The effects of small-scale disturbance on forest birds: a meta-analysis

Abstract

Small-scale disturbance is a significant process in all major forest biomes. Some silvicultural practices, particularly group selection harvesting, intend to emulate natural small-scale disturbance by harvesting small clearcuts in the continuous forest. We conducted a meta-analysis on the effects of small-scale harvesting on North American breeding forest birds. We extracted species richness and relative abundance of several functional bird groups and guilds from published studies and compared them between gap-dominated and unlogged forest as a function of forest type and the size and age of the gap. The abundance of many bird groups was higher in the gap-dominated than in the continuous forest. Species preferring interior parts of the forest had the most negative association with the presence of gaps but this relationship was not statistically significant. Abundances of many bird groups increased with increasing gap size, while its effect on abundance of some bird groups disappeared quickly. Our review suggests that silvicultural practices that bring about small gaps do not negatively affect the abundances of most forest birds and often even enhance it. However, more studies are needed to examine optimal size and abundance of gaps in a forest and whether emulated small-scale disturbance effectively mimics natural processes.