PNW Pacific Northwest Research Station I n s i d e Profiling the Pileateds ...... 2 A Landscape Transformed ...... 3 Surprising Results ...... 4 Fuel Reduction Versus Foraging Needs ...... 4 Take-Home Lessons ...... 5 FINDINGS issue one hundred nine / january 2009 “Science affects the way we think together.” Lewis Thomas
LOOKING OUT FOR THE PILEATED WOODPECKER
trees peppered with rectangular feeding holes, or spot a crow-sized, black-and-white bird i n S UMMA R Y with a sinuous neck and pointy scarlet crest
Evelyn Bull hammering away—that would be the pileated The pileated woodpecker is a species of woodpecker, the biggest of the tribe. Its quirky conservation concern and a keystone looks and laughing call inspired that early species in mature and old forests of the star of animation, Woody the Woodpecker. Pacific Northwest. In the Blue Mountains However, in real life, this bird—whose Latin of northeast Oregon, researchers from name, Dryocopus pileatus, means “tree the PNW Research Station in La Grande, cleaver”—is no cartoon character, but a major player in forest ecosystems. Its industrious Oregon, studied the effects of natural and tree excavating and foraging benefit as many human-caused disturbance on pileated as two dozen forest species and contribute populations and their habitat over a period generously to the recycling of forest nutrients. spanning from 1973 to 2005. During this These and other services have earned pileateds time, several pervasive insect outbreaks the status of a “keystone” species. transformed the forest characterized by predominantly live conifers with dense Because the older forests inhabited by the pileated are diminishing, it also is considered canopy cover (prime pileated habitat) a species of conservation concern. Guidelines to one with increasing numbers of snags for maintaining suitable habitat for the bird and downed wood. Logging for forest were issued following the National Forest restoration and fuel reduction treatments Management Act of 1976. Those initial also took place, further impacting habitat recommendations were derived from limited for the birds. knowledge gleaned from birds of eastern deciduous woodlands. Subsequent studies led The researchers were able to compare the by Evelyn Bull, a wildlife biologist with the effects on pileated populations at various Pacific Northwest (PNW) Research Station in stages as their environment changed. They Pileated woodpeckers craft new nest cavities La Grande, Oregon, revealed that pileateds of found, surprisingly, that despite heavy every year, sometimes trying out several sites before settling on their final choice. the interior Pacific Northwest have somewhat tree mortality, the number of nesting different needs and habits. These findings pairs, their reproductive success, and have led to revised habitat-management “Nature is a language, home range locations remained fairly recommendations. consistent—provided that dead trees and and every new fact that we logs remained abundant and extensive learn is a new word.” Forests are dynamic, constantly evolving places, and in northeastern Oregon’s logging had not occurred. Conversely, —Ralph Waldo Emerson Wallowa-Whitman National Forest, where nesting pair numbers and reproductive enture into a forest almost anywhere Bull began her work in 1973, a series of success decreased significantly where across the country and you might events has radically altered sections of the extensive regeneration cuts eliminated V hear the distinctive drumming of a forest over the last 30 years. many nest and roost trees, as well as snags woodpecker, 24 species of which live year- “The forests described in our earlier studies and downed wood where the birds forage round in North America. If you stumble on have changed from large, continuous areas for insects. of mature and old conifers with more than 70-percent canopy cover to relatively open K E Y f i n d i n G S canopies and an increasing number of snags [standing dead wood] and logs, so we no lon- • Pileated woodpeckers occupy the same home ranges for up to 30 years and possibly ger have the conditions that our guidelines for two to four generations. had been written for,” Bull explains. “The effects of natural disturbances have not been • Density of pileated woodpeckers decreased 80 percent after extensive harvesting. described for most of our forest species,” she adds. However, that changed for the pileated • Pileated reproductive success appears to be closely tied to the amount of unharvested, woodpecker with the recent publication of closed-canopy stands, and reproductive failure appears tied to the amount of harvested research spanning 30 years. stands.
• High tree mortality is not detrimental to pileated woodpeckers if abundant large snags persist.
PROFILING THE PILEATEDS ver two periods of early fieldwork live at least 9 years, mate for life, and repeat- (1973–83 and 1989–90), Bull and edly occupy territories of roughly a thousand her collaborators compiled a detailed acres year-round.
O Evelyn Bull profile of pileateds and their habitat in the “If one member of a nesting pair dies, the Blue Mountains in northeastern Oregon. survivor stays within the same home range. Using aerial photos and ground survey data, When the pair dies, the territory is likely to they evaluated forest type, structural stage, be occupied by offspring or other dispersing and amount of canopy closure in seven study birds,” Bull explains. The birds also frequent areas, totaling close to 30,000 acres of forest the same nesting and roosting areas over time. interspersed with grasslands. The studies underscored the importance of The researchers used ground surveys, snags, logs, and dying trees to the pileated’s color-banding, and radio telemetry to track lifestyle. “You need dead trees for many woodpecker whereabouts to help determine species to survive,” Bull says, “though the population densities, delineate home ranges, question has long been how many.” and characterize their nesting, foraging, and roosting habits. They learned that pileateds Chiseling holes into dead trees, pileateds craft new nest cavities every year, along with an abundance of roosts, which the Purpose of PNW Science Findings birds frequent at night and during inclement weather. Sometimes pileateds use living trees To provide scientific information to people with hollow chambers created by decaying who make and influence decisions about heartwood for roosts; these typically contain managing land. multiple entry holes to allow for escape from PNW Science Findings is published predators. “These cavities enable a range monthly by: of other species to access tree hollows they would otherwise be excluded from,” Bull Pacific Northwest Research Station explains. The secondary cavity nesters USDA Forest Service P.O. Box 3890 include numerous species of conservation Portland, Oregon 97208 concern including the fisher, American Pileateds use snags such as this ponderosa pine marten, bufflehead, flammulated owl, for nesting. Send new subscriptions and change western bluebird, Vaux’s swift, northern of address information to flying squirrel, and several bat species. [email protected] “Pileateds are opportunistic feeders and also eat budworms, bark beetles, and other pests,” Rhonda Mazza, editor Likewise, by foraging for insects in decaying [email protected] wood, pileateds accelerate the decomposi- says collaborator Jane Hayes, an entomologist tion process. Bull’s research team observed with the PNW Research Station in La Grande, Keith Routman, layout that the birds spent nearly 80 percent of their Oregon. “However, when environmental [email protected] feeding efforts on downed logs and snags. conditions allow pest populations to reach To analyze pileated diets, they collected scat epidemic levels, they overwhelm their United States Forest and ferreted out insect mouth parts to identify predators’ capacities to substantially reduce Department Service of Agriculture prey that included ants, beetles, and other the population,” she notes. invertebrates.
WRITER’S PROFILE Noreen Parks has written about science and the environment for more than 17 years. She currently resides in Port Townsend, Washington.
2 Evelyn Bull Evelyn Bull
To forage for insects, pileateds drill numerous Pileated woodpeckers find their primary prey, carpenter ants, by foraging on downed woody material. holes in dead wood, accelerating decomposition in the process.
A LANDSCAPE TRANSFORMED t was a series of such insect outbreaks, But as the insect outbreaks continued, beginning in the 1970s, that triggered a extensive logging for forest restora- series of landscape changes in northeast- tion was carried out in some areas.
I Evelyn Bull ern Oregon, affecting all the major tree spe- And, with the threat of wildfire cies favored by pileateds. First, mountain pine looming ever larger, forest personnel beetles erupted to attack mature ponderosa carried out fuel reduction treatments and lodgepole pines. Then, during the 1980s to clear woody debris from sections and 1990s, western spruce budworms and of the forest. Douglas-fir beetles swept through the forest. “The budworms’ repeated defoliation of the The overall outcome: a broad-scale trees was a painfully slow attack on the for- transformation of the forest, and est,” Hayes recalls. Large numbers of mature the rare opportunity to compare the trees eventually succumbed, although the full consequences for a long-lived species brunt of the devastation was not apparent until of concern, compared to the earlier years later. findings. So in 2003, armed with her data from more than a dozen “Natural disturbance events such as insect previous studies, Bull, along with activity, disease, wind, and fire are the pri- Hayes, Nicole Nielsen-Pincus—then mary mechanisms that insure a continuum of a graduate student at the University snags, downed dead wood, and live, decaying of Idaho—and others returned to the trees, which pileated woodpeckers depend research sites to investigate how the on,” Bull notes. Thus, the birds benefited to a pileateds were faring. degree. For example, ponderosa pines killed by beetles during the 1970s subsequently became nest sites.
Although pileateds forage on snags all year, dead trees such as this grand fir are particularly important in the winter when logs are inaccessible because of deep snow.
Science Findings is online at: http://www.fs.fed.us/pnw/ The site also includes Science Update—scientific knowledge for pressing decisions about controversial natural resource and environmental issues.
3 SURPRISING RESULTS he map of home ranges occupied by occupied,” Bull explains. “In the nesting pairs compiled between 1973 seventh area, extensive regeneration ‘‘ and 1983 indicated that the study harvests had taken place in 1991. We
T Evelyn Bull area had reached its carrying capacity in found that nesting pairs no longer terms of the number of nesting pairs it was occupied home ranges impacted by supporting,” notes Nicole Nielsen-Pincus, this logging activity, and the number now a wildlife biologist, “and the population of nesting pairs had decreased from appeared stable during the 1989–90 period.” the previous five, to one—a drop of 80 percent.” By 2003, however, tree density in many home ranges had greatly diminished. Fieldwork Similarly, a history of logging and geographic information system (GIS) activity proved to be the major factor studies showed that 75 percent of once lushly affecting pileated efforts in fledging canopied grand fir stands had shrunk to less young—a critical measure in how than 30-percent canopy closure. well the habitat is meeting their needs, as Bull points out. “The amount of “Going into the postdisturbance research, unharvested area and forest with more we expected to see that the birds had been than 60-percent canopy closure was most adversely affected by this loss. Instead, considerably greater, and the amount we found that even where mortality was of area harvested considerably less, high among grand fir and Douglas-fir, as in home ranges occupied by pairs that long as extensive logging and fuel reduction successfully raised young, compared to treatments had not occurred and an abundance pairs that failed to,” she explains. None of large live or dead trees and logs remained, of the other factors evaluated—forest the pileateds were still there,” Nielsen-Pincus type and structural stage (young, says. mature, or old-growth), differed Specifically, “in six of the seven study areas, between pairs that were successful in Pileateds use a number of different roosts where they producing offspring, and those that take shelter at night and during inclement weather. the number of nesting pairs remained the Roosts typically contain multiple entry holes to allow same or fluctuated by a single pair, and were not. for escape from predators—an advantage for secondary the same approximate home ranges were cavity-users as well.
FUEL REDUCTION VERSUS FORAGING NEEDS n 2004, Bull and colleagues also evalu- burned ones. “The lower occurrence of ants in opportunities in the short-term aftermath of ated the short-term effects of fuel the burned areas suggests that burning either burns as well. If maintaining biodiversity I reduction efforts on pileateds. Focusing directly eliminated the ants or rendered the and wildlife habitat are objectives, it is on foraging opportunities for the birds, habitat unsuitable for them,” Bull says. important to understand the consequences they tallied the numbers of logs, snags, and of fuel reduction and restoration treatments Other forest dwellers such as small mammals, stumps in study plots where mechanical on individual species—particularly those amphibians, rubber boas, martens, and thinning and clearing had occurred—with dependent on coarse woody debris that is bears may experience diminished feeding and without followup broadcast burning— removed during these treatments. compared to control plots in mature forest. Then the researchers surveyed the areas for evidence of foraging pileateds and the presence of ants, their primary food. The data revealed that whereas thinning greatly Evelyn Bull reduced the abundance of all forms of dead wood, subsequent burning removed more than twice as many logs and stumps as mechanical treatment alone. The contrasting effects on pileated foraging were substantial. “Both the control plots and those with mechanical removal treatments provided significantly more foraging habitat for pileateds, whereas the prescribed burn treatments provided significantly less,” Bull explains. Not surprisingly, although evidence of foraging pileateds was most common in the control areas, they were roughly twice as A mature forest on the Starkey Experimental Forest in Oregon’s Blue Mountains prior numerous in the thinned-only plots as in the to insect infestations in the 1970s that killed conifers favored by pileateds for nesting and roosting.
4 Take-Home Lessons he final leg of the pileated research Nielsen-Pincus concurs. “We now have a pileateds, feed primarily on ants found on rounded out a long-running documen- better understanding of what the pileateds dead wood during at least part of the year. T tation of a key, long-lived species truly need. Thirty years ago, dense canopy Thus, an environment that supports healthy of concern in its evolving habitat. “As cover in mature grand fir forests with old- populations of pileateds also ensures the researchers, we seldom have the opportunity growth structure was considered critical to availability of shelter and forage for other, for a multidecade study like this,” says Hayes. suitable pileated habitat. We now know that diverse wildlife. “Mostly our studies provide snapshots of canopy cover may not be as important, as Bull concludes, “While the future is hard ecosystems. We often speculate on ‘what long as enough large trees and downed logs to predict, one thing is certain: change is would happen if?’ and seldom get to find out. are maintained.” ongoing in dynamic forest ecosystems. With However, the temporal scope of this research With the fates of many other species tied to greater insight into the complex interactions has provided a unique opportunity to watch pileated woodpecker activity, lessons gleaned taking place, managers will be better able forest ecosystem processes in motion and from the research extend beyond habitat to strategically design restoration treatments played out on a wider screen by revealing requirements for the birds. For instance to enhance the resiliency of the landscape more of the complex interactions among as seemingly dissimilar as black bears while also protecting and maintaining species as disturbance processes shape the and western toads are, these species, like suitable habitats for numerous wildlife forest they inhabit over time.” species relying on large trees, snags, and down wood.”
“When we try to pick out anything by itself, we find it hitched to
Evelyn Bull everything else in the universe.” —John Muir
FOR FURTHER READING Bull, E.L.; Nielsen-Pincus, N.; Wales, B.W.; Hayes, J.L. 2007. The influence of distur- bance events on pileated woodpeckers in northeastern Oregon. Forest Ecology and Management. 243: 320–329. Bull, E.L.; Holthausen, R.S. 1993. Habitat use and management of pileated woodpeck- ers in northeastern Oregon. Journal of Wildlife Management. 57: 335–345. Bull, E.L. 1987. Ecology of the pileated woodpecker in northeastern Oregon. Journal of Wildlife Management. 51: 472–481. Bull, E.L.; Clark, A.A.; Shepherd, J.F. 2005. Short-term effects of fuel reduction on pileated woodpeckers in northeastern By the mid 1990s the majority of the grand fir and Douglas-fir had been killed by insects in some of the Oregon—a pilot study. Res. Pap. PNW- study areas. RP-564. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific North- west Research Station. 17 p. L A n d M A N AG E M e n t I M p l i c A t i o n s Bull, E.L.; Jackson, J.A. 1995. Pileated woodpecker (Dryocopus pileatus). In: Poole, • Extensive tree harvesting rendered habitat unsuitable for nesting pileated woodpeckers. A.; Gill, F., eds. The Birds of North America. • Retention of abundant large, dead trees and logs in mature and older stands with Philadelphia, PA: Academy of National high tree mortality provided sustainable habitat for pileated woodpeckers. Sciences and American Ornithologists’ Union. No. 148. • The same home ranges can be managed for pileated woodpeckers for decades, if large Nielsen-Pincus, N.; Garton. E.O. 2007. snags and logs exist or are retained. Responses of cavity-nesting birds to changes in available habitat reveal underlying • The home ranges of pileated woodpecker can be mapped and subsequently monitored determinants of nest selection. Northwestern with relative ease due to the high degree of fidelity. Naturalist. 88: 135–146. • Protection of relatively easily identified nesting stands is important for the sustainability of this species.
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scientist profile S
EVELYN L. BULL examines arthropod biological and ecological she continued to collaborate with scientists is a research wildlife interactions at the stand level and across forest at the PNW Research Station in La Grande biologist with the landscapes. Her studies focus on the role to further investigate the pileateds. USDA Forest Service, of disturbances in ecosystems and how the E-mail: [email protected] Pacific Northwest desirable and undesirable effects might best be Research Station. She managed. received her Ph.D. in Bull and Hayes can be reached at: COOPERATORS wildlife ecology at University of Idaho at USDA Forest Service/PNW Research Station Barb Wales, wildlife biologist, Moscow. Her research 1401 Gekeler Lane Pacific Northwest Research focuses on the effects of natural and human La Grande, OR 97850-3368 Station, La Grande, OR disturbances on western toads and Columbia Bull: La Grande Ranger District, spotted frogs and on old-growth dependent Phone: (541) 962-6547 Wallowa-Whitman National Forest species, including pileated woodpeckers and E-mail: [email protected] other cavity-nesting birds, great gray owls, Hayes: North Fork John Day Ranger District, Vaux’s swifts, and American martens. Phone: (541) 962-6549 Umatilla National Forest E-mail: [email protected] JANE L. HAYES is Starkey Experimental Forest and Range, a research biological Pacific Northwest Research Station NICOLE NIELSEN-PINCUS scientist with the received her M.S. in wildlife Richard Holthausen (retired), National USDA Forest Service, resources from the University Wildlife Ecology Unit, U.S. Forest Pacific Northwest of Idaho. After completing a Service Research Station. thesis on habitat selection in a She received her suite of cavity-nesting birds in Ph.D. in entomology northeastern Oregon, includ- at University of ing the pileated woodpecker, Kansas. Her research
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