PENNSYLVANIA GAME COMMISSION BUREAU OF WILDLIFE MANAGEMENT PROJECT ANNUAL REPORT

PROJECT CODE NO.: 06798

TITLE: Barn Owl Conservation Initiative

JOB CODE NO.: 79801

PERIOD COVERED: January – December, 2009

COOPERATING AGENCIES:

WORK LOCATION: Statewide

PREPARED BY: Dan Mummert, SE; Jamie Flickinger, SC; Mario Giazzon, NC; Richard Fritsky, NE; Tammy Colt, SW; Timothy Hoppe, NW.

DATE: 15 March, 2010

ABSTRACT The Regional Wildlife Diversity Biologists (RWDBs) began a Barn Owl Conservation Initiative (BOCI) in spring 2005 to study the biology and ecology of Pennsylvania's barn owl to better understand and conserve this species of concern. RWDBs conducted site visits to determine barn owl activity, monitor active nest sites, conduct public outreach to landowners, and distribute and/or install barn owl boxes. Barn owls were banded to provide information on longevity, causes of mortality, and dispersal. In 2009, RWDBs confirmed 71 active barn owl nests, of which 18 were new sites, bringing the total number of different nest sites to 122 since nest searches began in 2005. RWDBs banded 243 nestlings in 56 nests in 2009. Clutch size ranged from one to seven (average = 4). To date, 24 banded barn owls have been recovered of which 16 dispersed from their natal site with an average minimal dispersal distance of 73 miles (range = 1 - 325 miles). Of the 13 fledged barn owls that were recovered dead with a known period of death, longevity ranged from 5 months to 70 months with an average lifespan of 15 months.

OBJECTIVES

1. Assess the abundance and distribution of barn owls in Pennsylvania.

2. Evaluate barn owl habitat use and prey use in Pennsylvania.

3. Assess survival and dispersal of barn owls.

4. Improve nesting and foraging habitat and protect existing barn owl nest sites to encourage expansion of the barn owl population in Pennsylvania.

79801 2 5. Examine genetic diversity of barn owls in Pennsylvania.

INTRODUCTION

With 36 subspecies and populations found on every continent except Antarctica, barn owls (Tyto alba) are one of the world’s most widely distributed birds (Taylor, 1994). Though this species is globally secure, significant population declines have occurred in North America over the past 30 - 50 years (Colvin 1985, Marti 1992). Breeding Bird Survey (BBS) data has found that the North American barn owl population has declined by 1.8% annually between 1966 and 2005 (Sauer et al. 2007). Although insufficient barn owl data prevent BBS data from being used for determining regional or statewide trends, Colvin (1985) has found that barn owls have declined drastically in the upper Midwestern states and limited data suggest a general decline throughout the Northeast (Rosenburg et al. 1992).

In Pennsylvania, evidence is mounting that barn owls are declining and their distribution is contracting. According to McWilliams and Brauning (2000), “barn owl breeding populations are not monitored, but numbers apparently have dwindled since the late 1970s on Christmas Bird Counts.” McWilliams and Brauning (2000) also mention that “they are absent from Greene and Washington Counties, where they were formerly regular.” Comparing data from the 1st and 2nd Pennsylvania Breeding Bird Atlases (BBA) also provide evidence that barn owls are declining in both population size and distribution throughout the state. In the 1st BBA, which took place from 1984-1989, barn owls were observed in 251 (5.1%) blocks and confirmed in 107 (2.2%) of those blocks. In the 2nd BBA (2004-2008), barn owls were observed in 114 (2.3%) blocks and confirmed in 85 (1.7%) of those blocks. The barn owl is designated a “candidate at-risk” in Pennsylvania (Ornithological Technical Committee, PA Biological Survey) and is identified as a species of concern in the Wildlife Action Plan (WAP).

The Pennsylvania Game Commission’s (PGC) mission is to manage and conserve all wild birds and mammals, as well as their associated habitats. This project addresses Goals 1, 2, and 4 of the PGC’s Strategic Plan. By studying the current barn owl distribution and abundance, causes of mortality and habitat requirements and working to educate landowners on barn owl biology and habitat management techniques, this project will help maintain and possibly improve populations of barn owls and other grassland associated wildlife for nonconsumptive recreational use and their many public values (Goal 1). By working closely with landowners who have barn owls using their barns and silos, this project will provide outreach and education to landowners about the value and importance of barn owls and their associated grassland habitat (Goal 2). Through education about proper grassland management and by installing barn owl nest boxes, this project will protect, maintain, and enhance habitat on public and private lands for barn owls and other grassland associated species (Goal 4).

The project also addresses various priorities in the WAP. By conducting site visits and determining barn owl breeding activity, we are assessing the current status of the barn owl in Pennsylvania (Research and Survey Priority, Level 2). By building and inventory of known nest sites, developing links with landowners, and providing education and outreach to the public, we are protecting nest sites (Conservation Management, Implementation Priority 2). By providing nest boxes in areas that have suitable foraging habitat, defining the most suitable areas for concerted efforts to provide nest sites, and monitoring nest boxes, we are increasing nest site 79801 3 availability (Conservation Management, Implementation Priority 3). A future radio telemetry project that evaluates priority foraging habitats and acreages required per pair would address Conservation Management, Implementation Priority 4, which is to maintain or expand the availability of high quality foraging habitat.

Barn owls frequently have large clutches, are sexually mature at one year, and occasionally have two clutches per year (Taylor 1994). Barn owls are closely associated with humans in that they frequently use barns, silos, and other artificial structures. Efforts to offset population declines by providing nest boxes in appropriate locations have been successful in several areas (Marti 1992). These factors indicate that barn owls have high recovery and management potential and can be positively influenced by conservation efforts (Rosenburg 1992).

Barn owls have not been extensively studied in Pennsylvania. To properly manage for this species, information is especially needed in the areas of fledgling dispersal, habitat requirements, distribution, and population trends.

METHODS

The Barn Owl Conservation Initiative (BOCI) is a statewide project, assessing barn owl populations wherever they occur through the Regional Wildlife Diversity Biologists (RWDB) assigned working through the Game Commission’s regions. Methods to accomplish the objectives stated below are addressed as follows.

Assess Abundance and Distribution of Barn Owls in Pennsylvania (PA) RWDBs conducted site visits to locations where barn owls were expected to occur. During site visits, RWDBs determined presence or absence by searching for barn owls and fresh sign (e.g., pellets and “whitewash”). Locations of breeding activity were determined by the confirmation of eggs, nestlings, or recently fledged young. Global Positioning System devices were used to record location of active sites. Data related to site location, reproductive status, nest site characteristics, and adjacent land use were recorded. Data was submitted to Pennsylvania Natural Diversity Inventory (PNDI) and 2nd PA Breeding Bird Atlas (BBA).

Evaluate Barn Owl Habitat Use and Prey Use in PA Assistance was given to Dr. Karl Kleiner of York College who is the principal investigator of a pilot study to be conducted in the spring and summer of 2010 where radio telemetry will be used to determine home range and habitat use by adult barn owls during the breeding season. In addition, barn owl pellets were collected from active barn owl nest sites and will be analyzed by outside resources to determine prey usage.

Assess Survival and Dispersal of Barn Owls Barn owls were banded following standard protocol of the Patuxent Wildlife Research Center Breeding Bird Lab to provide information on longevity, dispersal and causes of mortality.

Improve Nesting and Foraging Habitat and Protect Existing Barn Owl Nest Sites to Encourage Expansion of the Barn Owl Population in PA 79801 4 RWDBs provided recommendations on grassland management to landowners with nesting barn owls, to those who receive nest boxes, and to landowners wishing to provide habitat for barn owls and other grassland associated species.

To provide additional nesting sites safe from predators and hazardous ledges, RWDBs installed barn owl nest boxes at appropriate locations with the permission and cooperation of landowners. Nest boxes were monitored by the RWDBs, volunteers, or the landowner to determine use and nesting success. Landowners with active or potential barn owl nest sites were given information on barn owls related to such topics as conservation status, habitat requirements, threats, causes of decline, habitat management recommendations, and proper nest box placement. RWDBs gave presentations on barn owl conservation to many different groups.

Examine Genetic Diversity of Barn Owls in PA RWDBs collected feathers from all banded barn owls. Dr. Karl Kleiner from York College and a student began analyzing these feathers to determine sex ratios. Further analysis of feathers will attempt to determine the genetic diversity of barn owls in Pennsylvania.

RESULTS AND DISCUSSION

Assess Abundance and Distribution of Barn Owls in PA In 2009, RWDBs confirmed 70 active barn owl nests (Table 1), bringing the total number of different nest sites to 122 since nest searches began in 2005 (Figure 1). Confirmed nests are concentrated in the central and southeastern parts of the Commonwealth. There were 6 confirmed second clutches in 2009, though RWDBs were not actively monitoring for them. Data were submitted to PNDI and the 2nd BBA.

Evaluate Barn Owl Habitat Use and Prey Use in PA RWDBs have helped with preliminary work for a pilot project being led by Dr. Karl Kleiner of York College where radio telemetry will be used from April-July 2010 to study home range size and nocturnal habitat preferences of adult barn owls during the breeding season. RWDBs continued to collect pellets from active barn owl nest sites to determine the selected prey of Pennsylvania’s barn owls. Preliminary results from dissections conducted by students at Lycoming College determined that at sites in Lycoming and Union counties, barn owls predominately fed on meadow voles (Microtus pennsylvanicus) and short-tailed shrews (Blarina brevicauda) with 78.9% and 18.4% of these prey species observed respectively in dissected pellets (Table 2). Results of additional collected pellets at other locations are pending.

Assess Survival and Dispersal of Barn Owls RWDBs banded 240 nestlings in 55 nests in 2009 (Table 1). The earliest nest was banded on 20 May and the latest nest was banded on 9 December; most nests were banded in June (Figure 2). Clutch size ranged from 1 to 7 (average = 4); majority of the nests banded had a clutch size of 2 to 6 (Figure 3). Because most nestlings were banded at approximately 5 to 7 weeks of age, and females incubate eggs for 32 days, and the owlets fledge approximately 60 days from the hatching date, it can be assumed that 1) eggs were laid between 7 March and 26 September, 2) hatching took place between 8 April and 28 October, and 3) the owls fledged between 7 June and 26 December.

79801 5 To date, 24 banded barn owls have been recovered of which 15 were recovered at least one month post-fledging and dispersed from the natal site (Figure 3). Of those recovered, 21 were banded in Pennsylvania and 3 were banded in other states by other banders. All were banded as nestlings and all but two were recovered dead.

Eight of the recoveries were recovered during winter providing information on locations of resident barn owls during this time of year. Fifteen of the 16 recovered barn owls dispersed at least 10 miles from their natal site (Figure 4) with an average minimal dispersal distance of 73 miles. Recovered owls dispersed in different directions without a trend towards any cardinal direction.

For the 13 owls that were banded and recovered with known periods of death, average lifespan was 15 months. In addition, two barn owls were recovered alive and released again aged 13.5 and 35.5 months of age. To date, the owl with the greatest longevity that was recovered during this study was banded in New Jersey and recovered 5 years 10 months later in Dauphin County, Pennsylvania.

Improve Nesting and Foraging Habitat and Protect Existing Barn Owl Nest Sites to Encourage Expansion of the Barn Owl Population in PA From the beginning of this program, RWDBs have continued to distribute and install barn owl nest boxes in appropriate locations. Nest boxes provide secure nesting structures and are frequently used by barn owls. In 2009, 68% (48 of 70) of confirmed nest sites were located in nest boxes (Figure 6). Landowners with active or potential barn owl nest sites were also given information on barn owls (e.g., status, identification, reproduction, habitat, threats/reasons for decline, management recommendations, nest box placement, etc). When appropriate, RWDBs provided recommendations on grassland management, specifically to landowners with barn owl nests, but also to other landowners through the Private Landowner Assistance Program (PLAP). In addition, in 2009 RWDBs gave 24 presentations on barn owls to an estimated 641 people.

Examine Genetic Diversity of Barn Owls in PA RWDBs collected feathers for the third year from all banded barn owls. Dr. Karl Kleiner and students from York College have begun analyzing feathers to help determine whether sex ratios of clutches at various nest sites vary from year to year in relation to abundance of food resources. Preliminary results, which have a small sample size of 60 nestlings from 5 nest sites, have not found such a trend but further analysis will continue with this research question. Analysis will also be done to learn more about the genetic diversity of barn owls in Pennsylvania.

RECOMMENDATIONS

It is recommended that RWDBs continue to conduct site visits to verify barn owl nest sites or sightings, monitor barn owl nests, conduct public outreach, determine suitability for barn owl box placement, distribute barn owl boxes, install barn owl boxes, collect pellets, band nestlings, and collect feathers to expand our knowledge of and work to conserve this declining species.

79801 6 Recommendations for expanding the project, based on recommendations stated in the barn owl species account in the PGC's WAP, are to evaluate habitat use and prey availability within the species’ core range by 1) using radio telemetry to evaluate foraging habitat use by adult barn owls throughout the breeding season and 2) live-trapping studies of small mammals within the farmland landscape to provide information on prey densities in the barn owl’s key foraging habitats (Wilson, 2005). These studies could then be used to devise models of landscape use by this species, which could then shed light on the local causes of the decline in numbers witnessed in recent decades. Volunteer, professors, and students should continue to be utilized when available.

LITERATURE CITED

Colvin, B. A. 1985. Common barn owl population decline in Ohio and the relationship to agricultural trends. Journal of Field Ornithology 56(3):224-235.

Marti, C. D. 1992. Barn owl (Tyto alba) Account in A. Poole, P. Stettenheim, and F. Gill. editors. The Birds of North America, 1:1-16. Academy of Natural Sciences, Philadelphia, Pennsylvania, and American Ornithologists’ Union, Washington, D. C., USA.

McWilliams, G. M., and D. W. Brauning. 2000. The Birds of Pennsylvania. Cornell University Press, Ithaca, New York, USA.

Pennsylvania Breeding Bird Atlas [BBA]. 2009. BBA home page. . Accessed 8 Oct 2008.

Rosenburg, C., G. Hammerson, M. Koenen, and D.W. Hehlman. 1992. Barn Owl. Species Management Abstract. The Nature Conservancy, Arlington, Virginia, USA.

Sauer, J. R., J. E. Hines, and J. Fallon. 2007. The North American Breeding Bird Survey, Results and Analysis 1966-2006. Version 10.13.2007. USGS Patuxent Wildlife Research Center, Laurel, Maryland, USA.

Taylor, I. 1994. Barn owls: Predator-prey relationships and conservation. Cambridge University Press, Cambridge, United Kingdom.

Wilson, A. 2005. Barn Owl (Tyto alba) species account. In Wildlife Action Plan. Pennsylvania Game Commission and Pennsylvania Fish and Boat Commission, Harrisburg, USA. 79801 7 Table 1. Summary of statewide Barn Owl Conservation Initiative activities conducted by PGC Regional Wildlife Diversity Biologists, January - December, 2009. Region Active Nest Sites New Nest Sites Nests Banded Owls Banded NW 0 0 0 7 a SW 0 0 0 0 NC 8 3 9 b 41 SC 25 5 16 b 61 c NE 13 4 12 b 59 SE 25 6 18 b 75 d Statewide 71 18 56 243 a raised at Erie Zoo and released at SGL218 where 2 nest boxes were placed b 12 clutches were banded at 10 locations, due to multiple clutches at 2 sites c includes 2 adults banded d includes 1 adult banded

Table 2. Number of prey species found in dissected barn owl pellets collected in 2008-2009 from sites in Lycoming and Union Counties, Pennsylvania. Site 1 Site 2 Site 3 Species Total (29 pellets) (33 pellets) (23 pellets) Microtus pennsylvanicus 72 91 43 206 Blarina brevicauda 10 2 35 48 Peromyscus sp. 2 0 0 2 Sorex sp. 0 1 0 1 Zapus hudsonius 0 0 1 1 Condylura cristata 2 0 0 2 Glaucomys volans 0 0 1 1 Avian sp. 1 0 0 1

79801 8

Figure 1. Barn owl nest sites, 2005-2009. Open circles indicate a nest that was last active between 2005 and 2008 (n=52) Solid circles indicate a nest that was active in 2009 (n = 70). Nests newly discovered in 2009 are identified with a red ring around the solid circle (n = 18).

Figure. 2. Number of barn owl nests banded per owl nests (2007; n=29, 2008; n=35, 2009; n=55) 79801 9

Figure 3. Clutch size of banded barn month (2007; n = 29, 2008; n = 35, 2009; n = 55).

Figure 4. Minimal dispersal distance for recovered barn owls banded between 2006 and 2009. 79801 10

Figure 5. Summary of barn owl recoveries with band number, distance between banding and recovery location, direction of dispersal, original banding date and location, and band recovery date and location.

79801 11

Figure 6. Nest sites for active barn owl nests (n=70), 2009.