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Article

Roadside Car Surveys: Methodological Constraints and Solutions for Estimating Parrot Abundances across the World

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Department of Conservation Biology and Integrative Biology, Doñana Biological Station CSIC, 41092 Sevilla, Spain
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Department of Physical, Chemical and Natural Processes, Universidad Pablo de Olavide, 41013 Sevilla, Spain
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Department of Ecology, Biosciences Institute, University of São Paulo, 05508-220 São Paulo, Brazil
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Department of Migration, Max Planck Institute of Animal Behavior, D-78315 Radolfzell, Germany
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Biodiversity Research Institute (CSIC, UO, PA), Oviedo University, 33600 Mieres, Spain
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Department of Evolutionary Ecology, Museo Nacional de Ciencias Naturales CSIC, 28006 Madrid, Spain
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CLB Foundation, Santa Cruz de la Sierra 5030, Bolivia
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Zoológico Municipal de Fauna Sudamericana, Santa Cruz de la Sierra 1026, Bolivia
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Laboratorio de Biología y Genética, Universidad Nacional de San Cristóbal de Huamanga, Ayacucho 05001, Peru
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Department of Health Sciences, Faculty of Biomedical and Health Sciences, Universidad Europea de Madrid, 28670 Madrid, Spain
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Department of Applied Biology, Universidad Miguel Hernández, Elche, 03202 Alicante, Spain
*
Author to whom correspondence should be addressed.
Academic Editor: Michael Wink
Received: 10 May 2021 / Revised: 25 June 2021 / Accepted: 29 June 2021 / Published: 1 July 2021
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. View Full-Text
Keywords: bird abundance; census; bird density; detectability; distance sampling; Psittaciformes bird abundance; census; bird density; detectability; distance sampling; Psittaciformes
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MDPI and ACS Style

Tella, J.L.; Romero-Vidal, P.; Dénes, F.V.; Hiraldo, F.; Toledo, B.; Rossetto, F.; Blanco, G.; Hernández-Brito, D.; Pacífico, E.; Díaz-Luque, J.A.; Rojas, A.; Bermúdez-Cavero, A.; Luna, Á.; Barbosa, J.M.; Carrete, M. Roadside Car Surveys: Methodological Constraints and Solutions for Estimating Parrot Abundances across the World. Diversity 2021, 13, 300. https://0-doi-org.brum.beds.ac.uk/10.3390/d13070300

AMA Style

Tella JL, Romero-Vidal P, Dénes FV, Hiraldo F, Toledo B, Rossetto F, Blanco G, Hernández-Brito D, Pacífico E, Díaz-Luque JA, Rojas A, Bermúdez-Cavero A, Luna Á, Barbosa JM, Carrete M. Roadside Car Surveys: Methodological Constraints and Solutions for Estimating Parrot Abundances across the World. Diversity. 2021; 13(7):300. https://0-doi-org.brum.beds.ac.uk/10.3390/d13070300

Chicago/Turabian Style

Tella, José L., Pedro Romero-Vidal, Francisco V. Dénes, Fernando Hiraldo, Bernardo Toledo, Federica Rossetto, Guillermo Blanco, Dailos Hernández-Brito, Erica Pacífico, José A. Díaz-Luque, Abraham Rojas, Alan Bermúdez-Cavero, Álvaro Luna, Jomar M. Barbosa, and Martina Carrete. 2021. "Roadside Car Surveys: Methodological Constraints and Solutions for Estimating Parrot Abundances across the World" Diversity 13, no. 7: 300. https://0-doi-org.brum.beds.ac.uk/10.3390/d13070300

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