Geographical analysis of California condor sighting data

282

Selected abstracts

movements of swans occur. Experience (age), bodyweight, breast muscle weakening and heavy metal (lead) loads strongly affect the changes of birds avoidingcollision; but, swans not belonging to these risk-groups are also killed. Different skeletal injuries were found in dead birds after collision but many of them were not lethal. Most collision-birds ultimately died from liver damage, probably caused by their heavy bodies hitting the ground. -from Author 93Z/00023 The status of the white-headed duck Oxy. ura leueocephala A. J. Green & S. Anstey, Bird Conservation International, 2(3), 1992, pp 185-200. The current world wintering population is estimated at 19 000 birds, with the likelihood that additional birds occur in unsurveyed wetlands in Asia. The population wintering in Pakistan appears to be declining, but there is no good evidence of current decline elsewhere in the range. The population resident in Spain is increasing. The greatest threat to the species is the spread of the introduced North American ruddy duck O. jamaicensis from the UK to the continent. Hybrids between the two species are fertile and have already been seen in Spain. -from Authors 93Z/00024 Geographical analysis of California condor sighting data D. M. Stoms & 6 others, Conservation Biology, 7(1), 1993, pp 148-159. Observation and habitat data were analyzed in conjunction with recovery planning for the endangered Gymnogyps californianus. A geographic information system was used to rovide a quantitative inventory of recent historical condor abitats, to measure the association of condor activity patterns and mapped habitat variables, and to examine spatiotemporal changes in the range of the sly.cies during its decline. Only 5% of the study area within the historic range is now used for urban or cultivated agricultural purposes. Observations of condor feeding, perching, and nesting were nonrandomly associated with mapped land cover. The precipitous decline in numbers of condors in this century produced only a small reduction in the limits of the observed species' range, as individual birds continued to forage over most of the range. Some critical risk factors such as shooting and lead poisoning, difficult to map, are not included in the database. -from Authors

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93Z/00025 Progress in restoration of the Mauritius kestrel T . J . Cade & C. G. Jones, Conservation Biology, 7(1), 1993, pp 169-175. In the 1970s Falco punctatus was the most endangered bird of prey in the world, at one time with only two known airs surviving in the remnant native forest of the Black vet Gorges. At the end of the 1991-92 breeding season a minimum of 30 nesting pairs and >170 individuals were distributed in four separate forested areas, thanks mainly to manipulation of the reproductive potential of the wild pairs, to captive propagation, and to restocking. Since 1984, 139 young have been reared from 618 eggs laid by captive kestrels, and 147 from 265 wild eggs incubated and hatched in the laboratory; 235 young kestrels have been released on Mauritius by hacking and fostering. Adjustments in feeding and nesting habits of kestrels hacked and released outside the Black River Gorges in areas dominated by exotic vegetation and agriculture have allowed these kestrels to survive and reproduce in an array of previously unused habitats. -from Authors 93Z/00026

Status of the Bengal florican Houbaropsts

bengalensis in India

A . R . Rahmani, G. Narayan, L. Rosalind, R. Sankaran & U. Gangnli, Journal - Bombay Natural History Society, 88(3), 1991, pp 349-375. This severely endangered species of bustard has been brought close to extinction by the indiscriminate conversion of grasslands into agricultural settlements with accompanying overgrazing. The results of a survey carried out in 1985-89 are reported for important florican areas, many of them wildlife santuaries. These were visited in the peak of the breeding season, and data are presented for

each site or region. Territorial males were easily seen during their aerial display and although fewer hens were seen, population estimates are based on the assumption that the sex ratio is equal. Recommendations point to the need for protection of the natural grasslands of the terai belt and the Assam Valley, especially the Brahmaputra islands and flood plains. -J.W.Cooper 937_,/00027 Augmenting small populations of plovers: an assessment of cross-fostering and c a p t i v e - r e a r l n g A . N . Powell & F. J. Cuthbert, Conservation Biology, 7(1), 1993, pp 160-168. Compared the growth and hehavioural development of parent-reared, cross-fostered, and captive-reared killdeer C~radrius vociferus chicks. Parent-reared chicks were raised naturally in the wild, cross-fostered chicks were raised by spotted sandpipers Actitis macularia in the wild, and captive-reared chicks were raised in captivity by humans. Both hatching and fledging success were significantiy increased by captive-rearing and cross-fostering produced approximately the same number of fledged young as natural parent-rearing. Captive-rearing is a viable management teclmiqiue for augmenting small populations of endangered shorebirds, such as piping plover Charadrius melodus. It is recommended over cross-fostering because captive-rearing is more flexible as a technique, PdrOduces more young, does not affect another species, and oes not produce potential imprinting problems. -from Authors 93Z/00028 Are declines in North A m e r i c a n insectivorous songbirds due to causes on the breeding range? K. Bohning-Gaese, M. L. Taper & J. H. Brown, Conservation Biology, 7(1), 1993, lap 76-86. Previous studies have reported a recent decline in breeding populations of migratory songbirds in E and C North America. Explanations have included deforestation on the wintering ground in the tropics and habitat loss, increase predation pressure, and increased cowbird parasitism on the breeding range. The author used these factors to assign 47 species of insectivorous passerines to groups with contrastm~ vulnerabiliw, then used the North American Breeding Bird Survey to a n a l y z e p o p u l a t i o n trends in these groups on a large continental scale. Variables indexing susceptibility to predation on the breeding ground were most strongly correlated with population trends: long-distance migrants to the neotropics exhibited a small, nonsignificant decreasing trend, whereas residents and short-distance migrants increased strongly. During the same time period, the group of species with low nest location, open nests, and high cowbird parasitism declined significantly. Analyses suggest that predation on the breeding ground in North America has played a larger role in the decline of migratory songbirds than deforestation on the wintering grounds in the tropics. -from Authors 93Z/00029 Primate conservation along the Tana River, Kenya: an examination of the forest habitat K. E. Medley, Cor~ervation Biology, 7(1), 1993, pp 109-121. The Tana River National Primate Reserve was established in 1976 to preserve the endemic and endangered Tana River red colobus Colobu$ badius rufomitratua and crested mangahey Cercocebus galeritus galeritus. Between 1975-1985 their populations declined by 80% and 45% respectively. The colobus and mangabey show positive relationships to interior-forest habitat and appear susceptible to forest disturbances that reduce forest area or that increase forest edge and intraforest disturbance. Forest loss, fragmentation, and consequent reduction in the area-to-perimeter ratio o f the remaining forest measured from 1960-1975 provide a partial explanation for the decline in primate propulations. A combmatiun of primary food items and seasonal food resources in large, high-stature., closed-canopy forests is the best predictor of highquality habitat for these monkeys. -from Author

93Z/00030 Determining minimum habitat a r e a s and habitat c o r r i d o r s for cougars P. Beier, Conserva~on Biology, 7(1), 1993, pp 94-108.