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

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.

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

Bird Conservation International ◽

10.1017/s0959270903003010 ◽

2003 ◽

Vol 13 (1) ◽

pp. 1-12 ◽

Cited By ~ 6

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.

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

Animal Conservation ◽

10.1111/j.1469-1795.2007.00102.x ◽

2007 ◽

Vol 10 (2) ◽

pp. 254-262 ◽

Cited By ~ 8

Author(s):

M. A. Banks ◽

E. R. Ellis ◽

Antonio ◽

P. C. Wright

Keyword(s):

Population Size ◽

Critically Endangered ◽

Global Population

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

Bird Conservation International ◽

10.1017/s0959270909990323 ◽

2010 ◽

Vol 21 (2) ◽

pp. 186-198 ◽

Cited By ~ 8

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.

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Population size and status of the Yellow-breasted Racquet-tail Parrot Prioniturus flavicans

Bird Conservation International ◽

10.1017/s0959270900000125 ◽

2000 ◽

Vol 10 (2) ◽

pp. 131-136 ◽

Cited By ~ 3

Author(s):

Jonathan S. Walker ◽

Alexis J. Cahill

Keyword(s):

Population Size ◽

National Park ◽

Nature Reserve ◽

Population Estimates ◽

Suitable Habitat ◽

World Population ◽

Restricted Range ◽

The North ◽

Density Values ◽

Lowland Rainforest

Densities and population estimates are presented for the little known Yellow-breasted Racquet-tail Parrot Prioniturus flavicans, a species endemic to the Indonesian island of Sulawesi. Sixteen months of fieldwork was conducted within two protected areas in the island's northern peninsula. Densities were found to be much greater in the Bogani Nani Wartabone National Park than in the Tangkoko Duasaudara Nature Reserve: 16.27 and 7.18 birds/km2, respectively. The species has a much more restricted range than previously thought, being confined to the eastern two-thirds of the north peninsula. The remaining suitable habitat within this range, lowland rainforest, is estimated to be c. 11,300 km2. Using this figure in conjunction with density values we estimate that the world population for this species may be greater than 44,650 birds. Whilst such a population size is higher than previously thought, the very restricted distribution of the species causes concern for its future as loss and fragmentation of forest habitat are ongoing within its range.

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Population size and habitat associations of the Long-tailed Ground-roller Uratelornis chimaera

Bird Conservation International ◽

10.1017/s095927090600058x ◽

2007 ◽

Vol 17 (1) ◽

pp. 1-12 ◽

Cited By ~ 4

Author(s):

NATHALIE SEDDON ◽

JOSEPH A. TOBIAS

Keyword(s):

Population Size ◽

Habitat Associations ◽

Suitable Habitat ◽

Mature Adults ◽

South West ◽

The Family ◽

Direct Association ◽

Size Population ◽

Global Population ◽

Effective Conservation

The Long-tailed Ground-roller (Uratelornis chimaera) is a globally Vulnerable, restricted-range species of dry forests in south-west Madagascar. We studied a population in 1997–2000, finding that nest-building was relatively synchronous and that pairs preferentially nested next to open areas, such as driveable tracks. By searching for trackside nests and for footprints, we conducted surveys throughout the known range of the species. Total transect coverage was 153 km, along which we encountered a minimum of 28 breeding pairs. By dividing the transects into 41 randomly distributed survey strips, each 1.2 km in length and 200 m broad, we intensively sampled an area of 9.84 km2. Using transect data, we made a tentative estimate of 5.7 mature adults km−2, from which we estimated a global population of 21,092 individuals, based on our calculation from satellite imagery that 3,706 km2 of suitable habitat remained. By comparing habitat data at points with and without ground-rollers we found that, contrary to previous statements, they prefer lower stature or degraded habitats, and have no direct association with the endemic cactus-like tree Didierea madagascariensis. We used a novel census technique to provide the first quantitative data on population size, population density, breeding behaviour and ecology in the Long-tailed Ground-roller, or any member of the family Brachypteraciidae, information that is crucial to the design of effective conservation programmes.

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Population size, distribution and status of the remote and Critically Endangered Bawean deer Axis kuhlii

Oryx ◽

10.1017/s0030605316000429 ◽

2016 ◽

Vol 51 (4) ◽

pp. 665-672 ◽

Cited By ~ 5

Author(s):

Dede Aulia Rahman ◽

Georges Gonzalez ◽

Stéphane Aulagnier

Keyword(s):

Population Size ◽

Faecal Pellet ◽

Iucn Red List ◽

Critically Endangered ◽

Density Estimates ◽

Distribution Maps ◽

Population Size Estimates ◽

Endangered Status ◽

Size Estimates ◽

Model Approach

AbstractConservation of rare ungulates requires reliable population size estimates and distribution maps for prioritizing investments and assessing the effectiveness of conservation measures. We used both camera trapping and a random encounter model approach, and faecal pellet group counts, to update the range and population size of the Bawean deer Axis kuhlii in the Bawean Island Nature Reserve and Wildlife Sanctuary, Indonesia. We studied 2-month periods to fulfil the assumption of population closure. Both methods provided similar population density estimates (higher in the dry season) of c. 227–416 individuals. The estimated range of the species is significantly narrower than previously reported. The main threats (habitat loss as a result of illegal logging, and disturbance by dogs and hunters) are ongoing. Based on these results we suggest that the species should retain its Critically Endangered status on the IUCN Red List.

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Waterbird population estimates for a key staging site in Kazakhstan: a contribution to wetland conservation on the Central Asian flyway

Bird Conservation International ◽

10.1017/s0959270908000087 ◽

2008 ◽

Vol 18 (1) ◽

pp. 71-86 ◽

Cited By ~ 8

Author(s):

Holger Schielzeth ◽

Götz Eichhorn ◽

Thomas Heinicke ◽

Johannes Kamp ◽

Maxim A. Koshkin ◽

...

Keyword(s):

Population Size ◽

Conservation Status ◽

Steppe Zone ◽

Wetland Conservation ◽

Conservation Strategies ◽

Population Estimates ◽

The South ◽

Migration Routes ◽

South West ◽

Population Size Estimates

AbstractRealistic population size estimates for waterbirds are crucial for the application of wetland conservation strategies, since the identification of internationally important wetlands is based on local numbers relative to the population size of the respective species. Central Asia is a poorly surveyed region that is situated at the intersection of migration routes that lead waterbirds from Western Siberia to the south-west (South-West Asia, East Africa) and to the south-east (South Asia, India). We calculated waterbird population estimates for the Tengiz–Korgalzhyn region, a large wetland complex in the steppe zone of Central Kazakhstan, based on waterbird surveys conducted between 1999 and 2004. For 20 of 43 species analysed the region supported more than 5% of the relevant flyway populations. Five species occurred with more than 40% of the flyway totals, including the Endangered White-headed Duck Oxyura leucocephala and the Vulnerable Dalmatian Pelican Pelecanus crispus. Peak numbers were recorded in summer and autumn and for most species numbers were more than an order of magnitude lower on spring migration compared with autumn migration. We identified 72 individual sites that held more than 20,000 waterbirds or more than 1% of a particular flyway population at least once. These sites are likely to constitute priorities for conservation. The general conservation status of the region is favourable, since many of the important sites are located within a strict nature reserve. However, outside the reserve hunting, fishing and powerline casualties represent conservation issues that should be monitored more carefully in the future.

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

Oryx ◽

10.1017/s0030605316000806 ◽

2016 ◽

Vol 52 (1) ◽

pp. 137-146 ◽

Cited By ~ 8

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.

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Fish population size estimates from a small intermittently open estuary in South Africa, based on mark-recapture techniques

Marine and Freshwater Research ◽

10.1071/mf99143 ◽

2001 ◽

Vol 52 (3) ◽

pp. 283 ◽

Cited By ~ 26

Author(s):

P. D. Cowley ◽

A. K. Whitfield

Keyword(s):

Population Size ◽

Total Population ◽

Fish Population ◽

Minimum Size ◽

Population Estimates ◽

Likelihood Estimator ◽

Mark Recapture ◽

Population Size Estimates ◽

Population Sizes ◽

Size Estimates

Population sizes of the migratory marine-spawning fishes in the small intermittently open East Kleinemonde Estuary (33º32′S, 27º03′E) were estimated during two independent mark–recapture studies between 1994 and 1996. Seines were used to sample fishes during the closed-mouth phase of the estuary. All individuals above a stipulated minimum size were marked by fin-clipping. Population estimates were obtained by use of two mark–recapture models (Schnabel and a maximum-likelihood estimator) and a derived method. The total population size was estimated at ~18 000 and ~133 000 individuals during the two study periods respectively. The large temporal (interannual) variability was ascribed to both abiotic (estuary mouth conditions) and biotic-conditions. The dominant species during both periods was Rhabdosargus holubi, which accounted for ~75% and ~80%of the total population of marine fishes in the estuary. The success of this species is attributed to an extended breeding season and the ability to recruit during mouth overwash events.

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Status and distribution of the endemic Bali starling Leucopsar rothschildi

Oryx ◽

10.1046/j.1365-3008.2000.00118.x ◽

2000 ◽

Vol 34 (3) ◽

pp. 188-197 ◽

Cited By ~ 5

Author(s):

S. (Bas) van Balen ◽

I Wayan A. Dirgayusa ◽

I Made W. Adi Putra ◽

Herbert H. T. Prins

Keyword(s):

Population Size ◽

Small Area ◽

Small Population ◽

Critically Endangered ◽

Suitable Habitat ◽

Pet Trade ◽

Monsoon Forest ◽

Habitat Conversion ◽

Natural Range ◽

Precarious Situation

AbstractThe Bali starling Leucopsar rothschildi is a passerine endemic to the dry monsoon forest of the island of Bali, Indonesia. Habitat conversion and excessive capture for the pet trade brought the species to the verge of extinction in the 1980s. The species is critically endangered because of 1) an extremely small population size, 2) restriction to a small area, 3) illegal trapping, and 4) diminishing suitable habitat left within its natural range. An intricate web of factors prevents the Bali starling from emerging from this precarious situation.

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