Predicting how seed-eating passerines respond to cattle grazing in a semi-arid grassland using seed preferences and diet

SAGARIO, M. CECILIA; CUETO, VÍCTOR R.; ZARCO, AGUSTÍN; POL, RODRIGO; MARONE, LUIS

AGRICULTURE, ECOSYSTEMS AND ENVIRONMENT

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2020 vol. 289

0167-8809

Numerical responses of animals to habitat perturbation often seeminconsistent, spreading skepticism about the predictive capacity of applied ecology.Domestic grazing changes several habitat variables that can affect seed-eatingbirds. Birds, in turn, show adaptations (e.g. in their feeding behavior) thatcould allow them to overcome habitat perturbations. Here we modelled habitatvariables (e.g. cover of different plants, panicles,soil seed bank) in grazed and ungrazed (or lightly grazed) habitats of thecentral Monte desert, Argentina, to detect those affected by grazing activity.There was no effect of grazing on shrub and tree cover, but grazing reduced theabundance mostly of large grass seeds but also of small grass and forb seeds.Then, we used model?s outputs and knowledge of feeding preferences of the fivemost common seed eating passerines in the Monte to make species-specific predictions:changes in abundance of grass seed specialists (Saltatricula multicolor, Microspingustorquatus and Porphyrospizacarbonaria) due to grazing activity should be consistent and should dependon large grass seeds (i.e. preferred seeds), whereas changes in abundance ofmore generalist species (Zonotrichiacapensis and Diuca diuca) shouldbe less consistent and explained also by the abundance of other seeds. Theabundance of large grass seeds was sufficient to predict the abundances of S. multicolor, M. torquatus and P.carbonaria. The best model for predicting the abundance of Z. capensis included large grass seedsas well as small grass or forb seeds. No model including the abundance of seedspredicted the abundance of D. diuca. Therefore, feeding behavior explained theabundance of four out of the five bird species. A review of the literatureshowed that feeding behavior is also a good predictor of habitat use in otherdesert grasslands. Conservative range management should consider, and evenmanipulate, the level of the seeds preferred by wildlife. Grazed grasslandsshould be rested from grazing on a rotational basis so that grasses, especiallythose whose seeds are preferred by birds, can seed.