Three's a crowd: Unusual mating system in the Burrowing Owl

NICOLAS LOIS; SOL RODRIGUEZ MARTÍNEZ; NATALIA REBOLO IFRÁN; JOSE LUIS TELLA; MARTINA CARRETE,

Puerto Iguazú

Congreso; Ornithological Congress of the Americas; 2017

Despite the well-documented negative impact of the development of urban centers on biodiversity, some native species have invaded these environments and developed stable populations. The Burrowing Owl (Athene cunicularia), in the city of Bahía Blanca (Buenos Aires, Argentina), has a stable population in which the presence of unusual reproductive units with more than two individuals has been detected. In this work, the factors that promote the occurrence of these reproductive units are investigated and the costs and benefits for their members are evaluated, discussing possible ecological and evolutionary connotations. Between 1% and 4% of the territories observed in the study population between 2009 and 2012 (n = 1210) opted for this strategy. Through kinship molecular analysis, it was determined that a reproductive pair shared the territory with a son of one or both members. These units tended to be formed in areas of higher quality and in territories more distant from conspecifics. However, neither the general aggregation of the territories nor the urbanization of the environment affect the formation of these breeding units, which rejects the hypotheses referring to urbanization as a promoter of these cooperative units. These units presented the same reproductive success as the couples and did not show significant differences in the defense of their territories, although productivity did increase. If not predated, the presence of non-reproductive individuals sharing the territory benefits the breeding pair by increasing the number of surviving chicks.