Date of Award

Summer 8-21-2020

Level of Access

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Wildlife Ecology and Wildlife Conservation

Advisor

Amber M. Roth

Second Committee Member

Erik Blomberg

Third Committee Member

Daniel Hayes

Additional Committee Members

Adrienne Leppold

Abstract

Forest reliant species may be significantly impacted by forest management practices. Understanding these impacts, and whether they are positive or negative, requires a species- specific understanding of habitat use. Bicknell’s thrush (Catharus bicknelli) is a range-restricted habitat specialist occurring in balsam fir (Abies balsamea) dominated montane forests that have been recently disturbed and are undergoing successional growth. While research investigating this species’ habitat use has been conducted throughout much of its breeding range, knowledge of Bicknell’s thrush habitat use in Maine is lacking. Greater understanding of habitat use in Maine would improve the ability of forest managers to promote conservation of habitat for this species of concern. We documented the use of a method for tracking small songbirds in a landscape disadvantageous to using very-high-frequency (VHF) telemetry. Given that the habitat Bicknell’s thrushes occupy is often characterized by rugged terrain and dense forest conditions, efforts to effectively track this species to estimate home-ranges and evaluate habitat use may be confounded. To ameliorate this, we explored the use of a combination tag with a global positioning system (GPS) and VHF component. All things considered, GPS+VHF telemetry was less expensive than VHF telemetry. However, VHF telemetry via triangulation was more accurate than GPS telemetry by 15.09 m. GPS+VHF tags provided greater spatial coverage by collecting data in areas we were otherwise unable to use VHF telemetry effectively. We conclude that GPS+VHF tags offer a feasible alternative to VHF telemetry in densely forested, rugged field conditions. We discuss the potential advantages and disadvantages to VHF- and GPS- based telemetry and make recommendations to researchers interested in employing these methods on small songbirds. We suggest that researchers consider the use of a GPS+VHF tag attached with a weak link leg-loop harness. We also recommend that while researchers should rely on the GPS component of the tag for the majority of their data, we also encourage researchers to continue to track individuals using the VHF tag component when study objectives deem it necessary.

We also captured and tracked 24 Bicknell’s thrushes during 2018-2019 in a harvested and non-harvested study area in Maine, USA, and evaluated the influence of forest structure and composition on habitat selection. At the landscape level, Bicknell’s thrushes demonstrated avoidance of tall canopy heights and a large proportion of hardwood tree. At the home-range level within the harvested area, Bicknell’s thrushes selected increasing numbers of small trees (2.54 to 10 cm dbh) and demonstrated a quadratic relationship for selection of canopy height. Similarly, at the home-range level within the non-harvested area, Bicknell’s thrush demonstrated a quadratic relationship for selection of the number of small trees and canopy height. We concluded that Bicknell’s thrushes use lower elevation forest stands in harvested landscapes in Maine. We recommend quantifying forest structure using LiDAR to identify and prioritize stands for use by Bicknell’s thrush.

Share