Shannon S. Badzinski

Associations between Breeding Marsh Bird Abundances and Great Lakes Hydrology

ABSTRACT We used Great Lakes hydrologic data and bird monitoring data from the Great Lakes Marsh Monitoring Program from 1995–2002 to: 1) evaluate trends and patterns of annual change in May–July water levels for Lakes Ontario, Erie, and Huron-Michigan, 2) report on trends of relative abundance for birds breeding in Great Lakes coastal marshes, and 3) correlate basin-wide and lake-specific annual indices of bird abundance with Great Lakes water levels. From 1995–2002, average May, June, and July water levels in all lake basins showed some annual variation, but Lakes Erie and Huron-Michigan had identical annual fluctuation patterns and general water level declines. No trend was observed in Lake Ontario water levels over this period. Abundance for five of seven marsh birds in Lake Ontario wetlands showed no temporal trends, whereas abundance of black tern (Chlidonias niger) declined and that of swamp sparrow (Melospiza georgiana) increased from 1995–2002. In contrast, abundances of American coot (Fulica americana), black tern, common moorhen (Gallinula chloropus), least bittern (Ixobrychus exilis), marsh wren (Cistorthorus palustris), pied-billed grebe (Podilymbus podiceps), sora (Porzana carolina), swamp sparrow, and Virginia rail (Rallus limicola) declined within marshes at Lakes Erie and Huron/Michigan from 1995–2002. Annual abundances of several birds we examined showed positive correlations with annual lake level changes in non-regulated Lakes Erie and Huron/Michigan, whereas most birds we examined in Lake Ontario coastal wetlands were not correlated with suppressed water level changes of this lake. Overall, our results suggest that long-term changes and annual water level fluctuations are important abiotic factors affecting abundance of some marsh-dependent birds in Great Lakes coastal marshes. For this reason, wetland bird population monitoring initiatives should consider using methods in sampling protocols, or during data analyses, to account for temporal and spatial components of hydrologic variability that affect wetlands and their avifauna.

Diets of Lesser and Greater Scaup During Autumn and Spring on the Lower Great Lakes

Abstract 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.

Autumn diet of greater scaup, lesser scaup, and long-tailed ducks on eastern Lake Ontario prior to zebra mussel invasion

Abstract Diving ducks staging on the lower Great Lakes have responded to the introduction and subsequent population increase of zebra mussels (Dreissena polymorpha) by consuming this readily available food. However, nutritional and contaminant-related implications of recent dietary shifts are hindered by the fact that few studies have documented foods consumed by diving ducks before zebra mussels invaded the Great Lakes in 1988. We examined diets of greater scaup (Aythya marila), lesser scaup (Aythya affinis), and long-tailed ducks (Clangula hyemalis) collected from eastern Lake Ontario during autumn 1986 and 1987 to determine differences among the 3 species. Gastropods were the main food item of greater (92% aggregate dry mass) and lesser scaup (86%), but they consumed relatively small amounts (3% and 7%, respectively) of amphipods. In contrast, amphipods made up 66% of the diets of long-tailed ducks; gastropods were 28% of their diet. Amphipod populations have increased and native gastropods decreased in the presence of zebra mussels in the lower Great Lakes, such that zebra mussel invasion likely has had greater dietary implications for scaup than for long-tailed ducks. Dietary shifts from nonfilter-feeding gastropods to filter-feeding zebra mussels likely contributed to elevated contaminant burdens in lesser and greater scaup on the lower Great Lakes. We encourage further research into the diet-, nutrient-, and contaminant-related implications of zebra mussel induced ecological changes to the Great Lakes.

Seasonal abundance and species richness of birds in common reed habitats in Lake Erie.

Abstract 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.

Lesser Scaup Spring Nutrient Reserve Dynamics on the Lower Great Lakes

Abstract The North American lesser scaup (Aythya affinis) population has declined since the mid-1980s. The acquisition of nutrient reserves during spring migration may play a role in explaining that trend. We studied nutrient-reserve dynamics of lesser scaup collected during spring at 3 major stopover sites and assessed whether reserves of birds on the lower Great Lakes (LGL) differed from those at other staging (or breeding) areas. At lakes Ontario and St. Clair, males had larger fat reserves than females, but no other substantial sex-related differences were observed in fat, protein, or mineral reserve levels of lesser scaup. Protein in males and mineral reserves of both sexes at lakes Erie and St. Clair did not change throughout spring. Male fat reserves remained constant at Lake Erie and increased at Lake St. Clair, whereas female fat and protein reserves increased at both stopover sites. Patterns of fat and protein dynamics in males partly may be due to energetic costs of courtship and pair-bond maintenance. However, maintenance and accumulation of fat reserves in both sexes while on the LGL is important for impending migration and subsequent reproduction. Female lesser scaup staging on the LGL had fat reserves comparable to, or slightly higher than, those reported in other studies of northern spring-staging and breeding birds. Fat reserves of LGL females, however, were much lower than those reported for birds at another midlatitude stopover site. These comparisons suggest that events occurring on Atlantic Flyway wintering areas or LGL staging areas are potential factors contributing to nutrient-reserve limitation and possibly to observed declines in scaup numbers in North America.

Relationships between hepatic trace element concentrations, reproductive status, and body condition of female greater scaup

We collected female greater scaup (Aythya marila) on the Yukon-Kuskokwim Delta, Alaska during two breeding seasons to determine if concentrations of 18 trace elements in livers and eggs were elevated and if hepatic concentrations correlated with body condition or affected reproductive status. Fifty-six percent, 5%, and 42% of females, respectively, had elevated hepatic cadmium (Cd: >3 microg g(-1) dry weight [dw]), mercury (Hg: >3 microg g(-1) dw), and selenium (Se: >10 microg g(-1) dw). Somatic protein and lipid reserves were not correlated with hepatic Cd or Hg, but there was a weak negative correlation between protein and Se. Hepatic Cd, Hg, and Se were similar in females that had and had not initiated egg production. In a sample of six eggs, 33% and 100%, respectively, contained Se and Hg, but concentrations were below embryotoxicity thresholds. We conclude that trace element concentrations documented likely were not adversely impacting this study population.

Diet of Mute Swans in Lower Great Lakes Coastal Marshes

Abstract During the past 30 years, nonnative mute swan (Cygnus olor) populations have greatly increased, and continue to increase, in the eastern United States and within the lower Great Lakes (LGL) region. As a result, there is much concern regarding impacts of mute swan on native waterfowl, aquatic plants, and marsh habitats. There are presently only limited dietary data for mute swans in North America and none exist for birds in the LGL region. Thus, in 2001, 2002, and 2004 we collected 132 mute swans from LGL coastal marshes in Ontario, Canada, to determine dietary composition and to evaluate 1) seasonal and sex-related variation in adult diets and 2) age-related dietary differences. Adult diets did not differ among years, collection sites, or seasons, but female diets contained more pondweed spp. (Potamogeton spp.) and less slender naiad (Najas flexilis) and common waterweed (Elodea canadensis) than did diets of males. Adult males, adult females, and cygnets had similar diets during summer and autumn. Overall, mute swan diets mainly consisted of above-ground biomass of pondweed spp., muskgrass (Chara vulgaris), coontail (Ceratophyllum demersum), slender naiad, common waterweed, wild celery (Vallisneria americana), and wild rice (Zizania palustris); below-ground parts of wild celery, sago pondweed (Stuckenia pectinatus), and arrowhead spp. (Sagittaria spp.) were eaten infrequently. Comparison of our findings with those of other diet studies suggested considerable dietary overlap between mute swans and several other species of native waterfowl. Thus, we suggest that mute swans have potential to compete with native waterfowl and impact aquatic plants that are important waterfowl foods within LGL coastal marshes. Further, our results can be used to assess which aquatic plant species may be most impacted by foraging activities of mute swans at other important waterfowl stopover and wintering sites in North America.

Factors influencing productivity of common loons (Gavia immer) breeding on circumneutral lakes in Nova Scotia, Canada

Common loons (Gavia immer) are top predators that are sensitive to biotic and abiotic conditions associated with their breeding lakes, so factors such as lake chemistry and human activity or disturbance are thought to influence their seasonal and long-term reproductive success. We used two indices of loon productivity to evaluate (1) temporal patterns and (2) relationships with physical and chemical lake characteristics and human activities. Data collected from 1991 to 2000 by volunteers of the Canadian Lakes Loon Survey (CLLS) in Nova Scotia showed that loon productivity, as indexed by both the proportion of resident pairs that produced at least one large young (P s1) and the proportion of successful pairs that produced two large young (P s2), did not vary substantially from year to year and showed no linear trend from 1991 to 2000. Average estimates (1991– 2000) for P s1 and P s2 were 0.49±0.02 and 0.43±0.03, respectively, and the mean number of chicks per residential pair over that time was 0.75±0.04. We found that human disturbance and shoreline development did not influence loon productivity during the prefledging stage on lakes surveyed by CLLS volunteers. Proportion of resident pairs rearing at least one large young was independent of dissolved organic carbon (DOC) concentrations of breeding lakes, but there was a positive relationship between the proportion of successful pairs rearing two large young and DOC. Both indices of loon productivity tended to be negatively correlated with lake pH. These results were not consistent with other findings that loon productivity generally declines with lake acidity, but likely reflect the preponderance of circumneutral (pH 6.5– 7.0) lakes surveyed by the CLLS volunteers in Nova Scotia.

Variation in Body Composition and Digestive Organs of Tundra Swans during Migration at Long Point, Lake Erie, Ontario

Abstract. Tundra Swans (Cygnus columbianus) spend a substantial portion of their annual cycle at migratory staging areas. Despite the potential importance of staging areas to conservation of Eastern Population (EP) Tundra Swans, few data are available to assess life-history strategies of the species during migration. During 1999 and 2000, 48 adult Tundra Swans were collected during peak periods of spring and autumn migration at Long Point, Ontario, Canada, to establish baselines on nutrient reserve levels and morphology of digestive organs. Results were compared to nutrient reserve data for EP Tundra Swans collected at a major wintering area in North Carolina, USA. Lipid reserve levels did not differ between sexes nor varied with body size, but lipid reserves were approximately two times greater in autumn than spring. Males had greater protein reserves than females, and protein reserves were similar during autumn and spring. Although digestive organs were predicted to be longer and heavier during autumn, no seasonal variation in digestive organs was detected. Lipid reserve levels of Tundra Swans at Long Point during spring were similar to those recorded for wintering birds in North Carolina, suggesting that lipid reserves catabolized from autumn through winter were not replenished prior to arriving at this initial spring staging area. The results highlight the importance of managing quality aquatic and terrestrial foraging habitats at staging areas for conservation EP Tundra Swans.

Artifact Ingestion in Sea Ducks Wintering at Northeastern Lake Ontario

Abstract. The incidence of lead shot ingestion in waterfowl has declined in the lower Great Lakes (LGL) following the 1999 Canada-wide ban on use of toxic shot for waterfowl hunting, but few data exist on ingestion frequencies of spent shot or fishing weights for sea ducks wintering at the LGL. Artifact ingestion was evaluated in 269 Buffleheads (Bucephala albeola), 224 Common Goldeneyes (B. clangula) and 256 Long-tailed Ducks (Clangula hyemalis) collected at Lake Ontario during winter 2002–03 and 2003–04. Long-tailed Ducks ingested total shot (lead and steel shot combined) more frequently (6.6%) than did Common Goldeneye (1.8%) and Bufflehead (0.4%). Lead shot was ingested by Long-tailed Ducks (5.1%) and Buffleheads (0.4%), but not by Common Goldeneyes. One Long-tailed Duck, 0.1 % of all specimens, ingested one lead fishing weight. Substrate type influenced artifact ingestion frequency and diving ducks that specialize on prey associated with hard substrates may continue to ingest artifacts more than ducks using soft substrate marshes. The results suggest lead toxicosis from spent shotgun pellets is presently non-existent to low in sea ducks wintering at northeastern Lake Ontario and that further restrictions on use of lead fishing tackle may have little implication for sea ducks in this region.