Resumen de The nestling diet of greenfich "Carduelis chloris" in orange groves of eastern Spain
José Antonio Gil-Delgado Alberti, Daniel Guijarro, Carmen Vives Ferrándiz
The diet of granivorous birds in agricultural areas requires special attention where changes in farm management have severely affected bird populations. Nevertheless, studies into the diet of cardueline species are scarce in southern Europe. Thus, this study aims to determine the nestling diet of greenfinches Carduelis chloris and its seasonal variation in an agricultural area of eastern Spain. The study area is an agricultural plot of 16.9 ha in Sagunto (Valencia, 39° 42'N, 0° 15'W, 30 m a.s.l.) used for growing orange trees. During the breeding seasons of 1998 and 1999, we obtained 47 food samples from the crops of 3- to 10-day old greenfinch nestlings from 29 monitored nests using a spooned spatula. Crop contents were identified and classified with a binocular magnifying glass, dried and weighed. Quadratic and linear regression analyses were fitted to the standardized data of the dry weight of each food type in order to assess seasonal trends of the diet elements. The results shows that greenfinch nestlings were mainly fed on seeds, leaves and bulbs, of which Erodium cicutarium seeds were the most consumed type food. Seeds of this seed-bearing plant were found in the nestlings' crops throughout the whole breeding season, but consumption decreased as the breeding season progressed. However, the consumption of bulbs, another common food type, increased. Aphids appeared in the crops at the beginning of the season but contributed little to the diet of the chicks. In conclusion, greenfinch nestlings fed on a wide range of food types, mainly vegetables, showing a more generalist diet than other cardueline species in the same study area.
