Long-term effects of different forest regeneration methods on mature forest birds
Changes in forest structure that result from silviculture, including timber harvest, can positively or negatively affect bird species that use forests. Because many bird species associated with mature forests are facing popu- lation declines, managers need to know how timber harvesting affects species of birds that rely on mature trees or forests for breeding, foraging, and other purposes. We used generalized linear mixed models to determine effects of clearcutting, shelterwood, single-tree selection, and group selection on detection of 18 species of bird associated with mature forests in the Ouachita Mountains of Oklahoma and Arkansas. We surveyed birds for 16 years after harvest. Most species (67%) responded positively to partial harvest that retained some overstory. Less intensive harvests had positive effects on more species and negative effects on fewer species than more intensive harvests, but responses to different treatments varied among species. Five species showed a significant positive response to the most intensive harvest (clearcuts), whereas 2 species showed a negative response. For the second most-intensive harvest (shelterwoods), 7 species showed a significant positive response and 1 species showed a negative response. For the less-intensive harvests, 9 species showed a positive response and no species had negative responses to single-tree selection, whereas 7 species had positive and no species showed negative responses to group selection. Ovenbird (Seiurus aurocapilla) and scarlet tanager (Piranga olivacea) responded negatively to all timber harvests; ovenbird appeared to be particularly susceptible to timber harvest, especially more intensive harvests such as clearcut and shelterwood. A variety of regeneration methods, including some more intensive treatments, along with maintenance of mature forest stands that retain well-developed midstories can be used to maintain the full suite of forest birds.