We are investigating the potential effects of the proposed exchange of lands in coastal redwood (Sequoia sempervirens) forests in Humboldt County, California on the Marbled Murrelet (Brachyramphus marmoratus). The region involved includes portions of the drainages of the Eel, Van Duzen, and Elk Rivers, which we refer to as the 'Southern Humboldt Bioregion.' The present report is an update of an evaluation of the effect of such a transfer on the murrelet's habitat and populations.
As we have reported before, two complementary approaches are being carried out in tandem to assess the overall strategy of the exchange. Our analyses focus on the conservation and management of habitat, and will estimate the likely murrelet population size under different harvest and preservation scenarios. The second analysis, the Population Viability Analysis (Akçakaya et al., in prep) is investigating the likelihood that the population will remain viable under these different conditions.
This report outlines an ongoing process that will entail much further analyses in a multi-tiered analysis. These results are a broad indication of the consequences of the proposed exchange. The many simplifying assumptions in this initial study preclude definitive conclusions. We have been able to include many, but not all, data, on both the birds and their habitats. To date, the sources of this information have been the Pacific Lumber Company and data compiled by the Redwood Sciences Laboratory. As the analyses proceed during 1997, we will refine and delimit the various assumptions, and include data from additional sources. We will also incorporate feedback from reviewers during these subsequent steps. Most importantly, we will be incorporating a wider range of management scenarios in the process. As various aspects of the analyses are completed over the next few weeks and months, they will be made available through the web page (Sustainable Ecosystem Institute, www.sei.org) of the effort.
Determination of population trends of the murrelet is an important component of any assessment of the species; it can give a direct indication of the health of the population. To this end, we have compiled and analyzed data on the murrelet population in 11 sections of the coast over the last 3 to 7 years.
METHODS
We have conducted marine surveys with collaborators since 1989 along various areas of the California coast (Table 1). For most of the sections, we have data available for most of the years from 1989 through 1995. The methods we have used are detailed in Ralph and Miller (1995); they involve surveying all birds seen from boats traveling along line transects 800 and 1400 m from shore. For analyses, we examined the coastal sections from Point Saint George (near Crescent City) to Shelter Cove (at the south end of the Bioregion). For each section, we calculated the mean number of birds surveyed per 2-km segment for each year. We have not yet calculated estimates of the total population in each section.
As a preliminary analysis of the data for significant trends, we calculated linear regression statistics on the relationship between the year and the mean number of birds per segment.
RESULTS
Using the two distances from shore for each of the 11 coastal sections yields a total of 22 separate analyses (Table 2). In two of these, a significant (p < 0.05) trend is indicated. One section, Big Lagoon to Trinidad at the 800 m distance from shore (p = 0.006), showed an increase (r = 0.94). In this same section at 1400 m from shore, the trend was also positive (r = 0.12), but not significant (p = 0.88). One trend, Humboldt Bay to Table Bluff, was significantly downward at both 1400 m (r = -0.86, p = 0.01) and 800 m (r = -0.71), though only marginally significant (p = 0.07) at 800 m.
DISCUSSION
We can conclude that there was no pervasive pattern of decline or increase in the area, based on the 22 analyses of the data now available. One would expect to find one or two of the 22 analyses to be significant by chance alone; we found two. The one significant decline took place offshore of one part of the Bioregion and may reflect an actual decline in this area. Other sections, however, had non-significant increases, including one within the Bioregion.
We will include data from the 1996 season in analyses in the near future, to estimate the total population and assess any trends. Preliminary study on the effect of adding these data does not indicate any amplification of the significant trends.
It is important to note that these data now represent mean birds surveyed per 2 km, rather than a total population estimate for each coastal section. Hence, the strength of the calculated correlation coefficient is overestimated and the associated p value is exaggerated. Full analyses will include estimates of the total population.
METHODS
To determine the relative numbers of birds using different land ownerships and forest stands within the Bioregion, we are first examining Marbled Murrelet habitat relationships within the region. Various data sources have been used to identify types and locations of potential murrelet nesting habitat.
Humboldt Redwoods State Park (HRSP)
Habitat data for HRSP were based on two sources. The first, compiled for
Pacific Lumber Company by Hammon, Jensen, Wallen, and Associates, Inc. (1996),
used interpretation of aerial photographs. From the interpretation of these
photographs, a geographic information system (GIS) (Arc/Info 1996) polygon
coverage was created that includes habitat patches classified by type of
stand structure and the density of trees, i.e., the percent cover of the
old-growth tree crowns. For the present report, we used only data for stands
considered potential Marbled Murrelet nesting habitat. This includes forest
structure types: "O", unharvested habitat characterized by tall
trees having large wide crowns, with or without a component of younger trees;
"R", partially harvested areas containing primarily old-growth
residual trees, with or without a mixture of young-growth trees. Two classes
of cover densities were designated: "1", crown cover of the dominant
trees of 50-100 percent; or "2", dominant crown cover less than
50 percent.
The second data source for HRSP, obtained in 1992 from Gary Emery at Humboldt State University, was a coverage of vegetation types defined by dominant plant species. For the current analysis, we selected only those areas of the map designated as old-growth forests. Emery obtained the old-growth information from a classification of old-growth forest habitat occurring within the Bull Creek watershed and compiled by Stephen Matthews (1986). Old-growth was defined using low-altitude aerial photographs, USDA soil-vegetation maps, local study results and other relevant literature. In addition, vegetation measurements from 120 relevé samples (Matthews 1986) were used to define five distinct vegetation classifications. Old-growth classifications were: (1) Sequoia sempervirens/Oxalis oregana, (2) Sequoia sempervirens/Pseudotsuga menziesii, Gaultheria shallon, (3) Sequoia sempervirens/Pseudotsuga menziesii, Vaccinium ovatum, (4) Sequoia sempervirens/Pseudotsuga menziesii, Arbutus menziesii, and (5) Pseudotsuga menziesii (Table 3). Matthews (pers. comm.) found 80 percent accuracy rate for a predictive model based on the classification types.
The two habitat coverages were examined for differences in the old-growth areas and we found them to be similar in area and location of old-growth patches. In our final analyses, we will quantify any error among the coverages. Through an overlay process in the GIS, attributes from both habitat maps were combined and new polygons designated, each containing components of structure type and species classification.
Pacific Lumber Company Lands (Palco)
Pacific Lumber Company provided a GIS coverage of the old-growth and residual
forest stands on their ownership. The coverage was visually examined and
compared with two alternate forms of habitat data: (1) a S.P.O.T. map (SPOT
Image Corp. 1994) and (2) a GIS coverage of old-growth stands compiled in
1992 from a Palco timber type map using criteria in Miller and Ralph (1995).
Timber types on the Palco coverages were determined from aerial photography
and detailed measurements from vegetation plot samples. Stand boundaries
and area were visually compared among the data sources and found to be similar.
We will validate the accuracy of the final map through a statistical comparison
using the program Fragstats (McGarigal and Marks 1994), a spatial pattern
analysis program.
From the original 99 timber types on the coverage, we aggregated polygons into patches of potential murrelet habitat. To allow a comparison of potential habitat within and between HRSP and Palco, we aggregated patches in two types (Tables 4 and 5): (1) old-growth, unharvested; or (2) residual, some partial harvesting with remaining old-growth trees. Each type was further defined by the percent of dominant-codominant crown cover: 50-100 percent or less than 50 percent. We then compared potential habitat within the Headwaters Agreement Area and within the remaining areas of Palco ownership. We are continuing to refine the habitat types and designate habitat stands using bird survey results. Of special interest are potentially large areas of residual old-growth that may not be completely mapped or surveyed for birds.
Marbled Murrelet inland surveys
All inland surveys were conducted using the Pacific Seabird Group Protocol
(Ralph et al. 1992, 1994). Surveys within the HRSP were conducted by Redwood
Sciences Laboratory in 1992 and by Wildland Resource Managers for Palco
in 1993. Surveys on Palco lands were conducted by Redwood Sciences Laboratory
in 1992 and by various consultants or Palco personnel for Palco from 1992
through 1995. All detections were standardized for seasonal variation in
detection levels using methods of Miller and Ralph (1995). For stations
with multiple surveys, we used the mean detection levels for our comparisons.
In addition, each station was assigned a status of: (1) no detections; (2)
presence, if murrelets were heard or seen; or (3) occupied, if birds were
seen below the canopy or circling above the stand.
RESULTS
The four habitat types and tree species groupings identified in HRSP and the Headwaters Agreement Area represent comparable classifications for evaluating potential murrelet nesting habitat at our current stage in the analyses.
Distribution of habitat types
Of the four habitat types identified in HRSP, the highest proportion (Table
6) of surveys were conducted in the old-growth with greater than 50 percent
crown cover. This habitat totals approximately 15,746 acres and comprises
about 68 percent of the 23,270 acres of potential habitat within the four
types. Approximately 14 percent of this habitat was surveyed throughout
the park in 1992 and 1993 and in the Bull Creek area in 1994 and 1995. Only
one station has been surveyed in the residual areas of the park.
Surveys in the Headwaters Agreement Area sampled a relatively high proportion of the potential habitat types (Table 7). The old-growth with greater than 50 percent crown cover represents approximately 73 percent of the potential habitat (Table 7). Most of the remaining 27 percent of the habitat is previously-harvested, residual old-growth with less than 50 percent crown cover. Over 65 percent of the residual habitat in this type has been surveyed, while 23 percent of the old-growth has been sampled. The comparable areas outside of the Headwaters Agreement Area in Palco lands have not been completely analyzed.
Abundance and distribution of birds
Mean detection levels per station for all stations in the Headwaters Agreement
Area were about twice as high as in the Park. The Park has more stations
without birds.
More than 80 percent of the stations in the dense (O1 and OY1), old-growth redwood habitat in the Park had presence, but only a small proportion of these had occupied behaviors (Table 6). Results were similar for dense old-growth, mixed redwood-Douglas-fir, with 51 percent of stations with detections and only 17 percent occupied.
By contrast, in the Headwaters Agreement Area (Table 7), all of the dense (01) old-growth redwood stations had both detections and occupied behaviors. Similarly, 94 percent of the dense, redwood-Douglas-fir areas had occupied behavior. In the well-sampled residual areas of the Headwaters Agreement Area, with less than 50 percent crown cover, the proportion of occupied stations also was very high: 60 percent in redwood and 100 percent in redwood-Douglas-fir mix.
DISCUSSION
The two areas, the Park and the Headwaters Agreement Area, were similar in vegetation types and bird distribution within the types. We found that birds were well-distributed throughout all old-growth redwood habitats. In addition, bird use of the residual and old-growth areas in the Headwaters Agreement Area was similar and these habitats contained substantial numbers of birds. The difference in the proportion of stations with presence only and occupied behavior between the two areas was marked, and may reflect some artifact of visibility at the stations.
Ongoing analyses will include: (1) addition of other Palco areas; (2) refinement of bird and habitat relationships, as well as the habitat types; (3) estimates of the proportion of birds in each area; and (4) potential impacts of various management scenarios.
For any management of murrelet nesting habitat, it is important to have some idea of the response of the species to disturbances at the nest. Possibly because of their unique nesting habits, the species differs from studies on similar species. Like other seabirds and waterbirds (Robert and Ralph 1975, Cairns 1980, Henson and Grant 1991, Piatt et al. 1990), murrelets appear to be most sensitive to disturbance during incubation, when birds have been flushed from nests (Naslund, pers. comm.; Brown, pers. comm. as cited in Nelson and Hamer 1995b: 94). This was observed mostly at more remote locations (private lands in southwestern Washington and islands in Alaska [Ritchie, pers. comm.; Naslund, pers. comm.]), rather than the more heavily-used public areas (e.g., Big Basin Redwoods State Park in California, and a public forest trail in the Cascade Mountains, Washington [Singer, pers. comm.; Hamer, pers. comm.]). Disturbance during incubation could cause nest failure because of nest abandonment, egg damage from a rapid departure, or a decrease in nest attentiveness leaving the egg vulnerable to predation. Adults coming in to feed the chicks also reacted to people at the nest itself, especially when they were handling the chick (Hamer, pers. comm). However, this is not likely to occur in the normal course of management activities.
Management activities with potential for disturbance from humans are logging, vehicles on nearby roads, and low-flying aircraft. Both adult and young murrelets were occasionally attentive to distant noises such as heavy machinery (greater than 1 mile away), but rarely did more than look toward the disruption. Murrelets near roadways also appeared undisturbed by most vehicular traffic, also generally only looking toward the noise. However, nearby sharp, sudden sounds, such as a car door slamming, has caused a chick to jump, which could lead to the chick leaving the nest cup. When aircraft or helicopters passed overhead at about 300 m, chicks sometimes crouched down, but no further reactions have been recorded.
It seems safe to deduce from these observations, detailed in Long and Ralph (MS), that most management activities would have little effect on murrelets more than a short distance away, perhaps a hundred meters.
In any investigation of a species, numerous assumptions are incorporated into the analysis. To ensure the quality of the data, we have investigated five major assumptions involved with the inland detection of murrelets and the associated habitat information.
(1) Seasonal Variation. Do detection levels differ at
different times of the year?
(2) Location. Are there differences in detection levels at
different locations?
(3) Environmental. Do detection levels vary under different
environmental conditions, such as weather and moon phase?
(4) Annual Variation. Are there differences between detection
levels among years?
(5) Relationship between Population Size and Detection Levels.
Is there a direct relationship between the actual number of birds using
a stand and the bird detection levels at the stand?
DATA
The available data included numbers of detections during morning surveys, as well as data on corresponding environmental conditions, for three high-detection-level, long-term monitoring sites in old-growth forests in northern California: (1) the U.S.D.A. Forest Service's Redwood Experimental Forest, near Klamath; (2) James Irvine Trail, Prairie Creek Redwoods State Park; and (3) Lost Man Creek, Redwood National Park. At these sites, intensive morning surveys have been conducted approximately weekly since 1989 during the summer breeding season, except 1991 at the Experimental Forest. We also collected environmental data on the percent of cloud cover, type of precipitation, and moon phase, as outlined below.
Murrelet detection data collected at ten low-detection sites were also available from Lee Folliard, of the Arcata Redwood Company, but without environmental data. These sites are all on private lands in the same region as the other three locations, and the data were combined and used as a fourth "location" data set.
ANALYSIS METHODS
To investigate the assumptions involving the relative importance of Julian date, year, location, cloud cover, precipitation type, and moon phase on the levels of murrelet detections, we used the maximum R2 improvement selection procedure of multiple linear regression analysis using SAS statistical software.
To compare the patterns of seasonal changes in detection levels in the four locations, we used polynomial regression. Since each of the locations has two peaks in mean detection levels per survey per 10-day period, a fourth-degree polynomial was used for each location. For this analysis, we used the percentage of the mean detection level for each location as a function of the Julian date.
RESULTS
Our interpretation of the influence of various factors on detection levels was based on the order in which variables were added in the multiple linear regression analysis. We found (Table 8) that the factors influencing detection levels at the three long-term sites fell into four categories: (1) the most important were always period and location; (2) moderately important was percent of cloud cover; (3) only slightly important (if at all) were year and phase of the moon; and (4) no effect from precipitation (though its effect could be masked by other variables). Specifically, after 10-day period and location are included in a model (Table 8) the value of R2 is about 30-35%. When data were transformed to reduce variability by location (right two columns in Table 8), inclusion of period alone had a corresponding R2 of about 20%. In either type of analysis, adding in percent cloud cover increased the R2 value by only about 5-6%. Addition of the other environmental variables explained much less of the variation in the model, increasing R2 by only 1-2%.
We found that the high-intensity sites did not differ significantly from the low-intensity sites in their pattern of changes in the levels of detections through the summer breeding season, even though the actual numbers of detections did differ markedly between locations; the polynomials for the four locations were not significantly different, based on F-test comparisons of corresponding parameter estimates on the polynomials (p > 0.90).
DISCUSSION
Because the day of the year (see Assumption #1) and the location (see Assumption #2) were found to account for the most significant differences in bird detection levels, this indicates that inland detection data at different locations can best be compared if differences due to seasonal patterns are taken into account. That is, detections, when standardized by 10-day period, allow comparisons among locations.
The environmental variables (see Assumption #3) that we studied seem to play a very minor role in the variability of detection levels, especially when compared with date and location, however, they may confound each other or be accounted for by other variables. There are, of course, additional variables which could be studied in the future, but we feel we examined those likely to have a major effect.
It also seems reasonable to conclude that data collected in different years (within or near the range of years studied) can be pooled, since a significant difference among years was not found (see Assumption #4).
This analysis is also evidence that at least the seasonal pattern of amplitude in detection levels is not dependent upon the presence of large numbers of individuals at the same site (see Assumption #5), since the pattern of seasonal changes in detections for each location are so similar. Therefore, on the basis of our analyses, when comparing differences among locations, standardization of detection data reduces variation associated with 10-day period and is an appropriate process applicable to any site, regardless of whether it has low or high detection levels.
Akçakaya, H.R. in prep. Applied Biomathemetics, 100 North Country Road, Setauket, NY 11733. 516 751-3435.
Arc/Info. Version 7.0.4. 1996. Environmental Systems Research Institute, Inc. (ESRI). 380 New York St., Redlands, CA 92373.
Cairns, D. 1980. Nesting density, habitat structure, and human disturbance as factors in Black Guillemot reproduction. Wils. Bull. 92(3): 352-361.
Hamer, T.E. pers. comm. Hamer Environmental, 2001 Hwy. 9, Mt. Vernon, WA 98273. Notes from telephone conversations with Linda Long, 8 and 26 July 1996 on file at USFS Redwood Sciences Laboratory, Arcata, CA.
Hammon, Jensen, Wallen, and Associates, Inc. 1996. 8407 Edgewater Dr., Oakland, CA 94621-1403, (510) 638-6122.
Henson, P. and T.A. Grant. 1991. Effects of human disturbance on Trumpeter Swan breeding behavior. Wildl. Soc. Bull 19:248-257.
Long, L.L. and C.J. Ralph. MS. Effect of human disturbance on nesting Marbled Murrelets, alcids, and other seabirds. A report to U.S.F.S. Region 6 on disturbance of nesting Marbled Murrelets.
McGarigal, K. and B.J. Marks. 1994. Fragstats: Spatial pattern analysis program for quantifying landscape structure, Version 2.0. Forest Science Department, Oregon State University, Chervils, Oregon 97331.
Matthews, S.T. 1986. Vegetation map and inventory of old-growth forests in Humboldt Redwoods State Park. 67 pp.
Matthews, S.T. 1986. Old-Growth Forest Associations of the Bull Creek Watershed, Humboldt Redwoods State Park, California. Master Thesis, Humboldt State University.
Miller, S.L. and C.J. Ralph. 1995. Relationship of Marbled Murrelets with habitat and vegetation characteristics at inland sites in California. pp 205-218 in Ralph, C.J., Hunt, G.L., Raphael, M.G., Piatt, J.F. (Technical Editors). Ecology and conservation of the Marbled Murrelet. Gen. Tech. Rep. PSW-GTR-152. Albany, CA. Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture.
Naslund, N.L. pers. comm. U.S. Fish and Wildlife Service, 1011 Tudor Rd., Anchorage, AK 99503. Notes from telephone conversation with Linda Long, 8 August 1996 on file at U.S.F.S. Redwood Sciences Laboratory, Arcata, CA.
Nelson, S.K. and T.E. Hamer. 1995. Nest success and the effects of predation on Marbled Murrelets. Ecology and Conservation of the Marbled Murrelet. Gen. Tech. Rep. PSW-152. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture; 89-98.
Piatt, J.F., B.D. Roberts, W.W. Lidster, J.L. Wells, and S.A. Hatch. 1990. Effects of human disturbance on breeding Least and Crested Auklets at St. Lawrence Island, Alaska. Auk 107: 342-350.
Ritchie, B. Pers. comm. Washington Department of Fish and Wildlife, 600 N. Capitol Way, Olympia, WA 98502. Notes from telephone conversations with Linda Long, 27 August and 17 September 1996 on file at U.S.F.S. Redwood Sciences Laboratory, Arcata, CA.
Ralph, C.J. and S.L. Miller. 1995. Offshore population estimates of Marbled Murrelets in California. pp. 353-360 in Ralph, C. J,. Hunt, George. L., Raphael, M. G., Piatt, J. F. (Technical Editors). Ecology and Conservation of the Marbled Murrelet. Gen. Tech. Rep. PSW-152. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture.
Ralph, C.J. and S.K. Nelson, compilers. 1992. Methods of surveying Marbled Murrelets at inland forested sites. Pacific Seabird Group, Oregon Cooperative Wildlife Research Unit, Oregon State University, Corvallis, OR; 21 p.
Ralph, C.J.; S.K. Nelson; M.M. Shaughnessy; S.L. Miller; T.E. Hamer; Pacific Seabird Group, Marbled Murrelet Technical Committee. 1994. Methods for surveying Marbled Murrelets in forests. Technical paper #1, revision. Available from: Oregon Cooperative Wildlife Research Unit, Oregon State University, Corvallis, OR; 48 p.
Robert, H.C. and C.J. Ralph. 1975. Effects of human disturbance on the breeding success of gulls. Condor 77(4): 495-499.
Singer, S.W. pers. comm. Santa Cruz Mountains Murrelet Group, P.O. Box 7422, Santa Cruz, CA 95061. Notes from telephone conversations with Linda Long, 30 July and 22 August 1996 on file at U.S.F.S. Redwood Sciences Laboratory, Arcata, CA.
SPOTView CD-ROM. 1994. Digital image data with 10 m resolution. California State Coverage, licensed by SPOT Image Corporation, Reston, Virginia.
These data are proprietary data; any use without permission is a breach of professional ethics. Contact C. John Ralph, U.S.D.A. Forest Service, Redwood Sciences Laboratory, Arcata, California 95521
Table 2. Correlation between year and mean number of birds per 2-km segment offshore of northern
California 1989-1995. These data are proprietary data; any use without permission is a breach of
professional ethics. Contact C. John Ralph, U.S.D.A. Forest Service, Redwood Sciences Laboratory,
Arcata, California 95521
800 m from shore 1400 m from shore
Correlation Correlation
Section (r) n slope p (r) n slope p
PSCB -0.43093 6 -0.229429 0.3936 0.28466 6 0.185429 0.5845
CBNC -0.28883 6 -0.415714 0.5788 -0.40439 6 -0.647429 0.4265
NCKR -0.76133 5 -3.166000 0.1348 -0.80049 5 -1.340000 0.1037
KRBL -0.06546 4 -0.153143 0.9345 0.90928 4 2.774857 0.0907
BLTR 0.93669 6 1.012857 0.0059 0.12280 5 0.087000 0.8440
TRMR -0.49546 5 -0.859000 0.3960 -0.25552 5 -0.171000 0.6782
MRHB -0.58415 6 -0.211143 0.2234 -0.14888 6 -0.038571 0.7783
HBTB -0.71405 7 -0.357143 0.0715 -0.85511 7 -0.290357 0.0142
TBFC -0.56110 6 -0.286571 0.2467 -0.73213 5 -0.287000 0.1596
FCCM 0.13391 6 0.062857 0.8003 -0.50002 5 -0.114000 0.3910
CMSC -0.83067 3 -0.435000 0.3759 -0.41475 3 -0.050000 0.7277
r = Pearson's correlation coefficient between year and mean number of birds per 2-km segment
n = number of years of data
slope = Estimate of linear regression slope parameter
p = p-value for test on Ho: slope=0
Table 3. Number of acres and hectares by type and species class,
including the number of habitat patches for each grouping in the
Humboldt Redwoods State Park. Species class variable "0" indicates
type patches from Pacific Lumber Company's coverage that are outside of
the Emery map old-growth patches and have no associated species
information. These data are proprietary data; any use without permission
is a breach of professional ethics. Contact C. John Ralph, U.S.D.A.
Forest Service, Redwood Sciences Laboratory, Arcata, California 95521
Species No. habitat
Type class patches Acres Hectares
O1 0 498 1,619.74 655.50
R 49 1,471.80 595.63
RD 792 12,259.64 4,961.41
D 66 393.11 159.09
O2 0 134 397.91 161.03
R 14 32.00 12.95
RD 497 3,514.23 1,422.19
D 43 254.04 102.81
R1 0 23 265.93 107.62
R 1 0.72 0.29
RD 13 98.37 39.81
D 1 1.54 0.62
R2 0 146 2,402.70 972.36
R 2 3.90 1.58
RD 125 523.56 211.88
D 9 29.75 12.04
Total 2,413 23,263.90 9,414.77
Type codes:
O = Old-growth
R = Residual old-growth trees in a harvested area
1 = 50-100% old-growth crown cover
2 = <50% old-growth crown cover
Species class codes:
0 = species class not available
R = Redwood (Sequoia sempervirens)
RD = Redwood - Douglas-fir (Pseudotsuga menziesii)
D = Douglas-fir
Table 4. Number of acres and hectares by type and species class,
including the number of habitat patches for each grouping for Palco land
in Headwaters Agreement Area. These data are proprietary data; any use
without permission is a breach of professional ethics. Contact C. John Ralph,
U.S.D.A. Forest Service, Redwood Sciences Laboratory, Arcata, California
95521
Species No. habitat
Type class patches Acres Hectares
O1 R 31 778.20 595.63
RD 56 2,093.20 847.11
D 0 0.00 0.00
O2 R 0 0.00 0.00
RD 16 245.20 99.23
D 0 0.00 0.00
R1 R 3 21.70 8.78
RD 0 0.00 0.00
D 0 0.00 0.00
R2 R 41 754.20 305.22
RD 1 48.20 19.51
D 0 0.00 0.00
Total 148 3,940.70 1,875.48
Type codes:
O = Old-growth
R = Residual old-growth trees in a harvested area
1 = 50-100% old-growth crown cover
2 = <50% old-growth crown cover
Species class codes:
R = Redwood (Sequoia sempervirens)
RD = Redwood - Douglas-fir (Pseudotsuga menziesii)
D = Douglas-fir
Table 5. Number of acres and hectares by type and species class,
including the number of habitat patches for each grouping for Palco land
in areas outside of Headwaters Agreement Area. These data are proprietary
data; any use without permission is a breach of professional ethics.
Contact C. John Ralph, U.S.D.A. Forest Service, Redwood Sciences Laboratory,
Arcata, California 95521
Species No. habitat
Type class patches Acres Hectares
O1 R 13 222.00 89.84
RD 51 1,676.30 678.90
D 62 1,322.10 535.05
O2 R 0 0.00 0.00
RD 13 175.80 71.15
D 114 3,376.40 1,366.41
R1 R 16 327.00 132.34
RD 32 453.70 183.61
D 0 0.00 0.00
R2 R 579 13,086.80 5,296.16
RD 112 2,206.10 892.80
D 144 4,712.80 1,907.24
Total 1,136 27,559.00 11,153.50
Type codes:
O = Old-growth
R = Residual old-growth trees in a harvested area
1 = 50-100% old-growth crown cover
2 = <50% old-growth crown cover
Species class codes:
R = Redwood (Sequoia sempervirens)
RD = Redwood - Douglas-fir (Pseudotsuga menziesii)
D = Douglas-fir
Table 6. Summary statistics for potential Marbled Murrelet habitat types in Humboldt Redwoods State Park. Surveys were conducted by Redwood
Sciences Laboratory in 1992 and for Pacific Lumber Company by Wildland Resource Managers in 1993 and others in 1994 and 1995. See Table 3 for
explanations of habitat type and species class codes. These data are proprietary data; any use without permission is a
breach of professional ethics. Contact C. John Ralph, U.S.D.A. Forest Service, Redwood Sciences Laboratory, Arcata,
California 95521
Acres No. Mean detections Approx ac. 31.06 ac Proportion of Estimated number
Habitat Species in stations per station surveyed x station stations with: of acres with:
type class class surveyed All Present and (31.06 ac Acres Presence Occupied Presence Occupied
stations occupied (n) x station) in class only behaviors only behaviors
O1 R 1,472.80 11 7.90 30.10 ( 9) 341.66 0.818 0.091 1,204.75 134.02
RD 12,260.64 58 6.31 12.20 (30) 1,801.48 0.517 0.172 6,338.75 2,108.83
D 393.11 1 0.00 0.00 31.06 -- -- -- --
0 1,619.74
15,746.29 2,174.20 0.138
O2 R 23.00 0 - - 0.00 -- -- -- --
RD 3,514.23 7 0.71 5.00 ( 1) 217.42 0.140 0.000 491.99 0.00
D 254.04 0 - - 0.00 -- -- -- --
0 397.91
4,198.18 217.42 0.052
R1 R 0.72 0 - - 0.00 -- -- -- --
RD 98.37 0 - - 0.00 -- -- -- --
D 1.54 0 - - 0.00 -- -- -- --
0 265.93
366.56 0.00 0.000
R2 R 3.90 0 - - 0.00 -- -- -- --
RD 523.56 1 0.00 0.00 ( 0) 30.16 -- -- -- --
D 29.75 0 - - 0.00 -- -- -- --
0 2,402.70
2959.91 30.16 0.013
Total acres 23,270.94
Table 7. Summary statistics for potential Marbled Murrelet habitat types on Pacific Lumber Company lands in Southern Humboldt County,
California. Survey stations are for all habitat included in the Headwaters Agreement Area. Surveys were conducted by Palco from 1992 through
1995. See Table 3 for explanations of habitat type and species class codes.
These data are proprietary data; any use without permission is a breach of professional ethics. Contact C. John Ralph,
U.S.D.A. Forest Service, Redwood Sciences Laboratory, Arcata, California 95521
Acres No. Mean detections Approx ac. 31.06 ac Proportion of Estimated number
Habitat Species in stations per station surveyed x station stations with: of acres with:
type class class surveyed All Present and (31.06 ac Acres Presence Occupied Presence Occupied
stations occupied (n) x station) in class only behaviors only behaviors
O1 R 778.20 4 10.93 10.93 ( 4) 124.24 0.000 1.000 0.00 778.20
RD/DR 2,093.64 17 12.36 12.36 (17) 528.02 0.059 0.940 123.49 1,967.42
D 0.00 - - - 0.00 -- -- -- --
2,871.20 652.26 0.227
O2 R 0.00 - - - 0.00 -- -- -- --
RD/DR 245.20 1 0.11 0.11 ( 1) 31.06 1.000 0.000 245.20 0.00
D 0.00 - - - 0.00 -- -- -- --
245.20 31.06 0.127
R1 R 21.70 0 - - 0.00 -- -- -- --
RD/DR 0.00 - - - 0.00 -- -- -- --
D 0.00 - - - 0.00 -- -- -- --
21.70 0.00 0.000
R2 R 754.20 11 7.83 7.83 (11) 341.66 0.180 0.818 144.43 656.36
RD/DR 48.20 2 15.91 15.91 ( 2) 62.12 0.000 1.000 0.00 48.20
D 0.00 - - - 0.00 -- -- -- --
802.40 403.78 0.503
Total acres 3,940.50
Table 8. Environmental and other variables that affect the number of murrelet
detections at inland sites. Each column corresponds to a different form of
the number of detections during a morning survey used as the dependent
variable. The rows correspond to different variations of independent
variables. Each interior cell lists the first six variables found to "best"
explain the detection level by using the maximum R2 improvement selection
procedure (the "+" indicates the next variable added in by the method in SAS),
along with the corresponding new value of R2.
These data are proprietary data; any use without permission is a breach of
professional ethics. Contact C. John Ralph, U.S.D.A. Forest Service, Redwood
Sciences Laboratory, Arcata, California 95521
Dependent variable
(I) (II) (III) (IV)
Original Square-root- Percent of Percent of
detection transformation mean number of maximum number
data (number of numbers of detection per of detections per
during a detections survey, by morning survey,
morning Location by Location
survey)
Independent variable added*, and associated new R2 value
Multiple (I) (II) (III) (IV)
Regression1 Period 12% Period 11% Period 21% Period 19%
+Location1 23% +Location1 24% +PctCloud 27% +PctCloud 26%
With +Location2 35% +Location2 37% +Location1 28% +Location2 28%
minimal +PctCloud 41% +PctCloud 42% +Year 28% +Location1 29%
alterations +Year 42% +Year 43% +MoonPh 28% +Year 30%
+MoonPh 42% +MoonPh 43% +Location2 29% +MoonPh 30%
Multiple (I) (II) (III) (IV)
Regression2 Period 12% Period 11% Period 21% Period 19%
+Location1 23% +Location1 24% +PctCloud 27% +PctCloud 26%
Dummy +Location2 35% +Location2 37% +Year_2 28% +Location2 28%
variables +PctCloud 41% +PctCloud 42% +Year_4 29% +Location1 29%
for year +Year_2 42% +Year_2 42% +Year_3 30% +Year_2 30%
+Year_3 43% +Year_3 43% +Year_6 31% +Year_3 31%
Multiple (I) (II) (III) (IV)
Regression3 Period 12% Period 11% Period 21% Period 19%
+Location1 23% +Location1 24% +PctCloud 27% +PctCloud 26%
Dummy +Location2 35% +Location2 37% +Year_2 28% +Location2 28%
variables +PctCloud 41% +PctCloud 42% +Year_4 29% +Location1 29%
for year +Year_2 42% +Year_2 42% +Year_3 30% +Year_2 30%
and period +Year_3 43% +Year_3 43% +Year_6 31% +Year_3 31%
replaced by
date
Multiple (I) (II) (III) (IV)
Regression4 Period11 10% Location1 9% Period11 13% Period10 14%
+Period10 20% +Location2 22% +Period10 28% +Period11 29%
Dummy +Location1 30% +Period11 31% +PctCloud 35% +PctCloud 35%
variables +Location2 41% +Period10 42% +Period9 40% +Period9 40%
for year +PctCloud 46% +Period9 47% +Period8 41% +Location2 41%
and period +Period9 51% +PctCloud 52% +Location1 42% +Period8 43%
*Multiple Regression Independent Variables
Period: 10-day periods, originally numbered 1 to 12, as "Quantities." In
Multiple Regression3, Periods 1 to 12 were replaced by Julian date for the 5th
day in the 10-day period, i.e., 109, 119, 129, 139, 149, 159, 169, 179, 189,
199, 209, 219.
Location1 and Location2: Two dummy variables for the three locations.
Year: 1989 to 1995, used as "Quantities" in Multiple Regression1. Dummy
variables used for Year: Year_1, Year_2, Year_3, Year_4, Year_5, and Year_6.
PctCloud: The arcsine of the square-root of the percent of cloud cover.
PrecDum1, -2, and -3: Three dummy variables for the four precipitation
categories: None, Fog, Drizzle, and Rain.
MoonPh: The sine of the ratio, scaled to pi/2, of number of nights since the
last new moon to the number of nights between the last and the next new moon.