Avian richness increases following group-selection timber harvests in west-central New Hampshire

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Date
2021-04-27
Keywords
Authors
Parks, Samuel D.
Description
Rapid loss of neotropical migrant songbirds (44% overall decline in the past 50 years) necessitates an urgent call for conservation. Disturbance-dependent early-successional species have experienced an especially large decrease at 58%. The greatest cause for these declines is loss of both breeding and overwintering habitat. Throughout the northeastern United States, post-European arrival, cultural shifts in land use have led to even-aged, mid-successional forests becoming the dominant forested habitat types on the landscape. This has resulted in a loss of young forest habitats required by earlysuccessional birds for nesting and by many forest-interior birds for critical postfledging cover and foraging. We used point counts to assess songbird community response to group-selection harvesting (0.2-1.0 ha openings) in a mixed hardwood/softwood forest in Canaan, NH and in an eastern hemlock (Tsuga canadensis) dominated forest in Lyme, NH. Counts in the mixed-wood forest were part of a 9-year-post-harvest study, while those in the eastern hemlock forest were conducted a year before and a year after a timber harvest. Group-selection openings in the mixed-wood stand created a multi-aged forest mosaic, leading to a fluctuation of species richness as the shrub layer grew in. Overall a net significant increase of species by year 9 post-harvest was observed during a period with no significant changes in background levels of avian richness in the region. Further, in the mixedwood forest we mapped territories of 60 individuals from 5 species in 2019 and 2020 and found territory sizes were generally smaller for young forest species than for forest-interior species. However, all mapped species utilized the early-successional habitat created from the timber harvest during the breeding season. We also documented pairing and fledging rates for several species and found high rates of pairing success and average rates of fledging success compared with other studies. In the eastern hemlock property immediately post-harvest, we observed a significant increase in bird species richness and abundance. As we continue monitoring the eastern hemlock property, we expect an overall increase in species richness that will last longer due to a slower regeneration time characteristic of eastern hemlock forests compared to mixed-wood forests. These results have forest management ramifications demonstrating how different approaches can be used to promote early-successional habitat, crucial habitat for disturbance-dependent species, generalists, and woodland dependent species. The findings of our project may aid in strategic consultation with landowners in the region, where a majority of timberlands are family owned and managed, to demonstrate how forest management strategies can support avian habitat.
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