Bird Conservation International最新文献

During their northward migration, Red Knots Calidris canutus rufa stop at the Lagoa do Peixe National Park in the extreme south of Brazil to build up fat reserves for their journey to their Canadian breeding grounds. We tracked five Red Knots with PinPoint Argos-75 GPS transmitters to investigate differences in migration strategies from this stopover. Tracked birds used two different routes: the Central Brazil route and the Brazilian Atlantic Coast route. One bird flew 8,300 km straight from Lagoa do Peixe to the Delaware Bay (USA). Another bird stopped in Maranhão (north-east Brazil) and a third one used a yet unknown environment for the species, the mouth of the Amazon River at Baía Santa Rosa, Brazil. These two birds made short flights, covering stretches of 1,600 km to 3,600 km between stop-overs, where they stayed from 4 to 18 days. Our study highlights the occurrence of intrapopulation variation in migratory strategies and reveals the connectivity of environments that are essential for the viability of rufa Red Knot populations.

This paper reports results from the eighth of a series of road transect surveys of Gyps vultures conducted across northern, central, western, and north-eastern India since the early 1990s. Populations of the White-rumped Vulture Gyps bengalensis, Indian Vulture G. indicus, and Slender-billed Vulture G. tenuirostris declined rapidly, beginning in the mid-1990s. The principal cause of the declines was poisoning due to widespread veterinary use of the non-steroidal anti-inflammatory drug (NSAID) diclofenac on cattle. The results of the current survey suggest that, while populations of all three species of vulture remain at a low level with no signs of recovery, they appear to have been approximately stable since veterinary use of diclofenac was banned in the mid-2000s. Population trends in India, where the illegal use of diclofenac and legal use of other toxic NSAIDs continues, are compared with more positive trends in Nepal, where the veterinary use of toxic NSAIDs appears to have been reduced to a low level.

Population size is one component of several criteria in the International Union for Conservation of Nature (IUCN) Red List of Threatened Species (Red List). For these criteria, the quality of the population estimation can therefore have significant impact on the assessed status. To evaluate population estimate quality, we selected 473 species of land birds from the Americas considered by the Red List to be “Critically Endangered”, “Endangered”, or “Vulnerable” at the end of 2021, of which 414 (88%) had a population size estimate. For these species, we determined the age of the estimate and how the population estimate was derived, grouped into eight categories. For 87 species (18%) the population estimate was derived by sampling a small area and extrapolating to the entire range of the species; for these, the population size estimate depends on the estimate of range size. For the subset of 22 of these with complete data, we compared range size estimates obtained from maps published by IUCN with maps produced using the methods of Huang et al. (2021) to see how range map differences could affect population size estimates and therefore Red List status. Potentially half of these species (11 of 22) could change status using the new maps. More than one-third of the population size estimates (38%, 161 species with a date of population estimate) were made in 2000 or earlier. A majority of the species, 63% (300 of 473 species), do not have population size estimates made using a scientific sampling method, although the majority since 2010 have been made using a sampling method, reflecting an effort by Red List assessors to include more scientific information. We encourage the ornithological community to work to obtain current, high quality population size and range estimates to improve the quality of Red List status assessments.

Many Afro-Palearctic songbird migrants have declined, with conservation efforts mainly focused on the restoration of breeding habitat. However, pressures outside the breeding season might play a role. This includes the possibility that local relict populations no longer maintain the original phenotypic variation in migration patterns, with a loss of flexibility. The Great Reed Warbler Acrocephalus arundinaceus kept stable population levels in central and eastern Europe, but was almost extinct in the western part of the breeding range. In the Rhine delta the population declined from 10,000 individuals around 1950, to fewer than 100 at present. Here we document migratory timing, routes, and destinations of members of this remnant songbird population. It turned out that the remaining adults still showed high diversity in migratory phenotypes. This is even true in each of the two last tiny subpopulations in the Netherlands (of 50 and 15 pairs). So, even very small populations maintain the possible adaptive phenotypic variation, and with hindsight this justifies the breeding habitat restoration efforts currently underway.

The Seychelles Kestrel Falco araeus is an endemic species confined to the larger granitic islands in the Seychelles archipelago. It is classified as “Vulnerable” and became extinct on Praslin and La Digue islands in the 1970s, leading to an attempt of reintroduction in 1977. This reintroduction was not a success, with the last census reporting only four breeding pairs on Praslin Island. Studies on the Seychelles Kestrel are very limited and dated, and a lack of data on the biology and ecology of the species has made it difficult to make a thorough assessment of the cause of the current decline of the Praslin population. In order to determine the limiting factors on Praslin we investigated the following ecological parameters: nest-site availability, trophic availability, predatory pressure, and interspecific competition. Data were collected on Mahé and Praslin islands in three habitats (i.e. urban, suburban, and forest areas) and compared to determine if limiting factors differed among islands, habitats, and islands*habitat. We only found a significant difference in nest-site availability, with Praslin showing a marked lack of nesting cavities. Breeding pairs on Praslin are probably forced to nest in suboptimal sites. Indeed, the breeding success rate on Praslin is very low, and most of the nests there fail. The Seychelles Kestrel population on Praslin is in decline and cannot be sustained without human intervention. Such an intervention must take into account the ecological parameters highlighted in the present study.