Abstract
The aim of this study was to assemble data on the summer feeding ecology of the Great Pampa-finch, Embernagra platensis at the Laguna de Guaminí, Buenos Aires, Argentina, and to explore the differences related to the dietary patterns for each sex between winter and summer when possible. The stomach contents of 43 birds were analyzed. The animal fraction was composed of Hymenoptera (45.1%), Coleoptera (32.4%), Lepidoptera (6.0%), Araneae (5%) and Orthoptera (3.2%). The application of the index of relative importance (IRI) resulted in 1490.4 for Coleoptera, 428.5 for Hymenoptera and 162.5 for Lepidoptera caterpillars. The vegetal fraction consisted of Triticum aestivum (26.9%), Cyperaceous (25%), Poaceae (Gramineae) (19.3%) and Panicum sp. (11.2%). The IRI values were 893.8 for Triticum aestivum, 174.5 for Gramineae, 126.5 for Panicum sp. and 112.8 for Scirpus sp. The food niche width was 0.33 for both sexes; the diversity index resulted in 1.06 for females and 1.33 for males and specific diversity ranged from 1.87 to 2.84. A canonical component analysis (CCA) was performed on environmental and morphometric variables, and a Monte Carlo test confirmed the canonical correlations. A t-test showed that some birds harmonized with a logarithmic model and some with a geometric curve. During the summer, Embernagra platensis ingests Hymenoptera and Coleoptera more often than seeds, suggesting that two biological mechanisms could be taking place in this bird.
Highlights
The Great Pampa-finch, Embernagra platensis, belongs to the Emberizinae finches, distributed from the southeast Brazil, through most of Paraguay, northwest Bolivia, and Uruguay, to central and south Argentina (Misiones, Formosa, Chaco, Santa Fé, La Pampa and Río Negro (Short 1975, Ridgely and Tudor 1989)).It inhabits open grasslands, often with scattered shrubs, and can fairly frequently be seen flying along and over roadsides, some prefer damp places
Analysis showed that the food (g) eaten by the Great Pampa-finch consisted primarily of arthropods (83%) and seeds (17%)
In order to discuss the feeding ecology of the Great Pampa-finch during the summer, we made some comparisons concerning the proportions and the diversity of prey items ingested between the two seasons when possible
Summary
The Great Pampa-finch, Embernagra platensis, belongs to the Emberizinae finches, distributed from the southeast Brazil (north of Minas Gerais to Espírito Santo), through most of Paraguay (local in the dry Chaco), northwest Bolivia (north to Beni), and Uruguay, to central and south Argentina (Misiones, Formosa, Chaco, Santa Fé, La Pampa and Río Negro (Short 1975, Ridgely and Tudor 1989)) It inhabits open grasslands, often with scattered shrubs, and can fairly frequently be seen flying along and over roadsides, some prefer damp places. The previously known facts about the dietary composition of the Great Pampa-finch were incomplete, based on a small number of samples or isolated data In this sense, the purpose of this study was to provide information about the feeding ecology of E. platensis during the summer, compare its diet between seasons and sexes at the Laguna de Guaminí, Province of Buenos Aires, Argentina
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