A field evaluation of the Finnish 3-man chain: a method for estimating forest grouse numbers and habitat use

Abstract

The Finnish 3-man chain, a strip transect method for estimating grouse numbers, was tested using radio-tagged birds, 20Capercaillie and39 Black Grouse, in 104 field trials . The proportion counted by the census chain was 54-58% for adult Capercaillie without young and 61-64% for Black Grouse . Only one Black Grouse brood of 11 was not recorded by the chain. Most uncounted Capercaillie ran aside from the strip, while most uncounted Black Grouse remained crouching on the strip. Overall about 80% of the combined number of adults and juveniles should be detected in an average production year with this transect method. The density of covering vegetation influenced the tendency of Black Grouse to remain on the strip. Nevertheless, since almost all of the observed birds moved only short distances, habitat estimates at sites where birds flew up appeared to be a good estimate of the habitat of undisturbed birds.