THE INFLUENCE OF THE ENVIRONMENT ON BREEDING SUCCESS OF A SUBURBAN POPULATION OF CRESTED BARBETS TRACHYPHONUS-VAILLANTII

I studied the breeding biology of the Crested Barbet Trachyphonus vail lantii in Colbyn, a suburb east of Pretoria, South Africa, for nine br eeding seasons from 1981 to 1989 to examine patterns in annual breedin g success, breeding attempt success in multiple broods, and rainfall. The modal incubation period was 14 days and the nestling period ranged from 28 to 31 days. Average clutch size for all the years was 3,3 egg s/clutch and there was no significant difference in clutch size or num ber of young fledged/nest between years. On average, Crested Barbet pa irs made 2,4 breeding attempts/season. There was no difference in clut ch size or breeding success between the breeding attempts. Crested Bar bets nesting in natural nests laid on average larger clutches than tho se in artificial nestboxes, but had non-significantly lower breeding c i success. Failure to raise Crested Barbet chicks was attributed to pa rasitism by Lesser Honeyguides Indicator minor, bee swarms occupying n estboxes, and flooding of natural nests. Breeding performance was not correlated with rainfall or adult body size. The suburban environment may be less variable than a natural environment, resulting in a stable breeding Crested Barbet population.