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Long-Eared Owl Nesting Phenology and Habitat in Central Alberta

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Long-Eared Owl Nesting Phenology and Habitat in Central Alberta LONG-EARED OWL NESTING PHENOLOGY AND HABITAT IN CENTRAL ALBERTA LISA TAKATS PRIESTLEY1 , CHUCK PRIESTLEY2 1 Beaverhill Bird Observatory 2 STRIX Ecological Consulting The Long-eared Owl (Asio initiated by Alberta Environment otus) is a secretive nocturnal and Sustainable Resource owl found in open and sparsely Development (Alberta ESRD) to forested habitats across North encourage raptor banders and America and Eurasia between 30° researchers to collect additional and 65°N latitude.12 In Alberta, information on nest locations and it is found in the Boreal Forest, breeding habitat use of birds of Foothills, Grassland, Parkland, prey. This program developed and Rocky Mountain Natural into the Prairie Nest Record Regions, where they prefer Scheme and Alberta Raptor Nest fragmented habitats containing Card Programs. The Alberta dense woodlands or shelterbelts Raptor Nest Card data are stored for nesting and roosting and with Beaverhill Bird Observatory open areas for hunting.7 It is and data are submitted to Alberta a year round-resident, but it's ESRD and the national NestWatch overwintering ecology is relatively Program run by Bird Studies unknown.2,7 The Long-eared Owl is considered `Secure` in Alberta,1 although information on populations, trends, specific habitat use and even distribution are poorly understood.9,12 Banding data from Saskatchewan suggest there is inconclusive evidence for population declines, and that populations are cyclical.10 The first step in managing wildlife populations is having knowledge of distribution and abundance.14 Owls are elusive, which makes them difficult to study and monitor.8 In 1988, a volunteer raptor nest card program was 124 Blue Jay Canada. The Beaverhill Bird flight feathers developing into their Observatory has been analyzing second week with vanes erupting the phenology of a variety of as they are ready to leave the raptor species from data collected nest in the third week. All data in the nest card program.16,17,18,19 was entered into Microsoft Excel This paper addresses the timing for analysis. of nesting and breeding habitat of Long-eared Owls nesting in The estimated date of Long- central Alberta, based on nest eared Owl hatching was calculated banding data collected between by subtracting the age (in days) of 1987 and 2011. the oldest-aged young from the date of banding. Laying date Methods was estimated by subtracting The study area was located in the number of days required for o central Alberta (latitudes 52.5 to incubation from the estimated o o o 54.6 , longitudes 110.5 to 114.2 ), hatch date. Fledging date was surrounding the city of Edmonton. estimated by adding the number Nests were located in the Aspen of days required for fledging to Parkland and Boreal Natural the estimated hatch date. The Regions. Nests were found by time required for incubation and one or more of: 1) visiting known fledging was determined as the nesting sites of other species largest number of days reported that build the stick nests; 2) in published literature. The looking for birds on territory in the estimated number of days needed spring; or 3) through contact with for incubation and fledging used landowners who found pairs or for this paper were 28 and 21 days nests on their land. For each nest, respectively.6,12,23 banders collected information on nest type (natural or man- Results and Discussion made), nest height, tree height, There were 59 nest records nest habitat, surrounding land submitted for Long-eared Owls. use, and banding data including The average laying date was an estimate of the age (in days) May 7 (range Apr. 11 to June 11) of the young at the banding (Figure 1), the average hatching time.3,20 The age at banding date was June 4 (range May 9 to was determined by experienced July 9), and the average fledging banders using descriptions of date was June 25 (range May 30 growth and development.20,23 to July 30) (Figure 2). In Idaho, Developmental changes include, first clutches were usually laid eyes open at five days, second between mid-March and mid- natal down at two weeks, and May.11 71 (3) September 2013 125 126 Alberta 1987to2010. central Figure 1.Estimatedegg layingdatesoftheLong-earedOwlin 6 4 2 Number of Nests 0 10- 15- 20- 25- 30- 05- 10- 15- 20- 25- 30- 04- 09- 14- Apr Apr Apr Apr Apr May May May May May May Jun Jun Jun Date Blue Jay Of the 59 nests, 6 failed (no There were habitat data young fledged) and 53 were available for 57 Long-eared Owl considered successful (one or nests. Fifty-four nests were more young were ready to fledge stick nests and three were man- at banding time). Egg counts made platforms. Twenty-six were present for 25 nests, and stick nests were described in averaged 4.9 eggs per nest (range further detail as being originally 3 to 7, SD=0.93). Murray (1976) built by American Crow (Corvus found the average clutch size for brachyrhynchos) (6), Black-billed Long-eared Owls in North America Magpie (Pica pica) (16), Cooper`s was 4.5 eggs per nest (range Hawk (Accipiter cooperii) (2), 2-10), and number increased Sharp-shinned Hawk (Accipiter as you went north and west. striatus) (1), and squirrel (1). Of the successful nests (n=52) Most (44%) nests were found in the average brood size was willow, and the average height of 3.7 young per nest (range 1-6). nests was 14.8 feet (range 7 to Average number of young fledged 36 feet, SD=7.04). Nests were per successful nest reported found most often in Grassland/ ranged from 3 to 4.5 in the United Shrubland (Table 2), and were States.5,12 usually in isolated groups of trees or shrubs surrounded by Table 1. Long-eared Owl nest-tree types in central Alberta. Nest Tree -type Number of Nests (%) Black Spruce (Live) 11 (19) Maple (Live) 1 (2) Trembling Aspen (Live) 6 (11) White Spruce (Live) 14 (25) willow (Dead) 2 (4) willow (Live) 23 (40) Table 2. Habitat-types surrounding Long-eared Owl nests in central Alberta. Habitat-type Number of Nests (%) Coniferous Forest 6 (11) Forest (type not specified) 2 (4) Grassland/Shrubland 28 (49) Mixedwood Forest 14 (25) Parkland 5 (9) Urban Treed/Shrub 2 (4) 71 (3) September 2013 127 crops. Other habitats described vegetation.11,23 They are capable nearby included horse pasture, of short flights at 35 days and overgrown fields, unoccupied and are fed by parents for up to 11 occupied farmsteads. Many nests weeks.22 Therefore, occupied were found in the same woodlots Long-eared Owl nests and the for multiple years, and on the rare adjacent habitat should not be occasion the same nest was used cleared from mid-April through in multiple years. mid-August in central Alberta. Throughout their North American Acknowledgements breeding range, Long-eared Owls Funding from Alberta Ecotrust, have been found nesting in dense Alberta Conservation Association, or brushy vegetation amidst open Alberta Sustainable Resource habitats.12 They used hedgerows Development, Alberta Sport, along farm fields in Montana (D. Recreation, Parks and Wildlife Holt pers. comm. 2010). Typically Foundation, Community Spirit stick nests were used and of Program, AGLC, Nature Canada 130 nests found in southwestern Charles Labatiuk Fund and Idaho, 91 were built by Black-billed Beaverhill Bird Observatory is Magpie, 38 by American Crow, greatly appreciated. The new and one in a cliff cavity.13 Long- raptor nest card template was eared Owls also commonly use produced in cooperation with nests built by Common Ravens Alberta Sustainable Resource (Corvus corax), Cooper’s Hawks, Development, Canadian and various Buteo spp.3,4,21 Wildlife Service, Federation of Alberta Naturalists, and Population declines of Long-eared Bird Studies Canada and is Owls have been caused by habitat available on Beaverhill Bird alteration, forest succession, Observatory’s website at http:// urbanization, competition with www.beaverhillbirds.com/ Great Horned Owls (Bubo bboraptorsnests.htm. We thank virginianus), loss of habitat for prey Ray Cromie, Al DeGroot, Hardy species, rodenticides, shooting, Pletz, Violet Pletz, and Beaverhill and habitat loss.9,12 If habitat Bird Observatory for their data alteration is to occur, occupied contributions. The continuing nest sites need to be protected. cooperation of landowners is Although young Long-eared Owls of great value to this program. leave the nest at about 21 days, We thank the editors and an they are still flightless (branching anonymous reviewer for their stage), and reside in surrounding comments on an earlier draft of this paper. 128 Blue Jay References General Technical Report NC- 1. Alberta Sustainable 190, St. Paul, MN. Resource Development (2010) The general status 3. Bent AC (1938) Life histories of of Alberta wild species 2010. North American birds of prey, pt. Alberta Sustainable Resource 2. U.S. Natl. Mus. Bull. No. 170. Development, Edmonton, AB. On-line at: http://www.srd.alberta. 4. Bloom PH (1994) The biology ca/FishWildlife/SpeciesAtRisk/ and current status of the Long- eralStatusOfAlbertaWildSpecies/ eared Owl in coastal southern tatusOfAlbertaWildSpecies2010/ California. Bull. S. Ca. Acad. Sci. SearchForWildSpeciesStatus. 93:1-12. aspx 5. Bull EL, Wright AL, Henjum MG 2. Beck BH, Beck JA Jr (1997) (1989) Nesting and diet of Long- Winter owl surveying in central eared Owls in conifer forests, Alberta. Page 518 in J. R. Duncan, Oregon. Condor 91:908-912. D. H. Johnson, and T. H. Nicholls (eds.) , Biology and conservation of owls of the Northern Hemisphere: 6. Cramp S (1985) The birds of the 2nd International Symposium, western Palearctic. Vol. 4. Oxford February 5-9 1997, Winnipeg, Univ. Press, Oxford.
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