Unmanned aircraft systems enable three-dimensional viewshed-based assessment of potential disturbance to nesting raptors by recreational rock climbing

Abstract

Unmanned aircraft systems (UAS) can be safer, less expensive, and less labor intensive than manned aircraft in wildlife conservation programs. Consequently, the use of UAS is increasing, but other than installation of line markers to reduce avian collision with power lines, UAS approaches generally involve passive observations. We wondered if UAS could more actively help guide conservation decision-making, so we used UAS-sourced photographs to create 3D models of cliffs to conduct viewshed-based assessments of potential disturbance to nesting raptors by recreational rock climbing. At Cathedral Spires Park and Clear Creek Canyon Park in Jefferson County, Colo., we collected 4790 photographs from which we constructed 3D models. We identified climbing routes and climbing areas with potential to disturb nesting Peregrine Falcons (Falco peregrinus) and Golden Eagles (Aquila chrysaetos). Our findings were useful in providing Jefferson County Open Space (JCOS) with quantitative data so that informed defensible resource management decisions could be made. This project provides an example of how UAS can be used to actively create products useful in wildlife conservation and management and, given the widespread and increasing popularity of rock climbing globally, likely can be generalized to other areas worldwide where rock climbers and nesting raptors share cliffs.

Full text

ARTICLE
Unmanned aircraft systems enable
three-dimensional viewshed-based assessment of
potential disturbance to nesting raptors by
recreational rock climbing
James F. Dwyer, Daryl D. Austin, and Chelsea Beebe
Abstract: Unmanned aircraft systems (UAS) can be safer, less expensive, and less labor
intensive than manned aircraft in wildlife conservation programs. Consequently, the use
of UAS is increasing, but other than installation of line markers to reduce avian collision
with power lines, UAS approaches generally involve passive observations. We wondered if
UAS could more actively help guide conservation decision-making, so we used UAS-sourced
photographs to create 3D models of cliffs to conduct viewshed-based assessments of poten-
tial disturbance to nesting raptors by recreational rock climbing. At Cathedral Spires Park
and Clear Creek Canyon Park in Jefferson County, Colo., we collected 4790 photographs
from which we constructed 3D models. We identified climbing routes and climbing areas
with potential to disturb nesting Peregrine Falcons (Falco peregrinus) and Golden Eagles
(Aquila chrysaetos). Our findings were useful in providing Jefferson County Open Space
(JCOS) with quantitative data so that informed defensible resource management decisions
could be made. This project provides an example of how UAS can be used to actively create
products useful in wildlife conservation and management and, given the widespread and
increasing popularity of rock climbing globally, likely can be generalized to other areas
worldwide where rock climbers and nesting raptors share cliffs.
Key words: UAS, Aquila chrysaetos,Falco peregrinus, Golden Eagle, Peregrine Falcon.
Résumé : Les systèmes aériens sans pilote (UAS) peuvent être plus sécuritaires, moins
coûteux et nécessiter moins de main-d’œuvre que les aéronefs pilotés dans les programmes
de conservation de la faune. Par conséquent, l’utilisation d’UAS augmente, mais à part l’in-
stallation de marqueurs de ligne pour réduire les collisions aviaires avec les lignes
électriques, les approches utilisant les UAS impliquent généralement des observations pas-
sives. Nous nous demandions si les UAS pourraient aider plus activement à guider la prise
de décisions en matière de conservation, alors nous avons utilisé des photographies prove-
nant d’UAS pour créer des modèles 3D de falaises afin de réaliser des évaluations, selon le
cône visuel, de la perturbation potentielle causée aux oiseaux nicheurs par l’escalade de
rochers à des fins récréatives. À Cathedral Spires Park et Clear Creek Canyon Park dans le
comté de Jefferson, Colorado, nous avons recueilli 4790 photographies à partir desquelles
nous avons construit des modèles 3D. Nous avons déterminé des voies d’escalade et des
zones d’escalade susceptibles de perturber les faucons pèlerins (Falco peregrinus) et les aigles
royaux (Aquila chrysaetos). Nos constatations ont fourni des données quantitatives à Jefferson
County Open Space (JCOS) permettant de prendre des décisions éclairées et défendables en
matière de gestion des ressources. Ce projet donne un exemple de la façon dont les UAS
Received 24 July 2019. Accepted 15 October 2019.
J.F. Dwyer and D.D. Austin. EDM International, Inc., 4001 Automation Way, Fort Collins, CO 80525, USA.
C. Beebe. Jefferson County Open Space, 700 Jefferson County Parkway, Suite 100, Golden, CO 80401, USA.
Corresponding author: James F. Dwyer (e-mail: jdwyer@edmlink.com).
Copyright remains with the author(s) or their institution(s). Permission for reuse (free in most cases) can be obtained from
RightsLink.
Pagination not final (cite DOI) / Pagination provisoire (citer le DOI)
1
J. Unmanned Veh. Syst. 00: 1–8 (0000) dx.doi.org/10.1139/juvs-2019-0014 Published at www.nrcresearchpress.com/juvs on 28 October 2019.
J. Unmanned Veh. Sys. Downloaded from www.nrcresearchpress.com by VIRGINIA POLYTECHNIC INST on 01/13/20
For personal use only.

peuvent être utilisés pour activement créer des produits servant à la conservation et à la ges-
tion de la faune et, compte tenu de la popularité généralisée et croissante de l’escalade
rocheuseàl’échelle mondiale, qui peuvent probablement être généralisés à d’autres
régions du monde où les grimpeurs et les rapaces nicheurs partagent des falaises. [Traduit
par la Rédaction]
Mots-clés : système aérien sans pilote (UAS), Aquila chrysaetos,Falco peregrinus, aigle royal, faucon
pèlerin.
Introduction
Unmanned aircraft systems (UAS) are increasingly being used in wildlife research and
conservation because UAS can be safer, less expensive, and less labor intensive than the
manned aircraft traditionally used in aerial wildlife surveys (McEvoy et al. 2016;Wich and
Pin Koh 2018). UAS can also be more efficient in accessing difficult terrain than researchers
on foot, and UAS-sourced counts can be more accurate and less disturbing to wildlife than
traditional ground-based counts (Sardà-Palomera et al. 2012;ChabotandBird2015). This
combination of features has led to a proliferation of UAS data collection on projects lacking
the financial resources needed for manned aircraft. For example, Bushaw et al. (2019) used
UAS to detect nocturnally active terrestrial mammalian mesocarnivores, and Hodgson et al.
(2013) used UAS to survey dugongs (Dugong dugon). In avian research, UAS have been used for
counting colonial nesting birds (Chabot and Bird 2012;Goebel et al. 2015), and for counting
and identifying waterfowl (Drever et al. 2015;McEvoy et al. 2016). UAS equipped with ther-
mal sensors may even be useful in identifying the cryptic nests of grassland birds; a task
typically accomplished with labor intensive, time intensive, and potentially damaging rope
dragging techniques (Fondell et al. 2000).
UAS may be particularly useful in studying raptors, whose nests are often high and inac-
cessible, limiting researchers’ability to efficiently quantify nest contents. For example,
Dwyer and Tincher (2018) used UAS to assess and quantify risk of entanglement in synthetic
baling twine in osprey (Pandion haliaetus) nests. The usefulness of UAS in quickly and effi-
ciently surveying raptor nests (Junda et al. 2015,2016) is positive, but passive. That is, the
UAS is simply a flying camera used to identify occupancy, productivity, or a potential dan-
ger, but not to actively resolve conservation concerns or potential dangers in any way. In
contrast, UAS can also be used to install devices on power lines that are intended to increase
the visibility of power lines to birds and thereby reduce bird collisions (Lobermeier et al.
2015;Dwyer et al. 2019). This approach actively involves UAS in a conservation action. We
wondered whether UAS may be useful in other missions with more immediate conserva-
tion implications, such as providing three-dimensional (3D) viewshed analyses of cliffs used
by nesting raptors and by recreational rock climbers, to identify climbing routes with the
potential to disturb nesting raptors.
Rock climbing can be correlated with variation in cliff bird communities (Camp and
Knight 1998;Covey et al. 2019), and even with raptor nest failures (Brambilla et al. 2004).
Along the Colorado Front Range west of Denver, Colo., Jefferson County Open Space
(JCOS) owns and manages numerous cliffs where recreational rock climbing and nesting
raptors coexist. However, as the popularity of the sport and the number of visitors to
JCOS parks grows, the potential exists for recreational rock climbing to have a negative
effect on the success of nesting raptors. Nesting raptors potentially vulnerable to disturb-
ance on cliffs managed by JCOS include Golden Eagles (Aquila chrysaetos)andPeregrine
Falcons (Falco peregrinus). Both of these species are protected by the Migratory Bird Treaty
Act (MBTA; 16 U.S. Code 703-712), and eagles are also protected by the Bald and Golden
Eagle Protection Act (BGEPA; 16 U.S. Code 668-668d). These acts define pathways for federal
Pagination not final (cite DOI) / Pagination provisoire (citer le DOI)
2 J. Unmanned Veh. Syst. Vol. 00, 0000
Published by NRC Research Press
J. Unmanned Veh. Sys. Downloaded from www.nrcresearchpress.com by VIRGINIA POLYTECHNIC INST on 01/13/20
For personal use only.

prosecution if active raptor nests (nests containing eggs or young) are disturbed, including
fines and jail time. To minimize the potential for rock climbing to disturb nesting raptors,
JCOS enforces seasonal closures of specific climbing areas. These closures are in effect only
from 1 February or 1 March, depending on the nesting species, through 31 July. JCOS balan-
ces the needs of the raptor population and the desires of the recreational rock-climbing
community using the best available research. Closure areas are based on established buffer
distance guidelines recommended by numerous state and federal agencies for protecting
nesting raptors from human disturbance (C. Beebe, unpublished data, 2018). With contin-
ued pressure to expand access for rock climbing, JCOS sought objective data to help refine
closures and make data-driven decisions regarding rock climbing.
We wondered if we could quantify potential disturbance by constructing 3D models of
two climbing areas and conducting viewshed analyses within those models. To do so, we
used UAS to make highly detailed, spatially accurate, full-color, 3D models of cliffs used
by nesting raptors and by recreational rock climbers. Because this project was purely meth-
odological, instead of a hypothesis-driven approach, we sought to identify whether we
could place ourselves virtually within raptor nest locations to evaluate the viewshed from
those nests as pertains to nearby rock-climbing areas.
Methods
After raptors nesting in the area had fledged young and dispersed from nesting territories
(C. Beebe, unpublished data, 2018), we conducted three UAS missions; one each on 8 August,
9 August, and 27 September 2018 (Table 1). We conducted each mission with a team of two
UAS pilots and two JCOS biologists. The pilots were certificated in accordance with the
Federal Aviation Administration’s (FAA) Code of Federal Regulations (CFR) Part §107 Small
Unmanned Aircraft Systems (FAA 2018), and were tasked with flying the UAS and monitoring
its approach distance to cliffs in light of strong gusty winds along the cliff faces. The JCOS
biologists had participated in or supervised monitoring in 2018 of the raptor nests used as
focal points for viewshed analyses, and were tasked with monitoring the cliff and nearby
airspace for raptors that might be disturbed by or approach the UAS.
We conducted two of the missions at JCOS’s Cathedral Spires Park. Cathedral Spires Park
contains granite cliffs and spires up to 150 m tall, projecting from the top of a 472 m tall
mountain in southern Jefferson County (UTM location: 13S 477774 m E, 4363639 m N)
approximately 40 km southwest of Denver, Colo., USA. Within Cathedral Spires Park,
climbing areas include Cynical Pinnacle, Sunshine Wall, and Block Tower (Haas et al.
2012). Other than foot trails and climbing routes, the area is undeveloped and characterized
by a coniferous mountain forest overlooking the North Fork of the South Platte
River, which is paralleled by a low-traffic paved mountain road. We conducted the third
mission at Highlander Crag and New River Wall in JCOS’s Clear Creek Canyon Park.
Highlander Crag is a granite cliff 149 m tall, approximately a third of the way up a 515 m
canyon in west-central Jefferson County (UTM location: 13S 472740 m E, 4398889 m N).
The New River Wall bouldering area is located at the base of the canyon wall containing
Highlander Crag and is immediately adjacent to a high-traffic two-lane paved road along
Clear Creek. The road connects Golden, Colo. to the east with Interstate 70 to the west.
Otherwise, the area is undeveloped except for foot trails and climbing routes and is charac-
terized by evergreen coniferous mountain forests.
Each mission consisted of approximately 4 h of UAS flight time with a DJI Phantom 4 Pro+
(Dà-Jiāng Innovations Science and Technology Co., Ltd., Shenzen, China). During each mis-
sion, we conducted an initial flight approximately 30 m above the base of the cliff and
5–15 m from the face of the cliff, depending on turbulence along the cliff face. We flew hori-
zontally parallel to the face of the cliff with the UAS camera pointing directly downward (90°)
Pagination not final (cite DOI) / Pagination provisoire (citer le DOI)
Dwyer et al. 3
Published by NRC Research Press
J. Unmanned Veh. Sys. Downloaded from www.nrcresearchpress.com by VIRGINIA POLYTECHNIC INST on 01/13/20
For personal use only.

and collected a photo approximately every 10 m. We then flew horizontally parallel to the
cliffintheoppositedirectionwiththeUAScamerapointingslightlytowardthecliff
(approximately 60°), again collecting a photo approximately every 10 m. Following the
initial flight, we flew additional flights using the same methodology in 30 m increments
(30 m above the base of the cliff, 60 m above the base, 90 m above, etc.) until the UAS
was approximately 30 m above the top of the cliff where we flew a grid of transects over
the top of the cliff. This approach resulted in numerous photos of all parts of each cliff
from multiple angles and heights, allowing construction of highly detailed spatially
accurate 3D models.
We used Pix4D (Lausanne, Switzerland) software to assemble UAS imagery into a 3D
model using an image stitching process called structure-from-motion (SFM; Pix4D 2018).
The SFM process uses numerous photos of the same subject taken from many different alti-
tudes and angles to infer 3D relationships between the various parts of the subject. After
each cliff was modeled, we completed a viewshed analysis by using tools within Pix4D to
overlay climbing routes and climbing areas on the 3D models, and to measure heights,
angles, and distances from raptor nests to climbing routes at Cathedral Spires Park and to
climbing areas at Highlander Crag.
Results
We were successful in collecting sufficient imagery (4790 images total) to create 3D
models of each of the sites we visited, and we did not observe any raptors in the area during
our missions. At Cathedral Spires Park, one Peregrine Falcon nest was present on Cynical
Pinnacle, where one rock climbing route, “Don’t Fear the Boogie”(Haas et al. 2012), passed
directly over the ledge where Peregrine Falcons nested (Fig. 1a). Another rock-climbing
route, “Choslandia Project”(Haas et al. 2012), passed between the nest and a roost site
25 m to the east that had been identified previously by JCOS (C. Beebe, unpublished data,
2018). Choslandia Project passed within 20 m of the Peregrine Falcon nest, and was visible
from the nest. Viewshed analyses indicated that these were the only two climbing routes
visible from the nest. Routes further to the west were blocked from view by outward bulges
of intervening rock (Fig. 1b) even though all climbing routes assessed were parallel to one
another on a south-facing cliff. No other climbing areas at Cathedral Spires (Sunshine
Wall, Block Tower, etc.) were visible from the nest.
At Highlander Crag, no climbing routes ascended the cliff used by nesting Golden Eagles
where four nests were present adjacent to one another (Figs. 1cand 1d). These nests were at
the same elevation as the base of the Highlander Crag cliff but were 310 m across Clear
Creek Canyon from the nest cliff. The north-northeast-facing nest cliff faced slightly away
from the climbing routes on Highlander Crag, which was situated to the north-northwest,
and the mostly southwest-facing Highlander Crag faced away from the nest cliff.
Viewshed analyses indicated that the Highlander Crag cliff was within sight of the Golden
Eagle nests, though some of the climbing routes on Highlander Crag were blocked from
view by the angles of the two cliff faces. Portions of the New River Wall area were also
Table 1. Dates, locations, and number of UAS photos taken during missions to collect data used
in constructing 3D models of cliffs where the potential existed for conflict between recreational
rock climbers and nesting raptors.
Date Mission location No. photos
8 August 2018 Cynical Pinnacle in Cathedral Spires Park 1380
9 August 2018 Highlander Crag in Clear Creek Canyon Park 1520
27 September 2018 Sunshine Wall and Block Tower in Cathedral Spires Park 1890
Pagination not final (cite DOI) / Pagination provisoire (citer le DOI)
4 J. Unmanned Veh. Syst. Vol. 00, 0000
Published by NRC Research Press
J. Unmanned Veh. Sys. Downloaded from www.nrcresearchpress.com by VIRGINIA POLYTECHNIC INST on 01/13/20
For personal use only.

visible from the Golden Eagle nests; however, because New River Wall was steeply over-
hung (the top of the boulder cliff extends outward above the bottom where Clear Creek
undercut the rock), most of the climbing routes in the New River Wall area were obscured
by intervening rock.
Discussion
Joshua Tree National Park, Boulder County Open Space, and numerous other land
managers around the U.S., including JCOS, implement cliff-specific seasonal rock-climbing
closures to minimize potential disturbance by recreational rock climbers to nesting rap-
tors. Many of these closures are based on the best available research and local knowledge
of the resource. Camp and Knight (1998), working at climbing areas in Joshua Tree
National Park, and Covey et al. (2019), working at climbing areas around Boulder, Colo.,
each found that rock climbing correlated with differences in avian cliff communities, so
this intuition has some quantitative support, but additional analyses may further improve
support for climbing closures, or conversely, indicate that some closures may be unneces-
sary. The work described here can likely be generalized to other areas such as these where
rock climbers and nesting raptors share cliffs. Because rock climbing is practiced globally
and is increasing in popularity, the technique described herein may be increasingly useful
in managing or reducing impacts of climbing on raptors worldwide.
Fig. 1. 3D model of Cynical Pinnacle at Cathedral Spires Park in Jefferson County, Colo. Climbing routes are
indicated in red. Climbing routes with potential to disturb nesting raptors are indicated by thick red lines. Nests
are indicated in green. (a) Overview. The Block Tower climbing area is modeled in the background at left. (b) Top
down view. 3D model of Clear Creek Canyon where four Golden Eagle nests exist near two climbing areas:
(c) New River Wall climbing area and (d) Highlander Crag climbing area. Yellow arrows illustrate distances and
angles of separation between the eagle nests and the climbing areas.
Pagination not final (cite DOI) / Pagination provisoire (citer le DOI)
Dwyer et al. 5
Published by NRC Research Press
J. Unmanned Veh. Sys. Downloaded from www.nrcresearchpress.com by VIRGINIA POLYTECHNIC INST on 01/13/20
For personal use only.

In this study, we leveraged UAS imagery to create 3D models of cliffs used by nesting
raptors and by recreational rock climbers. The results of this study directly impact climbing
management in Cathedral Spires Park and Clear Creek Canyon Park in two ways. First, at
Cathedral Spires Park, the seasonal closure remains in place because of the risk that climb-
ers in the area may inadvertently ascend or descend a climbing route that approaches the
Peregrine Falcon nest or a nearby roost site. However, a permitting request for a highline
submitted to JCOS was granted (C. Beebe, unpublished data, 2018; a highline is a type of
tightrope suspended between two prominent points, in this case Cathedral Spires and
nearby Block Tower). Permission was granted in part based on the viewshed analysis
described herein indicating that no portion of the highline would be visible from the
Peregrine Falcon nest, and in part because the highline would be installed and then
removed daily and activity was restricted to outside of the raptor breeding season.
At Clear Creek Canyon Park, our viewshed analyses indicated that climbing areas along
Clear Creek Canyon, including the New River Wall bouldering area were unlikely to be per-
ceived as a threat by nesting Golden Eagles, which nested 35 m above the New River Wall,
but climbers at Highlander Crag could be visible to nesting Golden Eagles. Consequently,
New River Wall is open year-round while Highlander Crag is closed seasonally (Fig. 2).
Fig. 2. Publicly available Jefferson County Open Space (JCOS) map of Clear Creek Canyon Park providing
geospatial information to recreational rock climbers on the seasonal closure intended to minimize disturbance
to nesting raptors at Highlander Crag climbing area. Reproduced with permission from JCOS (2017).
Pagination not final (cite DOI) / Pagination provisoire (citer le DOI)
6 J. Unmanned Veh. Syst. Vol. 00, 0000
Published by NRC Research Press
J. Unmanned Veh. Sys. Downloaded from www.nrcresearchpress.com by VIRGINIA POLYTECHNIC INST on 01/13/20
For personal use only.

Based on this work, and the direct management actions supported by this work, we con-
clude that the concept of using a UAS-sourced 3D model to conduct viewshed analyses of
raptor nests worked well. The 3D model and associated software also allowed for accurate
measurements of distance from nests to rock-climbing routes. We were able to identify
climbing routes and climbing areas that posed high potential for disturbance to nesting
raptors, and to identify mediating factors when disturbance issues may be less likely. It
would be interesting to compare nesting success with and without closures based on
UAS-derived viewshed analyses, but such comparisons were beyond the scope of this work.
Despite our successes, we were unable to fly as close to the cliff faces as we had intended
because of high winds, which, when they encounter a standing obstacle such as vertical rock
cliff, create potentially dangerous turbulence around the obstacle. This resulted in less fine-
scale detail in our 3D models than we had expected. Approaching a specific location was pos-
sible, however, so we were able to secure high-resolution photographs of nests. Use of a more
powerful UAS with a higher resolution camera and longer focal length lens, such as DJI’s
Matrice 210, would likely improve the products delivered by a UAS-based approach.
Additional research on the tolerance of disturbance at differing distances and angles will help
guide decisions for managing recreational rock climbing in nesting raptor areas.
We did not attempt to quantify noise associated with rock climbing. However, because
rock climbers can form large groups at the bases of cliffs, often call to one another while
climbing, and sometimes loudly express frustration or exuberance while climbing, there
is the potential for noise associated with climbing routes outside of the viewshed of a nest
to cause disturbance to that nest. Future work should quantify raptors’responses to noise
associated with climbing routes and use that quantification to refine the viewshed-based
assessment described here.
UAS missions can be effective if conducted responsibly, and to that end researchers have
begun exploring appropriate sizes, shapes, and configurations for aircraft, and appropriate
flight heights, velocities, directions, and boundaries to minimize disturbance to wildlife
(e.g., Drever et al. 2015;Junda et al. 2016;McEvoy et al. 2016;Wich and Pin Koh 2018). The
inverse is also true, with UAS-based projects having been proposed to explore the potential
for disturbance as an asset in managing vultures roosting at a power generation facility
(R.E. Harness and J.F. Dwyer, unpublished data, 2018), in hazing birds from crop fields
(Egan 2018;Wang et al. 2019), and at airports (Paranjape et al. 2018).
Though our results are positive, wildlife can show stress responses to UAS. For example,
black bears (Ursus americanus) respond with elevated heart rates even in the absence of
behavioral responses (Ditmer et al. 2015). The use of UAS around raptor nests could poten-
tially create hazardous conditions for raptors, the UAS aircraft, or people on the ground if
raptors physically contact the aircraft. Contact between a spinning rotor and a raptor’s
body may injure the bird involved and will very likely lead to loss of control of the aircraft.
If the aircraft crashes as a result, the aircraft is likely to be damaged or destroyed and there
is some risk that the aircraft could impact a person on the ground or create a dangerous
spark. To avoid disturbing nesting raptors, we conducted our study after young had fledged
and the adults had left the area. If surveying nest contents were also part of our mission, we
would have followed recommendations in Junda et al. (2015,2016) where raptor behaviors
in response to an approaching UAS are described.
Acknowledgements
We thank JCOS for financial support and for facilitating UAS missions necessary to con-
duct this work. We thank Drew Rayburn of JCOS for assisting us with the UAS missions
described herein, and for comments that improved this manuscript, and EDM
International Inc. for financial and material support.
Pagination not final (cite DOI) / Pagination provisoire (citer le DOI)
Dwyer et al. 7
Published by NRC Research Press
J. Unmanned Veh. Sys. Downloaded from www.nrcresearchpress.com by VIRGINIA POLYTECHNIC INST on 01/13/20
For personal use only.

References
Brambilla, M., Rubolini, D., and Guidali, F. 2004. Rock climbing and Raven Corvus corax occurrence depress breed-
ing success of cliff-nesting Peregrines Falco peregrinus. Ardeola, 51: 425–430.
Bushaw, J.D., Ringelman, K.M., and Rohwer, F.C. 2019. Applications of unmanned aerial vehicles to survey mesocar-
nivores. Drones, 3(1): 28. doi: 10.3390/drones3010028.
Camp, R.J., and Knight, R.L. 1998. Rock climbing and cliff bird communities at Joshua Tree National Park,
California. Wildl. Soc. Bull. 26: 892–898.
Chabot, D., and Bird, D.M. 2012. Evaluation of an off-the-shelf unmanned aircraft system for surveying flocks of
geese. Waterbirds, 35: 170–174. doi: 10.1675/063.035.0119.
Chabot, D., and Bird, D.M. 2015. Wildlife research and management methods in the 21st century: Where do
unmanned aircraft fit in? J. Unmanned Veh. Syst. 3: 137–155. doi: 10.1139/juvs-2015-0021.
Covey, N., Benedict, L., and Keeley, W.H. 2019. Rock climbing activity and physical habitat attributes impact avian
community diversity in cliff environments. PLoS ONE, 14(1): e0209557. doi: 10.1371/journal.pone.0209557.PMID:
30650086.
Ditmer, M.A., Vincent, J.B., Werden, L.K., Tanner, J.C., Laske, T.G., Iaizzo, P.A., et al. 2015. Bears show a physiological
but limited behavioral response to unmanned aerial vehicles. Curr. Biol. 25:2278–2283. doi: 10.1016/
j.cub.2015.07.024. PMID: 26279232.
Drever, M.C., Chabot, D., O’Hara, P.D., Thomas, J.D., Breault, A., and Millikin, R.L. 2015. Evaluation of an unmanned
rotorcraft to monitor wintering waterbirds and coastal habitats in British Columbia, Canada. J. Unmanned Veh.
Syst. 3: 256–267. doi: 10.1139/juvs-2015-0019.
Dwyer, J.F., and Tincher, M.C. 2018. Use of small unmanned aircraft systems (UAS) to assess and quantify risk of
entanglement in synthetic baling twine in Pandion haliaetus (Osprey) nests. Urban Nat. 17:1–6.
Dwyer, J.F., Collins, R.R., and Harness, R.E. 2019. Experimental small unmanned aircraft system (sUAS) field instal-
lation of line markers. Electric Power Research Institute, Palo Alto, Calif., USA.
Egan, C.C. 2018. Evaluating the potential utility of drones to deter birds from areas of human-wildlife conflict.
M.S. thesis, Departmentof Agriculture and Applied Science, NorthDakota State University, Fargo, N.D., USA. 93 pp.
Federal Aviation Administration (FAA). 2018. Unmanned aircraft systems (UAS). Available from https://www.faa.gov/
uas/ [accessed 15 August 2018].
Fondell, T.F., Hoekman, S.T., and Ball, I.J. 2000. Locating nests of birds in grasslands from a mobile tower blind.
Prairie Nat. 32: 201–208.
Goebel, M.E., Perryman, W.L., Hinke, J.T., Krause, D.J., Hann, N.A., Gardner, S., and LeRoi, D.J. 2015. A small
unmanned aerial system for estimating abundance and size of Antarctic predators. Polar Biol. 38: 619–630. doi:
10.1007/s00300-014-1625-4.
Haas, J., Schneider, B., and Weinhold, C. 2012. South Platte climbing: The northern volume. Fixed Pin Publishing,
LLC., Boulder, Colo., USA.
Hodgson, A., Kelly, N., and Peel, D. 2013. Unmanned aerial vehicles (UAVs) for surveying marine fauna: A dugong
case study. PLoS ONE, 8(11): e79556. doi: 10.1371/journal.pone.0079556. PMID: 24223967.
Jefferson County Open Space (JCOS). 2017. Climbing in Jefferson County Colorado. Available from https://
climbjeffco.com.
Junda, J.H., Greene, E., Zazelenchuk, D., and Bird, D.M. 2015. Proper flight technique for using a small
rotary-winged drone aircraft to safely, quickly, and accurately survey raptor nests. J. Unmanned Veh. Syst. 3(4):
222–236. doi: 10.1139/juvs-2015-0003.
Junda, J.H., Greene, E., Zazelenchuk, D., and Bird, D.M. 2016. Nest defense behaviour of four raptor species (osprey,
bald eagle, ferruginous hawk, and red-tailed hawk) to a novel aerial intruder —A small rotary-winged drone.
J. Unmanned Veh. Syst. 4: 217–227. doi: 10.1139/juvs-2016-0004.
Lobermeier, S., Moldenhauer, M., Peter, C.M., Slominski, L., Tedesco, R.A., Meer, M.V., et al. 2015. Mitigating avian
collision with power lines: A proof of concept for installation of line markers via unmanned aerial vehicle.
J. Unmanned Veh. Syst. 3: 252–258. doi: 10.1139/juvs-2015-0009.
McEvoy, J.F., Hall, G.P., and McDonald,P.G. 2016. Evaluation of unmanned aerial vehicle shape, flight path and cam-
era type for waterfowl surveys: Disturbance effects and species recognition. PeerJ, 4: e1831. doi: 10.7717/peerj.1831.
PMID: 27020132.
Paranjape, A.A., Chung, S.-J., Kim, K., and Shim, H. 2018. Robotic herding of a flock of birds using an unmanned
aerial vehicle. IEEE Trans. Robot. 34: 901–915. doi: 10.1109/TRO.2018.2853610.
Pix4D. 2018. Pix4D. Available from https://pix4d.com/ [accessed 15 August 2018].
Sardà-Palomera, F., Bota, G., Vinolo, C., Pallares, O., Sazatornil, V., Brotons, L., et al. 2012. Fine-scale bird monitor-
ing from light unmanned aircraft systems. Ibis, 154: 177–183. doi: 10.1111/j.1474-919X.2011.01177.x.
Wang, Z., Griffin, A.S., Lucas, A., and Wong, K.C. 2019. Psychological warfare in vineyard: Using drones and bird
psychology to control bird damage to wine grapes. Crop Prot. 120: 163–170. doi: 10.1016/j.cropro.2019.02.025.
Wich, S.A., and Pin Koh, L. 2018. Conservation drones: Mapping and monitoring biodiversity. Oxford University
Press, Oxford, UK.
Pagination not final (cite DOI) / Pagination provisoire (citer le DOI)
8 J. Unmanned Veh. Syst. Vol. 00, 0000
Published by NRC Research Press
J. Unmanned Veh. Sys. Downloaded from www.nrcresearchpress.com by VIRGINIA POLYTECHNIC INST on 01/13/20
For personal use only.