Ray B. Owen

Seasonal carcass composition and energy balance of female black ducks in Maine

Female Black Ducks (Anas rubripes) collected in Maine during the summer, fall, and winter of 1974-1976 showed significant seasonal variation in body weight, nonfat dry weight, gizzard and pectoral muscle weight, and fat, moisture, and protein content. Variation of body weight within and among seasons was correlated more strongly with carcass protein content, and with fat content during seasons of heavy lipid deposition, than with three structural size variables (culmen, tarsus, and sternum). Regression equations including fat and protein as independent variables accounted for 80-90% of the annual and seasonal variation in body weight; structural size variables alone accounted for less than 30%. Immature females averaged 54 and 99 g lighter, and carried 54 and 59 g less fat than adults during the fall and winter. Ducks of both age classes lost weight in December and January. Adult and immature females metabolized 59 and 64 g of fat and 17 and 25 g of protein in winter compared with 46 g of fat during the nesting season. Nutrient reserves are thus equally as important for the winter survival of these birds as for successfurl eproduction. Seasonalc hangesi n carcass composition suggest that (1) fat deposited in late fall provides an energy reserve during winter, (2) a reduction in lean weight during winter may lower daily energy requirements and increase the effective amount of energy reserves, and (3) declining body weights during late winter may be an endogenous rhythm that reflects a shift in the expected benefits of an energy reserve compared to the costs of carrying additional weight.

Energy Costs of Activity and Daily Energy Expenditure in the Black Duck

Heart rates of 3 wing-clipped black ducks (Anas rubripes) were successfully monitored for up to 11 days in the field. The energy costs of several activities, such as swimming, feeding, and preening, were calculated using regressions of metabolism on the heart rate previously determined in the laboratory for each duck. Total daily energy expenditure during midsummer using time-activity analyses of nonradioed black ducks was 1.5 to 2 times the resting metabolic rates measured in the laboratory. Preliminary data indicate that the energy costs for laying females may be as high as 3.4 times the resting rates. J. WILDL. MANAGE. 42(4):739-745 Investigations into the energy requirements of wild Anatidae have included feeding trails (Owen 1970, Penney and Bailey 1970, Sugden 1971, 1973, 1974, Sugden and Harris 1972, Miller 1974) and respiration calorimetry (Hartung 1967, Berger et al. 1970, Prange and Schmidt-Nielsen 1970, McEwan and Koelink 1973, Smith and Prince 1973, Wooley and Owen 1977). Recently, Dwyer (1975) estimated the energy requirements of free-living male gadwalls (Anas strepera) by extrapolation from time budget data. However, no direct measurements of metabolism under natural field conditions have been made. Owen (1969) and Wooley and Owen (1977) have discussed the relationship of metabolism to heart rate measured under laboratory conditions in blue-winged teal (Anas discors) and black ducks equipped with radio transmitters. We felt that this method offered promise for use with freeliving waterfowl to estimate the energy requirements for specific activities and to obtain daily energy budgets. The following report discusses the results of research on the energy requirements of semifree-living black ducks and the extrapolation of these data to free-living conditions. We thank C. J. Sniffen for his aid in laboratory work and statistical analysis, A. Fuller for his help in maintaining telemetry equipment, and the Maine Dept. of Inland Fisheries and Wildlife for supplying ducks. Special thanks are due to J. Sease, A. Lovewell, and M. Robson for aiding with field work.

Predicting occurrence of river otters by habitat on Mount Desert Island, Maine.

We developed a model predicting occurrence of river otters (Lutra canadensis) by comparing 19 watersheed used by otters with 14 unused watersheds during 1985-87. Of 39 habitat variables initially measured, 4 provided good discrimination between used and unused watershed. Otter use was negatively associated with the proportion of mixed hardwood-softwood stands in forested areas adjacent to waterways and positively associated with the number of beaver flowages, watershed length, and average shoreline diversity. Our model correctly classified 94% of the watersheds and demonstrated 88% better classification than could be achieved by chance alone

Heart rate, a measure of metabolism in blue-winged teal

Abstract 1. 1. Both existence metabolism (Y) and heart rate (HR) varied linearly with temperature, enabling one to formulate an equation for predicting metabolism from heart rate (Y = 37·35+0·268HR ± 11·934). 2. 2. In relation to existence metabolism, oxygen pulse decreased with decreasing temperature. 3. 3. Heart rates of teal living under semi-controlled free conditions were 52·6±12·6 ( X ± S.E. ) beats higher than under controlled conditions. This represented a metabolic increase of 14·3 ± 3·4 kcal/bird per day. 4. 4. The ecological implications of this research are discussed.

HABITAT MODELS FOR NESTING BALD EAGLES IN MAINE

We derived habitat models for nesting bald eagles (Haliaeetus leucocephalus) in river, lake, marine mainland, and marine island habitats. We measured 39 variables and used discriminant analysis to contrast 82 occupied nest sites and 88 random sites in Maine. Compared to random sites, bald eagle nests were located on river stretches with a larger basin area, less forest edge, and closer to the shore. The lake model indicated that bald eagle nests were positively associated with the number of superdominant trees and negatively associated with distance to water, area of land disturbed by humans, and area of land harvested for timber. The number of diadromous fish species and area of water <1.8 m deep at low tide were positively associated with bald eagle nests in marine mainland habitats; length of roads near nests was a negative variable. Nests were located on smaller marine islands than were random points (P < 0.005), resulting in nesting islands characterized by larger terrestrial and aquatic openings in the forest canopy, less forest edge, and a smaller area of combined shallow water and intertidal area. Correct classification rates for models varied from 75% for the marine island model to 100% for the river model. Similar classification rates, which never differed by more than 8%, occurred during cross validation. Validity of marine models was further suggested by the establishment of 4 bald eagle nests 51.9 km from random sites classified as nest sites; no nests have been established ?1.9 km from random sites classified as unused.

Metabolic rates and heart rate-metabolism relationships in the black duck (Anas rubripes)

Abstract 1. 1. All ducks exhibited a linear inverse relationship between metabolism and temperature below the lower critical temperature. 2. 2. Heavier male black ducks had a higher heat production on a per bird basis that did females. 3. 3. Heat production of ducks acclimated to 19°C was greater than that of birds acclimated to 5°C. 4. 4. Resting metabolism of ducks equipped with small radio transmitters was 19% higher than that of birds without radios. 5. 5. Significant correlations between heart rate and metabolism existed for most ducks.

Beaver populations and their relation to wetland habitat and breeding waterfowl in Maine

The influence of beaver (Castor canadensis) trapping on beaver and waterfowl densities and wetland habitat is not well understood, and this information is needed by managers trying to balance beaver densities and harvest and complaints of nuisance beaver with the abundance of wetlands and waterfowl. During 1988–92 in south-central Maine, we determined the density of beaver colonies and beaver harvest, wetland characteristics, and density of breeding pairs of waterfowl on a 111-km2 site recently closed to beaver trapping and a similar site open to trapping. Density of beaver colonies increased from 0.15 to 0.32/km2 (113%) on the untrapped site but changed little (0.19–0.20/km2) on the trapped site. The number of beaver dams maintained by beaver and the density of beaver colonies were correlated on the untrapped site (r=0.99, n=4,P=0.009) but not on the trapped site (r=−0.18, n=4,P=0.820). Number of wetlands was correlated with the density of beaver colonies during 1989–92 on the untrapped site (r=0.92, n=4,P=0.081) but not on the trapped site (r=−0.13, n=4,P=0.875). Total surface area of water on the untrapped site increased from 115 to 158 ha (36%); surface area of water remained stable on the trapped area. Species of waterfowl that increased on the untrapped site included Canada geese (Branta canadensis) (4–9/100 km2), hooded mergansers (Lophodytes cucullatus) (23–29/100 km2), and mallards (Anas platyrhynchos) (7–12/100 km2). Numbers of wetlands used by pairs of each species of waterfowl increased on the untrapped site. Overall, a ≥1-year closure of beaver trapping is sufficient to increase the density of beaver colonies, whereas a 2–3 year closure is necessary to increase wetland habitat. More than 3–4 years may be required to begin influencing the density of waterfowl and number of wetlands used by waterfowl.

Characteristics of Two Mineral Springs in Northern Maine

Abstract We sampled soil and water at two mineral springs (salt licks) in Baxter State Park, ME, and describe chemical characteristics of each. One site (Wadleigh) is a small spring-fed pond and the other site (Hudson) is a spring with water emerging at the base of a bedrock outcrop; both drain into nearby streams. These sites are frequently visited by Odocoileus virginianus (White-tailed Deer) and by Alces americanus (Moose). Potassium (K) and sodium (Na) concentrations in water were substantially higher at licks than at upstream control sites—Wadleigh Lick: K = 2.33 vs. 0.31 mg/L, Na = 15.7 vs. 1.9 mg/L; Hudson Lick: K = 0.95 vs. 0.19 mg/L, Na = 9.4 vs. 0.9 mg/L. Chloride at the Hudson Lick was 120 vs. 10.7 µeq/L in water upstream. Exchangeable calcium (Ca), K, and magnesium (Mg) in soil at the Wadleigh site were typical of Maine soils but Na was greatly elevated. The elevated concentrations of K and Na in the water are typical of groundwater that has circulated through bedrock, instead of overlying till.