Point transect sampling with traps or lures

Abstract Point-transect sampling is widely used for monitoring trends in abundance of songbirds. It is conceptualized as a “snapshot” method in which birds are “frozen” at a single location. With conventional methods, an observer records birds detected from a point for several minutes, during which birds may move around. This generates upward bias in the density estimate. I compared this conventional approach with two other approaches: in one, the observer records locations of detected birds at a snapshot moment; in the other, distances to detected cues (songbursts), rather than birds, are recorded. I implemented all three approaches, together with line-transect sampling and territory mapping in a survey of four bird species. The conventional method gave a biased estimate of density for one species. The snapshot method was found to be the most efficient of the point-sampling methods. Line-transect sampling proved more efficient than the point-sampling methods for all four species. This is likely to be generally true, provided that terrain and habitat allow easy use of a design with random transect lines. I concluded that the snapshot method is more appropriate than the conventional timed-count method for surveying songbirds. Although precision was rather poor with the cue-based method (partly because too few resources were devoted to cue rate estimation), it may be particularly useful for some single-species surveys. In addition, it is the only valid method for estimating abundance from surveys in which acoustic equipment is used to detect birds. Muestreos en Transectos Puntuales para Aves Canoras: Metodologías Robustas

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SEAGRESS COVERAGE AND ECOSYSTEM CONDITION AT THE COASTAL AREA OF MADASANGER, JELENGA AND MALUK, WEST SUMBAWA

Jurnal Ilmu dan Teknologi Kelautan Tropis ◽

10.29244/jitkt.v5i1.7744 ◽

2013 ◽

Vol 5 (1) ◽

Author(s):

Erny Poedjirahajoe ◽

Ni Putu Diana Mahayani ◽

Boy Rahardjo Sidharta ◽

Muhamad Salamuddin

Keyword(s):

Coastal Area ◽

Seagrass Species ◽

Seagrass Bed ◽

Water Turbidity ◽

Transect Sampling ◽

Sampling Points ◽

Ecosystem Condition ◽

High Turbidity ◽

Line Transects ◽

Seagrass Coverage

The increase of temperature might affect the distribution and reproduction of seagrass. This research aims to determine the seagrass bed coverage and the ecosystem condition. Three line transects were established perpendicular to the coastal line with the distance of 50-100 m, or up to the border of the intertidal area. In each transect, sampling points were determined with a distance of 10-20 m. At the sampling points, a plot of 50 cm x 50 cm was established to measure the coverage percentage of seagrass vegetation. The seagrass species were also observed and recorded along the line transects. The percentage of seagrass coverage was measured using a method from Saito and Atobe (1994). The results showed that the coastal area of Jelenga has the highest percentage of seagrass coverage (>60%, healthy) among other coastal areas. This may be caused by the characteristic of Jelenga coast which was relatively calm, few visitors, low water turbidity, and high light penetration. While, other transects have percentage coverage of less than 60% (less healthy). There was one transect on Maluk coast which has coverage percentage of less than 29% (lack of seagrass species). The small coverage percentage on Maluk coast can be caused by the high number of visitors and high activity of fishing boats around the coast which results in high turbidity. Keywords: coverage, ecosystem condition, seagrass bed, west Sumbawa.

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Estimating a resource selection function with line transect sampling

Journal of Applied Mathematics and Decision Sciences ◽

10.1155/s1173912602000159 ◽

2002 ◽

Vol 6 (4) ◽

pp. 213-228 ◽

Cited By ~ 13

Author(s):

Bryan F. J. Manly

Keyword(s):

Resource Selection ◽

Probability Function ◽

Resource Selection Function ◽

Line Transect ◽

Selection Function ◽

Line Transect Sampling ◽

Selection Probability ◽

Transect Sampling ◽

Conditional Maximum ◽

Habitat Variables

A resource selection probability function is a function that gives the prob- ability that a resource unit (e.g., a plot of land) that is described by a set of habitat variables X1 to Xp will be used by an animal or group of animals in a certain period of time. The estimation of a resource selection function is usually based on the comparison of a sample of resource units used by an animal with a sample of the resource units that were available for use, with both samples being assumed to be effectively randomly selected from the relevant populations. In this paper the possibility of using a modified sampling scheme is examined, with the used units obtained by line transect sampling. A logistic regression type of model is proposed, with estimation by conditional maximum likelihood. A simulation study indicates that the proposed method should be useful in practice.

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Population structure, density and biomass of large herbivores in the tropical forests of Nagarahole, India

Journal of Tropical Ecology ◽

10.1017/s0266467400006040 ◽

1992 ◽

Vol 8 (01) ◽

pp. 21-35 ◽

Cited By ~ 125

Author(s):

K. Ullas Karanth ◽

Melvin E. Sunquist

Keyword(s):

Population Structure ◽

Tropical Forests ◽

Primate Species ◽

Line Transect ◽

Large Herbivore ◽

Large Herbivores ◽

Transect Sampling ◽

Structure Density ◽

Density And Biomass ◽

Turn Over

ABSTRACTWe studied the population structure, density and biomass of seven ungulate and two primate species in the tropical forests of Nagarahole, southern India, using line transect sampling and roadside/platform counts, during 1986–87. The estimated ecological densities of large herbivore species in the study area are: 4.2 muntjac km−2, 50.6 chital km−2, 5.5 sambar km−2, 0.8 four-horned antelope km−2, 9.6 gaur km−2, 4.2 wild pig km−2, 3.3 elephant km−2, 23.8 hanuman langur km−2and 0.6 bonnet macaque km−2. Most ungulates have female-biased adult sex ratios. Among common ungulate species, yearlings and young of the year comprise about a third of the population, suggesting relatively high turn-over rates. Three species (muntjac, sambar and four-horned antelope) are solitary, while others form groups. The study area supports a wild herbivore biomass density of 14,744 kg km−2. Among the three habitat types within the study area, biomass is lower in dry deciduous forests when compared with moist deciduous or teak plantation dominant forests. Using our results, we have examined the factors that may contribute towards maintenance of high ungulate biomass in tropical forests.

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