Breeding biology of the grey-browed brushfinch Arremon assimilis (Aves: Passerellidae) in the Eastern Andes of Colombia

ABSTRACT

The timing of breeding is a key component of the life history of birds. In the tropics, where avian diversity is higher and environmental variability is less predictable than in temperate latitudes, breeding phenology patterns are poorly understood, and many other life-history traits remain largely unstudied. We describe the nest, egg, juvenile plumage, and breeding phenology of a population of the grey-browed brushfinch (Arremon assimilis assimilis, Passerellidae) from the Eastern Andes of Colombia. We found a single bluish-white unmarked egg in a cup-shaped nest. We also examined the relationship between photoperiod and precipitation with breeding phenology by monitoring 44 territorial pairs between 2017 and 2018. Arremon assimilis has two breeding peaks associated with the onset of rainfall in prior months: the first peak extends from mid-May to September, and the second from November and December to January. We also update a recent review of breeding biology data in Arremon and discuss how life-history traits may have evolved in light of the relationships among sparrows in this genus. Our study, one of few analyses of the breeding biology of a population in a montane species from the Andes, highlights the importance of such studies to further comprehend the general mechanisms that shape the breeding biology of tropical birds.

KEYWORDS:

• breeding phenology
• life history
• reproductive biology
• Passerellidae
• montane forest
• tropical birds

Acknowledgements

We thank Asofloresta, Martha Millán and forest owners for allowing us to conduct field work at Floresta de la Sabana. Special thanks to Miguel Moreno for useful advice on data analyses. Juliana Rodríguez and Paula Cardozo assisted with data collection. Members of the Laboratorio de Biología Evolutiva de Vertebrados and the TropBioLab gave useful advice and comments on this manuscript. Mist-netting, banding and collection of specimens were authorised by the Autoridad Nacional de Licencias Ambientales of Colombia through the Permiso Marco de Recolección de Especímenes granted to the Universidad de los Andes (decretos 1177 de 2014 and 1386 de 2015).

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

The code used to perform data imputation in R is available in the Supplementary material as a text file. Supporting information on juvenile plumage characterization (Figure S1) and raw breeding data used for analysis (ie raw breeding observations, precipitation and daylight duration data; Table S1) is included in the Supplementary material.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00222933.2023.2271607.

Additional information

Funding

This research was financially supported by the Programa Doctoral Becas Colciencias (Convocatoria 647), Animal Behaviour Society Developing Nations Award, E. Alexander Bergstrom Memorial Research Award of the Association of Field Ornithologists, FrançoisVuilleumier Fund of the Neotropical Ornithological Society, and Beca Proyecto Semilla of the Facultad de Ciencias (Convocatorias 2017-1 and 2019-1); Departamento Administrativo de Ciencia, Tecnología e Innovación (COLCIENCIAS).