ticks, lice, etc), though they do also feed on blood from open wounds. Continual pecking at these wounds is not always beneficial to their hosts, but they do keep these wound clean and prevent both bacterial infection and infestation by Calliphoridae blow-flies. Blue ticks Boophilus decoloratus and brown ear ticks Rhizicephalus appendiculatus are the preferred food tick species for oxpeckers, so the greatest benefit to host animals and game farm owners will be in regions where there are high densities of these tick species.
A bont tick Amblyomma hebraeum female, the main vector of heartwater disease, can produce as many as 18 000 eggs during her life. On average, Red-billed Oxpeckers Buphagus erythrorhynchus consume just over 400 ticks in a day, or about 150 000 annually. In captivity, up to 13 000 tick nymphs or 100 engorged adult ticks have been recorded as the daily requirements of Yellow-billed Oxpeckers Buphagus africanus. This species also has a larger bill size which enables it to feed on bigger tick species such as Amblyomma and Hyalomma.
Status of oxpeckers in South Africa
The status of Red-billed Oxpeckers in South Africa is improving with encouraging expansions from protected areas to farm lands. This species breeds successfully in captivity so re-introduction programs have also been conducted into previously considered marginal areas such as the E Cape. Yellow-billed Oxpeckers were considered to be extinct as a breeding species in South Africa as long ago as 1910, after which only vagrants were occasionally seen. This was mainly as a result of the use of arsenic and organophosphate compounds in cattle dips. Re-colonization took place during the late 1970’s and although the present population is considered still to be small, it is slowly expanding. It is still however regarded as a Red Data species, listed as Vulnerable because of concerns of changes in dipping practices and fears for any increase in the use of arsenic based dips, which could result in the rapid decline in these species once again.
Oxpecker host preferences.
By preference, oxpeckers select large sized hosts that support higher densities of ticks, or choose larger herds when attending smaller-bodied animals. Yellow-billed Oxpeckers normally prefer larger-bodied animals such as buffalo, but preference for host species does vary geographically. Elephants do not normally tolerate the presence of oxpeckers, and other animals such as Giraffe, Warthog, Waterbuck and Impala sometimes reject oxpeckers by head-tossing etc.