Filling latitudinal gaps in Tachycineta swallows: reproductive strategies in a South American species

ABSTRACT

Chilean swallows (Tachycineta leucopyga) are the southernmost swallows in the Tachycineta genus, breeding from central Chile to southern Chile and Argentina. Studies focused on a population breeding at 54°S in Tierra del Fuego, revealed differences in life-history traits compared to their Northern Hemisphere congeners, such as smaller clutch size, and greater male nest attendance during the incubation period. To assess the consistency of these patterns for the species, we studied breeding biology and parental care of Chilean swallows in Northwestern Argentine Patagonia (41°S). If austral population breeding traits reflect species traits, we predict smaller clutch size, higher female reproductive investment, and similar nest attendance by both sexes during incubation compared to Tachycineta species breeding at similar Northern Hemisphere latitudes. We also anticipate negative correlation between clutch size, egg size, and breeding success with laying date, as observed in Tachycineta species, including Chilean swallows. Surprisingly, clutch and egg sizes did not differ between northern and southern Patagonian populations. We did not find evidence of a negative relationship between clutch or egg size and laying date. Male nest attendance during incubation was variable and low, but their nestlings feeding rates equalled those of females. These findings suggest that Chilean swallows adopt diverse reproductive strategies across regions. This may help this species adapt to different environments and climates, ranging from the shorter breeding seasons and lower summer mean temperatures of Tierra del Fuego to the longer breeding seasons and higher seasonal and daily thermal amplitudes in continental north Andean Patagonia.

KEYWORDS:

• Tachycineta leucopyga
• egg size
• clutch size
• incubation behaviour
• nestling feeding rate

Acknowledgments

We thank the Fortín Chacabuco TNC crew (especially G. Hulsegge and N. Rodríguez Argumedo), El Desafío personnel (L. Bachmann, R. Soto and T. Crespo), and El Cóndor ranch. We are especially grateful to L. Chazarreta, A. Ortiz, G. Ortiz, M. N. Arregui, P. Canavari, A. Mayoral, and L. Casalins for the field support provided during this study. We are especially thankful to D. W. Winkler for playing a significant role in this research, providing constant guidance throughout the Project, critical feedback and support. This work was partially supported by Agencia Nacional de Promoción de la Investigación, el Desarrollo Tecnológico y la Innovación under grant PICT 2018-2756. It was conducted under permit No. 1523 to VO, No. 1593 to MB from Dirección Regional Patagonia Norte (DRPN, APN), and No. 023932-SAYDS-2018 from Secretaría de Ambiente y Cambio Climático, Río Negro.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary data

Supplemental data for this article can be accessed at https://doi.org/10.1080/01584197.2024.2353380.