Date of Award

Summer 8-3-2016

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Wildlife Ecology and Wildlife Conservation

Advisor

Daniel J. Harrison

Second Committee Member

Erik J. Blomberg

Third Committee Member

Brian Olsen

Additional Committee Members

Daniel G. McAuley

Abstract

Spruce grouse (Falcipennis canadensis) inhabiting the mixed coniferous-deciduous forests of the northeastern United States are at the southern extent of their range. These mixed forests are known collectively as the Acadian forest and represent the transitional zone between the boreal forest to the north and the deciduous northern hardwoods forests to the south. Often assumed to be associated with mature, unharvested forest in this region, few studies have assessed habitat relationships of the species within areas dominated by commercial forest management. We investigated the influence of stand maturity, vertical and horizontal cover, and patchiness on the occupancy and abundance of male spruce grouse during the breeding season (Chapter 1); as well as within stand-scale habitat selection of spruce grouse hens during the brood-rearing season (Chapter 2) in the commercial forests of northcentral Maine. Our study was comprised of six townships that covered 612 km2 within the largest contiguous undeveloped forest in the U.S.

Patterns of occupancy and abundance by male spruce grouse were examined by surveying 30 stands during each breeding season (May-June) in 2012-2014. Areas surveyed represented four forest harvest histories including regenerating clearcut (n = 10), pre-commercially thinned (n = 10), selection harvest (n = 4), and mature unharvested conifer (n = 6) stands. We constructed single season occupancy and abundance models with years and stand types considered as groups, while accounting for nuisance variables that could affect survey outcomes (e.g., weather, density of woody vegetation). Probability of detection given occupancy was 0.61, and the probability of occupancy varied by successional stage from 37.4 to 76.8. Across our study area, individual male grouse had a probability of detection of 0.24 and the abundance of male grouse also varied by successional stage from 0.67 to 2.75. Based upon the covariates included in the models, both occurrence and abundance of breeding male spruce grouse were highest in mid-successional, moderately dense, conifer dominated stands that have experienced intensive forestry practices such as clearcutting, herbicide application, and pre-commercial thinning to promote coniferous regeneration.

We investigated within stand-scale (i.e., 4th-order selection) habitat selection by female spruce grouse during the brood rearing season (June-October) in 2012-2014 by tracking 30 hens captured in 12 stands, which we equipped with VHF transmitters. We used general linear mixed models to construct resource selection functions to compare use to availability for each hen. Female spruce grouse selected for abundant low vegetation structure (

Spruce-fir forests in the region have declined in recent years and are predicted to decline further under all future climate scenarios. Thus, forms of harvesting and post-harvest treatments that promote moderately dense conifer-dominated regeneration are recommended to maintain spruce grouse presence in commercially managed forests within the Acadian region. Currently, these conditions selected for by spruce grouse occur predominantly in stands with a past history of clearcutting, followed by post-harvest herbicide application and/or pre-commercial thinning. Changing markets, regulations, and other factors have caused the majority of forest harvests to shift towards partial harvest methods in Maine. Given that the extent and size of residual conifer forest patches has declined substantially over the past three decades, opportunities to manage for spruce grouse and other conifer-dominant species in Maine’s commercially managed forests will require future attention and monitoring.

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