Problems of applying the line-transect method without repeated counts when the breeding season is long

The Finnish line-transect method has been used generally in Latvia since 1980, and since 1983 it has been used in ornithological monitoring and in computing relative densities of common species in different habitats. Material from Latvia was used for calculating species-specific coefficients of detectability (k). Data were grounded according to the value of the total main-belt percentage of the observations in the counts; this has several advantages. It is suggested that the coefficient k obtained in such a way compensates for the influence on the total breeding density results, on the density and development of the vegetation, on bird singing activity, on the relative number of "loud' birds, and on the variation in the individual skills of the observers. -from Authors