Avian community response to group-selection harvest on a mixed-forest American tree farm in west-central New Hampshire

Thumbnail Image
Pangman, Kelsey C.
Early-successional species of songbirds are in sharp decline especially in Eastern North America. These species colonize early-successional forest that are currently near historic lows for most of the Northeastern United States. Intentional management for these species often recruits predators, invasive plants or nest parasites, depending on landscape context. Managing for early-successional species can negatively affect late-successional species that depend on mature forest. Currently, habitat for arlysuccessional species is declining due to urban expansion and natural maturation of early-successional vegetation into more mature forests. By creating a mosaic of small group-selections within mature mixed deciduous-coniferous forest, we successfully recruited early-successional species without decreasing the abundance or reproductive performance of later-successional species. Through monitoring fledging success of three early-successional species, magnolia warbler (Setophaga magnolia), chestnutsided warbler (Setophaga penslyvanica), common yellow throat (Geothlypis trichas) and three late-successional species, black-throated blue warbler (Setophaga caerulescens), hermit thrush (Catharus guttatus) and ovenbird (Seiurus aurocapillus) we were able to assess the impact of the harvest on two suites of avian species. We conducted point counts one year prior to harvest and seven consecutive years postharvest, and documented habitat use of the post-harvest mosaic for these six species in 2017 and 2018. Though the first monitoring season (2017) did not include intensive monitoring of hermit thrush or ovenbird, both early and late successional species paired and fledged young at rates that suggest the habitat was suitable to each suite of species. Early-successional songbird species were 74% successful in fledging young when combining monitoring data from 2017 and 2018 and forest-interior species were 64% successful in fledging young. Point counts revealed that immediately postharvest, species richness increased and continued to increase significantly through the recruitment of several early successional species and persistence of the late successional species. We found that early-successional songbird species began to increase in abundance and richness after the fifth year post harvest with no negative pattern of decrease in forest-interior songbird species abundance and richness across years. We documented that through the group-selection cutting there were significantly more woody stems less than 2.5 cm in cut areas and less canopy cover when compared to mature forest. Contrary to our prediction there was no significant difference in the density of woody stems less than 8 cm in cut areas compared to mature forest. This is most likely due to the high amounts of herbaceous plants such as raspberry (Rubus spp.) in cut areas which did not contribute in the woody stem count. The density of stems less than 8cm was negatively correlated with nest success, though previous studies have shown opposite findings. None of the measured shrub and tree vegetation variables or ground cover variables had a significant correlation with successful nesting. The return rates of those species banded in 2018 were 39% for black-throated blue warblers, 25% for common yellow throats and 14% for chestnut sided warblers. More than half of New Hampshire is privately owned and so landowners and consulting foresters can play a critical role in sustaining early successional habitat without negatively impacting late-successional migratory birds.