SEASONAL USE BY BIRDS OF STREAM-SIDE RIPARIAN HABITAT IN CONIFEROUS FOREST OF NORTHCENTRAL BRITISH-COLUMBIA

To determine use of riparian habitats by birds in the northern conifer ous forest of British Columbia, we censused birds and vegetation along 500 m transects placed parallel and perpendicular to three second-ord er streams. Censuses were conducted during spring, summer, autumn, and winter to investigate how use of riparian habitat changed seasonally. Stream-side riparian zones were characterized by a dense understorey of deciduous vegetation not found in the upslope forest. Nine bird spe cies preferred the riparian understorey for breeding, six preferred it only during migration. Neotropical migrants (16 of 46 species) were m ore closely associated with stream-sides than year-round residents (11 species). Some breeding birds (five species) were significantly negat ively associated with riparian habitats. The density of riparian birds declined with distance upstream but did not decline up to 250 m away from the stream. The more extensive riparian areas downstream supporte d a greater density of birds in all seasons compared to upstream areas , but more species only in spring and autumn. Species that nested in n on-riparian areas in summer used riparian habitat in autumn, making ri parian corridors in the northern coniferous forest important during mi gration. Maintaining both riparian and upslope habitats is necessary t o preserve species diversity at the landscape level.