Recommended use: Absolute abundance; see Table 2 for species-specific recommendations.
Recommended for estimating total numbers of breeding birds in colonies. Estimates of the entire provincial breeding populations of Western Grebes and American White Pelicans can be made, but pelicans should not be routinely surveyed with this method.
This method is best for monitoring long-term population trends of specific colonies and for inventories involving analysis of reproductive success.
Counting nests requires visiting a colony and determining the status of each nest. Often, all or most potential habitat is searched and the contents of each nest is recorded (e.g., Breault et al. 1988; Butler 1989). Direct counts of active nests provide the most accurate data on numbers of breeding pairs and can also provide data on clutch sizes, microhabitat use and other characteristics which may be useful for management purposes. Nest counts require personnel that can correctly identify eggs and nests of each species, and can conduct themselves in a manner which minimizes disturbance to incubating birds, nests, and nesting habitat.
Grebe colonies can be surveyed by wading through nesting marshes, or in combination with a small boat in deeper water. If sufficient effort is expended, virtually all nests can be found. Great Blue Heron colonies can be inventoried from the ground by assessing each nest for presence of adults or young (Butler 1989), or by climbing trees and looking into each nest. It is best to survey nests from neighbouring trees rather than climbing the nest tree itself. Although American White Pelicans can be surveyed by visiting nesting islands and counting active nests, this is not recommended.
Because of the few number of colonies of Western Grebes and American White Pelicans in British Columbia, the entire provincial breeding population can be inventoried by this method (e.g., Dunbar (1984); Burger (1991); Table 1). Similarly, as the locations of the largest colonies of Eared Grebes (Breault et al. 1988; Campbell et al. 1990; Table 1) and Great Blue Herons (Mark 1976; Forbes et al. 1985; Breault 1988; Campbell et al. 1990; Butler 1991) have been documented, a large portion of the provincial breeding populations can also be surveyed this way. For Red-necked Grebes, representative colonies could likely be surveyed to provide data for comparisons over time.