Seed preferences in sparrow species of the Monte desert, Argentina: implications for seed-granivore interactions

CUETO, V.R.; L. MARONE; J. LOPEZ DE CASENAVE

AUK

American Ornithologists´ Union

Lugar: Waco, USA; Año: 2006 vol. 123 p. 358 - 367

 We assessed seed preference in four species of sparrows that were common in the central Monte desert of Argentina. Our hypotheses are: 1) sparrows always prefer grass over forb seeds, and 2) different species of sparrows show the same preferences when consuming seeds. We presented seeds from eight species of plants (four grasses and four forbs) in both choice and non-choice experiments. In general, sparrow species preferred grasses over forbs, although one of them (Rufous-collared Sparrow, Zonotrichia capensis) included one forb species (Parthenium hysterophorus) among its preferred seed items. Among grass seeds, sparrows avoided or showed less preference for the tiny seeds of Sporobolus cryptandrus, suggesting that seed weight might affect seed choice among grasses. Avoidance of most forb species, by contrast, could not be associated with seed size, probably due to the presence of unpalatable or toxic compounds in forb seeds. Experimental evidence suggests that the main feeding pressure of sparrows is clearly directed to grass seeds, which coincides with bird diet information previously reported. Results support assertions that sparrows could cause a negative impact on the composition and abundance of grass seeds in the soil seed bank, a necessary condition for birds playing a significant role on grass population dynamics in the central Monte desert of Argentina.