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

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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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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A Study of Population Size and Activity Patterns and Their Relationship to the Prey Species of the Eurasian Lynx Using a Camera Trapping Approach

Animals ◽

10.3390/ani9110864 ◽

2019 ◽

Vol 9 (11) ◽

pp. 864

Author(s):

Xiaoming Tang ◽

Shupei Tang ◽

Xiaoyu Li ◽

Dalai Menghe ◽

Wuliji Bao ◽

...

Keyword(s):

Community Structure ◽

Population Size ◽

Habitat Management ◽

Activity Patterns ◽

Management Strategies ◽

Camera Trapping ◽

Ecosystem Functions ◽

Lynx Lynx ◽

Eurasian Lynx ◽

Different Seasons

Revealing the behavioral relationships between predators and their prey is fundamental in understanding the community structure and ecosystem functions of such animals. This study aimed at detecting the population size and activity patterns of Eurasian lynx (Lynx lynx) (along with its prey) by camera trapping monitoring from 2014 to 2017 at the Saihanwula nature reserve in central Inner Mongolia. The total effective trapping days were 29,892 and 20 lynx were identified from 343 trapping photos based on the inner side patterns of their forelimbs. The daily activity rhythms of the lynx overlapped with those of different prey in different seasons. The yearly activity pattern of the lynx was influenced by its main prey’s biology. In conclusion, this study reveals that the activity patterns of the top predator matched those of its prey in different time periods. Habitat management strategies promoting the restoration of prey communities would benefit the lynx in maintaining a stable community structure.

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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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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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HIV/AIDS lowers UN's global population estimates

The Lancet ◽

10.1016/s0140-6736(03)12731-6 ◽

2003 ◽

Vol 361 (9360) ◽

pp. 841 ◽

Cited By ~ 1

Author(s):

Patricia Schlagenhauf ◽

Haroon Ashraf

Keyword(s):

Population Estimates ◽

Global Population ◽

Hiv Aids

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Marked Cards in the Pack: Using Playing Cards to Teach the Importance of Sample Size & Testing Assumptions in Capture–Recapture Estimations of Population Size

The American Biology Teacher ◽

10.1525/abt.2020.82.6.396 ◽

2020 ◽

Vol 82 (6) ◽

pp. 396-401

Author(s):

Michael Calver ◽

Timothy Blake

Keyword(s):

Secondary School ◽

Sample Size ◽

Population Size ◽

Confidence Intervals ◽

Population Ecology ◽

Simple Approach ◽

Population Estimates ◽

Index Method ◽

Capture Recapture ◽

Approach To Teaching

Estimating population size is essential for many applications in population ecology, so capture–recapture techniques to do this are often taught in secondary school classrooms and introductory university units. However, few classroom simulations of capture–recapture consider the sensitivity of results to sampling intensity, the important concept that the population size calculated is an estimate with error attached, or the consequences of violating assumptions underpinning particular capture–recapture models. We describe a simple approach to teaching the Lincoln index method of capture–recapture using packs of playing cards. Students can trial different sampling intensities, calculate 95% confidence intervals for population estimates, and explore the consequences of violating specific assumptions.

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Estimating brush-tailed rock-wallaby population size using individual animal recognition

Australian Mammalogy ◽

10.1071/am11005 ◽

2011 ◽

Vol 33 (2) ◽

pp. 228

Author(s):

Karl Vernes ◽

Stuart Green ◽

Piers Thomas

Keyword(s):

Population Size ◽

National Park ◽

New South ◽

Morphological Characters ◽

Population Estimates ◽

Individual Animal ◽

Mark Recapture ◽

South Wales ◽

North Eastern ◽

Estimate Population Size

We undertook surveys of brush-tailed rock-wallabies (Petrogale penicillata) at four colonies in Oxley Wild Rivers National Park, north-eastern New South Wales, with the aim of developing a technique based upon individual animal recognition that could be used to obtain robust population estimates for rock-wallaby colonies. We identified individuals on the basis of distinct morphological characters in each colony using visual observations, and used the data within a ‘mark–recapture’ (or sight–resight) framework to estimate population size. More than 37 h of observations were made over 10 sampling days between 18 May and 9 June 2010. We could identify 91.7% of all rock-wallabies that were independently sighted (143 of 156 sightings of 35 animals). A small percentage of animals could not be identified during a visit because they were seen only fleetingly, were in dense cover, or were partly obscured by rock. The number of new animals sighted and photographed declined sharply at the midpoint of the survey, and there was a corresponding increase in resighting of known individuals. Population estimates using the mark–recapture methodology were nearly identical to estimates of total animals seen, suggesting that this method was successful in obtaining a complete census of rock-wallabies in each colony.

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Estimating western ringtail possum (Pseudocheirus occidentalis) density using distance sampling

Australian Mammalogy ◽

10.1071/am09037 ◽

2010 ◽

Vol 32 (2) ◽

pp. 197 ◽

Cited By ~ 1

Author(s):

G. R. Finlayson ◽

A. N. Diment ◽

P. Mitrovski ◽

G. G. Thompson ◽

S. A. Thompson

Keyword(s):

Urban Development ◽

Population Size ◽

Western Australia ◽

Distance Sampling ◽

Reliable Estimate ◽

Population Estimates ◽

Density Estimates ◽

The Subject ◽

Ringtail Possum

A reliable estimate of population size is of paramount importance for making management decisions on species of conservation significance that may be impacted during development. The western ringtail possum (Pseudocheirus occidentalis) is regularly encountered during urban development and is the subject of numerous surveys to estimate its abundance. A variety of techniques have been used for this species with mixed results. This paper reports on a case study using distance sampling to estimate density of P. occidentalis in a small habitat remnant near Busselton, Western Australia. Density estimates obtained were within the range of previous studies of this species and we suggest that this technique should be employed in future surveys to improve the accuracy of population estimates for this species before development.

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Developing a census method based on sight counts to estimate rabbit (Oryctolagus cuniculus) numbers

Wildlife Research ◽

10.1071/wr02014 ◽

2003 ◽

Vol 30 (5) ◽

pp. 487 ◽

Cited By ~ 15

Author(s):

Dylan W. Poole ◽

Dave P. Cowan ◽

Graham C. Smith

Keyword(s):

Population Size ◽

Field Trials ◽

Population Estimates ◽

Economic Costs ◽

Natural Conditions ◽

Commercial Farms ◽

The Mean ◽

The Difference ◽

Study Sites ◽

Autumn And Winter

A rabbit-census method, based on systematic counts conducted at night or at dawn and dusk, was developed and validated in terms of estimating the total number of rabbits present in a given area. Initially, models were developed under semi-natural conditions to describe the relationships between the numbers of rabbits counted and population size. Confidence limits were also calculated. The models were developed by comparing rabbit counts with the actual number of rabbits present, from a known population of animals. Only spotlight counts at night were considered reliable enough to estimate rabbit population size. During the autumn and winter months these represented ~60% of the population present. The model was subsequently validated, in two different exercises, following a series of field trials conducted under a variety of conditions on commercial farms. Initially, population estimates derived from the model were compared with those calculated using an alternative census technique. Population estimates, using the two techniques, were very similar at nine of the ten study sites. A second validation exercise was also conducted whereby the number of rabbits removed at each of the sites was compared with the difference between the mean pre- and post-removal spotlight counts. The results further supported the proposition that spotlight counts represent ~60% of the population present, with the difference between the two mean spotlight counts representing 61.2% (± 11.0, s.d.) of the number of rabbits removed. The census method therefore shows considerable promise as a means to estimate rabbit numbers under a range of agricultural conditions and therefore has the potential to predict accurately the economic costs of rabbit damage and also to gauge the effectiveness of various methods of rabbit control.

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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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