Use of dredged material substrates by nesting terns and black skimmers

Article Abstract:

Shell substrates appear to be important to nesting terns and black skimmers for vegetation control, egg camouflage and reproductive success. This was gleaned from a study of black skimmers, least terns and gull-billed terns to find out if their reproductive success differed between shell substrates and fine-textured dredged material composed of a mixture of sand, silt and clay. Results revealed that the average proportion of eggs that hatched was higher for nests on shell than on fine-textured dredged material. Between substrates, however, the proportion of nests wherein at least one egg hatched was not different.

Behavior, Terns, Habitat selection

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Characteristics of forests at spotted owl nest sites in the Pacific Northwest

Article Abstract:

The forest and physiographic characteristics of spotted owl nest sites in western Oregon and the Olympic Peninsula were quantified. Majority of the nest sites were located from the middle to the bottom of the slopes. Nest sites had greater horizontal and vertical density of trees which provided a denser cover in the multiple layers of canopy. The combination of greater basal area of broken-top trees, greater basal area of small trees and larger volumes of logs and lower elevations best distinguished the nest sites.

Oregon, Spotted owl, Spotted owls, Olympic Peninsula

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Detectability analysis in transect surveys

Article Abstract:

Line transect sampling assumes that animal detectability decreases as the distance from the transect increases but adjustment for environmental variables can affect the analysis. An analysis strategy is illustrated and discussed that takes account of variables and which uses ordinary least squares regression analysis and a standard estimator of effective area. The approach is applied to a survey of cheloniid sea turtles in the eastern Pacific Ocean.

Usage, Surveys, Pacific Ocean, Observations, Regression analysis, Sea turtles, Marine fauna, Marine animals

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