Golden Eagle (Aquila chrysaetos) Management Indicator Species Assessment Ochoco National Forest

Transcription

1 Golden Eagle (Aquila chrysaetos) Management Indicator Species Assessment Ochoco National Forest I. Introduction The golden eagle was chosen as a terrestrial management indicator species (MIS) on the Ochoco National Forest (ONF) for cliff, talus or cave habitat (LRMP 4-245). II. Life History Species Distribution This species has a holartic distribution. In North America this species breeds from Alaska and Canada south to Central Mexico. In the U. S. it occurs primarily west of the east slope of the Rocky Mountains. In Oregon, golden eagles are common to uncommon year round residents in all counties east of the Cascade Range (Marshall, 2003). Figure 1. Golden Eagle Distribution in North America 1

2 On the Ochoco National Forest, including Crooked River National Grassland, there are historic records for 147 nesting sites. Of those, only 12 occur in Crook County. The majority of the rest are associated with extensive rimrock habitat present in Jefferson County. Habitat Characteristics The Golden Eagle inhabits shrub-steppe, grassland, juniper, and open ponderosa pine, and mixed conifer/deciduous habitats. It forages in a variety of habitat types and successional stages, preferring areas with an open shrub component that provides food and cover for prey. Suitable nesting and foraging habitat can be found in mountains, canyons, and rolling hills. Of 506 occupied nests in 1982, 35% were in mature trees and 65% on ledges along rims and cliffs (Isaacs and Opp 1991). Nest trees are typically large live ponderosa pine with sturdy open branching and a trunk dbh >30 in. Golden Eagles have large breeding territories ranging square miles. Nest territories may contain several alternate nests. Forage on a variety of prey species including: jackrabbit, cottontail, California and Belding s ground squirrels, marmots, woodrats, small mammals, fresh carrion, and a variety of bird species (Marshall 2003). Threats to the Species Historically golden eagles have been impacted by persecution and poisoning associated with predator control. However, with current protection under federal law, changes in public perspective, and with restrictions on certain poisons and improved methods of controlling non-target poisoning, there may be less impact from intentional and unintentional killing of this species than there was historically. However this species is very sensitive to disturbance during the nesting season and nest failures or abandonment due to human disturbance can be an issue, especially in areas being developed or locations with high recreational use early in the nesting season. Low altitude aircraft and disturbance from blasting may impact nesting success. Reduced prey abundance (jack rabbit populations) due to habitat alteration and agricultural practices may also impact golden eagles (Marshall, 2003). III. Conservation Status The conservation status of a species is an indicator of the likelihood of that species continuing to survive either in the present day or the future. Many factors are taken into account when assessing the conservation status of a species: not simply the number remaining, but the overall increase or decrease in the population over time, breeding success rates, known threats, and others. The conservation status of the golden eagle was identified at the global, national, and state of Oregon geographical areas by NatureServe; by listing status from Federal and State Threatened and Endangered Species lists and Sensitive Species lists; by the U.S. Fish and Wildlife Service Birds of Conservation 2

3 Concern; by the Oregon Conservation Strategy; and by the Partners in Flight bird conservation strategy - Conservation Strategy for Landbirds in the Northern Rocky Mountains of Oregon and Washington. NatureServe is a non-profit organization based in Arlington, Virginia that provides scientific information about rare and endangered species and threatened ecosystems. The information provided is based on biological inventories or natural heritage programs that operate in all 50 U.S. states, Canada, Latin America and Caribbean. NatureServe information and products are available to conservation groups, government agencies, academia, corporations, and the public. The U.S. Fish and Wildlife Service maintain a list of Birds of Conservation Concern. Birds of Conservation Concern are species, subspecies, and populations of all migratory nongame birds that, without additional conservation actions, are likely to become candidates for listing under the Endangered Species Act (ESA) of They represent species that have the highest conservation priorities in the United States, including island "territories" in the Pacific and Caribbean. The Oregon Conservation Strategy (Oregon Department of Fish and Wildlife 2006) identified strategy habitats and strategy species by conservation region (i.e. Blue Mountains eco-region). The Partners in Flight bird conservation plans identify priority habitats and species (focal species) that represent priority habitats within bird conservation regions (BCR). The Blue Mountains and WWNF are within the Northern Rockies BCR (BCR 10) which is addressed by the Conservation Strategy for Landbirds in the Northern Rocky Mountains of Eastern Oregon and Washington. Table 5. Conservation Status of the Golden Eagle. NatureServe Status Federal Status State Status Other Global Status *G5 Secure Widespread, abunda nt, secure National Status State Status Federally Listed, Proposed, Candidate, Delisted Species and Species of Concern N5B,N5N-- Securebreeding, Securenonbreedin g S4-- Apparen tly Secure Not listed Species of concern Regional Forester s Sensitive Species USFWS Birds of Conserv ation Concern Threatened, Endangered, and Candidate Fish and Wildlife Species in Oregon ODFW Sensitive Species List (2008) Not listed. Yes Not listed. **Vulner -able Oregon Conservation Strategy Not a Strategy Species in the Blue Mountains Eco-region. * NatureServe conservation status ranks are based on a one to five scale, ranging from critically imperiled (G1) to demonstrably secure (G5). Status is assessed and documented at three distinct geographic scales-global (G), national (N), and state/province (S). The numbers have the following meaning: Conservation Strategy for Landbirds in the Northern Rocky Mountains of Oregon and Washington Not a focal species. 3

4 1 = critically imperiled 2 = imperiled 3 = vulnerable 4 = apparently secure 5 = secure. **The Oregon Department of Fish and Wildlife Sensitive Species List status of Vulnerable signifies that the species are facing one or more threats to their populations and/or habitats. Vulnerable species are not currently imperiled with extirpation from a specific geographic area or the state but could become so with continued or increased threats to populations and/or habitats. Golden eagles are not listed as Threatened, Endangered or Sensitive Species. They are listed as a Bird of Conservation Concern by the USFWS, though they are listed as secure globally and nationally, and as apparently secure in the State of Oregon. They are not listed as a Strategy Species for the Blue Mountains Ecoregion in ODFW s Oregon Conservation Strategy, nor are they listed as a focal species in the Landbird Conservation Strategy for the Blue Mountains (Partners in Flight). Provisions of the bald eagle protection act were extended to the golden eagle in Central Oregon Counties (Deschutes, Jefferson, Crook and Wasco) have adopted ordinances to protect golden eagle nest sites on privately owned land. On lands under State or Federal Management regulations are in place to protect nest sites. IV. Population Trend The population trend in Oregon is unknown. In 2011 a state-wide effort is underway to determine the status of approximately 500 historic nesting territories across the State of Oregon. Golden Eagles counted during the mid-winter Bald Eagle survey in Oregon for have varied from 79 to 128 and averaged 97 (Isaacs 2001). The populations of resident golden eagles in the northern part of the Great Basin, particularly in Idaho and Northern Utah, have shown indications of a decline (Marshall, 2003). V. Habitat Analysis As noted above 65% of occupied nests studied by Isaacs and Opp in 1982 were on rock ledges. A forestlevel analysis was conducted in 2011 using updated GIS data on rock features. The output from this analysis reflects the majority of rock features with potential nesting habitat. Rock features identified in the GIS data are those that are of sufficient size to be detected from aerial photographs. The rock categories included in estimating potential nesting habitat for this species included the following: rimrock, rock, rock/limestone, rocky knob, talus, talus/rocky knob, talus/rimrock. The GIS data layer is estimated to be 80% accurate in detecting rock features with cliff faces that have any potential as nesting sites. Some small cliffs may have been overlooked in the aerial photo interpretation, and some rock features identified as potentially having cliff habitat, may not be suitable for nesting sites. However, this data is expected to be representative of the majority of suitable nesting substrate and of 4

5 sufficient accuracy for a comparison of potential rock habitat within the project area and across the landscape at a forest-wide scale. From this analysis it was estimated that at the forest level there are approximately 18,838 acres of potential cliff nesting habitat. There are a total of 34 watersheds (5 th field HUC) on Ochoco National Forest. Potential cliff nesting habitat for is distributed within all 34 of these watersheds, though some watersheds (Crooked River Grassland, Headwaters Deschutes River, Lake Billy Chinook, Lower Metolius River and Willow Creek) have substantially more cliff habitat than other watersheds across the Forest. Golden eagle nests that are not on cliffs are typically on large ponderosa pine trees or snags in open stands, or on scattered individual large pine trees in otherwise open habitat such as rocky canyons, shrub/steppe or grassland settings. These individual scattered pines may occur in a variety of plant associations including juniper woodland, juniper steppe or xeric ponderosa pine. 5