United States Department of Agriculture D E E Forest Service A Monitoring Challenge: P R A R U TM U LT ENT OF AGRIC Pacific Northwest Region Clark’s Nutcracker Population Trends 2011 ARE CLARK’S nutcrackers declining? Many resource What’s the current status How reliable are the managers think so, yet long-term national surveys say no. of Clark’s nutcrackers? surveys? Problem is, these birds are so hard to monitor. How can we improve on methods to accurately detect changes in Clark’s Breeding Bird Surveys These annual bird counts nutcracker populations? (conducted nationwide have limitations for projecting each May since 1966) show population trends in Clark’s a significant range-wide nutcrackers for several BACKGROUND increase in numbers of reasons: We investigated habitat use, caching behavior, and Clark’s nutcrackers from 1966 • Most routes are along migratory patterns in Clark’s nutcrackers in the Pacific through 2007. Christmas Bird established roads to Northwest using radio telemetry. Over 4 years (2006– Counts (done in December facilitate access by 2009), we captured 54 adult nutcrackers at 10 sites in the across the country since 1900) volunteer surveyors; Cascade and Olympic Mountains in Washington State. show fairly strong population species occupying remote We fitted nutcrackers with a back-pack style harness. fluctuations, but no overall terrain, like Clark’s The battery life on the radio tags was 450 days, and trend (either increasing or nutcrackers, might be we tracked nutcrackers year-round, on foot (to obtain decreasing). Data from these poorly sampled. behavior observations) and via aircraft (to obtain point annual surveys (shown in the • Clark’s nutcrackers breed locations). We obtained more than 6,000 telemetry point map and graph, next page) are in March, so May and locations on radio-tagged nutcrackers, and we observed valuable for assessing possible December surveys miss more than 1,000 seed-harvest events and 655 seed- long-term population trends breeding populations. caching events. because counts are conducted over large geographic areas • Nutcrackers move around Of nutcrackers captured in this study, we classified 20 and long time periods. a lot in search of cones; nutcrackers as residents and 21 as emigrants wintering their erratic movements on our study area. Among residents, 11 had home ranges Are Clark’s nutcrackers may artificially inflate or in whitebark pine stands and 9 had home ranges in considered an at-risk or deflate counts. ponderosa pine stands. sensitive species? • Counts rely on auditory The future of whitebark pine is of serious concern As of 2010, Clark’s or visual cues, but because of the species’ vulnerability to white pine blister nutcrackers were not nutcrackers are not rust, mountain pine beetle infestation, wildfires, and considered at-risk or sensitive territorial and, thus, are climate change. The Clark’s nutcracker is the primary by the U.S. Fish and Wildlife quiet and less noticeable means of whitebark pine seed dispersal. Service or by any state or during count periods; this province except Montana can result in inaccurately (because of concerns over low detection rates. habitat loss). The National Audubon Society and the • Nutcrackers occupy large IUCN rely on Breeding Bird home ranges, so even if Survey data (which show an nutcrackers are residents overall increase in nutcracker of a survey area, they may trends) and, consequently, not be present during a classify Clark’s nutcracker particular survey. as a species of least concern; they consider nutcracker populations stable or increasing. THE STUDY’S Clark’s nutcracker trap sites. FACT SHEET 6 of 8 David Herr LIKE CLARK’S nutcracker, the pinyon jay relies on pine seeds; however, pinyon jays are more easily monitored because they inhabit lowland areas frequented by humans. Survey data show that pinyon jay populations are rapidly declining, and they are considered an at-risk species in several western states (Balda 2002). These declines in pinyon jays suggest that we should look more closely at NUTCRACKERS ARE difficult to monitor because they occupy remote and rugged population trends in nutcrackers for terrain and they breed in late winter at a time when no surveys are being conducted. evidence of a decline. THESE FIVE nutcrackers were part of a larger flock of an estimated 1,000 birds that descended on our Washington study area to harvest ponderosa pine seeds in September 2009. Such flocks are wide-ranging and ever-changing, making monitoring efforts challenging at best. Nicholas Ernst Nicholas ARE CLARK’S nutcrackers declining? Many resource managers think so. However, a cursory look at survey data shows stable or increasing populations, with only a few regional and mostly non-significant declines. So, what if we take a THE MAP and bar graph below show trends in nutcracker abundance from 1966 through 2007 based closer look? on Breeding Bird Survey data. If we look just at regional trends by decade, we get a more sobering picture for Clark’s nutcrackers. As the bar graph shows, for the first 3 decades of surveys (1967–1997), population trends were strongly positive, with a couple of exceptions. However, in the last decade illustrated (1997–2007), all states and provinces within the range of whitebark pine show negative nutcracker population trends. This sudden switch ominously suggests recent population declines in nutcrackers that have not yet been detected in overall national trends. Is West Nile virus a threat to nutcracker populations? There are no published accounts of Clark’s nutcracker’s susceptibility to West Nile virus (WNv) or the effects of WNv on nutcracker populations, but the Clark’s nutcracker is listed as a carrier by the Centers for Disease Control. Since nutcrackers are corvids, and since corvids show high THIS GRAPH shows nutcracker detections from Christmas Bird Counts from 1938 to 2009. Based on these sources, nutcracker populations appear to be stable or increasing. mortality rates from WNv, we can assume that WNv is a threat to Clark’s nutcracker populations. However, evidence in other corvids suggests that populations can rebound from WNv-caused declines fairly rapidly. Habitat loss and declining cone production likely represent a larger threat to nutcracker populations. THE BOTTOM increasing detections of Monitoring nutcrackers: Farnsworth, G.L.; Pollock, LINE: MANAGER’S nutcrackers in late fall A cautionary note K.H. [et al.]. 2002. A removal PERSPECTIVE (October-November). Nutcrackers rely on method for estimating detection probabilities from What’s the best way to Improving on convention conifer cones, which are an point count surveys. Auk. 119: monitor nutcrackers? Counts should be long unpredictable and ephemeral food supply. As such, they 414-425. Conventional methods (minimum of 15–30 min for one transect or point count are exceptionally difficult Lorenz, T.J.; Sullivan, K.A. Two conventional methods to accurately monitor at 2010. Comparison of survey are used to monitor route, preferably 2+ hr) (Ralph et al. 1993). small scales because of methods for monitoring songbirds: their dramatic, irregular Clark’s nutcrackers and Walking transect • Survey large tracks of (“irruptive”) migrations—in predicting dispersal of surveys—observers walk a land (10-km transects) addition to the difficulties whitebark pine seeds. Journal predetermined distance and (Ralph et al. 1993). with monitoring protocols of Field Ornithology. 81: 430- record all birds heard and • Employ distance sampling mentioned earlier. Balda 441. seen along the way, useful for (Buckland et al. 2001) (2002) cogently summarized Ralph, C.J.; Geupel, G.R. species in open habitats. or time-to-detection the problem when describing [et al.]. 1993. Handbook of a monitoring program for the Point count surveys— methods (Farnsworth field methods for monitoring pinyon jay (a close relative of observers remain stationary et al. 2002) for more landbirds. Gen. Tech. Rep. Clark’s nutcracker): (multiple individual stations accurate estimates of PSW-GTR-144. Albany, along a single route) and density and detectability. “Conventional methods CA: U.S. Department of record birds within a • Conduct cone counts for censing . are doomed Agriculture, Forest Service, predetermined time interval, at the same sites as to fail because the birds Pacific Southwest Research useful for monitoring species nutcracker surveys have large home ranges, Station. 41 p. in forested habitats (Ralph et and weight counts by range widely throughout Breeding Bird Survey data. al. 1993). an estimate of cone these areas, and are always http://www.pwrc.usgs.gov/ united in a flock. .finding In conjunction with our production. BBS/. a flock is often like finding telemetry study, we monitored • Rely on long-term the proverbial needle in a Christmas Bird Count data. Clark’s nutcrackers at 8 sites (10+ years) changes in haystack.” http://www.audubon.org/ to determine the most cost- detection rates to assess Bird/cbc/. effective, accurate method changes in population FURTHER READING for monitoring populations. size. Balda, R.P. 2002. Pinyon jay FOR FURTHER We compared detection Collaborate with resource • (Gymnorhinus cyanocephalus). INFORMATION rates among 4 survey types: managers in other regions In: Poole, A.; Gill, F., eds. Carol Aubry transects, point counts, for a concerted, large- The birds of North America, Olympic National Forest driving surveys, and “playback scale, united monitoring no. 605. Washington, DC: 1835 Black Lake Blvd., Suite A point counts” (broadcasting program. nutcracker calls), and have the American Ornithologists’ Olympia, WA 98512 following recommendations: • Include lowland conifer Union. forests in surveys for Buckland, S.T.; Anderson, Phone: (360) 956-2361 • Either transects or point nutcrackers—in addition D.R.; [et al.]. 2001. Email: [email protected] counts could be used. to high-elevation Introduction to distance For monitoring local whitebark pine forests— • sampling. Oxford, UK: The USDA is an equal nutcracker populations, because, in many regions, opportunity provider and Oxford University Press. counts should be nutcrackers spend much employer.