Avian schistosomatids are blood flukes parasitizing a wide spectrum of aquatic birds. However, its research in the Neotropics is ongoing with several putative new taxa pending description. Although waterfowl represent the most important avian hosts for these flukes, only a small proportion of these birds have been assessed for schistosomatids. This study aimed to describe avian schistosomatids from two native ducks from the Southern Cone of South America. A total of 24 Chiloe wigeon (Mareca sibilatrix) and three Cinnamon teals (Spatula cyanoptera) from different localities in Chile and Argentina were dissected to retrieve schistosomatids. The retrieved worms were described through an integrative approach considering morphology (staining and SEM) and molecular tools (PCR: COI, 28S rRNA genes). The new schistosomatid: Trichobilharzia kulfu sp. nov. was recovered from the viscera of Chiloe wigeon. It was closely related to other undescribed Trichobilharzia taxa from the United States, also from Mareca ducks. The new species was morphologically and molecularly different from other Trichobilharzia species, and it was included in the clade Q. In addition, SEM imaging proved to be an important tool to describe unnoticed traits on the tegument of worms. This new species represents the second Trichobilharzia taxon from the Neotropics described through an integrative approach. Furthermore, the Cinnamon teals harboured Trichobilharzia querquedulae. Considering there are several avian schistosomatids described only through morphological or molecular tools, there is a clear need to include a comprehensive approach in the description of avian schistosomatids, considering the remarkable richness of schistosomatids in Neotropics.

Birds possess the most diverse assemblage of haemosporidian parasites, although the true diversity is unknown due to high genetic diversity and insufficient sampling across all avian clades. Waterfowl (Order Anseriformes) are an ideal group to discover hidden parasite diversity and examine the role of host ecology in parasite transmission. Waterfowl contain 2 distinct feeding guilds, dabbling and diving, which differ in niche utilization that likely alters vector encounter rates and haemosporidian parasite risk. To determine the role of feeding guild in haemosporidian parasitism we analysed 223 blood samples collected by hunters from the upper Midwest of the United States from 2017 to 2019. Fifty-four individuals were infected by haemosporidian parasites (24·2% prevalence). Infection prevalence differed significantly between dabbling (34·9%, n = 109) and diving (14·0%, n = 114) ducks. Feeding guild was the only host trait that could predict haemosporidian infection risk, with a significantly higher risk in dabbling ducks. Twenty-four haemosporidian lineages were identified, with 9 identified for the first time. Thirteen lineages were found only in dabbling ducks, 5 only in diving ducks and 6 in both feeding guilds. Community analysis showed that each feeding guild harboured a unique parasite community. There was no phylogenetic signal of feeding guild within a phylogenetic reconstruction of North American waterfowl haemosporidian lineages. Our results demonstrate that waterfowl contain a diverse and distinct community of haemosporidian parasites. The unique composition of each feeding guild determines not only haemosporidian infection risk but also community structure. This is the first report of such an impact for waterfowl feeding guilds.