scholarly journals Population estimates and habitat use by the Critically Endangered Taita Apalis Apalis fuscigularis in south-eastern Kenya

2010 ◽  
Vol 20 (4) ◽  
pp. 440-455 ◽  
Author(s):  
LUCA BORGHESIO ◽  
DAINA SAMBA ◽  
MWANGI GITHIRU ◽  
LEON BENNUN ◽  
KEN NORRIS
Keyword(s):  
Habitat Use ◽  
Population Size ◽  
Habitat Structure ◽  
Predictive Power ◽  
Total Population ◽  
Distance Sampling ◽  
Critically Endangered ◽  
South Eastern ◽  
Forest Sites ◽  
Global Population

SummaryThe Taita Apalis Apalis fuscigularis (IUCN category: Critically Endangered) is a species endemic to south-eastern Kenya. We assessed population size and habitat use in the three forest sites in which it is known to occur (Ngangao, Chawia and Vuria, totalling 257 ha). The estimate of total population size, derived from distance sampling at 412 sample points, ranged from 310 to 654 individuals, with the northern section of Ngangao fragment having 10-fold higher densities than Chawia (2.47–4.93 versus 0.22–0.41 birds ha−1). Ngangao north alone hosted 50% of the global population of the species. The highly degraded Vuria fragment also had moderately high densities (1.63–3.72 birds ha−1) suggesting that the species tolerates some human disturbance. Taita Apalis prefers vegetation with abundant climbers, but the predictive power of habitat use models was low, suggesting that habitat structure is not a primary cause for the low density of the species in Chawia. Protecting the subpopulation in the northern section of Ngangao is a priority, as is identifying factors responsible of the low abundance in Chawia, because ameliorating conditions in this large fragment could substantially increase the population of Taita Apalis.

Global population size of a critically endangered lemur, Perrier's sifaka

2007 ◽  
Vol 10 (2) ◽  
pp. 254-262 ◽  
Author(s):  
M. A. Banks ◽  
E. R. Ellis ◽  
Antonio ◽  
P. C. Wright
Keyword(s):  
Population Size ◽  
Critically Endangered ◽  
Global Population

scholarly journals Decline towards extinction of Mexico's vaquita porpoise ( Phocoena sinus )

2019 ◽  
Vol 6 (7) ◽  
pp. 190598 ◽  
Author(s):  
Armando M. Jaramillo-Legorreta ◽  
Gustavo Cardenas-Hinojosa ◽  
Edwyna Nieto-Garcia ◽  
Lorenzo Rojas-Bracho ◽  
Len Thomas ◽  
...  
Keyword(s):  
Population Size ◽  
Total Population ◽  
Population Decline ◽  
Credible Interval ◽  
Critically Endangered ◽  
Posterior Mean ◽  
Bayesian Credible Interval ◽  
Independent Estimate ◽  
Rate Of Decline ◽  
Passive Acoustic

The vaquita ( Phocoena sinus ) is a small porpoise endemic to Mexico. It is listed by IUCN as Critically Endangered because of unsustainable levels of bycatch in gillnets. The population has been monitored with passive acoustic detectors every summer from 2011 to 2018; here we report results for 2017 and 2018. We combine the acoustic trends with an independent estimate of population size from 2015, and visual observations of at least seven animals in 2017 and six in 2018. Despite adoption of an emergency gillnet ban in May 2015, the estimated rate of decline remains extremely high: 48% decline in 2017 (95% Bayesian credible interval (CRI) 78% decline to 9% increase) and 47% in 2018 (95% CRI 80% decline to 13% increase). Estimated total population decline since 2011 is 98.6%, with greater than 99% probability the decline is greater than 33% yr −1 . We estimate fewer than 19 vaquitas remained as of summer 2018 (posterior mean 9, median 8, 95% CRI 6–19). From March 2016 to March 2019, 10 dead vaquitas killed in gillnets were found. The ongoing presence of illegal gillnets despite the emergency ban continues to drive the vaquita towards extinction. Immediate management action is required if the species is to be saved.

scholarly journals Protected by dragons: Density surface modeling confirms large population of the critically endangered Yellow-crested Cockatoo on Komodo Island

The Condor ◽  
2020 ◽  
Author(s):  
Anna Reuleaux ◽  
Benny A Siregar ◽  
Nigel J Collar ◽  
Maria R Panggur ◽  
Ani Mardiastuti ◽  
...  
Keyword(s):  
Population Size ◽  
Local Density ◽  
Large Population ◽  
Distance Sampling ◽  
Surface Modeling ◽  
Habitat Associations ◽  
Critically Endangered ◽  
Topographic Wetness Index ◽  
Monsoon Forest ◽  
Density Surface

Abstract Intense trapping of the critically endangered Yellow-crested Cockatoo (Cacatua sulphurea) for the international pet trade has devastated its populations across Indonesia such that populations of >100 individuals remain at only a handful of sites. We combined distance sampling with density surface modeling (DSM) to predict local densities and estimate total population size for one of these areas, Komodo Island, part of Komodo National Park (KNP) in Indonesia. We modeled local density based on topography (topographic wetness index) and habitat types (percentage of palm savanna and deciduous monsoon forest). Our population estimate of 1,113 (95% CI: 587–2,109) individuals on Komodo Island was considerably larger than previous conservative estimates. Our density surface maps showed cockatoos to be absent over much of the island, but present at high densities in wooded valleys. Coincidence between our DSM and a set of independent cockatoo observations was high (93%). Standardized annual counts by KNP staff in selected areas of the island showed increases in cockatoo records from <400 in 2011 to ~650 in 2017. Taken together, our results indicate that KNP, alongside and indeed because of preserving its iconic Komodo dragons (Varanus komodoensis), is succeeding in protecting a significant population of Indonesia’s rarest cockatoo species. To our knowledge this is the first time DSM has been applied to a critically endangered species. Our findings highlight the potential of DSM for locating abundance hotspots, identifying habitat associations, and estimating global population size in a range of threatened taxa, especially if independent datasets can be used to validate model predictions.

scholarly journals Out of the darkness: the first comprehensive survey of the Critically Endangered Anjouan Scops Owl Otus capnodes

2014 ◽  
Vol 25 (3) ◽  
pp. 322-334 ◽  
Author(s):  
KATHLEEN E. GREEN ◽  
BRONWEN M. DANIEL ◽  
SAMUEL P. LLOYD ◽  
ISHAKA SAID ◽  
AMELAID HOUMADI ◽  
...  
Keyword(s):  
Population Size ◽  
Conservation Status ◽  
Distance Sampling ◽  
Bird Species ◽  
Iucn Red List ◽  
Critically Endangered ◽  
Encounter Rate ◽  
Wet Season ◽  
Point Counts ◽  
Comprehensive Survey

SummaryAlthough birds are among the best studied taxa, many of the globally threatened species lack the information required to fully assess their conservation status and needs. One such species is the Anjouan Scops Owl Otus capnodes which was presumed extinct until its rediscovery to science in 1992. Based on the limited extent and decline of the moist forests in the highlands of Anjouan in the Comoro Islands, a population size of only 100–200 pairs was estimated and the species was classified as ‘Critically Endangered’. The current study is the first comprehensive survey ever conducted on this species, and aimed to establish the current distribution and population size. Point counts with distance sampling were conducted across the agroforestry and forest zones of Anjouan in both a dry and wet season. A niche suitability model predicted the species distribution to be wider than expected with owls observed as low as 300 m altitude and in highly modified agroforestry habitats. However, the encounter rate in natural relatively undisturbed forest was significantly greater than in other habitats. The wider than expected geographic range of O. capnodes supports a possible downlisting of this species on the IUCN Red List to ‘Endangered’. Population size was found to be far greater than previously thought, at approximately 3,450 individual owls in the dry season and 5,450 in the wet season. These results show the importance of investing in robust surveys of poorly known and cryptic bird species, and provide up to date and important information for landscape scale conservation planning in the Comoros Islands.

scholarly journals Hierarchical distance sampling reveals increased population size and broader habitat use in the endangered Bahama Oriole

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Michael G. Rowley ◽  
Richard C. Stanley ◽  
Janine M. Antalffy ◽  
Jennifer L. Christhilf ◽  
Daniel C. Stonko ◽  
...  
Keyword(s):  
Habitat Use ◽  
Population Size ◽  
Distance Sampling

Leaf Surface-Structure and the Distribution of Phytoseius Mites (Acarina, Phytoseiidae) in South-Eastern Australian Forests

1992 ◽  
Vol 40 (6) ◽  
pp. 593 ◽  
Author(s):  
DE Walter
Keyword(s):  
Species Diversity ◽  
Surface Structure ◽  
Plant Species ◽  
Woody Plants ◽  
Habitat Structure ◽  
Leaf Surface ◽  
Important Determinant ◽  
Phytoseiid Mites ◽  
South Eastern ◽  
Forest Sites

Habitat structure, at a scale at which we do not normally perceive it, can be an important determinant of species diversity and distribution in arboreal mites. Phytoseiid mites (1552 individuals) collected from the leaves of 75 species of woody plants from 55 forest sites between Noosa Head, Queensland and the Hartz Mountains, Tasmania were found to represent 28 species in four genera: Phytoseius, Typhlodromus, Amblyseius and Iphiseius. About half (38) of the plant species from which phytoseiid mites were collected had leaves with well-developed coverings of hairs on their abaxial surfaces, especially along the veins. Species in the genus Phytoseius were the most abundant mites (46.4% of total), and they were almost entirely restricted to leaves with well-developed tomenta (714 of 720 Phytoseius mites collected from 34 of 38 plant species with hairy leaves). In a test of these observations at three sites in Victoria, phytoseiid mites in general were more abundant on leaves with well-developed tomenta, but only Phytoseius mites were restricted to hairy leaves.

scholarly journals Status assessment of the Critically Endangered Azores Bullfinch Pyrrhula murina

2011 ◽  
Vol 21 (4) ◽  
pp. 477-489 ◽  
Author(s):  
RICARDO S. CEIA ◽  
JAIME A. RAMOS ◽  
RUBEN H. HELENO ◽  
GEOFF M. HILTON ◽  
TIAGO A. MARQUES
Keyword(s):  
Population Size ◽  
Conservation Status ◽  
Distance Sampling ◽  
Iucn Red List ◽  
Range Size ◽  
Critically Endangered ◽  
Survey Method ◽  
Mountain Range ◽  
Laurel Forest ◽  
Area Of Occupancy

SummaryThe Azores Bullfinch is endemic to the island of São Miguel (Azores, Portugal). Its status was uplisted to Critically Endangered in 2005 on the basis of an extremely small and declining population that was considered to be restricted to a very small mountain range (43 km2), in a single location, within which the spread of invasive plants constituted a threat to habitat quality. Nevertheless, information was mostly inferred, or the product of, non-systematic studies. In order to carry out a complete assessment of the conservation status we analysed: (i) population trend, calculated from annual monitoring 1991–2008, (ii) population size, and (iii) range size, obtaining estimates in a single morning study in 2008 involving the simultaneous participation of 48 observers. Contrary to previous inferences, the population is no longer decreasing, although quality of laurel forest habitat continues to decline due to the persistent threat of invasive species. Population size (mean ± SE) was estimated at 1,064 ± 304 individuals using distance sampling methods, although the estimate was very sensitive to the survey method used. Range size estimates (extent of occurrence and area of occupancy) were 144 km2 and 83 km2 respectively. Given the present information, we propose the downlisting of Azores Bullfinch to Endangered on the IUCN Red List.

scholarly journals First formal estimate of the world population of the Critically Endangered spoon-billed sandpiper Calidris pygmaea

Oryx ◽  
2016 ◽  
Vol 52 (1) ◽  
pp. 137-146 ◽  
Author(s):  
Nigel A. Clark ◽  
Guy Q. A. Anderson ◽  
Jing Li ◽  
Evgeny E. Syroechkovskiy ◽  
Pavel S. Tomkovich ◽  
...  
Keyword(s):  
Population Size ◽  
Breeding Population ◽  
Critically Endangered ◽  
World Population ◽  
South East Asia ◽  
Russian Arctic ◽  
Age Classes ◽  
Long Distance ◽  
The World ◽  
Global Population

AbstractThe spoon-billed sandpiper Calidris pygmaea is a Critically Endangered shorebird that breeds in the Russian arctic and winters in coastal and estuarine habitats in South-east Asia. We report the first formal estimate of its global population size, combining a mark–resighting estimate of the number of leg-flagged individuals alive in autumn 2014 with an estimate of the proportion of birds with flags from scan surveys conducted during the same period at a migration stop-over site on the Jiangsu coast of China. We estimate that the world breeding population of spoon-billed sandpipers in 2014 was 210–228 pairs and the post-breeding population of all age classes combined was 661–718 individuals. This and related methods have considerable potential for surveillance of the population size of other globally threatened species, especially widely dispersed long-distance migrants.

First systematic sampling approach to estimating the global population size of the Critically Endangered Blue-throated Macaw Ara glaucogularis

2020 ◽  
pp. 1-19 ◽  
Author(s):  
SEBASTIAN K. HERZOG ◽  
OSWALDO MAILLARD Z. ◽  
TJALLE BOORSMA ◽  
GUSTAVO SÁNCHEZ-ÁVILA ◽  
VÍCTOR HUGO GARCÍA-SOLÍZ ◽  
...  
Keyword(s):  
Population Size ◽  
Critically Endangered ◽  
Population Estimates ◽  
Suitable Habitat ◽  
Landsat 8 ◽  
Entire Area ◽  
Positive Effects ◽  
Population Size Estimates ◽  
Global Population ◽  
Sampling Approach

Summary Reliable population size estimates are imperative for effective conservation and management of globally threatened birds like the ‘Critically Endangered’ Blue-throated Macaw Ara glaucogularis. Endemic to one of South America’s largest grassland floodplains, the Llanos de Moxos in northern Bolivia, the species’ global population size is uncertain. The region’s inaccessibility renders the application of traditional methods for obtaining bird population estimates impracticable or cost prohibitive. We developed a simultaneous, multilocality, double-sampling approach combined with quantitative habitat availability analyses to obtain the first rigorous population size estimate for the Blue-throated Macaw. We established 11 survey areas across its three subpopulations that were visited twice by one team in each subpopulation over a 23-day period in the 2015 dry season and obtained additional count data from two roost sites. We classified suitable habitat (palm forest islands) using Landsat 8 images and CLASlite forest monitoring software. We extrapolated the number of macaws detected (conservative estimate of the total number of macaws [CETN], highest single count [HSC]) per 100 ha of suitable habitat in each survey area to the entire area of suitable habitat in all subpopulations combined, corrected for the species’ range occupancy of 34.3%. The total number of Blue-throated Macaws detected by survey (CETN) and roost site counts was 137. Across all survey areas, the number of macaws per 100 ha of suitable habitat was 4.7 for the first and 4.4 for the second period for CETN and 3.2 and 3.4, respectively, for HSC data. Corresponding global population estimates were 426–455 (CETN) and 312–329 (HSC) individuals. Other recent research and anecdotal data support these estimates. Although it would be premature to propose downlisting the species to ‘Endangered’, our findings indicate that it has a larger population and slightly larger range than previously thought, and that the positive effects of conservation actions are now becoming apparent.

A distance sampling survey of the Critically Endangered Straw-headed Bulbul Pycnonotus zeylanicus in Singapore

2020 ◽  
pp. 1-13
Author(s):  
WEN XUAN CHIOK ◽  
ELIZE Y. X. NG ◽  
QIAN TANG ◽  
JESSICA G. H. LEE ◽  
FRANK E. RHEINDT
Keyword(s):  
Sampling Method ◽  
Total Population ◽  
Distance Sampling ◽  
Critically Endangered ◽  
Population Estimate ◽  
Density Estimates ◽  
Field Surveys ◽  
Census Methods ◽  
Systematic Field ◽  
Regional Conservation

Summary The Straw-headed Bulbul Pycnonotus zeylanicus is one of South-East Asia’s most threatened songbirds due to relentless demand for the regional cage-bird trade. The species was recently uplisted from ‘Endangered’ to ‘Critically Endangered’ only two years after its previous uplisting. Intriguingly, populations in highly urbanised Singapore appear relatively secure. However, the last Singaporean density estimates, derived from traditional census methods, were obtained nearly two decades ago in 2001. A recent population estimate in 2016 was derived from the census work in 2001 coupled with relative abundance indices from population trends. We thus performed systematic field surveys using the distance sampling method, estimating 573 ± 185 individuals nation-wide, with a break-down of 217 ± 81 on the main island of Singapore and 356 ± 104 birds on the satellite of Pulau Ubin. Taken together, the total population estimate reported here comprises 22.9–57.3% of the global wild population, underscoring the importance of Singapore as a stronghold for the species. In spite of its apparently secure status in Singapore, the species remains susceptible to local and foreign trapping pressures. Based on our assessment, we propose a number of local and regional conservation measures to ensure the continued survival of populations in Singapore.

Sign in / Sign up

Export Citation Format

Share Document