Assessing changes in bird communities along gradients of undergrowth deterioration in deer-browsed hardwood forests of western Japan

•Impact of deer on forest ecosystems has been spreading rapidly in western Japan.•We used the shrub-layer decline rank (SDR) as a measure of habitat change.•SDR-dependent differences in bird communities were detected at a regional scale.•Six bird species were identified as being closely associated with reduced damage sites.•SDR-guided deer management strategy might also be preferable for bird conservation.