Common reed (Phragmites australis) forms dense stands with deep layers of residual organic matter that negatively affects plant diversity and possibly habitat use by wetland birds. We sought to determine whether seasonal relative abundance and species richness of birds varied among 3 habitat types in Great Lakes coastal wetland complexes recently invaded by common reed. We used fixed-distance point counts to determine species relative abundances and species richness in edge and interior locales within common reed, cattail (Typha spp.), and meadow marsh habitats of various sizes during 2 summers (2001 and 2002) and 1 autumn (2001) at Long Point, Lake Erie, Ontario, Canada. We found that total relative abundance and species richness of birds were greater in common reed habitat compared to cattail or meadow marsh habitats. However, we also found that relative abundance of marsh-nesting birds was greater in meadow marsh habitat than in cattail and common reed during summer. Lastly, we found that, irrespective of habitat type, habitat edges had higher total relative abundance and species richness of birds than did habitat interiors. Our results show that common reed provides suitable habitat for a diversity of landbirds during summer and autumn but only limited habitat for many marsh-nesting birds during summer. Based on these results, we recommend restoration of meadow marsh habitat through reduction of common reed in Great Lakes wetlands where providing habitat for breeding marsh-nesting birds is an objective. Managers also might consider reducing the size of nonnative common reed stands to increase edge effect and use by birds, possibly including wetland birds.
Identifying environmental metrics specific to lesser scaup (Aythya affinis; scaup) spring migration chronology may help inform development of conservation, management and population monitoring. Our objective was to determine how environmental conditions influence spring migration of lesser scaup to assess the effectiveness of the Waterfowl Breeding Population and Habitat Survey in accurately estimating scaup populations. We first compared peak timing of mallard (Anas platyrhynchos) and scaup migration from weekly ground surveys in North Dakota, USA because the Waterfowl Breeding Population and Habitat Survey is designed to capture annual mallard migration. As predicted, we detected that peak timing of scaup and mallard migrations differed in 25 of 36 years investigated . We marked scaup with satellite transmitters (n ¼ 78; 7,403 locations) at Long Point, Lake Erie, Ontario, Canada; Pool 19 of the Mississippi River, Iowa and Illinois, USA; and Presque Isle Bay, Lake Erie, Pennsylvania, USA. We tested the assumption that our marked scaup were representative of the continental population using the traditional survey area by comparing timing of migration of marked birds and scaup counted in the North Dakota Game and Fish Department survey. We detected a strong positive correlation between marked scaup and the survey data, which indicated that marked scaup were representative of the population. We subsequently used our validated sample of marked scaup to investigate the effects of annual variation in temperature, precipitation, and ice cover on spring migration chronology in the traditional and eastern survey areas of the Waterfowl Breeding Population and Habitat Survey, 2005-2010. We evaluated competing environmental models to explain variation in timing and rate of scaup migration at large-scale and local levels. Spring migration of scaup occurred earlier and faster during springs with warmer temperatures and greater precipitation, variables known to influence energy budgets and wetland availability. Our results suggest that surveys designed to index abundance of breeding mallards is imprecise for estimating scaup abundance, and inaccurate at estimating breeding population size by survey stratum. Ó 2016 The Wildlife Society.
We examined diets of lesser scaup (Aythya affinis) and greater scaup (A. marila) during autumn 1999 and spring 2000 at 3 major stopover sites on lakes Erie, Ontario, and St. Clair in southern Ontario, Canada. Overall dietary composition did not differ between sexes in lesser or greater scaup. We also did not detect interspecific or sex‐related differences in average size of zebra mussels (Dreissena polymorpha) consumed by scaup, but both species ate slightly larger zebra mussels during spring, as compared with autumn. Dietary intake of lesser scaup differed between seasons and among stopover sites. Lesser scaup generally ate more zebra mussels during spring and more gastropods and plants during autumn. Lesser scaup at Lake Ontario, Lake Erie, and Lake St. Clair, respectively, consumed more zebra mussels, nonmollusk animal matter (crustaceans and insects), and plant matter than did conspecifics at the other 2 locations. Greater scaup diets differed depending on both season and stopover site. At Lake Ontario greater scaup diets contained more zebra mussels but fewer gastropods during spring as compared with autumn, but there were no seasonal differences in consumption of those 2 food items at Lake Erie. Greater scaup at both Lake Ontario and Lake Erie did not show seasonal differences in consumption of plant matter, but autumn‐staging birds at Lake Erie contained more plant matter than did autumn‐staging birds at Lake Ontario. Interspecific comparisons of dietary intake of scaup staging at lakes Erie and Ontario showed that greater scaup generally ate more gastropods and plant matter than did lesser scaup, whereas lesser scaup consumed more zebra mussels than did greater scaup. Overall, our study showed that zebra mussels, gastropods, and submerged aquatic plants all currently are important foods during both autumn and spring for lesser and greater scaup staging on the lower Great Lakes (LGL). Consumption of zebra mussels by scaup is of particular concern because of the hypothesized link between scaup foraging ecology, zebra mussels, and elevated selenium burdens documented recently in scaup staging on the LGL. Thus, our findings that both scaup species generally ate more and larger zebra mussels during spring illustrates the need for further investigation into contaminant acquisition and burdens in wintering, staging, and breeding scaup, particularly those using, or originating from, the LGL region.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.