Dietary similarities among eight granivorous birds at “La Iguana” Experimental Station, Guárico state, Venezuela.

Abstract

We compared the diets of the eight most common savanna granivorous birds coexisting in “La Iguana” Experimental Station, Guárico State: EMBERIZIDAE, Sporophila minuta (6.6 g), Volatinia jacarina (8.4 g), Ammodramus humeralis (15.0 g); COLUMBIDAE: Columbina minuta (31.1 g), C. passerina (34.2 g), Scardafella squammata (52.9 g), Zenaida auriculata (101.6 g); PHASIANIDAE: Colinus cristatus (138.6 g). A total of 462 individuals was collected during four sampling dates. All specimens were weighed and seeds contained in crops (Columbidae, Phasianidae) or gizzards (Emberizidae) were sorted and counted by morphotypes. Afterwards, the 88.5% of the seeds found in crops or gizzards was identified to species level. A negative relationship between dietary overlap, both in seed sizes as well as plant species used, and morphological differences among birds was detected. All diets were based mainly on the consumption of grasses and sedges and, predominantly, on seeds with weigths between 0.4 and 3.2 mg. The smallest bird, Sporophila minuta, have a less diverse diet, restricted to seeds up to 3.2 mg. The two larger birds, Z. auriculata and C. cristatus, differed from the others by the consumption of legume seeds and a large proportion of seeds with weights above 3.2 mg. Birds with intermediate sizes had more similar diets, both in seed sizes and plant genera used.