The raptor community of Nias Island, Sumatra: Survey and conservation

During a short survey of the diurnal raptor community on the island of Nias in July 1992,I found. seven species of Falconiformes. Three of them were hawk-eagles: Spizaelus alboniger last confirmed in 1886, S. nanus, presumed to be extinct and S. cirrhatus, never cited for the island. These three eagles appeared to be highly endangered because of heavy deforestation but the future of the other raptor species seems more secur

Using Africa’s protected area network to estimate the global population of a threatened and declining species: a case study of the critically endangered White-headed Vulture Trigonoceps occipitalis

The White-headed Vulture Trigonoceps occipitalis (WhV) is uncommon and largely restricted to protected areas across its range in sub-Saharan Africa. We used the World Database on Protected Areas to identify protected areas (PAs) likely to contain White-headed Vultures. Vulture occurrence on road transects in Southern, East, and West Africa was adjusted to nests per km2 using data from areas with known numbers of nests and corresponding road transect data. Nest density was used to calculate the number of WhV nests within identified PAs and from there extrapolated to estimate the global population. Across a fragmented range, 400 PAs are estimated to contain 1893 WhV nests. Eastern Africa is estimated to contain 721 nests, Central Africa 548 nests, Southern Africa 468 nests, and West Africa 156 nests. Including immature and nonbreeding birds, and accounting for data deficient PAs, the estimated global population is 5475 - 5493 birds. The identified distribution highlights are alarming: over 78% (n = 313) of identified PAs contain fewer than five nests. A further 17% (n = 68) of PAs contain 5 - 20 nests and 4% (n = 14) of identified PAs are estimated to contain >20 nests. Just 1% (n = 5) of PAs are estimated to contain >40 nests; none is located in West Africa. Whilst ranging behavior of WhVs is currently unknown, 35% of PAs large enough to hold >20 nests are isolated by more than 100 km from other PAs. Spatially discrete and unpredictable mortality events such as poisoning pose major threats to small localized vulture populations and will accelerate ongoing local extinctions. Apart from reducing the threat of poisoning events, conservation actions promoting linkages between protected areas should be pursued. Identifying potential areas for assisted re-establishment via translocation offers the potential to expand the range of this species and alleviate risk

Another continental vulture crisis: Africa's vultures collapsing toward extinction

Vultures provide critical ecosystem services, yet populations of many species have collapsed worldwide. We present the first estimates of a 30-year Pan-African vulture decline, confirming that declines have occurred on a scale broadly comparable with those seen in Asia, where the ecological, economic, and human costs are already documented. Populations of eight species we assessed had declined by an average of 62%; seven had declined at a rate of 80% or more over three generations. Of these, at least six appear to qualify for uplisting to Critically Endangered. Africa's vultures are facing a range of specific threats, the most significant of which are poisoning and trade in traditional medicines, which together accounted for 90% of reported deaths. We recommend that national governments urgently enact and enforce legislation to strictly regulate the sale and use of pesticides and poisons, to eliminate the illegal trade in vulture body parts, as food or medicine, and to minimize mortality caused by power lines and wind turbines

Ecologie de migrateurs tropicaux dans une zone préforestière de Côte d’Ivoire

Rollers (Coraciadidae) and Ree eaters (Meropidae) have been studied during three years in a guinean savanna — with galleries and patches of dense forest — in the Ivory Coast. Annual censuses of the breeding populations of savanna Rollers have been made by dilferent methods. For the two species a mean density of 1 individual per 4 or 5 hectares has been recorded with a production of young of 22 to 26 %, mainly in May. Three pairs of related species ( Merops gularis and M. albi- collis ; Eurystomus gularis and E. glaucurus ; Coracias cyano- gaster and C. naevius) are compared from an ecological and phy siological stand-point. The first-mentioned species of each pair is sedentary, the second migratory. Two of the three sedentary species are forest birds, while all the migrants are savanna birds, with the exception of M. albicollis which also lives in cleared and cultivated forest. Competition is avoided between the two popu lations through the occupancy of separate ecological niches. Congeneric species live in dilferent biotopes (or at least vege tation layers). Sedentaries hunt more easily in and around dense vegetation (adaptation to the conditions prevailing during the wet season), while the migrants prefer the most open spaces. The diet of the resident birds is more varied, the migratory species being more specialised in their feeding on swarms of winged ants and termites. Migratory species are much better adapted to the exploi tation of this seasonal production or to the appearance of newly accessible prey (ground insects on recently burnt patches of savanna), being able to move rapidly from one place to another and to concentrate locally in large numbers. Dates of arrivals and departures are compared with the calendar of rains and it is suggested that the timing of the migra tory movements in the northern part of the breeding area of these birds is more under the dépendance of the seasons than influen ced by local conditions. But it is possible that the rainy season in the Ivory Coast would be too wet to allow a good survival for the populations of these species ; this could also explain the disappea rance of our breeding Eurystomus glaucurus from June to Sep tember. Merops albicollis, a typical intra-african migrant, shows a premigratory fattening of about 7 %. This occurs at the end of the prenuptial moult and coincides with the beginning of the increase in the size of the gonads

Capacités prédatrices et budgets d'activité chez l'aigle pêcheur, Haliaeetus vocifer

Ten pairs of Fish Eagles Haliaeetus vocifer taken among a dense population in Uganda, were followed at the end of the breeding season to compare the time and energy budgets of breeding and non breeding adults. Fish are usually obtained by diving from a waterside tree. If unsuccessful, the bird searches in flight, an energy-expensive but very rewarding method. The additional food necessary to feed the young is provided m ainly by the male through fishing flights. Another source of increase in energy expenditure related to breeding activities is the more active territorial defense by adults with young than without young. The food consumption of the former is higher than that of the latter ; but the difference is smaller than the increase of the energetic cost of breeding (42 % and 64 % for 1 and 2 fledged young). Thus brood size seems to be limited by the ability of the parents to feed their young and maintain a territory of adequate size or quality, even in the optimal conditions studied. Immature birds suffer he avily from the adults'territorial behaviour, which forces them to make extensive flights and confines them to marginal food sources. This may explain their high mortality rate (83 % during the first four years

Les migrations de rapaces en Afrique Occidentale : adaptations écologiques aux fluctuations saisonnières de production des écosystèmes

Seasonal changes of abundance of diurnal birds of prey have been studied for 50 months in West Africa. Population move ments have been traced through seasonal variations of abundance in adjacent biomes. Relative densities of various species have been estimated by monthly “ road-side counts ”, and correlated with seasonal changes in climate, vegetation structure and availa bility of prey. Five species of West-African Falconiformes perform erratic movements, 13 are partial migrants and 6 undertake regular, long-distance migrations from the rain forest zone to the edge of the desert. Moreover, 17 palearctic birds of prey species occur seasonaly in the area, mostly from September to May. Premigratory fat deposition is uncommon among African migrants, and the moult often takes place during their short range movements. Migrant birds of prey differ in many ways from their sedentary relatives : they are morphologically adapted to hunting in open habitats ; they tend to be very mobile and to exploit locally abundant but transient food sources ; their repro ductive rate is high ; they appear to be very sensitive to the dry heat of the Sahel. On the whole, there is very little ecological overlap between migrant and sedentary birds of prey in the study area. The timing of migratory movements is closely correlated with the onset of the rains, the birds following the seasonal changes of the inter-tropical front : they move northwards with the first rains in spring and southwards at their end in the autumn. This seasonal shift of habitat is also correlated with an increase in the height of the grass cover and sometimes with flooding. The ultimate cause of these seasonal movements appears to be an optimization of the diet of the migrant population. A good correlation has been found between the abundance of migrant birds of prey and that of the grasshopers, their major insect prey. Urban populations of tropical African kites, which benefit from more stable food sources than “ bush ” populations, are also more sedentary. The availability of adequate sources of drinking water in the Sahel zone, is also an important synchronizer for some species. The northern limit of the seasonal movements, as well as the arrival and departure dates of the migrant populations, are on the whole dependent upon the abundance and availability of their major prey species. African migrants generally stay in the southern savannas du ring the dry season when food is abundant and hunting conditions are good. During the rains, they move to the northern grasslands where they take advantage of the seasonal food surplus left unu sed by the sparse populations of resident species. Depending upon the length of the dry season, the proportion of sedentary birds of prey increases from the South to the North of the West African savanna belt. African migrants are the only ones to invade seasonaly the northernmost grasslands. The sou thern ones (the “ guinean savannas ”) are used both by palearctic and african migrants, during the breeding season of the resident species. Palearctic migrants are only found in intermediate latitu des outside the breeding season. Palearctic migrants which have similar diets and hunting methods as african migrants never co-exist with them during the dry season, thus avoiding any competition

Le peuplement avien. Essai d’étude quantitative

The avifauna of the Lamto area has been studied during a two year period. 263 species have been recorded and the habitat prefe rences, diet, breeding periodicity and fecundity of the major species studied. 43 % of the birds are forest species. Only very few of them are abundant, eight species accounting for half of the total numbers of birds counted. Migrants are numerous in the savanna ; one third of them are palearctic passerines, while local migrants are represented mainly by non-passerine families. 90 % of the species are more or less omnivorous, but all migrants show a distinct preference for insect food. Breeding occurs throughout the year : among the 124 commoner species, 62 % breed during the rains and 23 % during the dry season. Fecundity is low and the same female seldom reproduces twice during the year. Counts have been made regularly on a line-transect 12.5 km long and 40 m wide. Monthly variations of numbers and biomasses are given in tables V and VI. Contrary to the situation further North, seasonal variations are small in the forest-savanna mosaic. There are two peaks : the first one, from February to May, corres ponds to an intlux of northern migrants ; the second, from July to September, is attributable to the natural increase of sedentary species and an intlux of fruit-eaters. Minimum values are found in December, at the beginning of the dry season. The average yearly biomass of birds for the Lamto savanna is in the order of 1 kg/ha (fresh weight)

Besoins alimentaires quantitatifs de quelques oiseaux tropicaux

The daily consumption of food by some tropical, mostly insectivorous, birds has been studied in Ivory Coast savana-forest mosaic. Different techniques were used : weights of the stomach contents at the end of the activity period, estimates of the quantity of food brought to nestlings at the end of their growth period, estimates of the number of prey items caught by adults during the day, amount of food eaten by captive individuals. For birds whose body weights ranged from 100 to 1,500 g, the daily ration was on average only half of that of their pale- artic or nearctic counterparts. The overall food consumption of the Rollers and Raptors in the Lamto savana averaged 12 g/ha/day - which, on a yearly basis, corresponds to about half of the production of the prey species concerned

Species abundance patterns in an ecosystem simulation studied through Fisher's logseries

We have developed an individual-based evolving predator-prey ecosystem simulation that integrates, for the first time, a complex individual behaviour model, an evolutionary mechanism and a speciation process, at an acceptable computational cost. In this article, we analyse the species abundance patterns observed in the communities generated by our simulation, based on Fisher's logseries. We propose a rigorous methodology for testing abundance data against the logseries. We show that our simulation produces coherent results, in terms of relative species abundance, when compared to classical ecological patterns. Some preliminary results are also provided about how our simulation is supporting ecological field results