The ecology of bustards in Nairobi National Park and the Kitengela conservation area, Kenya.

Abstract

Field research was done on various aspects of bustard ecology in Nairobi National Park and the Kitengela Conservation Area, between October 1986 and September 1987. The Kori (Ardeotis kori), White-bellied (Eupodotis senegalensis) Black-bellied (E.melanogaster) and Harlaub's (E.hartlaubii) Bustards were found in the study area during this period. Population densities of the four species were estimated by the road transect method. A series of thirty four estimates were made, covering all the seasons included in the stuJy. The White-bellied Bustards were found in the highest densities, whi le Kori Bustards had the lowest throughout the study. Seasonal differences were significant for the Whi te-bellied, Black-bellied and Hartlaub's Bustards, but not for the Kori Bustard. Activity budgets for White-bellied and Kori Bustards were constructed using the scan and instantaneous point sampling techniques. Both species exhibited noticeable acti vi ty patterns on a diurnal scale, wi th feeding featuring most prominently during early mornings and late afternoons. Resting was concentrated in the early afternoon hours. Results obtained by the two techniques showed cons ide rable agreement. Habitat utilization was, analyzed on the basis of the encounters made with bustards in the various hab itat types available in the study area. Grasslands were found to be the most preferred habi tat for .Forag ing by both Whi te-bellied and Kori Bustards. The preference for more woody" habitats increased when temperatures were high, as in the middle hours of the day or during the dry seasons. Group sizes for White-bellied Bustards ranged from 1 to 6 with a mean of 2.2 individuals while Kori Bustard groups ranged from 1 to 5 with a mean of 1.4. Sex ratios for both species of bustards did not differ significantly from unity. Home ranges were estimated for five g'roups of White -bellied Bust ards, based on the observer's accummu1ated knowledge of their space utilization. Results indicated that White-bellied Bustards maintain definite home ranges, at least over some period of time. Kori Bustards did not display any home range behaviour. The food habi ts of bustards were studied by direct observation. The faecal pellet analysis technique was also used in the case of tkQ.. White-bellied Bustard. Bustard diets were found to be comprised of both plant and animal materials. It was not possible to quantify the breeding behaviour of bustards, as only one case of nesting was observed in the Kori Bustard during this study. In this case, a female was found sitting at the nest on every visit, with no other Kori Bustards in the close vicinity