HELMINTH COMMUNITY STRUCTURE AND PATTERN IN SYMPATRIC POPULATIONS OF BLACK-BELLIED AND FULVOUS WHISTLING-DUCKS

Helminth communities of 25 black-bellied (Dendrocygna autumnalis) and 25 fulvous (Dendrocygna bicolor) whistling-ducks from south Texas vari ed in composition, prevalence, dominance, and abundance. Twenty-eight helminth species were found, of which 20 occurred in each host species population. Twelve species co-occurred between host populations. Blac k-bellied and fulvous whistling-ducks averaged 3.0 +/- 0.3 (SE) and 5. 0 +/- 0.4 species, respectively. Fifteen common species were found, of which 8 and 11 species commonly occurred in black-bellied and fulvous whistling-ducks, respectively. Four species (Apatemon gracilis, Tanai sia bragai, Sobolevicanthus gracilis, and Epomidiostomum uncinatum) we re common in both host species. Prevalences varied in 4 of 8 helminth species co-occurring in both host species; 3 helminth species had high er prevalences in fulvous whistling-ducks. Black-bellied and fulvous w histling-ducks averaged 7.8 +/- 1.4 and 44.8 +/- 11.9 helminth individ uals, respectively. Eleven of 15 common helminth species varied in abu ndance between host species populations; 4 species had higher abundanc es in black-bellied whistling-ducks and 7 had higher abundances in ful vous whistling-ducks. Our results suggest that although these duck spe cies are sympatric, differences in feeding behavior may be most import ant in determining helminth community structure and pattern.