Artículo
Diet switching of seed-eating birds wintering in grazed habitats of the central Monte Desert, Argentina
Título:
Modificación de la dieta invernal de las aves granívoras en hábitats sujetos a pastoreo de la porción central del Desierto del Monte, Argentina
Marone, Luis
; Olmedo, Matías; Valdés, Daniela Y.; Zarco, Agustín
; Lopez de Casenave, Javier Nestor
; Pol, Rodrigo Gabriel
![Icon](/themes/CONICETDigital/images/conicet.png)
![Icon](/themes/CONICETDigital/images/conicet.png)
![Icon](/themes/CONICETDigital/images/conicet.png)
![Icon](/themes/CONICETDigital/images/conicet.png)
Fecha de publicación:
08/2017
Editorial:
Cooper Ornithological Society
Revista:
The Condor
ISSN:
0010-5422
Idioma:
Inglés
Tipo de recurso:
Artículo publicado
Clasificación temática:
Resumen
Although bird population declines associated with land degradation are common, the initial response of organisms to rapid human-induced environmental change is usually behavioral. Reductions in seed availability due to cattle grazing may trigger diet switching in seed-eating birds, but empirical examples of such behavior are lacking. We asked whether cattle grazing changed the composition and reduced the size of seed reserves, and whether seed shortage caused diet shifts in 4 species of seed-eating birds wintering in the central Monte Desert, Argentina. We assessed the soil seed bank composition and the granivorous fraction of each species? diet. Digestive tract or crop contents were obtained by using the flushing method on individuals captured with mist nets, and seeds were sorted and assigned to 1 of 3 functional groups (small grass seeds, large and medium-sized grass seeds, or forb seeds). Cattle grazing reduced the abundance of the preferred large and medium-sized grass seeds by 60?90%. The grass-seed specialists Manycolored Chaco Finch (Saltatricula multicolor) and Ringed Warbling-Finch (Microspingus torquatus) did not change their diets in grazed areas, but the expanding specialists Common Diuca-Finch (Diuca diuca) and Rufous-collared Sparrow (Zonotrichia capensis) incorporated increased proportions of small grass seeds as well as forb seeds into their diets. These results were correctly predicted from species-specific differences in feeding flexibility previously established in cafeteria experiments. Based on species-specific diet composition, the energy reward of seeds by unit mass consumed decreased moderately (5?21%) in the grazed sites for S. multicolor, M. torquatus, and D. diuca. Starch content was similar between grazing conditions for all 3 birds. Although such deficits might be compensated for by a slight increase in absolute mass of seeds or alternative food items consumed in degraded lands, substantial reduction in the availability of grass seeds may reduce the capacity of degraded lands to support specialist granivorous birds.
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Citación
Marone, Luis; Olmedo, Matías; Valdés, Daniela Y.; Zarco, Agustín; Lopez de Casenave, Javier Nestor; et al.; Diet switching of seed-eating birds wintering in grazed habitats of the central Monte Desert, Argentina; Cooper Ornithological Society; The Condor; 119; 4; 8-2017; 673-682
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