Abstract Wintering northern saw-whet owls in Johnson County, Indiana natural areas Franklin College Biology Department Student: Daniel Morris Advisor: Dr. Ben O Neal Predatory owls play a vital role in many communities. Knowledge of their ecology can aid in assessing the overall health of natural systems. However, the collection of data is difficult, especially for migratory species such as the northern saw-whet owl (Aegolius acadicus). This project sought to expand the collective data for saw-whets by surveying natural areas in Johnson County, Indiana, where the owls were postulated, but not yet confirmed, to overwinter. Callback surveys were conducted in Atterbury State Fish and Wildlife Area (Indiana Department of Natural Resources) during January of 2012 and 2013 and in the Laura Hare Preserve at Blossom Hollow (Central Indiana Land Trust Incorporated) in February 2013. Saw-whets were documented at both sites. These confirmations led to the first recorded presence of saw-whets in the individual natural areas and Johnson County as a whole. Annual replication of the study would further support the importance of these specific properties and potential others as wintering habitat. Investigating the presence and distribution of this species more broadly could also elucidate the population-level significance that Indiana holds for this species. Introduction The northern saw-whet owl (Aegolius acadicus; ) is a cryptic species native to North America (BLM, 2013). Little was known about this species until recent decades, when mist netting studies began to reveal new aspects of the species ecology. One of the largest contributing factors to their cryptic nature is their small size and slow speed compared to their predators, such as the great horned owl (Brittain, 2011). Through the Migratory Bird Treaty Act, are a protected species, but not one that is officially threatened or endangered (BLM 2013). Because these owls rely on a thick upper- to middle-canopy to shield themselves from predators, unsustainable logging practices, which remove preferred cover, can reduce survival (Brinker et al., 1997; Brittain, 2008). In addition, residential development, which fragments their habitat, forces them to travel in the open for extended periods of time, raising their likelihood of predation (Brinker et al., 1997; Brittain, 2011). The can be either sedentary, with permanent habitat as far north as Alaska and as far south as Central America, or migratory, with a wintering range that spans from Canada to northern Florida (Ridgely, 2003). Indiana supports some sedentary individuals, but it primarily serves as habitat for migratory populations of. Migratory individuals have been recorded throughout the state, with 727 sightings in a total of 54 counties since 1883 (Figure 1; Ridgely, 2003; Brittain, 2013; Brock, 2013). The main purpose of this study was to determine if were present in Johnson County, an area lacking any previous sightings and generally thought to have little habitat (Brittain, 2008; Brock, 2013). Secondary goals were to provide supplemental biodiversity data for the Page 1 of 5
managers of the properties surveyed, and to build a network between the Franklin College Department of Biology and local conservation organizations (IDNR, CILTI). Methods Callback surveys were performed at two natural areas in Johnson County, IN. As this study was not intended to further categorize habitat preferences, but rather to identify their presence or absence in Johnson County, survey locations were chosen based on likelihood of housing wintering owls instead of a random or stratified approach. Four locations in the Atterbury State Fish and Wildlife Area (ASFWA) were surveyed in January of 2012 and 2013, and three locations in the Laura Hare Preserve at Blossom Hollow (LHPBH) were surveyed during January and February of 2013. Potential survey locations within ASFWA were first identified with satellite imagery. Locations were then visually assessed for concordance with known preferred habitat (Brittain, 2008). Final locations were chosen based on habitat suitability and accessibility (Figure 2; Figure 3) Surveys were performed as per the methods outlined by Brittain (2008) in previous surveys of southern Indiana. Surveys took place on calm nights (wind <5 mph) with no precipitation, between dusk and midnight. Two recordings of male wintering vocalizations were played at 55 db for 30-minute intervals at each site, beginning with a 5-minute period of silence to allow any startled owls to regain composure. vocalizations were listened for both during and after the recordings were played, and if any were heard during the recordings, the equipment was turned off in order to avoid overly stressing the organisms. Vocalizations of owl species that prey upon were also recorded. The presence/absence and abundance of owls were recorded for each site. Results Location Year 2012 2013 Date 1/23 1/26 1/28 1/29 1/14 1/17 1/28 2/2 2/7 2/9 2/11 ASFWA 1 0 0 0 0 0 0 0 0 NA ASFWA 2 0 0 0 0 0 0 0 0 NA ASFWA 3 EASO (>1) ASFWA 4 0 0 LHPBH 1 0 0 LHPBH 2 NA 0 0 0 LHPBH 3 NA 0 0 (2) Table 1: Northern saw-whet owls Johnson County survey locations and associated owl observations for 2012 and 2013 [Atterbury State Fish and Wildlife Area = ASFWA; Laura Hare Preserve at Blossom Hollow = LHPBH; Northern saw-whet owl = ; Great horned owl = GHOW; Eastern Screech Owl = EASO; Barred Owl = ]. 0 0 0 NA 0 0 NA 0 GHOW NA (>1) Page 2 of 5
Discussion The confirmations at these sites marked the first recorded presence of in Johnson County, IN. This suggests that there is more suitable habitat in this county than previously known (Brittain, 2011). This study was also able to contribute to the growing inventory of wildlife diversity in ASFWA and LHPBH, identifying wintering habitat consistent with established literature (Brinker et al., 1997; Ridgely, 2003; Brittain, 2008) Expansion of this research into counties neighboring Johnson County that also lack historical sightings of this species (e.g., Morgan, Shelby, and Bartholomew) may help elucidate the relationship between and Indiana s remaining natural areas. Furthermore, the success of this study may encourage research in other counties across the state that lack historical data on the presence of and thus have not facilitated study of their distribution. Continuation of this study in ASFWA and LHPBH by Franklin College students may also facilitate a better understanding of the distribution of these birds within the local natural areas. Figures Figure 1. Map of northern saw-whet owl sightings in Indiana by county (Brock, 2013). Yellow square denotes Johnson County, IN. Page 3 of 5
Figure 2. Map of survey locations for Atterbury State Fish and Wildlife Area, Johnson County, IN (2012 and 2013). Figure 3. Map of survey locations for Laura Hare Preserve at Blossom Hollow, Johnson County, IN (2013) Page 4 of 5
Works Cited Brinker, David F., Katharine E. Duffy, David M. Whalen, Bryan D. Watts, and Kevin M. Dodge. 1997. Autumn Migration of Northern Saw-whet Owls (Aegolius acadicus) in the Middle Atlantic and Northeastern United States: What Observations from 1995 Suggest. Biology and conservation of owls of the Northern Hemisphere: 2nd International symposium. General Technical Report NC-190. St. Paul, MN: U.S. Dept. of Agriculture, Forest Service, North Central Forest Experiment Station. Brittain, Ross A. Characterizing Northern Saw-whet Owl (Aegolius acadicus) winter habitats in south-central Indiana. Proceedings of the Indiana Academy of Science 117.1 (2008): 71-80. Brittain, Ross A. "Correspondance concerning Northern Saw-whet Owls." Personal interview. Nov. 2011. Brock, Kenneth. Indiana Records. 13 Mar. 2013. Raw data. Indiana, n.p. Brock, Kenneth. Map 09. Digital image. N.p., n.d. Web. 13 Mar. 2013. Bureau of Land Management. Raptor Information Sheet - Northern Saw-whet Owl."BLM - U.S. Department of the Interior, n.d. Web. 6 Mar. 2013. <http://www.blm.gov/wo/st/en.html>. Morris, Daniel J. Locations of ASFWA survey sites, 2012-2013. Digital image. Google Maps. Google, Inc., n.d. Web. Jan. 2012. Outline of Laura Hare Preserve at Blossom Hollow. Digital image. Central Indiana Land Trust, Inc., n.d. Web. 29 Jan. 2013. Ridgely, R. S., T. F. Allnutt, T. Brooks, D. K. McNicol, D. W. Mehlman, B. E. Young, and J. R. Zook. 2003. Northern Saw-whet Owl Range Map. Map. Sdakotabirds.com. NatureServe, n.d. Web. Page 5 of 5