Studies on the linetransect census method of the woodland bird populations

IV. Effect of vegetation feature on the census effectivity

Abstract

1. The census effectitvities of every species which inhabits more than two study areas are shown in Table 1. The vegetation profile of each study area is illustrated as in Fig. 1.
2. The differences of the census effectivity of every species in Table 1 are almost not significant between study areas. But, when the census effectivities of all species inhabiting some two areas are compared disregarding the confidence limits, there is general trend such as the census effectivities of all species are higher in one of the two study areas excluding a few species. This trend is considered to be caused mainly by the change of the visual and auditorial range for observer reflecting every vegetation feature. The difference of the census effectivity between study areas will become more clear when more samples are collected.
3. The census effectivities of Erithacus cyane and Cettia diphone did not show a certain trend between two areas, because they are almost recorded by extraordinary loud songs in census. The census effectivity of Lanius bucephalus at Takizawa shows a adverse trend compared with that of the other species which inhabit the same area. This phenomenon was caused by exceptional case in Takizawa, where the linecensus route penetrates accidentally the center of every home range of Lanius bncephalus.
4. The relative differences of the census effectivities between every two study areas are calculated (Table 2), disregarding the confidence limits and excluding three species mentioned above. And finally, these relative values are standardized as shown in the bottom column of Table 2, In conclusion, the difference of vegetation feature as shown in Fig. 1 would give rise to about +38.4--27.9 relative % difference of the census effectivity. It was considered that the difference grade are derived from combination effects of tree height and tree density of stand.