Three is a Crowd: Unusual Mating System in the Burrowing Owl

LOIS, NICOLÁS A.; RODRIGUEZ-MARTINEZ, M. SOL; REBOLO-IFRÁN, NATALIA; CARRETE, MARTINA

Puerto Iguazú, Misiones

Congreso; Ornithological Congress of the Americas; 2017

Aves Argentinas

Despite the well-documented negative impacts of urban development on biodiversity, some native species have invaded these environments and established stable populations. The Burowing Owl (Athene cunicularia) has stable urban and rural populations in Bahía Blanca (Buenos Aires, Argentina), where the presence of unusual reproductive units with more than two individuals has been detected. In this work, we investigated factors promoting the occurrence of these reproductive units and the costs and benefits for their members, discussing possible ecological and evolutionary consequences. Between 1% and 4% of the territories used between 2009 and 2012 (n = 1210) were occupied by three or four breeding adults, normally . a reproductive pair and one of the sons of one or both members. These units tended to be more frequent in high quality areas and in territories farther from conspecifics. However, neither the general aggregation of the territories nor the degree of urbanization of the environment affect the probability of finding these breeding units. These units presented the same reproductive success as breeding pairs formed by two individuals as well as similar antipredator behaviors, although productivity was higher in the former than in the latter. If not predated, the presence of more adults in a territory benefits the breeding pair by increasing the number of fledging.