Use of lakes by black duck broods in relation to biological, chemical, and physical features

Abstract

Characteristics of 32 freshwater lakes in central and western Nova Scotia were quantified to determine the relative influence of various biological, chemical, and physical factors on habitat selection by black ducks (Anas rubripes Brewster) during brood-rearing. Acidity and trophic status varied greatly among the waterbodies, of which 20 were used by black ducks for rearing their young. Duck brood density was positively related to lake trophic status. The highest brood densities occurred on hypertrophic waterbodies with a large anthropogenic input of nutrients.Lakes with black duck broods had significantly higher concentrations of phosphorus and nitrogen, darker water with more dissolved organic carbon, and within the littoral zone, greater macrophyte cover, greater density and biomass of pelagic invertebrates, gentler slopes, and a softer, more organic substrate. Similar trends were observed within a subset of 17 acidic lakes (pH < 5.5), 8 of which supported black ducks.The density of black duck broods was significantly correlated with 17 of 20 variables, most notably total phosphorus (r = + 0.81). Partial correlation (removing the effect of total phosphorus) revealed that brood density was significantly correlated with the abundances of pelagic (r= + 0.77) and benthic (r = + 0.68) invertebrates, macrophyte cover (r = + 0.52), and substrate score (r = + 0.57), but not with other chemical variables, including pH.Our results suggest that quality brood-rearing habitat is distinguished by a combination of factors, especially available nutrients, macrophyte cover, and invertebrates, subject to constraints imposed by physical characteristics of the littoral zone of the lake. The abundance of invertebrates, the primary food of young black ducks, emerged as the most important biological factor influencing the density of black duck broods.

Macroinvertebrate abundance, water chemistry, and wetland characteristics affect use of wetlands by avian species in Maine

“…Seventy-seven percent of all broods for all years (Table 8) were raised on wetlands with pH £ 5.51, which supports the comment of Staicer et al (1994: 195) that, 'Moreover, total phosphorus was statistically more important than pH in predicting use of lakes by black ducks'. In our study the amount of total phosphorus predicted mean number of Insecta per wetland and mean brood density, which reinforces findings of Staicer et al (1994). Our findings and that of Staicer et al (1994), and Parker et al (1992) in New Brunswick, however, are in contrast with DesGranges & Houde (1989) in Quebec who stated that black ducks avoid acidic lakes.…”

“…Our findings regarding association of waterfowl broods with biological and physical characteristics of wetlands are similar to those of Staicer et al (1994) for Nova Scotia. Although wetlands in the northeast are mostly oligotrophic or mesotrophic, duck broods used wetlands with the highest trophic status, reflected in higher levels of total phosphorus but low pH, which did not affect use by brood-rearing females.…”

“…Loss of fish and aquatic invertebrates were being documented, but effects of acidification on aquatic avifauna in areas with low acid-neutralizing capacity (ANC) were less well known. Since 1982 knowledge of biological, chemical, and physical characteristics of wetlands that affect water birds has increased substantially (DesGranges & Gagnon, 1994;Staicer et al, 1994;McNicol et al, 1998). Previous studies emphasized effects of acidification (McNicol et al, 1987;Parker et al, 1992), especially on fish (DesGranges & Darveau, 1985;Elmberg et al, 1994), that affect trophic levels (i.e., macroinvertebrates) (Eriksson et al, 1980;Mallory et al, 1994), and subsequently duckling foods (DesGranges & Rodrigue, 1986;McNicol & Wayland, 1992).…”

The ecology of sewage treatment gradients in relation to their use by waterbirds

“…However, the young of some species often feed on plankton. The abundance of young of American black duck (Anas rubripes Brewster) for example were found to be significantly, and positively, correlated with both planktonic and benthic invertebrate biomass across 32 freshwater lakes in western Nova Scotia (Staicer et al, 1994).…”

Breeding waterbird wetland habitat availability and response to water-level management in Saint John River floodplain wetlands, New Brunswick

“…Variables such as elevation, juxtaposition, vegetative composition and availability of surrounding upland and wetland habitat probably influence the distribution and movement of waterfowl broods on floodplain wetlands. Staicer et al (1994) found that a number of variables including invertebrates and macrophyte cover, affect the density and distribution of American Black Duck broods on freshwater lakes in Nova Scotia. Data is limited on brood movements and habitat use and therefore a number of variables must be carefully considered when evaluating the need and location of new impoundments created for brood-rearing waterfowl along the Saint John River floodplain.…”