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Roadside Car Surveys: Methodological Constraints and Solutions for Estimating Parrot Abundances across the World
- Source :
- Digital.CSIC. Repositorio Institucional del CSIC, instname, Diversity, Vol 13, Iss 300, p 300 (2021), Diversity; Volume 13; Issue 7; Pages: 300
- Publication Year :
- 2021
- Publisher :
- Multidisciplinary Digital Publishing Institute, 2021.
-
Abstract
- Parrots stand out among birds because of their poor conservation status and the lack of available information on their population sizes and trends. Estimating parrot abundance is complicated by the high mobility, gregariousness, patchy distributions, and rarity of many species. Roadside car surveys can be useful to cover large areas and increase the probability of detecting spatially aggregated species or those occurring at very low densities. However, such surveys may be biased due to their inability to handle differences in detectability among species and habitats. We conducted 98 roadside surveys, covering > 57,000 km across 20 countries and the main world biomes, recording ca. 120,000 parrots from 137 species. We found that larger and more gregarious species are more easily visually detected and at greater distances, with variations among biomes. However, raw estimates of relative parrot abundances (individuals/km) were strongly correlated (r = 0.86–0.93) with parrot densities (individuals/km2) estimated through distance sampling (DS) models, showing that variability in abundances among species (>40 orders of magnitude) overcomes any potential detectability bias. While both methods provide similar results, DS cannot be used to study parrot communities or monitor the population trends of all parrot species as it requires a minimum of encounters that are not reached for most species (64% in our case), mainly the rarest and more threatened. However, DS may be the most suitable choice for some species-specific studies of common species. We summarize the strengths and weaknesses of both methods to guide researchers in choosing the best–fitting option for their particular research hypotheses, characteristics of the species studied, and logistical constraints.<br />This research was funded by Fundación Biodiversidad (Spanish Ministerio de Medio Ambiente, project 52I.CA2109), Fundación Repsol, Spanish Ministerio de Ciencia e Innovación (Project CGL2015-71378-P), and mostly by Loro Parque Fundación (Project SEJI/2018/024).
- Subjects :
- 0106 biological sciences
Census
census
QH301-705.5
Biome
Population
bird density
010603 evolutionary biology
01 natural sciences
Psittaciformes
bird abundance
Distance sampling
Common species
Abundance (ecology)
Biology (General)
education
Nature and Landscape Conservation
Bird abundance
education.field_of_study
Ecology
Bird density
010604 marine biology & hydrobiology
Ecological Modeling
distance sampling
Agricultural and Biological Sciences (miscellaneous)
detectability
Detectability
Geography
Habitat
Threatened species
Conservation status
Subjects
Details
- Database :
- OpenAIRE
- Journal :
- Digital.CSIC. Repositorio Institucional del CSIC, instname, Diversity, Vol 13, Iss 300, p 300 (2021), Diversity; Volume 13; Issue 7; Pages: 300
- Accession number :
- edsair.doi.dedup.....1c35393efdf6ce6b4ff41303f0cae53a