Linkhart, Brian D. and Richard T. Reynolds. 1997. Territories of flammulated owls (Otus flammeolus): is occupancy a measure of habitat quality? Pages 250-254 in J.R. Duncan, D.H. Johnson, and T.H. Nicholls, editors. Biology and Conservation of Owls of the Northern Hemisphere. U.S.D.A. Forest Service General Technical Report NC-190.
RELEVANT TO: |
FOREST MANAGEMENT |
WILDLIFE |
|
PONDEROSA PINE OLD GROWTH |
DOCUMENT DESCRIPTION
This study examined annual territory occupancy by flammulated owls from 1981 to 1996 in central Colorado. The study area, 452 ha, contained 14 owl territories. Little is known about habitat selection for the owl which is an obligate cavity-nester and commonly breeds in ponderosa pine, Jeffery pine, and mixed-conifer forests of western North America.
The researchers tested the Fretwall and Lucas (1970) model of habitat selection, in which organisms settle first in high quality habitat (habitats that have high reproductive success) until they are filled, then settle into habitats of poorer quality where reproduction may be lower. Their hypothesis was that territories occupied by breeding pairs every year are the highest quality and the poorer quality territories are occupied only occasionally by breeding adults.
MAJOR FINDINGS
- Each territory was occupied by breeding pairs and unpaired males a mean of 8.9 years, ranging from 3 to 16 years. (p.251)
- Each year 3 to 6 territories were occupied by breeding pairs and 3 to 7 territories were occupied by solitary males. (p.251)
- Occupancy of breeding pairs was positively correlated with the amount of old growth ponderosa pine/Douglas fir in habitat circles and negatively correlated with the amount of young Douglas fir/blue spruce in habitat circles. (p. 252)
- Three categories of years that breeding pairs occupied territories were established. 1) 12 or more years 2) 6 and 7 years 3) 4 or fewer years. Territories occupied for 12 or more years had habitat circles containing more than 75 percent old growth (200-400 years) ponderosa pine/Douglas fir, with less than 13 percent of any other type of vegetation. (p.252)
- Solitary males occupying territories that breeding pairs rarely occupied had habitat circles containing 27 to 68 percent of other vegetation types.
- Territories most consistently occupied by breeding pairs contained the highest percentage of old ponderosa pine/Douglas-fir, while territories least occupied by breeding pairs contained the least amount of this vegetation type. (p.253)
- "The data suggest that territory occupancy may be an indicator of habitat quality for Flammulated Owls. Old ponderosa pine/Douglas-fir appears to be the best breeding habitat for the owls." (pp. 252-253)
QUESTIONS RAISED FOR FORESTS
1) Do current forest management polices preserve old growth Ponderosa pine?
2) Do the forests have a management plan to secure Flammulated Owl habitat?
3) Is the Flammulated Owl an candidate for being an MIS for old growth forest?
FOREST MANAGEMENT SIGNIFICANCE
Flammulated Owls require old growth ponderosa pine/Douglas fir to sustain and increase populations. Recommendations include:
- Ending all timber sales of old growth trees
- Managing ponderosa pine forest to ensure stands will reach old growth age
- Maintaining approximately 1.3 snags per hectare for nesting purposes (p. 250)