Avian Response to Group Selection Harvest in Northern Hardwoods, Aitkin County, Minnesota

Abstract

The breeding bird communities of the western Great Lakes region have among the richest diversity of breeding bird species in North America (Neimi et al. 2016). The importance of this diversity and past concerns about potential declines of some species has led to a strong interest in studying forest bird populations in relation to forest management in the region (Hanowski and Niemi 1995, Niemi et al. 2016). Northern hardwood forests provide habitat for a variety of breeding bird species, including many long-distance migrants. Before European settlement, northern hardwoods (e.g., sugar maple and black ash) comprised approximately 20% of Minnesota’s forest (5.3 million acres). Over the past century, almost 4 million acres of northern hardwood stands in Minnesota have converted to other forest types, primarily shade-intolerant species such as aspen, and today northern hardwoods account for approximately 12% of forestlands in the state. There has been a recent interest in limiting future loss of northern hardwoods in Minnesota by managing this forest type on an uneven-aged basis. The Aitkin County Forestry Department has recently started implementing an uneven-aged approach using a group or patch selection for managing northern hardwood forests across the landscape. The goal of this management approach is to retain mature northern hardwood species throughout each rotation while providing wood resources for local industry and promoting regeneration and growth of high-value hardwood trees. Because northern hardwood forests provide habitat for a variety of breeding bird species, it is important to document potential shifts in breeding bird communities associated with forest management practices. To do this, we implemented a BACI (Before, After, Control, Impact; Conquest 2000) monitoring framework to assess the effect of uneven-aged management on breeding bird communities in Minnesota’s northern hardwood forests. This assessment is important because although the response of breeding birds to successional forest stages—from clear-cut to mature stand ages—are relatively well known for northern Minnesota forests, breeding bird response to uneven-aged management, specifically group selection, in northern hardwoods has not been thoroughly studied in Minnesota. We hypothesized that mature forest breeding species abundance will decrease after harvest and that abundance of early-successional species would increase to correspond with the newly created habitat on the treatment plot. This report summarizes breeding bird surveys completed pre-harvest in two mature forest stands in Aitkin County, Minnesota, 2013–2015 and the two years of post-harvest surveys that occurred in 2020– 2021. Our overall objectives were to: 1) conduct breeding bird surveys in northern hardwood study plots, 2) document bird community composition and species abundances, and 3) determine whether there are differences between breeding bird communities in the control (not harvested) versus the treatment (harvested) areas.