Appendix C. Habitat capability index for Olive-sided Flycatcher (Contopus cooperi).
Developers: David Vesley, Michael T. McGrath, and Brenda C. McComb
Reviewers: Jennifer Weikel, Bob Altman, Gary Roloff, Doug Runde, Marie Morin, and Dominick DellaSala
In the Douglas-fir (Pseudotsuga menziesii) region, Olive-sided Flycatchers nest in or on the edges of stands >40 yr old (Meslow and Wight 1975). Altman and Sallabanks (2000) reported that the species nests in habitat along forest edges and openings, including burns; natural edges of bogs, marshes, and open water; semi-open forest; and harvested forest with some retained structure.
Olive-sided Flycatchers forage on flying arthropods by sallying from perches in trees (Csuti et al. 1997). Abundance of the species is positively correlated with the amount of old-growth-clearcut edge in a landscape (Rosenberg and Raphael 1986) and landscape fragmentation (McGarigal and McComb 1995) .
Overall habitat capability index
The habitat capability model developed for the Coast Range includes sub-indices for nesting and foraging habitats. The lower score of the two sub-indices determines habitat capability in a potential home range. That is, we hypothesize that overall habitat capability can be no greater than the most limiting habitat component. We assume that nesting habitat capability; for Olive-sided Flycatchers improves with increasing densities of trees and snags >10 cm dbh, and decreasing canopy closure, based on the findings of research on the species in the Oregon Cascades and Coast Range (Altman 2000). Because Altman (2000) indicates Olive-sided Flycatcher reproductive success is inversely related with increasing canopy closure, it is assumed that the response function for live tree density (dbh >10 cm) is quadratic. The index is calculated using the following equation:
where HCI = habitat capability index, NCI = nesting capability sub-index, LCI = landscape capability sub-index, and f = focal patch.
Nesting capability index
All metrics for this index are calculated for a focal pixel at the center of a 3×3 “moving window.” This moving window of pixels averages conditions for the 0.5625 ha surrounding the “focal” pixel (i.e., 3×3 pixels). The averaging is done to: (1) smooth inter-pixel variation and (2) provide a “patch” or “stand” level summary, which is consistent with the scale of the stand modeling and stand inventory data. The nest index is calculated with the equation:
where NCI = nesting capability sub-index, f = focal pixel, S1 = canopy closure index, S2 = live tree index for trees >10 cm dbh, and S3 = snag index for snags >10 cm dbh.
Canopy closure index
The canopy closure index is based on canopy closures observed at successful Olive-sided Flycatcher nests (i.e., fledged ≥1 young) in western Oregon (Altman, unpublished data). Essentially, maximum suitability is designated at the upper 95% confidence limit, as observed in Altman’s unpublished data, and is hypothesized to decrease in intervals of 2 standard errors. The canopy cover index covers a broader range of values to compensate for irregularities in the CLAMS simulation model (Fig. C1, specifically 2050% canopy cover is underrepresented in the 2003 CLAMS tree growth tables.
|If CCi < 5 Then S1i = 0.2 * CCi||
|If CCi ≥ 5 and CCi < 35 Then S1i = 1|
|If CCi ≥ 35 and CCi < 65 Then|
|S1i = (-0.03333 * CCi) + 2.16667|
|Else S1i = 0|
where S1 = canopy closure index, i = pixel, and CC = percent canopy closure.
|FIG. C1. Relationship between index and percent canopy closure.|
Live tree index
The live tree index (Fig. C2) is based on densities of trees >10 m in height, observed at successful Olive-sided Flycatcher nests (i.e., fledged ≥1 young) in western Oregon (Altman 2000). Essentially, maximum suitability is designated at the upper 95% confidence limit, as observed in Altman’s unpublished data, and is hypothesized to decrease in intervals of 2 standard errors. The shown equation is an alternate hypothesis that occurs over broader ranges.
where S2 = live tree index for trees dbh >10 cm, i = pixel, and DEN = density (trees/ha) of live trees, dbh >10 cm.
|FIG. C2. Relationship between index and density of live trees.|
Snag density index
The snag density index (Fig. C3) is based on densities of snags >10 m in height (changed to 5 m for CLAMS purposes), observed at successful Olive-sided Flycatcher nests (i.e., fledged ≥1 young) in western Oregon (Altman 2000). Essentially, maximum suitability is designated at the upper 95% confidence limit, as observed in Altman’s unpublished data, and is hypothesized to decrease in intervals of 2 standard errors. The index is calculated with the following equation:
where S3 = snag density index for snags dbh >10 cm, i = pixel, and DEN = density (trees/ha) of snags, dbh >10 cm.
|FIG. C3. Relationship between index and density of snags.|
Landscape capability sub-index
We assume that optimum foraging areas occur at the interface between forest openings and closed canopy, old-growth; edges with lower height contrast have lower foraging suitability for Olive-sided Flycatchers. The foraging suitability sub-index in the HSI model is based upon the relative density of high-contrast edges in a potential home range (i.e., 360-m radius circular landscape). Altman and Sallabanks (2000) estimated defended territories for this species of between 40 and 45 ha (approximately 360-m radius). Edge contrast is measured by the difference in average height of dominant trees between two patches. Maximum foraging suitability is attained at edge segments having a height contrast ≥50 m (165 ft). This value represents the difference between a patch without trees and a 200-yr-old Douglas-fir stand on an average quality site (McArdle et al. 1949; see Fig. C2). The index is calculated using the following equation:
If absolute value (patch1_tophgt – patch2_tophgt) ³50 m then EC = 1.0;
Else EC = [absolute value (patch1_tophgt – patch2_tophgt)]*0.02
where LCI = landscape capability sub-index, f = focal pixel, n = number of edges in a 360-m radius analytical window, L = edge segment length (m), i = segment, TE = total edge length in window, and EC = edge contrast.
Altman, B. 2000. Olive-sided flycatcher nest success and habitat relationships in post-fire and harvested forests of western Oregon, 19971999. Annual report. Avifauna Northwest, Boring, Oregon, USA.
Altman, B., and R. Sallabanks. 2000. Olive-sided flycatcher. In A. Poole and F. Gill, editors. The birds of North America, no. 502. The Birds of North America, Inc., Philadelphia, Pennsylvania, USA.
Csuti, B., A. J. Kimerling, T. A. O'Neil, M. M. Shaughnessy, E. P. Gaines, and M. Huso. 1997. Atlas of Oregon wildlife: distribution, habitat, and natural history. Oregon State University Press, Corvallis, Oregon, USA.
McArdle, R. E., W. H. Meyer, and D. Bruce. 1949. The yield of Douglas-fir in the Pacific Northwest. USDA Technical Bulletin no. 201, Washington D. C.
McGarigal, K., and W. C. McComb. 1995. Relationships between landscape structure and breeding birds in the Oregon Coast Range. Ecological Monographs 65:235260.
Meslow, E. C., and H. M. Wight. 1975. Avifauna and succession in Douglas-fir forests of the Pacific Northwest. Pages 266271 in D. R. Smith. Proceedings of the symposium on management of forest and range habitats for non-game birds. USDA Forest Service General Technical Report WO-1.
Rosenberg, K., and M. G. Raphael. 1986. Effects of forest fragmentation on vertebrates in Douglas-fir forests. In J. Verner, M. L. Morrison, and C. J. Ralph, editors. Wildlife 2000: modeling habitat relationships of terrestrial vertebrates. University of Wisconsin Press, Madison, Wisconsin, USA.