The endohelminth fauna of nestlings from a great blue heron (Ardea herodias) population during development from Port Lavaca, Texas

Abstract

A study of great blue heron nestlings was undertaken in order to understand trends in the endohelminth fauna of nestling birds as they mature from hatching to fledging. Fourteen birds were collected from Port Lavaca, Texas during the spring of 1994. Their age was determined, and the nestlings were separated into four different age groups: 1-2 weeks old, 3-4 weeks old, 5-6 weeks old, and 7 weeks and older. Five different species of endohelminths were recovered from the nestlings: Phagicola sp., Stephanoprora sp., Contracaecum sp., a cestode, and an acanthocephalan. Phagicola sp. specimens were found in extremely high numbers (range= 0 37467) and comprised a majority of the parasites recovered. The species of Phagicola recovered was difficult to determine due to inconsistencies in the literature about the taxonomy of Phagicola. Analysis of variance of the number of parasites in the different age groups of nestlings revealed that there were statistical differences (p=.045). The number of overall parasites as well as the number of Phagicola increased as the age of the nestlings increased. Phagicola specimens were proven statistically to be more common in one area of the intestine relative to the three other areas of the intestine examined. The correlation between the number of Phagicola and the weight of the birds was significant (r=.748), and the data shows a parabolic increase in Phagicola as the weight of the nestling increased. Parasite diversity did not change significantly, and the diversity of parasites was low in comparison to other studies of bird endohelminth populations. The lack of diversity may be a direct result of the high mercury levels in Port Lavaca Bay.