Statistical Treatment of the ‘Inconspicuousness Problem’ in Animal Population Surveys

Energy consumption of ducks on øvre Heimdalsvatn

“…1. Number of observations, theoretical maximum number of observations and the discovery chance (Seierstad et al 1965 were found, none in 1971, and the two young velvet scoters, Melanitta fusca, were the only ones observed in 1972.…”

“…The density of the various species was very low, making it easy to distinguish between the individual birds on the lake. The discovery chance (Seierstad et al 1965) was estimated by counting non-flying juveniles and their parents during a period in 1972. The mean weights of the duck species were based on information given by Haftorn (1971).…”

Estimating Relative Densities of Breeding Birds by the Line Transect Method. II. Comparison between Two Methods

“…Several authors (Seierstad et al 1965, Enemar & Sj6strand 1967, Blondel 1969a, p. 135, Emlen 1971, Jarvinen & Viisinen 1975a have agreed that the line transect method can hardly be substituted by other methods in quantitative studies of breeding land birds in extensive geographical areas. For small areas the mapping method (Enemar 1959, and later developments) is certainly superior; for certain species no method except individual ringing appears to be accurate enough (e.g.…”

Diversity and abundance of water birds in a subarctic lake during three decades

“…If they have, they do not sit on the nest to brood because the clutches are not complete, and the females are seen on the lake along with the males most of the time. The discovery chance (Seierstad et al 1965) for breeding pairs is high at this time. The first few days after ice-break are therefore the best time for obtaining good density estimates of ducks and divers (Haapanen & Nilsson 1979).…”