Avian communities of mature balsam fir forests in Newfoundland: Age-dependence and implications for timber harvesting

The amount of old growth balsam fir (Abies balsamea) forest (80+ years) in Newfoundland, Canada has declined and management towards a 60-year rotation age will further reduce the availability of old forest as wildlife habitat. We distinguished among three mature age-classes of forests (40-59, 60-79, and 80+ years) based on tree density, canopy gaps, woody debris, and moss and litter cover on the ground. Canonical correspondence analysis revealed two groups of stands: one containing all of the 40-year-old stands and most 60-year-old stands, and a second that included old growth stands and 4 of 10 60-year-old stands. Forest birds were separated into four groups: one preferring the youngest stands, another observed primarily in old stands, and two others that were intermediate. Bird species richness was greater in 40-year-old forests than in 60+ and 80+-year-old stands. Black-backed Woodpecker (Picoides arcticus) and Gray-cheeked Thrush (Hylocichla minima) were most abundant in old forests. Six other species also were grouped together with the latter two as an old forest group. We observed mon species and more total birds breeding on productive forest site types than on less-productive sites based on a forest ecosystem classification, and five species showed significant relationships between density and site quality. We observed few relationships between stand age and migratory strategy. The only guild for which there was a significant relationship of abundance with forest age was cone seed-eaters, which were more common in second-growth forests than in old forest. To maintain avian diversity in these forest landscapes, some stands must be allowed to develop as old growth.