Movements by animals can serve different functions and occur over a varietyof spatial and temporal scales. Routine movement types, such as residency(localized movements) and migration, have been well studied. However, non-routine movement types, such as dispersal, prospecting, and nomadism, areless well understood. Documenting these rarely detected events requires track-ing large numbers of individuals across all age classes. We studied >500 goldeneagles (Aquila chrysaetos) tracked by telemetry over a 10-year period in west-ern North America, of which 160 engaged in nonroutine, long-distance(>300 km) movements. We identified spatial and temporal correlates of thosemovements at both small and large scales, and we quantified movementtiming and direction. We further tested which age and sex classes of eagleswere more likely to engage in these movements. Our analysis of 88,093 dailytracks suggested that distances traveled by eagles were responsive to theupdraft potential of the spatial and temporal landscape they encountered.Tracks covered longer distances at locations and times of higher updraft poten-tial, and older birds traveled farther than younger birds. By contrast, afterdecomposing daily tracks into 563 nonroutine, long-distance movementsmeasured at a multiday scale, only the duration of travel was responsive toenvironmental conditions encountered by eagles. Multiday trips that werelonger were those initiated in open and warm landscapes and those that endedin mountainous regions. Finally, long-distance movements were morefrequently made in seasons other than winter, in north–south directions, andby young birds. We documented clear correlates of nonroutine, long-distancemovements by golden eagles at small, local scales but found little evidence ofsuch correlates at larger, regional scales. Most long-distance movements we documented fit patterns associated with traditional definitions of prospectingand nomadism but not migration. Our study is the first to describe these move-ment types by golden eagles, and as such provides a foundation for subsequentstudy into the movement ecology of other species.
An animal's movement is expected to be governed by an interplay between goals determined by its internal state and energetic costs associated with navigating through the external environment. Understanding this ecological process is challenging when an animal moves in two dimensions and even more difficult for birds that move in a third dimension. To understand the dynamic interaction between the internal state of an animal and the variable external environment, we evaluated hypotheses explaining association of different covariates of movement and the trade-offs birds face as they make behavioural decisions in a fluctuating landscape. We used ~870 000 GPS telemetry data points collected from 68 Golden Eagles Aquila chrysaetos to test demographic, diel, topographic and meteorological hypotheses to determine (1) the probability that these birds would be in motion and (2), once in motion, their flight speed. A complex and sometimes interacting set of potential internal and external factors determined movement behaviour. There was good evidence that reproductive state, manifested as age, sex and seasonal effects, had a significant influence on the probability of being in motion and, to a lesser extent, on speed of motion. Likewise, movement responses to the external environment were often unexpectedly strong. These responses, to northness of slope, strength of orographic updraft and intensity of solar radiation, were regionally and temporally variable. In contrast to previous work showing the role of a single environmental factor in determining movement decisions, our analyses support the hypothesis that multiple factors simultaneously interact to influence animal movement. In particular they highlighted how movement is influenced by the interaction between the individual's internal reproductive state and the external environment, and that, of the environmental factors, topographic influences are often more relevant than meteorological influences in determining patterns of flight behaviour. Further disentangling of how these internal and externals states jointly affect movement will provide additional insights into the energetic costs of movement and benefits associated with achieving process-driven goals.
Molecular markers can reveal interesting aspects
of organismal ecology and evolution, especially when
surveyed in rare or elusive species. Herein, we provide a
preliminary assessment of golden eagle (Aquila chrysaetos)
population structure in North America using novel single
nucleotide polymorphisms (SNPs). These SNPs included
one molecular sexing marker, two mitochondrial markers,
85 putatively neutral markers that were derived from
noncoding regions within large intergenic intervals, and 74
putatively nonneutral markers found in or very near protein-coding genes. We genotyped 523 eagle samples at
these 162 SNPs and quantified genotyping error rates and
variability at each marker. Our samples corresponded to
344 individual golden eagles as assessed by unique multilocus genotypes. Observed heterozygosity of known
adults was significantly higher than of chicks, as was the
number of heterozygous loci, indicating that mean zygosity
measured across all 159 autosomal markers was an indicator of fitness as it is associated with eagle survival to
adulthood. Finally, we used chick samples of known
provenance to test for population differentiation across
portions of North America and found pronounced structure
among geographic sampling sites. These data indicate that
cryptic genetic population structure is likely widespread in
the golden eagle gene pool, and that extensive field sampling and genotyping will be required to more clearly
delineate management units within North America and
elsewhere.
Bird movements vary spatially and temporally, but the primary drivers that explain such variation can be difficult to identify. For example, it is well known that the availability of updraft influences soaring flight and that topography interacts with weather to produce these updrafts. However, the influences of topography on flight are not well understood. We determined how topographic characteristics influenced flight altitude above ground level (AGL) of a large soaring bird, the Golden Eagle (Aquila chrysaetos), over several regions within the State of California, USA. Primary drivers of flight AGL, those to which eagles showed the same response at all spatial scales, were topographic roughness, ground elevation and the east-west component of aspect (eastness). Each of these is related to formation of thermal updrafts. Secondary drivers, those to which eagles showed region-specific patterns, included topographic position, percent slope, and the north-south component of aspect (northness). In contrast to primary drivers, these secondary drivers were related to formation of both thermal and orographic updrafts. Overall, drivers of flight altitudes that were related to thermal updrafts showed different levels of complexity due to spatial and temporal variation of those drivers than did flight altitudes related to orographic updrafts.
Bird movements vary spatially and temporally, but the primary drivers that explain such variation can be difficult to identify. For example, it is well known that the availability of updraft influences soaring flight and that topography interacts with weather to produce these updrafts. However, the influences of topography on flight are not well understood. We determined how topographic characteristics influenced flight altitude above ground level (AGL) of a large soaring bird, the Golden Eagle (Aquila chrysaetos), over several regions within the State of California, USA. Primary drivers of flight AGL, those to which eagles showed the same response at all spatial scales, were topographic roughness, ground elevation and the east-west component of aspect (eastness). Each of these is related to formation of thermal updrafts. Secondary drivers, those to which eagles showed region-specific patterns, included topographic position, percent slope, and the north-south component of aspect (northness). In contrast to primary drivers, these secondary drivers were related to formation of both thermal and orographic updrafts. Overall, drivers of flight altitudes that were related to thermal updrafts showed different levels of complexity due to spatial and temporal variation of those drivers than did flight altitudes related to orographic updrafts.
A central theme for conservation is understanding how animals differentially use, and are affected by change in, the landscapes they inhabit. However, it has been challenging to develop conservation schemes for habitat-specific behaviors. Here we use behavioral change point analysis to identify behavioral states of golden eagles (Aquila chrysaetos) in the Sonoran and Mojave Deserts of the southwestern United States, and we identify, for each behavioral state, conservation-relevant habitat associations. We modeled behavior using 186,859 GPS points from 48 eagles and identified 2,851 distinct segments comprising four behavioral states. Altitude above ground level (AGL) best differentiated behavioral states, with two clusters of short-distance movement behaviors characterized by low AGL (state 1 AGLÂ =Â 14Â m (median); state 2 AGLÂ =Â 11Â m) and two associated with longer-distance movement behaviors and characterized by higher AGL (state 3 AGLÂ =Â 108Â m; state 4 AGLÂ =Â 450Â m). Behaviors such as perching and low-altitude hunting were associated with short-distance movements in updraft-poor environments, at higher elevations, and over steeper and more north-facing terrain. In contrast, medium-distance movements such as hunting and transiting were over gentle and south-facing slopes. Long-distance transiting occurred over the desert habitats that generate the best updraft. This information can guide management of this species, and our approach provides a template for behavior-specific habitat associations for other species of management concern.
In 2005, WRI and the United States Forest Service
(USFS), launched satellite telemetry to track the
movements of Golden Eagles in Southern California.
Since that time we have secured additional funding
and sponsors to broaden this research to also include
Golden Eagles from our banding stations in Montana.
All of the data is truly amazing and could not have
come at a better time. As you read this, maps are
being drawn with plans for wind and solar farms in
California, Baja, and all points north. It is critical
that these potential sites use the known migration,
hunting, and nesting patterns of the remaining Golden
Eagles. Only satellite data can scientifically prove
what areas the birds rely on to exist.
In conjunction with release of a final environmental assessment of this action, the U.S. Fish and Wildlife
Service (??we?? or ??the Service??) is finalizing permit regulations to authorize limited take of bald eagles
(Haliaeetus leucocephalus) and golden eagles (Aquila chrysaetos) under the Bald and Golden Eagle Protection Act (Eagle Act), where the take to be
authorized is associated with otherwise
lawful activities. These regulations also establish permit provisions for intentional take of eagle nests under particular, limited circumstances.
Recording for the May 26, 2021 SDMMP Mgmt. and Mon. Coordination Meeting. Robert Fisher (USGS) and Gonzalo de Leon-Giron share "Outcomes from Golden Eagle Research in Southern California and Northern Baja California"
Recording from the January 24, 2024 SDMMP Management and Monitoring Coordination Meeting. Presentation from Robert Fisher (USGS) on the Golden Eagle Management Plan update.
Beginning in 2014, the U.S. Geological Survey, in collaboration with Bloom Biological, Inc., began telemetry research on golden eagles (Aquila chrysaetos) captured in the San Diego, Orange, and western Riverside Counties of southern California. This work was supported by the San Diego Association of Governments, California Department of Fish and Wildlife, the U.S. Fish and Wildlife Service, the Bureau of Land Management, and the U.S. Geological Survey. Since 2014, we have tracked more than 40 eagles, although this report focuses only on San Diego County eagles. An important objective of this research is to develop habitat selection models for golden eagles. Here we provide predictions of population-level habitat selection for golden eagles in San Diego County based on environmental covariates related to land use and terrain.
Beginning in 2014, the U.S. Geological Survey, in collaboration with Bloom Biological, Inc.,
began telemetry research on golden eagles (Aquila chrysaetos) captured in the San Diego, Orange, and western Riverside Counties of southern California. This work was supported by the San Diego Association of Governments, California Department of Fish and Wildlife, the U.S. Fish and Wildlife Service, the Bureau of Land Management, and the U.S. Geological Survey. Since 2014, we have tracked more than 40 eagles, although this report focuses only on San Diego County eagles. An important objective of this research is to develop habitat selection models for golden eagles. Here we provide predictions of population-level habitat selection for golden eagles in San Diego County based on environmental covariates related to land use and terrain.
Golden Eagles are a top predator and, within the San Diego Multiple Species Conservation Plan (SD MSCP) area, have territories of 20 to 30 square miles. They have survived by nesting in the most remote parts of the county where they are subject to minimal human disturbance. After 22 years of consistent monitoring and historical data research, we estimate that 32 pairs formerly occupied the San Diego MSCP. Today 11 pairs are still active, 3 are inactive, and 18 pairs have been extirpated. Most of these extirpations occurred in the last 40 years. The 11 breeding pairs of Golden Eagles remaining in the SD MSCP represent 24% of all the breeding Golden Eagles remaining in San Diego County. Seven of the 11 remaining active pairs within the SD MSCP are in serious jeopardy of being extirpated in the next 5 to 10 years. The 3 pairs considered inactive are predicted to become extirpated and may, in fact, already have been lost.
As in 2005, WRI recommends the following for the SD MSCP: an annual survey of Golden Eagle breeding territories utilizing a cost-effective approach, using only properly trained and experienced observers for aerial monitoring from helicopters and ground surveys, where necessary; interpretation of the findings within the context of the long history of data that WRI has collected; and annual distribution of the monitoring results to all resource and planning agencies that have a "need to know" so that they may further protect nest sites. We also recommend the examination of proposed private and public land-use changes and human activities for their impact on the remaining Golden Eagles, maintenance of the Golden Eagle Database at WRI, and the consideration of selectively re-introducing (hacking) young eagles into areas where extirpation has occurred but the cause of extirpation has essentially been removed and suitable habitat still exists.
Because of a lack of clarity about the status of golden eagles (Aquila chrysaetos) in coastal southern California, the U.S. Geological Survey, in collaboration with U.S. Fish and Wildlife Service, California Department of Fish and Wildlife, Bureau of Land Management, and San Diego Management and Monitoring Program, began a multi-year survey and tracking program of golden eagles to address questions regarding habitat use, movement behavior, nest occupancy, genetic population structure, and human impacts on eagles. Golden eagle trapping and tracking efforts began in September 2014. During trapping efforts from September 29, 2014, to February 23, 2017, 37 golden eagles were captured. During trapping efforts from February 24, 2017, to December 2, 2019, an additional 7 golden eagles (4 females and 3 males) were captured, and one previously captured female was recaptured in San Diego County. Biotelemetry data for 27 of the 44 golden eagles that were transmitting data from February 24, 2017, to December 2, 2019, are presented. These eagles ranged as far north as British Columbia, Canada, and as far south as Ciudad Insurgentes, Baja California, Mexico.
The status of golden eagles (Aquila chrysaetos) in coastal
southern California is unclear. To address this knowledge
gap, the U.S. Geological Survey (USGS) in collaboration
with local, State, and other Federal agencies began a multiyear
survey and tracking program of golden eagles to address
questions regarding habitat use, movement behavior, nest
occupancy, genetic population structure, and human impacts
on eagles. Golden eagle trapping and tracking efforts began in
October 2014 and continued until early March 2015. During
the first trapping season that focused on San Diego County,
we captured 13 golden eagles (8 females and 5 males). During
the second trapping season that began in November 2015, we
focused on trapping sites in San Diego, Orange, and western
Riverside Counties. By February 23, 2016, we captured an
additional 14 golden eagles (7 females and 7 males). In this
report, biotelemetry data were collected between November
22, 2014, and February 23, 2016. The location data for eagles
ranged as far north as San Luis Obispo, California, and as far
south as La Paz, Baja California, Mexico.
Because of a lack of clarity about the status of golden eagles (Aquila chrysaetos) in coastal southern California, the U.S. Geological Survey, in collaboration with U.S. Fish and Wildlife Service, California Department of Fish and Wildlife, Bureau of Land Management, and San Diego Management and Monitoring Program, began a multi-year survey and tracking program of golden eagles to address questions regarding habitat use, movement behavior, nest occupancy, genetic population structure, and human impacts on eagles. Golden eagle trapping and tracking efforts began in September 2014. During trapping efforts from September 29, 2014, to February 23, 2017, 37 golden eagles were captured. During trapping efforts from February 24, 2017, to December 2, 2019, an additional 7 golden eagles (4 females and 3 males) were captured, and one previously captured female was recaptured in San Diego County. Biotelemetry data for 27 of the 44 golden eagles that were transmitting data from February 24, 2017, to December 2, 2019, are presented. These eagles ranged as far north as British Columbia, Canada, and as far south as Ciudad Insurgentes, Baja California, Mexico.
The status of golden eagles (Aquila chrysaetos) in coastal southern California is unclear. To address this knowledge gap, the U.S. Geological Survey (USGS) in collaboration with local, State, and other Federal agencies began a multi-year survey and tracking program of golden eagles to address questions regarding habitat use, movement behavior, nest occupancy, genetic population structure, and human impacts on eagles. Golden eagle trapping and tracking efforts began in October 2014 and continued until early March 2015. During the first trapping season that focused on San Diego County, we captured 13 golden eagles (8 females and 5 males). During the second trapping season that began in November 2015, we focused on trapping sites in San Diego, Orange, and western Riverside Counties. By February 23, 2016, we captured an additional 14 golden eagles (7 females and 7 males). In this report, biotelemetry data were collected between November 22, 2014, and February 23, 2016. The location data for eagles ranged as far north as San Luis Obispo, California, and as far south as La Paz, Baja California, Mexico.
Because of a lack of clarity about the status of golden
eagles (Aquila chrysaetos) in coastal southern California, the
USGS, in collaboration with local, State, and other Federal
agencies, began a multi-year survey and tracking program
of golden eagles to address questions regarding habitat use,
movement behavior, nest occupancy, genetic population
structure, and human impacts on eagles. Golden eagle trapping
and tracking efforts began in September 2014. During
trapping efforts from September 29, 2014, to February 23,
2016, 27 golden eagles were captured. During trapping efforts
from February 24, 2016, to February 23, 2017, an additional
10 golden eagles (7 females and 3 males) were captured in San
Diego, Orange, and western Riverside Counties. Biotelemetry
data for 26 of the 37 golden eagles that were transmitting data
from February 24, 2016, to February 23, 2017 are presented.
These eagles ranged as far north as northern Nevada
and southern Wyoming, and as far south as La Paz, Baja
California, Mexico.
In 2018, the U.S. Geological Survey (USGS) published an Open-File Report (Tracey and others, 2018) presenting a Bayesian habitat selection model for golden eagles (Aquila chrysaetos) in San Diego County, California. The model used telemetry data to examine the effects of urban development, exurban development, and topography (characterized by a topographic position index and a vector ruggedness measure, TPI and VRM respectively) on golden eagle habitat selection probability. Based on figures 3 and 6 of Tracey and others (2018), we received inquiries from cooperators (U.S. Fish and Wildlife Service and California Department of Fish and Wildlife) about how the probability of eagle use declines with decreasing distance to the urban edge. Here, we clarify our results by addressing that question.
This biological resources report was prepared for the County of San Diego (County) in order to
provide information on baseline biological conditions prior to the Cedar Fire of 2003 and to assist in
the formation of Area Specific Management Directives (ASMDs) for the Barnett Ranch Open Space
Preserve (Preserve) on the approximately 728-acre Barnett Ranch located in the unincorporated
Ramona Community Planning Area of central San Diego County east of State Route (SR) 67 and
south of SR 78.
The project site supports 16 vegetation communities: southern coast live oak riparian forest, southern
willow scrub, freshwater seep, riparian scrub, open water, open Engelmann oak woodland, coast live
oak woodland, wildflower field, Diegan coastal sage scrub (including disturbed), coastal sage-chaparral
scrub, southern mixed chaparral, non-native grassland, eucalyptus woodland, extensive agriculture,
disturbed habitat, and developed land.
No federally or state listed threatened or endangered plant species were observed on site; however,
one plant species of federal special concern was observed: felt-leaved monardella (Monardella hypoleuca
ssp. lanata). In addition, four plant species recognized as sensitive by the California Native Plant
Society and/or the County were observed: delicate clarkia (Clarkia delicata), San Diego County
viguiera (Viguiera laciniata), Engelmann oak (Quercus engelmannii), and ashy-spike moss (Selaginella
cinerascens).
No animal species listed as threatened or endangered by the U.S. Fish and Wildlife Service (USFWS)
or California Department of Fish and Game were observed on the site; however, 10 animals observed
on site are federal species of concern: orange-throated whiptail (Cnemidophorus hyperythrus beldingi),
coastal whiptail (Cnemidophorus tigris stejnegeri), coastal rosy boa (Lichanura trivirgata roseofusca),
southern California rufous-crowned sparrow (Aimophila ruficeps canescens), loggerhead shrike (Lanius
ludovicianus), California thrasher (Toxostoma redivivum), white-tailed kite (Elanus leucurus), Costa's
hummingbird (Calypte costae), lark sparrow (Chondestes grammacus), and Pacific slope flycatcher
(Empidonax difficilis). Ten animals observed on site are California species of special concern: silvery
legless lizard (Anniella pulchra pulchra), prairie falcon (Falco mexicanus), northern red-diamond
rattlesnake (Crotalus exsul), golden eagle (Aquila chrysaetos), Cooper's hawk (Accipiter cooperi), sharpshinned
A 3-year raptor study was initiated by the County of San Diego Department of Parks and Recreation (DPR) to collect baseline information on eagle and other raptor activity at the Preserve. Raptor foraging surveys and golden eagle nest monitoring was conducted by AECOM at the Preserve from September 2013 through August 2014 on behalf of the County DPR. AECOM worked in partnership with the U.S. Fish and Wildlife Service to complete these surveys. This report summarizes the results of Year 1 (September 2013 through August 2014) of the 3-year study. AECOM will continue surveys for Year 2 and Year 3.
Monitoring of raptors is a critical component of the MSCP. This project, specifically, addresses
monitoring the raptor species identified as target species for MSCP monitoring with one
exception--the Burrowing Owl (BO; Athene cunicularia hypugaea). In addition to the
Burrowing Owl, the MSCP Biological Monitoring Plan (Ogden, 1996) identified the following
raptor species (hereafter referred to as the “target” species) to be monitored: Golden Eagle (GE;
Aquila chrysaetos), Bald Eagle (BE; Haliaeetus leucocephalus), Peregrine Falcon (PF; Falco
peregrinus), Northern Harrier (NH; Circus cyaneus), Ferruginous Hawk (FH; Buteo regalis),
Swainson’s Hawk (SH; Buteo swainsoni), and Cooper’s Hawk (CH; Accipiter cooperii). Prior to
the subject work, no comprehensive study had been conducted for any of these species, within
the geographical limits of the MSCP.
The original project objectives (taken from the contract's scope of work) are as follows:
-Determine where breeding and wintering individuals (of the target species) are located within the study areas.
-Wherever possible, document the breeding success of active pairs.
-Characterize situations of both successful and less successful or unsuccessful habitat.
-Identify, modify, or create, if necessary, survey raptor monitoring methods, based on scientific principles that would be appropriate to meet the objectives of the MSCP Monitoring Plan.
-Identify management, including research, needs and enhancement opportunities.