Non-Invasive Sex Determination of Nestlings and Adult Bonelli’s Eagles Using Morphometrics

SIMPLE SUMMARY: This study explores the use of biometric analysis to identify the sex of Bonelli’s eagles, a bird species with reverse sexual dimorphism where females are usually larger than males. By using linear discriminant analysis of biometric variables, we were able to obtain equations that ac...

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Autores principales: Estellés-Domingo, Irene, López-López, Pascual
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2023
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10093107/
https://www.ncbi.nlm.nih.gov/pubmed/37048457
http://dx.doi.org/10.3390/ani13071201
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author Estellés-Domingo, Irene
López-López, Pascual
author_facet Estellés-Domingo, Irene
López-López, Pascual
author_sort Estellés-Domingo, Irene
collection PubMed
description SIMPLE SUMMARY: This study explores the use of biometric analysis to identify the sex of Bonelli’s eagles, a bird species with reverse sexual dimorphism where females are usually larger than males. By using linear discriminant analysis of biometric variables, we were able to obtain equations that accurately distinguished between male and female eagles, using just two measurements. The study included 137 Bonelli’s eagles, 82 nestlings and 55 adults, sampled in eastern Spain from 2015 to 2022. The validation procedure reduced the number of variables used, increasing the accuracy of sexing and saving time. Results showed that the lateral tarsus length and dorso-ventral tarsus length measurements were the most effective in distinguishing between male and female eagles of all age classes, while other variables showed some overlap between sexes. This non-invasive method has multiple applications, including estimation of sex ratio for further studies on population dynamics and extinction risk assessments, which could contribute to the conservation of this endangered species. ABSTRACT: Biometric analysis allows the sexing of most vertebrates, particularly birds. Birds of prey, and, especially, the Bonelli’s eagle (Aquila fasciata), show reverse sexual dimorphism (i.e., females are usually larger than males). In contrast to blood sampling, the use of morphometrics allows sex determination using a non-invasive method, and, therefore, it facilitates fieldwork. By means of a linear discriminant analysis of biometric variables, we obtained different equations that allow the sexing of nestlings and adult Bonelli’s eagles. We sampled 137 Bonelli’s eagles, 82 nestlings and 55 adults in eastern Spain during the period 2015–2022. The sexes obtained after linear discriminant analysis were compared with their molecular sexing. The validation procedure of the linear discriminant equations facilitated the reduction of the number of variables used and, consequently, optimised working time and sexing accuracy. After validation, some equations showed a 100% sexing efficiency for Bonelli’s eagles, particularly for adults. Our results showed that the variables with smaller overlap between the sexes were the lateral tarsus length and dorso-ventral tarsus length, particularly in nestlings. The rest of the variables showed some overlap between the sexes in both age classes. The results we obtained enable the sexing of juvenile and adult Bonelli’s eagles in the field using just these two measurements. Hence, this is an easy, accurate, quick and non-invasive method with multiple applications, including in studies on population dynamics, survival analysis or extinction risk assessments, which, ultimately, could contribute to the improvement of the conservation status of this endangered species.
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spelling pubmed-100931072023-04-13 Non-Invasive Sex Determination of Nestlings and Adult Bonelli’s Eagles Using Morphometrics Estellés-Domingo, Irene López-López, Pascual Animals (Basel) Article SIMPLE SUMMARY: This study explores the use of biometric analysis to identify the sex of Bonelli’s eagles, a bird species with reverse sexual dimorphism where females are usually larger than males. By using linear discriminant analysis of biometric variables, we were able to obtain equations that accurately distinguished between male and female eagles, using just two measurements. The study included 137 Bonelli’s eagles, 82 nestlings and 55 adults, sampled in eastern Spain from 2015 to 2022. The validation procedure reduced the number of variables used, increasing the accuracy of sexing and saving time. Results showed that the lateral tarsus length and dorso-ventral tarsus length measurements were the most effective in distinguishing between male and female eagles of all age classes, while other variables showed some overlap between sexes. This non-invasive method has multiple applications, including estimation of sex ratio for further studies on population dynamics and extinction risk assessments, which could contribute to the conservation of this endangered species. ABSTRACT: Biometric analysis allows the sexing of most vertebrates, particularly birds. Birds of prey, and, especially, the Bonelli’s eagle (Aquila fasciata), show reverse sexual dimorphism (i.e., females are usually larger than males). In contrast to blood sampling, the use of morphometrics allows sex determination using a non-invasive method, and, therefore, it facilitates fieldwork. By means of a linear discriminant analysis of biometric variables, we obtained different equations that allow the sexing of nestlings and adult Bonelli’s eagles. We sampled 137 Bonelli’s eagles, 82 nestlings and 55 adults in eastern Spain during the period 2015–2022. The sexes obtained after linear discriminant analysis were compared with their molecular sexing. The validation procedure of the linear discriminant equations facilitated the reduction of the number of variables used and, consequently, optimised working time and sexing accuracy. After validation, some equations showed a 100% sexing efficiency for Bonelli’s eagles, particularly for adults. Our results showed that the variables with smaller overlap between the sexes were the lateral tarsus length and dorso-ventral tarsus length, particularly in nestlings. The rest of the variables showed some overlap between the sexes in both age classes. The results we obtained enable the sexing of juvenile and adult Bonelli’s eagles in the field using just these two measurements. Hence, this is an easy, accurate, quick and non-invasive method with multiple applications, including in studies on population dynamics, survival analysis or extinction risk assessments, which, ultimately, could contribute to the improvement of the conservation status of this endangered species. MDPI 2023-03-30 /pmc/articles/PMC10093107/ /pubmed/37048457 http://dx.doi.org/10.3390/ani13071201 Text en © 2023 by the authors. https://creativecommons.org/licenses/by/4.0/Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Estellés-Domingo, Irene
López-López, Pascual
Non-Invasive Sex Determination of Nestlings and Adult Bonelli’s Eagles Using Morphometrics
title Non-Invasive Sex Determination of Nestlings and Adult Bonelli’s Eagles Using Morphometrics
title_full Non-Invasive Sex Determination of Nestlings and Adult Bonelli’s Eagles Using Morphometrics
title_fullStr Non-Invasive Sex Determination of Nestlings and Adult Bonelli’s Eagles Using Morphometrics
title_full_unstemmed Non-Invasive Sex Determination of Nestlings and Adult Bonelli’s Eagles Using Morphometrics
title_short Non-Invasive Sex Determination of Nestlings and Adult Bonelli’s Eagles Using Morphometrics
title_sort non-invasive sex determination of nestlings and adult bonelli’s eagles using morphometrics
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10093107/
https://www.ncbi.nlm.nih.gov/pubmed/37048457
http://dx.doi.org/10.3390/ani13071201
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