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 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.

scholarly journals Updated range metrics and a global population estimate for the Critically Endangered Philippine Eagle using a spatial ensemble habitat model

2021 ◽  
Author(s):  
Luke J Sutton ◽  
Jayson C Ibañez ◽  
Dennis I Salvador ◽  
Rowell L Taraya ◽  
Guiller S Opiso ◽  
...  
Keyword(s):  
Population Size ◽  
Species Distribution Model ◽  
Extinction Risk ◽  
Habitat Model ◽  
Critically Endangered ◽  
Biological Information ◽  
Distribution Model ◽  
Population Estimate ◽  
Area Of Occupancy ◽  
Global Population

Many range-restricted taxa are currently experiencing severe population declines yet lack fundamental biological information regarding distribution and population size. Establishing baseline estimates for both these key biological parameters is however critical for directing long-term monitoring and conservation planning for at-risk range-restricted species. The International Union for the Conservation of Nature (IUCN) Red List uses three spatial range metrics that define species distributions and inform extinction risk assessments: extent of occurrence (EOO), area of occupancy (AOO) and area of habitat (AOH). However, calculating all three metrics using standard IUCN approaches relies on a geographically representative sample of locations, which for rare species is often spatially biased. Here, we apply model-based interpolation using an ensemble Species Distribution Model (SDM), correlating occurrences with remote-sensing derived environmental covariates, to calculate IUCN range metrics and a global population estimate for the Critically Endangered Philippine Eagle (Pithecophaga jefferyi). Our ensemble averaged SDM had high predictive accuracy and was able to identify key areas of Philippine Eagle habitat across the species global range. We estimated an AOH = 49,426 km2 and from this metric calculated a maximum EOO = 609,697 km2 and a minimum EOO = 273,794 km2, with an AOO = 54,695 occupied cells. Based on inferred habitat from the AOH metric and territorial habitat area from home range estimates, we provide an updated global population estimate of 677 breeding pairs (range: 549-772 pairs), or 1354 mature individuals, across the entire Philippine Eagle range. We demonstrate that even when occurrence sampling is geographically biased, robust habitat models can be built which enable quantification of IUCN range metrics and a baseline population size estimate. In the absence of adequate location data for many rare and threatened taxa, our method is a promising spatial modelling tool with widespread applications, in particular for island endemics facing high extinction risk.

scholarly journals First census of the white-shouldered ibis Pseudibis davisoni reveals roost-site mismatch with Cambodia's protected areas

Oryx ◽  
2012 ◽  
Vol 46 (2) ◽  
pp. 236-239 ◽  
Author(s):  
Hugh L. Wright ◽  
Nigel J. Collar ◽  
Iain R. Lake ◽  
Net Norin ◽  
Rours Vann ◽  
...  
Keyword(s):  
Protected Areas ◽  
Population Size ◽  
Critically Endangered ◽  
Population Estimate ◽  
Term Survival ◽  
Long Term Survival ◽  
Global Population

AbstractThe population size of the Critically Endangered white-shouldered ibis Pseudibis davisoni has always been poorly known. The first-ever census across Cambodia in 2009–2010 using simultaneous counts at multiple roost sites found substantially more birds than previously estimated, with a minimum of 523 individuals. The census allowed us to make a revised global population estimate of 731–856 individuals, increasing hope for the species' long-term survival. However, the largest subpopulations are imminently threatened by development and c. 75% of the birds counted in Cambodia were outside protected areas.

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.

scholarly journals Estimating change in the geographical range and population size of Hinde's Babbler Turdoides hindei

2003 ◽  
Vol 13 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Philip Shaw ◽  
John Musina ◽  
Patrick Gichuki
Keyword(s):  
Protected Areas ◽  
Population Size ◽  
Geographical Range ◽  
Population Estimates ◽  
Extent Of Occurrence ◽  
Area Of Occupancy ◽  
Species Area ◽  
Gains And Losses ◽  
Global Population

Hinde's Babbler Turdoides hindei is a globally threatened Kenyan endemic, which during the 1990s, was known from just seven localities. Based mainly on surveys undertaken in 2000–2001, we estimate the species's global population size and compare recent changes in its “extent of occurrence” and “area of occupancy”. Historically, Hinde's Babbler has been recorded from c. 40 10 × 10 km squares; 27 pre-1980 and 19 subsequently, suggesting that its area of occupancy has declined by about 30%. In contrast, its extent of occurrence has declined by only 8%, this measure being less sensitive to the balance of gains and losses occurring near the centre of its range. During surveys in 1994 and 2000–2001, 157 groups were located, containing 665 birds, 75% of which were found at two intensively cultivated sites. Some 97% of birds were located in, or adjacent to, five Important Bird Areas, but only 8% were found within legally protected areas. Two extrapolated population estimates are presented, based on the number of birds likely to have been missed at survey sites, and the species' area of occupancy. These suggest that the global population of Hinde's Babbler is likely to fall within the range of 1,500–5,600 birds.

scholarly journals A first survey of the global population size and distribution of the Scottish Crossbill Loxia scotica

2010 ◽  
Vol 21 (2) ◽  
pp. 186-198 ◽  
Author(s):  
RON W. SUMMERS ◽  
STEPHEN T. BUCKLAND
Keyword(s):  
Population Size ◽  
Habitat Management ◽  
Disjunct Distribution ◽  
Population Estimates ◽  
Modal Number ◽  
Habitat Requirement ◽  
Bird Population ◽  
Different Seasons ◽  
Common Crossbill ◽  
Global Population

SummaryA survey of Scottish Crossbills Loxia scotica was carried out in 3,506 km2 of conifer woodland in northern Scotland during January to April 2008 to provide the first estimate of the global population size for this endemic bird. Population estimates were also made for Common Crossbills L. curvirostra and Parrot Crossbills L. pytyopsittacus within this range. Crossbills were lured to systematically selected survey points for counting, sexing and recording their calls for later call-type (species) identification from sonograms. Crossbills were located at 451 of the 852 survey points, and adequate tape-recordings made at 387 of these. The Scottish Crossbill had a disjunct distribution, occurring largely within the eastern part of the study area, but also in the northwest. Common Crossbills had a mainly westerly distribution. The population size of post-juvenile Scottish Crossbills was estimated as 13,600 (95% C.I. 8,130–22,700), which will approximate to 6,800 (4,065–11,350) pairs. Common Crossbills were more abundant within this range (27,100, 95% C.I. 14,700–38,400) and Parrot Crossbills rare (about 100). The sex ratio was not significantly different from parity for Scottish Crossbills. The modal number at survey points was two but numbers were larger in January than later in the survey. The numbers and distribution of all crossbill species are likely to vary between years, depending upon the size of the cone crops of the different conifers: all were coning in 2008. Common Crossbill and Parrot Crossbill numbers will also be affected by irruptions from continental Europe. A monitoring scheme is required to detect any population trend, and further work on their habitat requirement (e.g. conifer selection at different seasons) is needed to inform habitat management of native and planted conifer forests to ensure a secure future for this endemic bird.

Extreme rainfall-related clutch size variation in the Critically Endangered Raso Lark Alauda razae of the arid Cape Verde islands

2018 ◽  
Vol 29 (2) ◽  
pp. 321-326 ◽  
Author(s):  
M. de L. BROOKE
Keyword(s):  
Population Size ◽  
Clutch Size ◽  
Size Variation ◽  
Extreme Rainfall ◽  
Cape Verde ◽  
Critically Endangered ◽  
Strongly Correlated ◽  
Cape Verde Islands ◽  
Rainy Period ◽  
Island Endemic

SummaryThe Raso Lark Alauda razae is a single island endemic confined to the island of Raso in the Cape Verde islands. It has been studied via short (11–20 day), similarly-timed visits every year from 2001 to 2017. These November/December visits have occurred towards the end of the main rainy period (August–October) in the Cape Verdes. Average clutch size ranged from zero (no nests found) to 3.57 in different years and was strongly correlated with rainfall in the three months preceding the year’s visit, but not with population size, which varied 25-fold during the study period. Since the nomadic pursuit of rain is not an option for the Raso Lark, the species adjusts clutch size according to conditions prevailing on Raso.

scholarly journals Microhabitats Affect Population Size and Plant Vigor of Three Critically Endangered Endemic Plants in Southern Sinai Mountains, Egypt

Land ◽  
2019 ◽  
Vol 8 (6) ◽  
pp. 86 ◽  
Author(s):  
Amal M. Fakhry ◽  
Ali El-Keblawy ◽  
Hatem A. Shabana ◽  
Ibrahim El Gamal ◽  
Amir Shalouf
Keyword(s):  
Climate Change ◽  
Population Size ◽  
Endemic Species ◽  
Climate Changes ◽  
Small Population ◽  
Critically Endangered ◽  
High Mountains ◽  
Habitat Types ◽  
Growing Seasons ◽  
Steep Slopes

Endemic species on mountains often have narrow altitudinal ranges and are more threatened at the higher altitudes, especially with climate changes. However, plants could use special microhabitats at the mountain tops as proper places for surviving the climate change (i.e., refugia). We assessed population attributes of three critically endangered endemic species (Primula boveana Decne ex Duby, Rosa arabica Crep., and Silene leucophylla Boiss.) in two growing seasons (2006/2007 and 2013/2014), differing in the received rainfalls in microhabitats at the high mountains of southern Sinai. Both P. boveana and S. leucophylla had very small population size, but significantly increased in the 2013/2014 growing season which received above average rainfalls. The population of R. arabica is the smallest (around 40 individuals) and did not increase, even after the increase in rainfalls. Whereas P. boveana is present in fewer sites and grew in small number of specific microhabitats, both S. leucophylla and R. arabica were recorded in most studied sites and habitat types. Unlike R. arabica, both P. boveana and S. leucophylla were recorded in caves and steep slopes and on the top of the mountains. This indicates that these sheltered mist microhabitats are the best for future conservation of these species after climate change.

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