Arthropod prey availability associated with breeding territories of the threatened strange-tailed tyrant (Alectrurus risora).

ZERMOGLIO, P.F.; DI GIACOMO, A.S.; DI GIACOMO, A.G.; CASTELO, M.K.

ORNITOLOGIA NEOTROPICAL

NEOTROPICAL ORNITHOLOGICAL SOC

Lugar: ALEMANIA; Año: 2016 vol. 27 p. 259 - 266

1075-4377

Knowledge about the extent of the breeding season and food resources for reproduction of subtropical birds is scarce. The Strange-tailed Tyrant, Alectrurus risora, is an insectivorous flycatcher (Tyrannidae) endemic to the remaining natural tall grasslands of northern Argentina and southern Paraguay, which has a shorter breeding season than most other tyrants reported. Alectrurus risora has a polygynous mating system and the abundance of arthropods could be a major determinant for the establishment of male breeding territories and the extent of the breeding season. To investigate this hypothesis we examined the abundance of arthropods in upland and lowland breeding habitats where the species seems to have differential reproduction (i.e., more nests in upland grasslands). Data from one year showed that, for both grasslands, a greater availability of arthropods coincides with the beginning of the breeding season, and that the short observed reproductive season of A. risora can be explained by a general lower availability of prey during February and March in the study area. In upland territories, males attracted more females and had more active nests than males holding territories in lowland grasslands. However, the abundance and biomass of total arthropods and of potential prey were higher in lowland than in upland grasslands, with the exception of the abundance of Orthoptera, which could represent one of the major prey items. Therefore, we conclude that 1) the availability of arthropod prey may be important in determining the extent of the breeding season, and 2) female preference for males in upland grasslands cannot be explained by higher arthropod prey availability.