Estimating occupancy rates of the elusive and threatened species, Bicknell’s Thrush (Catharus bicknelli), in managed forests of northern New Brunswick
Faculty of Forestry and Environmental Management
University of New Brunswick
Why Bicknell’s Thrush?
The Bicknell’s Thrush (BITH) is a rare songbird that breeds in high elevation forests of northern NB. Research focusing on this elusive songbird is becoming increasingly important as population numbers have declined by 11.5%/year from 2002-2011 (Campbell & Stewart, 2012). Though cutting of winter habitat in the Greater Antilles greatly contributes to this decline, forest practices in the NB breeding range may be having an impact on successful nesting locations. Much of the breeding habitat in NB is crown land leased to forest companies and therefore habitat is subject to management schemes including clear cutting, strip cutting and pre-commercial thinning (PCT). The traditional habitat of BITH is very thick regenerating fir dominated stands which are common at high elevations due to strong winds leading to blow downs. PCT treatments reduce the stem density and thus may be less appealing to nesting birds. However, regenerating clear-cuts may consistently provide suitable habitat for these birds.
What We Are Doing?
The main goal of my project is to determine whether BITH will use stands that have been treated (PCT, etc) and also if they occupy stands outside the range of "traditional" habitat (11-20 years). Songmeters are used to determine BITH presence or absence. These instruments are digital recorders that can be programmed to record sounds at a given time. We place them in stands of various age and treatment types and set them to record at peak singing times, dawn and dusk. These recordings will then be run through software trained to locate the specific song pattern of the Bicknell’s Thrush. My hope is to link BITH presence to specific stands and create a habitat model that can better estimate the potential habitat of the species across northern New Brunswick.
By getting a better idea of the stand types and ages occupied by this threatened songbird, managers can create or alter existing harvesting regulations in order to give the BITH a fighting chance during the breeding season. This could include reserving treatments until the conclusion of the breeding season (mid July) or implementing management regimes to ensure a cycle of stands preferred by BITH.
This project is a contribution to the Bicknell's Thrush Conservation Plan (IBTCG 2010), and is a collaboration with Bird Studies Canada, Environment Canada, Canadian Wildlife Service, and NB Department of Natural Resources, who provide funds and material and logistic support.
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