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

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

Bird Conservation International ◽

10.1017/s0959270920000283 ◽

2020 ◽

pp. 1-19 ◽

Cited By ~ 1

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.

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Conservation status of the narrow endemic gypsophile Ononis tridentata subsp. crassifolia in southern Spain: effects of habitat disturbance

Oryx ◽

10.1017/s0030605312001688 ◽

2013 ◽

Vol 47 (2) ◽

pp. 199-202 ◽

Cited By ~ 5

Author(s):

Miguel Ballesteros ◽

Ana Foronda ◽

Eva María Cañadas ◽

Julio Peñas ◽

Juan Lorite

Keyword(s):

Population Size ◽

Seedling Recruitment ◽

Conservation Status ◽

Iucn Red List ◽

Endemic Plant ◽

Negative Effects ◽

Field Surveys ◽

Narrow Endemic ◽

Area Of Occupancy ◽

Species Area

AbstractOnonis tridentata L. subsp. crassifolia (Leguminosae) is a narrow endemic plant restricted to gypsum outcrops in south-east Spain. Its habitat and populations are currently threatened by anthropogenic disturbance. Because of the paucity of information concerning its distribution, abundance and response to disturbance, we assessed its status and evaluated the impacts of quarrying, ploughing, grazing and afforestation. Distribution and population size were estimated by field surveys, censuses and mapping. We measured cover, plant volume, fruit and seed production, seed predation and seedling recruitment to asses any effects of disturbance. The species’ area of occupancy is 1.6 km2 and its extent of occurrence 337 km2, in 29 habitat patches and 16 populations between 705 and 1,125 m altitude, and its population size was estimated to be 531,605. Quarrying, ploughing, overgrazing and afforestation negatively affected the species, in this order. We recommend this subspecies be categorized as Vulnerable on the IUCN Red List. A species recovery plan is required, and the ecological restoration of altered areas would mitigate negative effects on the species and improve the overall conservation of gypsum habitats.

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Using Ecological Niche Models for Population and Range Estimates of a Threatened Snake Species (Crotalus oreganus) in Canada

Diversity ◽

10.3390/d13100467 ◽

2021 ◽

Vol 13 (10) ◽

pp. 467

Author(s):

David Anthony Kirk ◽

Sahebeh Karimi ◽

Jared R. Maida ◽

Jessica A. Harvey ◽

Karl W. Larsen ◽

...

Keyword(s):

Land Cover ◽

Protected Areas ◽

Population Size ◽

Small Area ◽

Ecological Niche ◽

Population Estimates ◽

Ecological Niche Models ◽

Crotalus Oreganus ◽

Niche Models ◽

Suitable Land

Modelling the distribution and abundance of species at risk is extremely important for their conservation and management. We used ecological niche models (ENMs) to predict the occurrence of western rattlesnakes (Crotalus oreganus) in British Columbia (BC), Canada. We applied this to existing population estimates to support a threshold of occurrence for management and conservation. We also identified predictors influencing rattlesnake distribution and abundance in this region. Using a Geographic Information Systems platform, we incorporated ENMs, capture–mark–recapture (CMR) and radio-telemetry results, province-wide observations, Landsat imagery and provincial databases for agricultural land use to produce quantitative, spatially explicit, population estimates across BC. Using available western rattlesnake habitat estimated at 183.9 km2 and averaging estimates calculated from densities in three study populations, we generated a mean adult population size of 9722 (±SD 3009; 0.8 relative index of occurrence [RIO] threshold). Only a small area (21.6 km2) of suitable land cover was located within protected areas, potentially protecting an estimated 1144 (±354) adults. Most suitable land cover was within 500 m of roads (170.6 km2), representing potential habitat being used by an estimated 9017 (±2791) adults. At the threshold RIO value chosen (0.8), only a very small area of farmland provided suitable land cover. Our results highlight the possibility of high mortality rates for western rattlesnakes near roads and the fact that protected areas do not provide sufficient coverage to conserve the population. Given that this species has relatively low mobility and high site fidelity to home ranges, our population estimate for BC provides a useful reference for the northern part of the species’ range. It also fulfills a need to estimate population size within political jurisdictions where conservation management decisions are made, as well as presenting a method that can be applied to other parts of the range, including the southern United States. Our study provides an important benchmark for future monitoring of western rattlesnakes in BC using a repeatable and transparent approach. Similar applications can be extrapolated and applied for other threatened species to identify and quantify population distributions and threats, further supporting conservation prioritization tools to be used to maximize the effectiveness of conservation strategies under financial constraints.

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

10.1101/2021.11.29.470363 ◽

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.

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Distribution and Ecology of a New Species of Water-lily, Nymphaea loriana (Nymphaeaceae), in Western Canada

The Canadian Field-Naturalist ◽

10.22621/cfn.v130i1.1787 ◽

2016 ◽

Vol 130 (1) ◽

pp. 25

Author(s):

Diana Bizecki Robson ◽

John H. Wiersema ◽

C. Barre Hellquist ◽

Thomas Borsch

Keyword(s):

Population Size ◽

Boreal Lakes ◽

Water Lily ◽

East Central ◽

Extent Of Occurrence ◽

Area Of Occupancy ◽

The Status ◽

Schoenoplectus Tabernaemontani ◽

Distribution And Ecology ◽

Potamogeton Natans

Nymphaea loriana Wiersema, Hellq. & Borsch (Lori’s Water-lily) is a newly described, Canadian endemic species that has been found in central Manitoba and east-central Saskatchewan. To assess the status of a species, data regarding its distribution, population size, habitat, and search effort are needed. The purpose of this paper is to document these factors for this species. The extent of occurrence of N. loriana is approximately 15 100 km2 but the known area of occupancy is a mere 20 km2. The estimated population size of N. loriana is about 750 individual plants, although more may exist on poorly explored rivers and lakes within the extent of occurrence and possibly in northeastern Ontario. Nymphaea loriana occurs in fresh, stagnant, or slowly moving water in boreal lakes and rivers and is typically associated with N. leibergii (Dwarf Water-lily), Schoenoplectus tabernaemontani (Soft-stemmed Bulrush), Potamogeton natans (Floating-leaved Pondweed) and Nuphar variegata (Variegated Pondlily). Potential threats to the persistence of this species include low water quality resulting from mining, forestry, and agriculture, and changes to water flow because of dam construction and climate change. Monitoring known populations and searching for additional ones may be needed to assess the status of this species.

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

Oryx ◽

10.1017/s0030605311001165 ◽

2012 ◽

Vol 46 (2) ◽

pp. 236-239 ◽

Cited By ~ 2

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.

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An assessment of the distribution, population size and conservation status of the Santa Marta Foliage-gleaner Automolus rufipectus: a Sierra Nevada de Santa Marta endemic

Bird Conservation International ◽

10.1017/s0959270914000513 ◽

2015 ◽

Vol 25 (4) ◽

pp. 451-465 ◽

Cited By ~ 3

Author(s):

ESTEBAN BOTERO-DELGADILLO ◽

NICHOLAS BAYLY ◽

CAMILA GÓMEZ ◽

PAULO C. PULGARÍN-R. ◽

CARLOS ANDRÉS PÁEZ

Keyword(s):

Population Size ◽

Sierra Nevada ◽

Forest Cover ◽

Conservation Status ◽

Bird Species ◽

Environmental Niche ◽

Coffee Plantations ◽

Habitat Transformation ◽

Elevation Range ◽

Area Of Occupancy

SummaryThe Santa Marta Foliage-gleaner Automolus rufipectus is one of 19 endemic bird species found in the Sierra Nevada de Santa Marta (SNSM) in northern Colombia but until recently it was considered a sub-species of the Ruddy Foliage-gleaner Automolus rubiginosus. Consequently, published information on its distribution and ecology is lacking, and while it is classified as near- threatened, this designation was based on limited quantitative data. To improve our knowledge of the Santa Marta Foliage-gleaner’s geographical distribution, elevation range, population density, habitat use and conservation status, we analysed both historical and recent site locality records and carried out variable distance transects within forested habitats and shade coffee plantations. We modelled the environmental niche of the species and subsequently estimated its extent of occurrence and area of occupancy, as well as population size. Our results consistently showed that the distribution of the Santa Marta Foliage-gleaner is more restricted than previously considered, both geographically and by elevation (we redefine elevation range as 600–1,875 m). This suggests that the species is more at risk of habitat transformation and combined with our estimates of population size (< 10,000 individuals), it is likely that the species will be uplisted to a higher threat category. More positively, and contrary to published accounts, we found that approximately 40% of the species’ range lies within protected areas. Nevertheless, we recommend the implementation of strategies to maintain forest cover on the western flank of the SNSM and further research to better define the species’ habitat needs and population dynamics.

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