Appendix B. Habitat capability index for Pileated (Dryocopus pileatus)

Developers: Brenda McComb, David Vesely, Michael McGrath

Reviewers: Joan Hagar, S. Kim Nelson

Background

Pileated occur in every physiographic province of western Oregon (Csuti et al. 1997). The species is generally absent from landscapes dominated by non-forested plant communities and agricultural lands.

Pileated woodpeckers lay three to five eggs in nests they excavate in dead or dying trees. (Harris 1980) found that cavity selection is based upon the structural quality of the wood and that they will occasionally excavate cavities in live trees with soft heartwood. Mellen et al. (1992) reported that nests occur in trees or snags having a mean diameter of 71 cm dbh and a minimum diameter of 40 cm. Nelson (1989) reported similar nest tree diameters: the mean diameter was 67 cm dbh and minimum was 47 cm dbh. In Oregon, pileated woodpeckers usually nest in forest stands >80 years in age (Mellen 1992, Nelson 1989).

The diet of pileated woodpeckers consists primarily of wood-boring , particularly carpenter ants (Genus Camponotus) which they extract from snags and stumps (Bull 1975, McClellard 1979). In western Oregon, snags and logs are the most frequently used foraging substrates (Mannan 1984). Bull (1975) reported that the abundance of coarse woody debris (CWD) was significantly greater in stands used by pileated woodpeckers than was generally available. Pileated woodpeckers do forage in young stands (age <40 years) but shrub cover in clearcuts may limit accessibility to stumps and logs (Bull 1975).

Habitat capability index model

The pileated woodpecker habitat capability index model assessment includes two sub-indices for nesting and foraging habitat. The lower score of the two sub-indices determines the overall HCI score in a potential home range. We assume that high quality foraging habitat cannot compensate for lesser quality nesting habitat, and vice versa. The model assumes that nesting habitat quality is most limited by the availability of snags >50 cm dbh to construct a nest cavity. The relationship between snag density (snags per ha) and nesting habitat quality is assumed to be linear up to a threshold of 3.5 snags/ha for snags having a dbh from 50 - 75 cm (Figure B1) and 1.9 snags/ha for snags >75cm (Figure B2) based on upper 95% confidence limits of median snag densities in the region. Large snags (dbh > 75 cm) receive greater weight in scoring than snags 50 < dbh ≤ 75 cm because we assume woodpeckers can construct cavities having greater volume in larger snags.

The quality of pileated woodpecker foraging habitat is assumed to be limited by the proportion of the home range that is has > 25 trees per ha > 25 cm dbh, and that the quadratic mean diameter of trees in the home range is of sufficient size for foraging (> 15 cm dbh). The foraging

Brenda C. McComb, Thomas A. Spies, and Keith A. Olsen. 2007. Ecology and Society 1 habitat sub-index is an additive function with truncation that assumes components of the sub- index do not modify one another and are compensatory unless the sum is above the optimal threshold (Van Horne and Wiens 1991). Foraging habitat was assessed at the scale of the home range, approximately 480 ha (1236 m radius) (Bull and Jackson 1995).

Habitat capability index

pileated HCIf = minimum (NCIf , LCIf) (B.1)

Where HCI = Habitat capability index NCI = Nesting capability index LCI = Landscape capability index f = focal pixel

Nesting capability index

All metrics for this index are calculated for a focal pixel at the center of a 3 x 3 “moving window.” This moving window of pixels averages conditions for the 0.5625 ha surrounding the “focal” pixel (i.e., 3 x 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.

NCIf = (0.4 * S1f )+(0.6 * S2f ) (B.2)

Where

NCI = Nesting capability index S1 = medium snag score S2 = large snag score f = focal pixel

IF S5075Tf ≥ 3.5 THEN S1f = 1.0, ELSE S1f = S5075Tf * 0.2857 (B.3)

Where S5075T = number of snags (50 < dbh ≤ 75 cm) / ha S1 =medium snag score f = focal pixel

Brenda C. McComb, Thomas A. Spies, and Keith A. Olsen. 2007. Ecology and Society 2 Medium Snag Index

1 0.9 0.8 0.7 0.6 0.5 MSI 0.4 0.3 0.2 0.1 0 00.511.522.533.54 Snags 50-75 cm dbh per ha

Figure B1. Relationship between medium snag index and snags 50-75 cm dbh per ha.

IF S75Tf ≥ 1.9 THEN S2f = 1.0, ELSE S2f = S75Tf * 0.5263 (B.4)

Where S75T = number of snags (dbh >75-cm and height >5-m) / ha S2 = large snag score f = focal pixel

Large Snag Index

1 0.9 0.8 0.7 0.6 0.5 LSI 0.4 0.3 0.2 0.1 0 0 0.5 1 1.5 2 2.5 3 Snags > 75 cm dbh per ha

Figure B2. Relationship between large snag index and snags >75 cm dbh per ha.

Landscape capability index

LCI f = NR f * Ff * MinDenf (B.5)

Where: LCIf = The Landscape capability index

Brenda C. McComb, Thomas A. Spies, and Keith A. Olsen. 2007. Ecology and Society 3 NRf = Nesting and roosting habitat index Ff = Foraging habitat index MinDenf = The minimum tree density index f = focal pixel

1.4165 NR = truncated to 1.0 (B.6) f ⎛ P − 0.6052 ⎞ () −⎜ n ⎟ 1+ e ⎝ 0.1664 ⎠

Where: NRf = Nesting and roosting habitat index e = Euler’s constant Pn = the proportion of nesting and roosting habitat located within 1236 m of the focal pixel. Nesting and roosting habitat is defined as forested pixels with QMD of dominant conifers > 22.5 cm. f = focal pixel

1 0.9 0.8 0.7 0.6 oosting index oosting 0.5 0.4 0.3 0.2 0.1

Nesting and r 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Proportion of Home Range in Nesting and Roosting Habitat

Fig B3. Relationship between nesting and roosting index and the proportion of forested pixels with QMD of dominant conifers > 22.5 cm within a 1236-m radius analytical window.

⎛ ⎞ ⎡ Pf − 0.7763 ⎤ ⎜ −0.5⎢ ⎥ ⎟ ⎜ ⎢ 0.1344 ⎥ ⎟ ⎝ ⎣ ⎦ ⎠ (L2) Ff = 1.0866*e ()truncated to 1.0 (B.7)

Where: Ff = Foraging habitat index

Brenda C. McComb, Thomas A. Spies, and Keith A. Olsen. 2007. Ecology and Society 4 e = Euler’s constant Pf = the proportion of foraging habitat located within 1236 m of the focal pixel. Foraging habitat is defined as forested pixels with QMD of dominant conifers > 15 cm. f = focal pixel

1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2

Foraging habitat index 0.1 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Proportion of Home Range in Foraging Habitat

Fig B4. Relationship between foraging habitat index and the proportion of forested pixels with QMD of dominant conifers > 15.0 cm within a 1236-m radius analytical window.

MinDenf : If tph25f < 25, MinDenf = 0.1, else MinDenf = 1.0 (B.8)

Where: MinDenf = The minimum tree density index tph25f = All trees > 25cm dbh per hectare f = focal pixel

Literature Cited

Bull, E.L. 1975. Habitat utilization of the pileated woodpecker, Blue Mountains, Oregon. Thesis, Oregon State University, Corvallis. 57 p.

Bull, E. L., and J. E. Jackson. 1995. Pileated Woodpecker (Dryocopus pileatus). In The of , No. 148 (A. Poole and F. Gill, eds.). The Academy of Natural Sciences, Philadelphia, PA, and The American Ornithologists' Union, Washington, D. C.

Harris, R.D. 1980. Decay characteristics of pileated woodpecker nest trees. USDA Forest Service General Technical Report RM-99.

Brenda C. McComb, Thomas A. Spies, and Keith A. Olsen. 2007. Ecology and Society 5 Mannan, R.W. 1984. Summer area requirements of pileated woodpeckers in western Oregon. Wildlife Society Bulletin:265-268.

McClelland, B.R. 1979. The pileated woodpecker in forests of the northern Rocky Mountains. in J.G. Dickson, R.N. Conner, R.R. Fleet, J.C. Kroll and J.A. Jackson, Editors. The role of insectivorous birds in forest ecosystems. Academic Press, New York. 381 p.

Mellen, T.K., E.C. Meslow and R.W. Mannan. 1992. Summertime home range and habitat use of pileated woodpeckers in western Oregon. Journal of Wildlife Management 56:96-103.

Nelson, S.K. 1989. Habitat use and densities of cavity nesting birds in the Oregon Coast Ranges. Thesis, Oregon State University, Corvallis. 157 p.

Spies, T.A. and J.F. Franklin. 1991. The structure of natural young, mature, and old growth Douglas-fir forests in Oregon and Washington. USDA Forest Service General Technical Report PNW-285. pp. 533.

Van Horne, B. and J.A. Wiens. 1991. Forest Habitat Suitability Models and the development of general habitat models. U.S. Fish and Wildlife Service Fish and Wildlife Research 8. pp. 31.

Brenda C. McComb, Thomas A. Spies, and Keith A. Olsen. 2007. Ecology and Society 6