Abstract
Wind generated energy is a relatively new addition to the commercial energy market that is displaying phenomenal growth on a global scale. During the last decade, global wind energy capacity has doubled every three years, about a 30% increase annually (CanWEA 2006). Contrary to past perceptions of the industry, wind power is now modeled as a stable, cost-competitive sector that can substantially contribute to future power generation portfolios. This new stability has come from technological advancements, making the industry more economically competitive, and also from the continuing global demand for renewable energy sources (Andersen & Jensen 2000; Menz & Vachon 2006). In Canada the trend continues with expectations of 10,000 megawatts of wind capacity to be installed by 2010 (CanWEA 2001).
The Atlantic Provinces are poised to substantially contribute to the growth of wind energy in Canada. Objectives for installed capacity in the region are to reach 1,130 megawatts by 2015 (Hornung 2006). In Nova Scotia, wind energy will take a leading role in achieving the requirement for new renewable energy sources to comprise 5% of electricity by 2010 (Hornung 2006). Clearly as wind energy expands in the province, the role of identifying and selecting wind power sites which meet criteria set by government, industry and the public will become increasingly important.
Wind power is commonly cited as a model of an 'environmentally friendly' renewable resource because it does not contribute direct atmospheric emissions, has minimal economic expenditure following decommission and uses limited land area for operation (Andersen & Jensen 2000). Despite these environmental advantages, bird and bat mortalities have been documented for several wind generation facilities across the globe (Ahlén 2003; Johnson et al. 2003b; Johnson et al. 2004; Kerns & Kerlinger 2004; Osborn et al. 2000; Young et al. 2003). In comparison to avian fatalities, the documentation and analysis of bat fatalities at wind facilities is relatively recent and is gaining considerable attention.
Bat mortality as a result of collisions with man-made structures is not unique to wind turbines, with reports of bats colliding with such structures as lighthouses, communication towers and buildings dating as far back as 1930 (Johnson et al. 2004). Bat collision mortality from wind turbines first made its way into the media in North America following a large bat kill at a West Virginia wind farm in 2003 (Williams 2003 in Johnson et al. 2004). Since that time there has been many documented bat fatalities at wind development sites. Estimates of bat fatalities are highly variable ranging from less than 3 bats/turbine/year (Johnson et al. 2003a; Johnson et al. 2004) to 20-50 bats/turbine/year (Jain et al. 2007; Kern s et al. 2005; Nicholson 2003). Species composition of collision fatalities is typically comprised of hoary bats (Lasiurus cinereus), silver-haired bats (Lasionycteris noctivagans), eastern red bats (Lasiurus borealis), and big brown bats (Eptesicus fuscus), with smaller numbers of eastern pipistrelles (Perimyotis subflavus), northern long-eared (Myotis septentrionalis) and little brown bats (Myotis lucifugus) predominantly in eastern North America.
Occurrence records exist for seven species of bats in Nova Scotia, the same seven species with documentations of fatalities at wind turbine sites listed above (Broders et al. 2003a; van Zyll de Jong 1985). Nova Scotia is close to the northern periphery of the current known range for each of these species, with the exceptions of the northern long- eared and the little brown bat (van Zyll de Jong 1985). These two species, as well as the eastern pipistrelle, are the only bat species with significant populations in Nova Scotia (Broders et al. 2003a; Farrow 2007).
The eastern pipistrelle is a non-migratory bat specie s found throughout the eastern forests of North America (Fujita & Kunz 1984; Veilleux et al. 2004). This species occurs in very low numbers in southern coastal New Brunswick (Broders et al. 2001) and in 2001, Broders (2003a) discovered the first concentration of eastern pipistrelles in Nova Scotia at Kejimkujik National Park. Subsequent ultrasonic monitoring throughout mainland Nova Scotia confirmed the presence of a significant population of this species in the province, yet indicated restriction of the population to southwest Nova Scotia in the summer (Farrow 2007; Rockwell 2005). The restriction of this population to southwest Nova Scotia suggests that the population of eastern pipistrelles is disjunct, at least during the summer (Broders et al. 2003b; Farrow 2007).
Only the northern long-eared and little brown bat are common in Nova Scotia (Broders et al. 2003a) and they both have distributional ranges that extend into Newfoundland (Grindal & Brigham 1999; van Zyll de Jong 1985). They are therefore likely ubiquitous throughout the province (Broders et al. 2003a). The northern long- eared bat is a forest interior species (Broders et al. 2003a; Henderson 2007; Jung et al. 2004), while the little brown bats is more of a generalist species, associated with forests, as well as human-dominated environments (Barclay 1982; Jung et al. 1999). Both of these species are year-round residents in the province with over-wintering documented at a number of hibernacula located throughout central Nova Scotia (Garroway 2004; Moseley 2007; Tutty 2006).
The hoary bat, silver-haired bat and eastern red bat, are all migratory species with extensive distributional ranges in North America (van Zyll de Jong 1985). Historically, there have been few occurrence records for these species in Nova Scotia, though several reports of these species flying ashore in Massachusetts and aboard ships off the coast of Nova Scotia in the fall, suggest the possibility of a migratory movement across the Gulf of Maine (Broders et al. 2003a). In 2001, Broders (2003a) recorded greater than 30 000 echolocation sequences from May to September at Kejimkujik National Park and Brier Island, yet fewer than fifteen of these, all in September, were attributed to any of the migratory species. Therefore, it was suggested that there are no significant migratory movements of these species through Nova Scotia and the incidence of individuals of these species during the summer are low (Farrow 2007; Rockwell 2005; Garroway and Broders unpublished data).
Localized over-wintering and reproduction records have been recorded for big brown bats in New Brunswick in low numbers, where their presence was associated with buildings. McAlpine et al. (2002) subsequently suggested that the species may exist in that province in low numbers where it is closely associated with human occupied buildings. Taylor (1997) identified 3 big brown bats hibernating in a hibernaculum in Nova Scotia. These findings indicate that the conditions may exist for year round- residency of the species in the province. However, a general lack of evidence for their presence given the increased research effort since Taylor's work suggests that if the species is present in Nova Scotia they are very localized and in very low numbers.
Echolocation is the primary sensory means by which all of these microchiropteran bat species orient themselves and hunt for prey (Fenton 1997; Fenton & Griffin 1997), where they emit vocalizations and analyze the returning echoes created when these sounds encounter objects (Fenton 2003). Instruments sensitive to these frequencies are referred to as bat detectors and allow investigators to record, hear, and even visualize the otherwise inaudible echolocation calls of bats (O'Farrell et al. 1999). Detectors permit identification of many bat species by their calls (Fenton & Bell 1981; O'Farrell et al. 1999; Thomas et al. 1987), assessment of activity patterns, and studies of behavior and habitat relationships of many species of echolocating bats (Fenton 1997). Bat detectors often permit investigators to sample a much larger area than conventional capture techniques and generally yield a more complete inventory of bat species than captures alone (O'Farrell & Gannon 1999).