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Species Natural History Project Diana Molina LA 541 10.21.10 Part 1: Species Natural History Account OWL LIFE CYCLE WESTERN SCREECH OWL 4 1 2 3 A young Western Screech Owl talks with Santa. 3 Family: Strigidae Scientific Name: Megascops kennicotti (formerly Otus kennicotti) Common Name: Western Screech Owl (Little Horned Owl, Dusk Owl, Ghost Owl, Mouse Owl, Cat Owl, Little Cat Owl, Puget Sound Screech Owl, Washington Screech Owl, and Coastal Screech Owl) 1. STAGE 1: NEST No nest material is added and nests are kept clean. 2-5 eggs are laid on natural sawdust on the floor of tree cavities. Eggs are laid every 1 to 2 days and the incubation period lasts 26 days on average. Females incubate brood while males bring food to the nest.1 2. STAGE 2: FLEDGLING 4-5 week stage. During this stage, owls like to climb on tree snags and branches. Fledglings are lighter in coloring but more patterned than adult owls.2 3. STAGE 3: YOUNG ADULT Young adults disperse from natal area on average 58 days post-fledgling, predominantly during the autumn months.1 4. STAGE 4: ADULT – 1-20 YEARS Western Screech owls nest almost exclusively in tree cavities.1 They require cavities from trees with a Dbh of at least 12 inches.5 Nest cavities are at least 20 feet from the ground and up to 50 feet. Nests are almost always in deciduous trees. Pairs will often reuse nest sites in consecutive years and will mate for life. Adults tend to remain near breeding areas and aggressively defend their nests.1,2 2 Diana Molina Principles of Applied Ecology A. Preferred Local Habitats: • • • • breeding season very little overlap occurred within pairs. We did not detect overlap between neighboring pairs.!" ! Riparian Forest/Woodland: Hunting and habitat areas. Wet Prairie: Hunting areas6 Oak-Pine Woodland: Thought to breed where oaks occur. Western Screech owls are dependent on deciduous woodlands or open mixed forests that have suitable nesting sites and sufficient prey densities. Densities are highest in riparian zones.1 Spatial and Landscape Data: • • B. Life History & Description: Home range: 3-9 hectares (8-22 acres). Home ranges of Western Screech-owls were highly associated with riparian forests; most screech owls had ≥10 ha (25 acres) of riparian-forested habitats within their home ranges#!" ! ! Territory size: Moderately widespread. (See Figure 1). Elevation range 500-4000 ft. Figure 2 1 Life Cycle Stages and Life Span: • Age at cessation of parental care: Fledge at 4-5 weeks. Disperse from natal area on average 58 days post-fledging. 1 • Life span: 12 years on average and 20 years maximum.2 • Appearance: Juveniles have a more intricately variegated plumage with many feathers tipped with white. Adults in the southwest are paler grey, while birds in the northwest are darker and browner. A cinnamon coloring is rare and found only in the Pacific Northwest.1 • Habits: Predominantly nocturnal with activity beginning 20-30 minutes after sunset. Very territorial and aggressive when defending a nest site. May attack humans.1 Hunts mainly from a perch in open woodlands, along the edges of open fields, or wetlands, or makes short forays into open fields. They also capture insects while in flight.1 Size: • Female: Avg. length : 23cm (9.2”) Wingspan 56cm (22”)1 • Male: Avg. length: 21cm (8.2”) Wingspan 54cm (21”)1 • Weights of different subspecies vary widely. In general weights decrease for owls found in southern areas. “An average of 186g (6.5 oz) for females and 152g (5.3 oz) for males in a northern population to 123g (4.3oz) and 111g (3.9oz) for females and males in southern populations, respectively.2 Reproduction and Population Data:2 • Age at first breeding: 1 year • Breeding areas: Nests in natural cavities, woodpecker holes (Flicker and Pileated) and in nest boxes. • Offspring per litter (eggs per clutch): 2-4 • Litters per year: 1 Seasonal Activity and Movements: • Breeding period: March to August • Migration: Owls occur all year and are not known to migrate. Altitudinal migration is speculated.! • Distance between natal and breeding area:!Unknown"!!During the breeding season, males and females of a single pair overlapped extensively, whereas outside the • Population and meta-population needs: Because breeding owls will often reuse nest sites in consecutive years and pairs mate for life, preservation of habitat over the long-term (stability) is key to owl survival. Further, adults tend to remain near their breeding areas year-round and defend nest sites vigorously.1 Due to the lack of migration and significant population movement new habitats must be connected to existing habitats through natural corridors and allocated to ensure minimal overlap between breeding pairs. 3 Diana Molina Principles of Applied Ecology 4 • Diet and foraging locations: Varied diet includes voles, deer mice, shrews, harvest mice, kangaroo rats, pocket gophers and bats. Preferred bird prey includes house sparrows and starlings. Preferred amphibian prey: lizards, salamanders, frogs, and small fish. Insect prey includes beetles, cicadas, ants, grasshoppers, worms and centipedes.2 • Range of environmental tolerances: Owls will avoid densely forested areas, such as old growth coniferous forests that are home to Great Horned Owls, which are predators.4 Owl/human relationship: Although this owl is known to aggressively defend its territory, it can survive in wooded suburban areas and city parks as long as it is not directly persecuted or disturbed by humans.1 E. Willamette Valley Habitats and Species Status: Which are the most important Willamette valley habitat types for this species? Cavities for nesting and roosting in trees with a minimum dbh of 12 inches. Strongest Oregon habitat association in Douglas Fir-White Oak Forest and Western Oregon riverine woodland.5 Humid Douglas-fir, western hemlock, western red cedar, and Sitka spruce forests along the edges of clearings, rivers, and lakes are the preferred Willamette valley habitat types for the Western Screech owl. 1 Of secondary importance is open Oak savanna areas where the owl is thought to hunt.2 C. Habitat Elements and Processes: Are there specific habitat elements necessary to this species, and in what ways are they used? Are there key ecological processes that these species rely on for establishment, persistence, or reproduction? Does it require interior or edge conditions? The Western Screech owl is an edge condition species, as it relies on open areas to hunt and mixed-deciduous/coniferous forests for shelter. Western Screech owls thrive in edge habitats that are made up of mixed deciduous forest to nest in, riparian forest to nest and hunt and open Oak savanna (also to hunt). Of paramount importance are tree cavities in dead and dying trees that are required for nesting and tree snags and leaning trees that juvenile owls like to climb. 1,2 What is the species status in the Willamette Valley? Although the Western Screech owl is not endangered, they are difficult to survey because of their secretive nature.!$ These owls rely on natural forest vegetation succession cycles and use gaps in the forest, caused by natural disturbance regimes, as primary hunting areas. Areas of old growth provide suitable habitat and nesting sites, while areas of young growth provide open space to facilitate spotting prey. Is it known to be declining or decreasing? The meta-population is not under threat due to its wide range along the western coast of the U.S. into Canada and Mexico. However populations are decreasing due to increasing urbanization and silviculture practices that reduce the number of available tree cavities and rotting trees used for nesting. What are the key threats this species faces or is likely to face in Eugene and the surrounding environment? A limiting factor in their numbers is the available of suitable nest cavities. Urban development is a threat to habitat, although these owls will breed in suburbs and city parks with established trees.2 D. Key Ecological Functions: What is the species role in the ecosystem, food web, and relationships with other species? The Washington Breeding Bird Survey has recorded a decline in numbers in recent years throughout the species' range, and declines have also been observed in southern British Columbia. There is speculation that predation from the expanding population of Barred Owls, recent arrivals in some areas, is a factor.1 The Western Screech Owl is a heterotrophic consumer and primary predator (or primary carnivore). It consumes terrestrial vertebrates and invertebrates that are often secondary consumers. It also preys on primary consumers such as flying insects and worms. They can fall prey to Northern Goshawks, Cooper’s Hawks and Great Horned, Barred, Spotted, and Long-eared Owls, all of which are larger in size than the Western Screech Owl.1 Other predators include weasels, raccoons, snakes and crows.1 Owls depend on woodpeckers that create tree cavities in which to nest. Specifically, the Flickered and Pileated woodpeckers.2 5 Diana Molina Principles of Applied Ecology 6 GENERAL GUIDELINES AND RECOMMENDATIONS Home range and territory size: 7.5 to 150 acres, with territories as close as 165 feet apart.1 Recommended number of cavities or snags or volumes of large downed wood per unit area: Western Screech Owls Vary in appearance.5 Part 2: Design, Planning and Management Guide Because Western Screech Owls usually reuse nesting sites, it is more crucial to provide large habitat patches that contain mature deciduous forests than to focus on General guidelines and recommendations Diagram 1: Residential House/Yard Scale Diagram 2: Urban Park Scale Diagram 3: Urban Open Space System (Larger scale) providing a specific number of cavities or snags. That said, it is a good idea to provide a variety of cavities at heights between 20-50 feet that are near riparian zones, where owls like to feed. How could your design recommendations be strengthened by specific aesthetic approaches to make them a desirable part of the urban fabric, especially if those recommendations are not part of common landscape practices or aesthetics? What critical knowledge gaps might exist for this species? Western Screech Owls thrive in lands containing a variety of vegetative species but which are generally not densely covered. This makes suburban and residential forest areas suitable habitat provided that water sources and larger habitat patches are nearby. Fortunately, humans also prefer open turf, deciduous trees, and water features in their own habitat, so there is great potential for transforming the urban landscape into a more owl-friendly environment. However, owls require the use of dying and decaying trees and snags, both as nesting ground and a source of food for their prey. Wetland or water areas that contain rotting tree trunks, rocks and a good mix of shrub and canopy layer attract a variety of species on which the owls feed. While it is difficult to convince human residents to let go of their manicured, English garden aesthetic, applying a combination of open 7 Diana Molina Principles of Applied Ecology 8 neatly trimmed lawn (native grasses) and wet, brushy, and naturalistic areas can help to maintain a sense of order while also providing owls with the variety of spaces they DIAGRAM 1: RESIDENTIAL HOUSE AND YARD need to survive. 9 Further, since owl territories are generally much larger than the typical residential lot, designing effective owl habitat requires cooperation at the neighborhood scale. If 8 7 1 neighbors agree to create a more unified habitat collectively, they will be more accepting of more “radical” design solutions if they see their neighbors doing the 6 same. 2 The following diagrams make suggestions for improving the urban fabric for owls at three different scales: residential, urban park, and city. Little is known about the 5 distance between natal area and breeding sites.2 This information would be of great use when designing suitable habitat, as provision of sufficient nesting sites could be 3 anticipated and provided if more was known about population behavior. 30-50 Ft. (Avg. residential lot width) 4 1. Preserving and protecting large tree species on site is essential for providing owl habitat. Trees should be at least 12”dbh to serve as nesting areas. 2. Providing a mix of deciduous (large trees) and evergreen shrubs ensures that there is vegetation year round. This provides suitable prey hiding areas and helps to soften the edge of built structures, which can disrupt vegetation/habitat corridors. 3. Addition of features such as green roofs can provide foraging areas for small prey (rodents, insects etc). and double as an “open savanna-like” feeding area. Owls can hunt here while perched on tall trees. 4. Eliminating or reducing fences allows owl prey to move more freely between residential lots and between residential lots and denser forested habitat. 5. Mixing old established trees with younger trees provides a canopy height variety from which owls can perch undetected while slowly approaching prey. 6. Water features such as ponds and swales provide excellent amphibian and small rodent habitat, especially if they remain wet year round. 9 Diana Molina Principles of Applied Ecology 10 7. Western Screech owls favor riparian trees such as poplars and ashes. Planting trees near water allows the owls to hunt more effectively from a perched position. 8. Downed wood and rotting wood can become an excellent insect habitat and draw small birds into the area. Owls feed on both insects and smaller birds. Keeping a discrete edge between the naturalistic water area and a neat and trim lawn helps to maintain a sense of order while also providing the necessary “messiness” that comes with allowing rotting and decomposing elements to remain in the landscape. 9. Native grasses can take the place of chemically treated lawn. These grasses must be allowed to yellow and dry in the winter, when food is scarcer for owls. The remaining wetness of the water feature thus becomes a magnet for owl prey since it will act as a magnet for remaining prey. DIAGRAM 2: URBAN PARK 11 1 10 2 9 3 2. Whenever possible, large trees or large patches of mature forest should be preserved or established. 3. Water features should occur near forested areas. Although creeks or streams are preferable, ponds can also provide suitable frog and insect habitat. Edges of water features should be more naturalistic in appearance. Retaining walls and cement edges are prohibitive for migrating and terrestrially bound owl prey. Ponds or streams should have a shallow pool edge, as small birds enjoy bathing and feeding in these areas. By maintaining an open edge, owls are given more visibility to hunt prey from a perched position. 4. Human activity areas should be buffered by low vegetation on at least one side. This allows a degree of separation between owl nesting habitat and humans. Owls are aggressive defenders of their nests and prefer humans at a distance. 5. Paths should make up a small percentage of park space and not bisect open areas whenever possible. 6. A mix of treed and open areas is ideal for both owls and humans. 7. Younger trees or taller shrub layers can provide a variety of heights from which owls can perch. This is also more aesthetically pleasing to humans. 8. Adjacent building setbacks should be increased for new construction to allow space for planting deciduous street trees. Enough space for trees to mature is preferable to connect owl habitat corridors. 9. Some use of evergreen trees is also necessary to provide hiding areas for owls year round. 10. Roofs of large structures could be planted to connect green corridors in the urban environment. 11. Car traffic should be slowed down as much as possible. Eliminating fast, wide streets and pass-through traffic will help create a calmer environment more suitable for Western Screech owls, especially because they roost during the active urban daytime hours. 4 5 200 Ft. 6 7 8 1. Planting street trees along edges of parks and in between built structures helps to maintain a more connected habitat corridor for owls and for their prey. 11 Diana Molina Principles of Applied Ecology 12 DIAGRAM 3: URBAN OPEN SPACE SYSTEM 1 4. Because owls need at least 7 acres per breeding pair, urban residential grid areas can be planted with deciduous trees and owl habitats fashioned at the neighborhood scale. #" Existing large, forest habitat near urban areas should be preserved, especially around the edges between denser forest and open space. This makes ideal Western Screech owl habitat.! $" Large areas of impervious cover and lack of trees are least suitable owl feeding and nesting habitat and should be mitigated by the use of street trees, green streets, and water features.! %"Denotes highway.! &" Low-density development is suitable for owls, particularly when it occurs near undeveloped forest. These neighborhoods tend to have more canopy cover, and house a variety of rodent and insect species upon which owls feed.! '" Every effort to connect existing open space should be made to improve habitat for a variety of species, not just owls.! 10 2 3 9 4 8 5 7 6 1 mile 1. Unimproved pasture areas might provide alternative feeding and breeding areas for owls, especially in shelterbelts, hedgerows with trees and adjacent remnant woodlots. 2. Riparian areas should be restored where not vegetated. Owls prefer poplars, ashes, alders, and even willows, especially near water. Dense urban development, channelized streams or rivers, and too much impervious cover can significantly reduce owl habitat. 3. Industrial areas can be planted, and impervious cover reduced to provide habitat corridor. While owls are not likely to breed or nest in these areas, large industrial zones can help owl prey connect from denser forest to riparian zones that are often areas of industry. 13 Diana Molina Principles of Applied Ecology 14 Resources/Works Cited: 1. Owl Pages. < http://www.owlpages.com/owls.php?genus=Megascops&species=kennicottii> 2. Wildlife Habitats CD. Northwest Habitat Institute. Query: Western Screech Owl. 4. Seattle Audobon. <http://www.seattleaudubon.org/birdweb/bird_details.aspx?id=242> 5. US Forest Service : Deschutes & Ochoco National Forests Crooked River National Grassland <http://www.fs.fed.us/r6/centraloregon/wildlife/species/birds/birdsofprey-owls.shtml> 6. Davis, Helen and Weir, Richard D. “Home Ranges and Spatial Organization of Western Screech-Owls in Southern British Columbia” Northwestern Naturalist 91(2):157-164. 2010. Published November 10, 2009. Photo Credits in order of appearance: 1. Little Pearls, “Wild and Free: A Screech Owl Named Pinkey”. <www.littlepearls.org > 2. US Forest Service : Deschutes & Ochoco National Forests Crooked River National Grassland <http://www.fs.fed.us/r6/centraloregon/wildlife/species/birds/birdsofpreyowls.shtml> 3. Widescreen Wallpapers. <www.widescreenwallpapers.com> 15 Diana Molina Principles of Applied Ecology