Exploring food preferences and the limits of foraging flexibility of seed-eating desert birds

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

EMU

CSIRO PUBLISHING

Lugar: Collingwood; Año: 2015 vol. 115 p. 261 - 269

0158-4197

Habitat degradation like cattle grazing may be a serious threat for seed-eating birds because the availability of profitable seeds usually diminishes in grazed areas. Phenotipically flexible species might however circumvent food deprivation via changes in foraging behaviour, avoiding population declines. We studied the limits of feeding flexibility and factors affecting seed preferences in Zonotrichia capensis, Saltatricula multicolor and Diuca diuca. We experimentally assessed preferences for seeds of eight grass and eight forb species by using a protocol that combines choice and nonchoice trials, and employ a different batch of experiments to evaluate some plausible causes of different foraging flexibility. On average, birds consumed 45-140 % more grass than forb seeds, confirming previous results. Z. capensis, preferred several grass and forb seeds, and showed maximum foraging flexibility. S. multicolor was a grass specialist, and D. diuca was intermediate. S. multicolor and D. diuca preferred large and medium-sized grass seeds. Seed-coat thickness did not seriously affect consumption levels in the three species. Birds showed low ability to feed resources characteristic of degraded environments (i.e. annual grass seeds). Differences in behavioural flexibility allow predict species-specific behavioural and numerical responses of seed-eating birds to habitat degradation by cattle grazing.