Review Article
First indications of a sharp population decline in the globally threatened Spoon-billed Sandpiper Eurynorhynchus pygmeus
- P. S. Tomkovich, E. E. Syroechkovski, Jr., E. G. Lappo, C. Zöckler
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- Published online by Cambridge University Press:
- 16 July 2002, pp. 1-18
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Spoon-billed Sandpiper Eurynorhynchus pygmeus is classed as globally Vulnerable, based on the only available population estimate, made in 1977, of 2,000–2,800 pairs. Surveys for breeding Spoon-billed Sandpipers were carried out in summer 2000 on the Anadyr estuary coast, the Chukotka autonomous region, Russia. Although six new breeding sites were found, only 16–17 breeding males/pairs were recorded on the northern coast of the Anadyr estuary and five males/pairs on the southern coast and more southerly lagoons. These numbers were much lower than expected, and the species was not recorded in several apparently suitable areas. Four formerly known breeding sites held only one displaying male between them. At no site was there evidence of an increasing or stable local population. Together with other indicative data these suggest a sharp decline in the population of Spoon-billed Sandpiper. The previous population size estimate obviously requires updating, both because there were some incorrect assumptions in the calculations made for the first population estimate, and also due to a recent population decline. It is likely that the current population numbers under 1,000 breeding pairs. Given that the population of this species may be substantially lower than the only previous estimate, and the evidence for a possible rapid decline in its population described in this paper, it is recommended that its IUCN status is changed from Vulnerable to Endangered. No reasons for the apparent rapid rate of decline are evident within the breeding range. “Bottle-necks” should be looked for at migration sites or wintering grounds, but currently, monitoring of the population is only possible on the breeding grounds.
The Great Bustard Otis tarda population in Morocco 1998–2001
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- Joachim Hellmich, Youssef Idaghdour
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- Published online by Cambridge University Press:
- 16 July 2002, pp. 19-33
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The Moroccan population of Great Bustard Otis tarda was surveyed in the four years 1998–2001. Highest numbers were counted in December 1998 (21 males, 62–65 females, four first-year males: total c. 90) and March 2001 (15 males, 60–66 females, four first-year males: total 75–81). Combining enquiry results from local people with these data, the population size for spring is estimated at 92–111 individuals, and 117–133 for winter. Reproduction is confirmed. Threats to the population include illegal hunting, habitat loss through agricultural intensification (irrigation, use of pesticides) and infrastructural changes (construction of a motorway and a powerplant), disturbance, and accidents at powerlines and antennas. Several conservation measures are suggested: cease hunting; maximize the attention given to display sites; encourage villagers to carry out “Great Bustard-friendly” land use and adapt animal stocks to the carrying capacity of their regions; clarify the situation of genetic exchange between Spanish and Moroccan populations; study movements between the Moroccan sites; monitor the size and trends of the most important subpopulations; and conduct education campaigns in schools and increase public awareness among adults.
Population trends and priority conservation sites for Mexican Duck Anas diazi
- A. Perez-Arteaga, K. J. Gaston, M. Kershaw
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- Published online by Cambridge University Press:
- 16 July 2002, pp. 35-52
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Little is known about Mexican Duck Anas diazi biology and populations. We analyse long-term (1960–2000) trends of Mexican Duck numbers in Mexico and employ contemporary count data (1991–2000) from the U.S. Fish and Wildlife Service midwinter surveys to identify key sites for conservation using a complementarity approach. The overall Mexican Duck population showed a significant long-term increase of 2.5% per year, with large fluctuations throughout the study period. The Northern highlands population increased at an annual rate of 7.7%, while the Central highlands population showed no significant long-term trend. During the last decade, counts in both the Northern and Central highlands exhibited no significant change. At the site level, significant long-term increases occurred in four localities in the Northern highlands (Laguna Bab�cora +13.9% annually, Laguna Bustillos +25.9%, Laguna Mexicanos +20.4% and Laguna Santiaguillo +16.9%) and in three localities in the Central highlands (Languillo +15.3% annually, Presa Solís +8.9%, Zacapu +13.4%). Two sites in the Central highlands showed significant declines, in the long term (Lago de Chapala, -5.2% per year) and during the last decade (Lerma, -11.8% per year). The Northern highlands held 16% and the Central highlands 84% of the Mexican Duck population in the period 1960–2000; during the last decade, these figures were 31% and 69%, respectively. A set of priority sites for conservation of the Mexican Duck was identified, consisting of 15 sites holding more than 70% of the midwinter Mexican Duck counts in Mexico. Ten sites from the priority set also qualify for designation as wetlands of international importance under the Ramsar Convention on Wetlands, by holding ≥ 1% of the estimated population. Four of the priority sites are in the Northern highlands and 11 in the Central highlands, of which eight are distributed along the Rio Lerma drainage. The most urgent actions that need to be undertaken are to estimate the current minimum population size in Mexico; to establish a programme for monitoring populations in the priority sites, especially those located within the highly degraded Rio Lerma drainage; and to determine the most feasible management actions for the species, concentrating efforts around the priority sites.
Population sizes and the status of endemic and restricted-range bird species on Sangihe Island, Indonesia
- Jon Riley
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- Published online by Cambridge University Press:
- 16 July 2002, pp. 53-78
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The island of Sangihe, Indonesia, was visited in 1998–99 with the aim of producing population estimates of the island's endemic and other restricted-range bird species, some of which were poorly known and thought to be at risk of extinction due to habitat change. The study focused on the last remaining patch of primary forest, on Mount Sahendaruman in southern Sangihe, home to three critically endangered endemic species: Cerulean Paradise-flycatcher Eutrichomyias rowleyi, Sangihe Shrike-thrush Colluricincla sanghirensis, and Sangihe White-eye Zosterops nehrkorni. Population densities were estimated from primary forest and secondary habitats across Sangihe to assess species dependency on primary habitat. Twenty of 24 restricted-range, globally threatened or endemic taxa were recorded and density estimates were calculated for 15 of these. The endemic Red-and-blue Lory Eos histrio is extinct on Sangihe as a result of lowland forest loss. Six species (Nicobar Pigeon Caloenas nicobarica, Sulawesi Dwarf Kingfisher Ceyx fallax, Golden Bulbul Ixos affinis, E. rowleyi, C. sanghirensis, and Z. nehrkorni) were either not recorded or have very small populations and are critically endangered on Sangihe; two species of Tanygnathus parrot are also facing local extinction on the island. The major threat to all these species is the destruction of primary forest; larger species are also threatened by hunting. The remaining endemic and restricted-range species (Blue-tailed Imperial Pigeon Ducula concinna, Sangihe Hanging-parrot Loriculus catamene, Sangihe Scops-owl Otus collari, Lilac-cheeked Kingfisher Cittura cyanotis and Elegant Sunbird Aethopyga duyvenbodei) were more widespread and occurred in secondary habitats. I recommend that L. catamene and A. duyvenbodei, currently treated as globally endangered, be reclassified as near-threatened and vulnerable respectively because of their large populations and tolerance of disturbed habitats. Species with wide global ranges that are represented by endemic subspecies have the greatest tolerance for disturbed habitat. The widespread deforestation of Sangihe has had serious consequences for many bird species and today the island supports the most threatened assemblage of single-island endemic species in Indonesia. Species-specific research to determine the status and ecology of E. rowleyi, C. sanghirensis and Z. nehrkorni, and monitoring of the Sahendaruman forest are desperately needed as a basis for future conservation efforts.
The breeding status and colony dynamics of Cape Vulture Gyps coprotheres in Botswana
- Wendy D. Borello, Remigio M. Borello
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- Published online by Cambridge University Press:
- 26 September 2002, pp. 79-97
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Cape Vulture Gyps coprotheres is endemic to southern Africa and is globally threatened. Colonies in Botswana comprise part of one of the two core breeding areas in the species's range, and very little has previously been published about them. Ground censusing of 11 Cape Vulture sites in Botswana was undertaken from 1992 to 1999, continuing a monitoring programme initiated by the authors in 1984. Survey methods and census procedures are documented. The potential Cape Vulture breeding population in Botswana is estimated to be about 600 pairs, comprising at least 100 pairs at Mannyelanong in the south-east and about 500 pairs in eastern Botswana. This represents an increase from previous estimates, and reflects improved census techniques rather than an increase in population size. The mean turnover rate of nest site usage from one year to the next averaged 21% at Mannyelanong, and was about 26% at Manong Yeng in eastern Botswana. Annual productivity of nest sites increased with the number of years the site had been occupied. Over the eight years of study eggs were laid in at least 436 of 477 nests (91.4%) at Mannyelanong; chicks survived to mid season (60–80 days old) in 327 nests (75% of eggs laid), and fledged (best estimate) in 248 nests (56.9% of eggs laid and 52% of pairs attempting to breed). In eastern Botswana eggs were laid in at least 1,825 of 2,101 nests (86.9%); chicks survived to mid season in 1,272 nests (69.7% of eggs laid). Two seasons have been excluded for eastern Botswana (1994 and 1995) due to incomplete data, and breeding success can be estimated only from 1997 to 1999: of 990 eggs laid out of 1,108 nests, chicks fledged in 384 nests (38.8% of eggs laid and 34.6% of pairs attempting to breed). The eastern Botswana breeding population remains in a state of flux following the collapse of a primary colony that was the country's Cape Vulture stronghold. Conservation concerns and the vulnerability of Cape Vulture sites are discussed.