Food of Night Heron (Nycticorax nycticorax) chicks in the Ebro delta, NE Spain

Full article

Published:

Volume 39(1), June 1992. Pages 25-34.

Language:

Spanish

Original title:

Alimentación de los pollos de Martinete (Nycticorax nycticorax) en el delta del Ebro

Keywords:

diet, Ebro delta, Night Heron, rice-fields.

Abstract:

In this paper we describe the feeding habits of Night Heron chicks in the Ebro Delta during the breeding seasons of 1990 and 1991. Data coming from the inspection of regurgitated food boluses collected in the breeding colonies are grouped according to taxonomic, typologic and biomass criteria, in order to analyze the importance of the different prey items, either from the ecological interaction (number) or from the energy supply (biomass) perspectives. We found that coleoptera and cyprinid fishes are the main prey items in our analysis. The former, mainly big larvae of Hydrous piceus, are easier to catch than the latter, but offer, on average, lower gain per item than fishes. It can be considered that coleoptera, the staple food, are eaten while Night Herons are standing for the capture of fishes, which are more difficult and more profitable prey items. When comparing the results from 1990 with those of 1991, it stands out that coleoptera and cyprinid fishes were more available in 1990 than in 1991. In this latter year they were partially substituted by ducklings and other chicks, crustacea and other complementary prey items. The comparison of trophic niche width and diet composition of Night Herons in the Ebro Delta with several other localities shows that values reached in the Ebro Delta are very similar to those obtained in Camargue and other European localities. However, in relation to diet composition it is interesting to note that ornithophagy has been well documented, up to now, only in America.