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

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

Outline

One of three subspecies of spotted owl Live in old-growth forests Color is dark-to-chestnut brown Round or oval white spots Primarily nocturnal hunters Habitat loss  Population Decline! Very territorial & intolerant of habitat disturbance

Introduction to Strix occidentalis caurina

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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

Northern Spotted Owl Habitat

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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

Life History Strategies

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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)

Threats Faced By Northern Spotted Owls

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!

Potential Competition & Displacement

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!

Summary

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
• ccidentalis): 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)

References