Conservation Threats to the Northern Spotted Owl Andrew J. Abraham - PowerPoint PPT Presentation

Conservation Threats to the Northern Spotted Owl Andrew J. Abraham BSCI462 – Population Ecology Spring 2013

Outline Introduction to the Northern Spotted Owl Describe It’s Habitat Describe It’s Life History Strategies Threats Faced By Northern Spotted Owls Focus on Potential Competition & Displacement

Introduction to Strix occidentalis caurina One of three subspecies of spotted owl Live in old-growth forests Color is dark-to-chestnut http://graphics8.nytimes.com/images/2011/07/01/us/JP- brown OWL-1/JP-OWL-1-articleLarge.jpg Round or oval white spots Primarily nocturnal hunters Habitat loss  Population Decline! Very territorial & intolerant of habitat disturbance http://1.bp.blogspot.com/_zNH- Z92VFDA/TDvffxT8IHI/AAAAAAAAEBA/1mmHFOU5zps/s1600/web- Northern-Spotted-Owl.jpg

Northern Spotted Owl Habitat Prefer old-growth forests High & open tree canopies Large trees w/ broken tops, deformed limbs, or large holes Nesting sites Need large area Hunting & Nesting May migrate due to seasonal changes Ex. Heavy Snow  Affects Hunting http://ipsnews.net/pictures/timber.jpg

Life History Strategies Form long-term pair bonds Significant Parental Investment Associated w/ Higher Offspring survival Mating Season: Feb. or Mar. Gestation: 1-2 months Clutch Size: 2-3 eggs Tend to stay put at suitable habitats http://cdn.c.photoshelter.com/img-get/I0000sz7qJTyAThc/s/860/860/20100810- Bannick-Spotted-Owl-2918-PSM-T-PaulBannick.jpg

Threats Faced By Northern Spotted Owls Primary Threat – Loss of old- growth forests Solely prefer these forests ; heavily affected by clear- cut logging Influx of the Barred Owl Outcompeting for suitable habitats  Reduces it’s reproductive success Use of Detection Dogs To Survey Owl Occupancy ( Wasser S. K. et al., 2012 )

Potential Competition & Displacement Barred & Spotted Owls have home ranges w/ similar characteristics Share similar prey species, nesting requirements Both show territorial behavior toward one another Strongly suggests competition ( Dugger KM et al., 2011 ) Partitioning of resources Barred Owls appear more dominant Spotted owls are being displaced!

Summary Northern Spotted Owl populations have decreased drastically Impacted by the loss of old-growth forests Outcompeted by Barred Owls  Increased Displacement Conservation? Efforts to maintain the old-growth forests Possibly lead to both Barred & Spotted Owls coexisting together!

References Dugger KM, Anthony RG, Andrews LS. (2011) Transient dynamics of invasive competition: Barred Owls, Spotted Owls, habitat, and the demons of competition present. Ecological Applications 21(7) Livezey KB (2010) Killing Barred Owls to Help Spotted Owls I: A Global Perspective. NorthWestern Naturalists 92: 107-133 M. Zachariah Perry, R. J. Guitierrez. (2013) Life-History Tradeoffs in Spotted Owls (Strix occidentalis): Implications for Assessment of Territory Quality. The Auk 130(1) Noon BR, McKelvey KS. (1996) Management of the Spotted Owl: A Case History in Conversation Biology. Annu. Rev. Ecol. Syst. 27: 135-162 Rockweit JT, Franklin AB, Bakken GS, Gutiérrez RJ (2012) Potential Influences of Climate and Nest Structure on Spotted Owl Reproductive Success: A Biophysical Approach. PLoS ONE 7(7) Thome DM, Zabel CJ, Diller LV. (1999) Spotted Owl Turnover and Reproduction In Managed Forest of North-Coastal California . J. Field Ornithol 71(1) Wasser SK, Hayward LS, Hartman J, Booth RK, Broms K, et al. (2012) Using Detection Dogs to Conduct Simultaneous Surveys of Northern Spotted ( Strix occidentalis caurina ) and Barred Owls ( Strix varia ). PLoS ONE 7(8)