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D.G. Krementz

Publications and source records attributed to D.G. Krementz.

45 records · Page 3Linked to original sources
USGS1992

Comparative productivity of American black ducks and mallards nesting on Chesapeake Bay Islands

The authors estimated laying dates, clutch sizes, and nest success rates of sympatrically breeding populations of American black ducks (Anas rubripes ) and mallards (Anas platyrhynchos ) on Chesapeake Bay islands between 1986 and 1989. Neither average laying date nor clutch size differed between black ducks and mallards. Nest success rates were higher for mallards in 2 of 4 years, but were area dependent.

Canadian Journal of Zoology↗
USGS1991

Movements and survival of American black duck and mallard broods on Chesapeake Bay

We attached radio transmitters to day-old American black duck (Anas rubripes) and mallard (A. platyrhynchos) ducklings and monitored duckling habitat use, brood movements, and survival rates for 30 days. Ducklings moved an average of 2.3 km within the first 24 hours and another 1.5 km thereafter. After the initial move, broods usually moved once more. No differences in initial movement distance, subsequent movement distance, or total number of movements were found between black duck and mallard broods. There was some evidence that broods in more human developed areas moved more than broods in less human-developed areas. Black duck duckling survival rates were greater than mallard survival rates in 1 of 2 study years.

Chesapeake Bay↗
USGS1990

Fat scoring: Sources of variability

Fat scoring is a widely used nondestructive method of assessing total body fat in birds. This method has not been rigorously investigated. We investigated inter- and intraobserver variability in scoring as well as the predictive ability of fat scoring using five species of passerines. Between-observer variation in scoring was variable and great at times. Observers did not consistently score species higher or lower relative to other observers nor did they always score birds with more total body fat higher. We found that within-observer variation was acceptable but was dependent on the species being scored. The precision of fat scoring was species-specific and for most species, fat scores accounted for less than 50% of the variation in true total body fat. Overall, we would describe fat scoring as a fairly precise method of indexing total body fat but with limited reliability among observers.

Condor↗
USGS1989

Model-based estimates of annual survival rate are preferable to observed maximum lifespan statistics for use in comparative life-history studies

Estimates of longevity are available for many animals, and are commonly used in comparative life-history analyses. We suggest that annual survival rate is a more appropriate life history parameter for most comparative life history analyses. Observed maximum lifespans estimate complicated functions of survival and sampling probabilities. Annual survival rate estimates derived from modern band-recovery statistical procedures are becoming available for a variety of organisms. We compiled annual survival rate estimates and observed maximum longevities derived from band recovery data for North American waterfowl. Observed maximum longevities were not correlated with the annual survival rate estimates and appear to be unstable over time. We recommend that observed maximum lifespans not be used in life history analyses.

Oikos↗