STRIEN A VAN, VOS P, HAGEMEIJER W, VERSTRAEL T & MEYLING AG (1994) The sensitivity of two national bird monitoring programmes. LIMOSA 67 (2): 69-75.

Knowledge of the sensitivity for detection of trends in bird population size by means of monitoring programmes is vital for interpretation of data resulting from such programmes. Therefore, the sensitivity has been computed for the Breeding Bird Monitoring Programme (BMP) and the Point-Transect-Counts for wintering birds (PTT). Important ingredients in the computations were the year-to-year variance, the year-plot variance per species and the number of plots or routes where birds were counted. These variances were related to several ecological characteristics of species. The sensitivity has been expressed as the changes that would be detectable in a 5 or 10 years' detection period, using a probability of detection of 80%. The BMP appeared to be rather sensitive for most breeding species. In a ten year period a 50% or smaller change would be detectable for 79 out of 89 species. As expected, the sensitivity of the PIT appeared to be considerably lower: a 50% or smaller change would be detectable for about half the number of species. That is due to the higher variances in the PTT. The best strategy to improve the sensitivity depends on the species: for some species it is best to seek more plots, while for other species it is better to adjust for factors causing the variability in numbers

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