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Reactions of Sandhill Cranes Approaching a Marked
Transmission Power Line
Robert K. Murphy, James F. Dwyer,* Elizabeth K. Mojica, Michelle M. McPherron, Richard E. Harness
R.K. Murphy, M.M. McPherron
Department of Biology, University of Nebraska–Kearney, Kearney, Nebraska 68849
Present address of R.K. Murphy
: U.S. Fish and Wildlife Service, Albuquerque, New Mexico 87103
Present address of M.M. McPherron
: U.S. Army Corps of Engineers, 1616 Capitol Avenue, Omaha, Nebraska 68102
J.F. Dwyer, E.K. Mojica, R.E. Harness
EDM International, Inc., 4001 Automation Way, Fort Collins, Colorado 80525
Abstract
Sandhill cranes Antigone canadensis, formerly Grus canadensis, are of widespread management focus, particularly
where collisions with power lines are an important cause of mortality. Collision mitigation focuses on marking power
lines to increase visibility, but collisions persist, perhaps because power line markers are not sufficiently visible in all
conditions. Our objective was to compare reaction distances and reaction behaviors during daylight when power lines
are presumably more visible, and during darkness when power lines are less visible. The power line we studied was
fitted with glow-in-the-dark power line markers intended to increase nocturnal visibility. We found that during
daylight, flocks generally avoided the power line by climbing gradually and passed above without making sudden
evasive maneuvers. During darkness, flocks, particularly small flocks, were almost equally likely to make sudden evasive
maneuvers as to climb gradually. Collision monitoring on the power line we studied conducted concurrent to our
study indicated that 94% of collisions occurred during darkness, linking the behaviors we observed to actual mortality.
Sandhill cranes also reacted at greater distances and with fewer sudden evasive maneuvers to the glow-in-the-dark-
marked power line we studied than to nearby power lines without glowing markers evaluated in a prior study,
suggesting that either glowing markers, smaller gaps between markers, or both, improved sandhill cranes’ ability to
perceive and react to the power line we studied. By correlating behavioral observations with mortality, our study
indicates that proactive low-intensity behavioral observations might be useful surrogates to reactive high-intensity
carcass searches in identifying high-risk spans. This approach may also be effective for other species.
Keywords: Antigone canadensis; collision; Lillian Rowe Sanctuary; mortality; Platte River
Received: May 18, 2016; Accepted: September 26, 2016; Published Online Early: September 2016; Published: December
2016
Citation: Murphy RK, Dwyer JF, Mojica EK, McPherron MM, Harness RE. 2016. Reactions of sandhill cranes approaching a
marked transmission power line. Journal of Fish and Wildlife Management 7(2):480-489; e1944-687X. doi: 10.3996/
052016-JFWM-037
Copyright: All material appearing in the Journal of Fish and Wildlife Management is in the public domain and may be
reproduced or copied without permission unless specifically noted with the copyright symbol &. Citation of the
source, as given above, is requested.
The findings and conclusions in this article are those of the author(s) and do not necessarily represent the views of the
U.S. Fish and Wildlife Service.
* Corresponding author: jdwyer@edmlink.com
Introduction
Sandhill cranes Antigone canadensis, formerly Grus
canadensis, are of management focus throughout the
species’ range (Gerber et al. 2014, 2015) due primarily to
three factors: recovery from population lows in the early
20th century, high value as a game bird, and utility as a
model species for endangered whooping cranes Grus
Journal of Fish and Wildlife Management | www.fwspubs.org December 2016 | Volume 7 | Issue 2 | 480
americana. Nonhunting mortality of sandhill cranes is
poorly understood (Gerber et al. 2014) beyond observa-
tions that predation is a primary cause of mortality on
breeding grounds (Olsen 2004; Nesbitt et al. 2008), and
collisions with power lines are an important cause of
mortality during migration and wintering (Brown et al.
1987; Morkill and Anderson 1991; Murphy et al. 2009).
Collisions with power lines also cause mortality of
species of conservation concern such as whooping crane
(Miller et al. 2010; Folk et al. 2013; Stehn and Haralson-
Strobel 2014), sarus crane Antigone antigone (Sundar and
Choudhury 2005), and blue crane Anthropoides paradi-
seus (Shaw et al. 2010). Because sandhill crane is
ecologically and physiologically similar to other crane
species, but more abundant than some at-risk species,
this species can serve as a model to facilitate assessment
of the effectiveness of collision mitigation measures for
crane species in general (Morkill and Anderson 1991;
Brown and Drewien 1995).
The primary assumptions underlying mitigation of
avian collisions are that birds fail to see wires in their
flight path until the wires are too close to avoid and that
increasing the visibility of wires can reduce collisions
(Martin and Shaw 2010; Avian Power Line Interaction
Committee [APLIC] 2012). Collision mitigation is typically
accomplished by installing power line markers on
suspended wires (Sporer et al. 2013; Luzenski et al.
2016; Murphy et al. 2016). On transmission power lines
(60 kV; APLIC 2012), markers are typically installed only
on overhead shield wires for two reasons: first, because
corona discharge produces electromagnetic interference,
audible noise, a visible glow, and reduced transmission
efficiency when power line markers are installed on
energized conductor wires (Hurst 2004); and second,
because overhead shield wires are involved in collisions
more often than are energized conductor wires (76% on
average; Faanes 1987; Pandey et al. 2008; Murphy et al.
2016).
Power line markers seem least effective for species
with high wing loading and high flight speeds (Sporer et
al. 2013) and for species flying at night (Murphy et al.
2016). The effectiveness of power line marking may be
limited by the distance at which the markers become
visually prominent in flight. Birds such as sandhill cranes
with relatively poor maneuverability may not perceive
markers until they are too close to the power line to
make effective evasive maneuvers, particularly during
nocturnal flights (Murphy et al. 2016). This may be
particularly true if the field of vision for a bird in flight
fails to include all wires of a power line upon close
approach (Martin and Shaw 2010).
Given that collisions tend to persist on marked power
lines (Morkill and Anderson 1991; Brown and Drewien
1995; Barrientos et al. 2011), there may be room for
improvement in collision mitigation through increasing
the low-light visibility of, or decreasing the spacing
between, power line markers. To evaluate these hypoth-
eses, we investigated reaction distances and reaction
behaviors of flocks of sandhill cranes as they approached
a transmission power line during daylight and during
darkness. The markers included glow-in-the-dark com-
ponents to improve low-light prominence. We compared
our behavioral data to data collected in a previous study
on power lines marked with more widely spaced
nonglowing markers, and on unmarked power lines
(Morkill and Anderson 1991). We compared our reaction
distance and reaction behavior data to actual collision
mortality in a previous study (Morkill and Anderson 1991)
and to a concurrent study (Murphy et al. 2016) on the
power line we monitored, to correlate reaction data to
mortality data. We also evaluated the relationship
between the field of vision of blue cranes described by
Martin and Shaw (2010) in the context of the actual
power line dimensions at our study site to identify
whether any types of power line markers were likely to
occur within visual fields of crane species generally
during flight.
Study Site
Greater than 500,000 sandhill cranes, and most of the
migratory population of whooping cranes, migrate
annually through Nebraska (Krapu et al. 2014; Pearse et
al. 2015; Urbanek and Lewis 2015). Many of these sandhill
and whooping cranes use the Platte River Valley in south
central Nebraska as a migratory stopover site (Harner et
al. 2015). Within the valley, the Platte River was
historically described as a mile wide and an inch deep,
and it remains composed of a wide, shallow, braided
river channel with extensive sandbar habitat (Krapu et al.
2014). The National Audubon Society’s Lillian Rowe
Sanctuary (hereafter Rowe) near Gibbon, Nebraska, is a
9.8-km
2
wildlife refuge along the banks of the Platte
River and is situated among a matrix of roosting and
foraging habitats. Rowe has been a focal point for
studies of sandhill crane collisions with power lines
because two sets of 69-kV transmission lines cross the
Platte River within the sanctuary (Figure 1). Each of the
two power lines has a history of sandhill crane collision
mortalities (Murphy et al. 2009, 2016; Wright et al. 2009).
Methods
From 4 March to 8 April 2009, we observed the 283-m
span of a power line where it crossed the Platte River
within Rowe. This was the same span observed in a
concurrent study of crippling and nocturnal biases in
estimates of collision mortality of sandhill cranes
(Murphy et al. 2016), and the eastern span of two spans
studied in 2006 and 2007 (Wright et al. 2009) to identify
baseline values for sandhill crane collision mortalities at
Rowe. The span we studied was marked with both spiral
vibration dampers (PreFormed Line Products, Cleveland,
OH) and FireFlyeHW Bird Flapper devices (FireFly
Diverters LLC, Grantsville, UT; P&R Tech, Beaverton, OR),
the latter of which included a reflective sticker and a
glow-in-the-dark sticker on each side (e.g., Figure 2).
Reflective stickers were intended to increase the FireFly’s
visual contrast, improving daytime visibility. Glow-in-the-
dark stickers were charged daily by exposure to full sun
while hanging on the power line, and they were
intended to increase nocturnal visibility. FireFlys were
Journal of Fish and Wildlife Management | www.fwspubs.org December 2016 | Volume 7 | Issue 2 | 481
Sandhill Crane Reactions to a Power Line R.K. Murphy et al.
attached at 12-m intervals to each of the two overhead
shield wires, in an alternating arrangement so that when
viewed from perpendicular to the power line, FireFlys
occurred at 6-m intervals. These were interspersed with
spiral vibration dampers installed several years prior
(Wright et al. 2009). We placed a blind on the river bank
at each end of the observed span and recorded flocks of
sandhill cranes reacting to the power line from 0.5 h
before sunset through 2 h after sunset. We used 10 350
binoculars to observe sandhill cranes during daylight,
and 33or 53generation II night-vision spotting scopes
to observe sandhill cranes during darkness (Murphy et al.
2016). We used radios to communicate between blinds
to avoid creating duplicate records.
We documented flock size, reaction distance, and
reaction behavior for sandhill cranes flying toward the
power line, making flocks rather than individual sandhill
cranes our sampling unit. To maintain independence of
samples, we defined a flock as any individual or group
separated by at least 30 m from any other individual or
group (Morkill and Anderson 1991), and we only
collected data for the first flock observed in each 5-min
interval during each survey. We categorized flock sizes as
small (one to three individuals) or large (more than four
individuals; as in Morkill and Anderson 1991). We
categorized reaction distances as 1–5, 6–25, and .25
m from the power line, to facilitate comparison to Morkill
and Anderson (1991) who studied similarly configured
power lines over uplands within the Platte River Valley.
Similar to Morkill and Anderson (1991), we categorized
reaction behaviors as 1) no reaction, 2) gradual climb, 3)
flare (i.e., sudden climb), and 4) reversed flight path. We
only recorded data for flocks flying ,10 m above the
overhead shield wires because flocks flying higher were
not at risk of collision (Morkill and Anderson 1991).
For analysis, we divided our data into two temporal
subsets: 1) diurnal (30 min before to 45 min after sunset)
and 2) nocturnal (46–120 min after sunset). This
facilitated comparison of our diurnal data with the
evening diurnal data collected by Morkill and Anderson
(1991). We used v
2
tests of independence to compare
reaction distances and behaviors by flock size and time
period. We excluded ‘‘no reaction’’ data from analyses
because in our study, sample sizes were prohibitively
small for inclusion in v
2
tests. This occurred by design
because we specifically focused on flocks at risk of
collision (i.e., flying ,10 m above the power line). In
Morkill and Anderson (1991) more than half of all flocks
recorded were well above the power lines involved. In
these flocks, there was no collision risk, and thus no
reactions by sandhill cranes. Our design prevented
disproportionate sample sizes of flocks not likely to
result in a collision from precluding detection of an effect
of power line markers for flocks that were at risk of
collision.
We also used v
2
tests to compare reaction distances
and behaviors in this study to data reported in Morkill
and Anderson (1991) from nearby power lines marked
with yellow aviation balls, and from nearby unmarked
transmission power lines. In this analysis, we compared
only data where sandhill cranes reacted to power lines
because Morkill and Anderson (1991) included hundreds
of records of sandhill cranes not reacting when flying
well above power lines, as would be expected given that
no collision risk existed in those overflights. Thus, we
conducted four v
2
tests: 1) reaction distances by lighting
and flock size (Table 1, reaction distances block), 2)
Figure 1. Sandhill cranes Antigone canadensis in flight at a migratory stopover roost on the Platte River where from 4 March to 8
April 2009 we studied their reactions to a marked transmission power line bisecting the National Audubon Society’s Lillian Rowe
Sanctuary in Gibbon, Nebraska (credit: JFD).
Journal of Fish and Wildlife Management | www.fwspubs.org December 2016 | Volume 7 | Issue 2 | 482
Sandhill Crane Reactions to a Power Line R.K. Murphy et al.
Figure 2. Examples of power line markers with reflective and glow-in-the-dark components designed to increase visual prominence
to birds during low-light conditions and thus maximize their effectiveness in reducing avian collisions with power lines in a study of
sandhill crane Antigone canadensis reaction behavior. Manufacturers are, from left to right, P&R Tech (Beaverton, OR), P&R Tech,
Power Line Sentry (Fort Collins, CO), and TE Connectivity (Berwyn, PA). The two P&R Tech markers on the left are the most similar to
those we observed in a study of reaction behavior from 4 March to 8 April 2009 at a marked transmission power line bisecting the
National Audubon Society’s Lillian Rowe Sanctuary in Gibbon, Nebraska.
Table 1. Counts of reaction distances and reaction behaviors by flocks of sandhill cranes Antigone canadensis in flight toward a
marked transmission power line bisecting the National Audubon Society’s Lillian Rowe Sanctuary in Gibbon, Nebraska, from 4 March
to 8 April 2009. Small flocks were composed of one to three individuals; large flocks were composed of four or more individuals
(Morkill and Anderson 1991).
Reaction distance (m)
No reaction Row total.25 6–25 1–5
Diurnal small flocks 92 27 3 NA
a
122
Diurnal large flocks 98 24 0 NA 122
Nocturnal small flocks 20 69 44 NA 133
Nocturnal large flocks 29 36 6 NA 71
Reaction distance total 239 156 53 NA 448
Reaction behavior
No reaction
b
Row totalClimb Flare Reverse
Diurnal small flocks 105 8 9 0 122
Diurnal large flocks 102 3 16 1 122
Nocturnal small flocks 53 44 30 6 133
Nocturnal large flocks 44 11 16 0 71
Reaction behavior total 304 66 71 7 448
a
NA ¼not applicable.
b
No reaction data were not included in analyses because small sample sizes violated assumptions of v
2
tests.
Journal of Fish and Wildlife Management | www.fwspubs.org December 2016 | Volume 7 | Issue 2 | 483
Sandhill Crane Reactions to a Power Line R.K. Murphy et al.
reaction distances by power line marker type (Table 2,
reaction distances block), 3) reaction behaviors by
lighting and flock size (Table 1, reaction behaviors block),
and 4) reaction behaviors by power line marker type
(Table 2, reaction behaviors block). We applied Bonfer-
roni corrections for multiple comparisons (Sokal and
Rohlf 1995). Given an initial critical value of a¼0.05, for
the four comparisons made, we considered a¼0.01 to
indicate statistical significance.
In a concurrent study on crippling and nocturnal
biases in collision mortality estimates, Murphy et al.
(2016) documented collisions of sandhill cranes with the
power line observed in this study. Therein, 117 collisions
were observed via night-vision optics, and 321 collisions
were recorded via automated electronic Bird Strike
Indicators (EDM International, Fort Collins, CO). We
compared the reaction timing and behaviors observed
in our study to collision timing in Murphy et al. (2016) to
examine the assumption that increased reaction intensity
and decreased reaction distances correlated with in-
creased collision risk.
Results
We recorded the reactions of 448 flocks of sandhill
cranes to the eastern power line at Rowe in 2009 (Table
1; Table S1). Flock size averaged 18.5 (SE ¼4.8)
individuals, with a minimum of 1, median of 3, and
maximum of 2,000. Consolidating across analyses, flocks
tended to climb gradually .25 m from the power line
marked with spiral vibration dampers and FireFly Bird
Flapper devices, and flare or reverse direction ,25 m
from power lines marked with aviation balls or from
unmarked power lines.
Reaction distances
Proportions of reaction distances differed in daylight
vs. night (v
2
¼171.34; df ¼6; P,0.001). Specifically,
flocks tended to react .25 m from the power line during
daylight and ,25mfromthepowerlineduring
darkness, regardless of flock size. Reactions within 5 m
were particularly different; the reactions of only 1.2% of
244 diurnal flights occurred within 5 m, and the reactions
of 24.5% of 204 nocturnal flights occurred within 5 m.
Proportions of reaction distances also differed in our
study compared to the Morkill and Anderson (1991)
study of sandhill cranes approaching power lines marked
with yellow aviation balls and unmarked power lines (v
2
¼217.7; df ¼4; P,0.001; Table 2; Figure 3). Specifically,
flocks tended to react from .25 m away when
approaching the power line we studied (85.2% of diurnal
observations). Flocks tended to react from ,25 m away
Table 2. Counts of reaction distances and reaction behaviors by flocks of sandhill cranes Antigone canadensis in flight toward a
transmission power line marked with FireFlys and Swan Flight Diverters bisecting the National Audubon Society’s Lillian Rowe
Sanctuary in Gibbon, Nebraska, from 4 March to 8 April 2009, compared to flights toward power lines marked with aviation balls and
toward unmarked power lines reported in Morkill and Anderson (1991). Small flocks were composed of one to three individuals;
large flocks were composed of four or more individuals (Morkill and Anderson 1991).
Reaction distance (m)
No reaction Row total.25 6–25 1–5
FireFlys 190 51 3 NA
a
244
Aviation balls 128 197 106 NA 431
Unmarked 100 189 119 NA 408
Reaction distance total 418 437 228 NA 1,083
Reaction behavior
No reaction
b
Row totalClimb Flare Reverse
FireFlys 207 11 25 1 244
Aviation balls 454 19 114 768 587
Unmarked 397 36 92 1,200 525
Reaction distance total 1,058 66 231 1,969 1,355
a
NA ¼not applicable.
b
No reaction data were not included in analyses because Morkill and Anderson (1991) included hundreds of records of sandhill cranes not reacting
when flying well above power lines, as would be expected given that no collision risk existed in those overflights.
Figure 3. Frequency distribution of reaction distances by
sandhill cranes Antigone canadensis from 4 March to 8 April
2009 to a marked transmission power line bisecting the
National Audubon Society’s Lillian Rowe Sanctuary in Gibbon,
Nebraska, compared to other nearby power lines. Flock
reactions (n¼244) to FireFlys were observed in this study;
reactions to power lines marked with aviation balls (n¼1,199)
and unmarked power lines (n¼1,608) and to were observed by
Morkill and Anderson (1991).
Journal of Fish and Wildlife Management | www.fwspubs.org December 2016 | Volume 7 | Issue 2 | 484
Sandhill Crane Reactions to a Power Line R.K. Murphy et al.
when approaching aviation balls (70.3% of aviation ball
observations), or unmarked power lines (75.5% of
unmarked power line observations; Morkill and Anderson
1991).
Reaction behaviors
Proportions of reaction behaviors differed with day-
light versus night (v
2
¼89.6; df ¼6; P,0.001).
Specifically, flocks tended to react with gradual climbs
during daylight, and to flare or reverse flight paths
during darkness, regardless of flock size. Reactions
involving gradual climbs were particularly different,
including on 85.2% of diurnal flights and 49.0% of
nocturnal flights. Proportions of reaction behaviors also
differed between our study and the Morkill and
Anderson (1991) study for sandhill cranes approaching
power lines marked with yellow aviation balls and
unmarked power lines (v
2
¼18.1; df ¼4; P¼0.001;
Table 3; Figure 4). Specifically, flocks tended to react with
gradual climbs when approaching the power line we
studied (85.2% of diurnal observations). Flocks were less
likely to climb gradually when approaching aviation balls
(77.3% of aviation ball observations) or unmarked power
lines (75.6% of unmarked power line observations;
Morkill and Anderson 1991).
Mortalities
Murphy et al. (2016) found 6% of 117 observed
collisions during daylight and 94% during darkness,
where diurnal and nocturnal survey periods were
identical to those used in this study. Consolidating
across analyses, flocks tended to climb gradually .25 m
away from the power line during daylight (37.5% of all
observations; 68.9% of diurnal observations) when
collisions were rare. Flocks more often flared or reversed
directions ,25 m from the power line during darkness
(19.9% of all observations; 43.6% of nocturnal observa-
tions) when collisions were comparatively frequent. Of
36 collisions reported in Morkill and Anderson (1991),
69.4% occurred on unmarked power lines, correlating
reaction distances and behaviors with actual mortality
because the number of cranes flying over marked power
lines and unmarked power lines did not statistically
differ.
Discussion
Sandhill cranes reacted at greater distances and with
more gradual avoidance behaviors during daylight than
during darkness. Sandhill cranes also reacted at greater
distances and with more gradual avoidance behaviors to
the power line marked with FireFlys and Swan Flight
Diverters than to the power line marked with aviation
balls, and reaction distances were greater when ap-
proaching the power line marked with aviation balls
compared to unmarked power lines (Morkill and
Anderson 1991). Mortalities also were less prevalent
during daylight than during darkness on the power line
we studied (Murphy et al. 2016), and they were less
prevalent on power lines marked with aviation balls than
on unmarked power lines (Morkill and Anderson 1991),
confirming that flight reaction behavior has direct
inference to collision mortality. Thus, closely spaced
glow-in-the-dark markers were more effective in miti-
gating collision mortality than widely spaced nonglow-
ing markers, although nonglowing markers did reduce
collision compared to unmarked wires.
The differences we found in reaction distances and
behaviors were particularly pronounced for small flocks.
In previous studies, individual birds in larger flocks were
perceived as being at higher risk of collision (Brown
1993; APLIC 2012) because maneuvering room can be
reduced within flocks, and because leading birds obscure
the view of trailing birds. The apparent paradox between
our findings and previous studies is resolved by
considering relative detection probabilities of power
lines for individuals within flocks during diurnal and
nocturnal flights. During a diurnal flight, the odds that an
individual bird within a small flock will see an approach-
ing power line may be relatively high, as may be the
odds that trailing birds in that flock, if present, will see
and follow the bird into a gradual climb. During a
nocturnal flight, the odds that an individual bird within a
small flock will see an approaching power line may be
relatively low, as may be the odds that trailing birds in
that flock, if present, will be able to precisely follow a
sudden evasive maneuver immediately before collision if
they do not know what the obstacle is or where in their
path the obstacle lies.
These observations facilitate increased understanding
of when and how collision mitigation devices work and
thus where continued innovation may facilitate in-
creased effectiveness. Apparently, when sandhill cranes
flew together, the likelihood that one of them would see
and react to power line markers earlier upon approach
increased with increasing numbers of birds. This
indicates that power line markers were visible, but not
Figure 4. Frequency distribution of behavioral responses by
sandhill cranes Antigone canadensis from 4 March to 8 April
2009 to a marked transmission power line bisecting the
National Audubon Society’s Lillian Rowe Sanctuary in Gibbon,
Nebraska,comparedtoothernearbypowerlines.Flock
reactions (n¼243) to FireFlys were observed in this study;
reactions to power lines marked with aviation balls (n¼587)
and unmarked power lines (n¼525) and to were observed by
Morkill and Anderson (1991).
Journal of Fish and Wildlife Management | www.fwspubs.org December 2016 | Volume 7 | Issue 2 | 485
Sandhill Crane Reactions to a Power Line R.K. Murphy et al.
always sufficiently prominently for sandhill cranes to
correctly conceptualize in three-dimensional space.
Presumably, if power line markers were more prominent,
either through increased visibility of individual markers
or though reduced spacing between markers, then
markers would become apparent to sandhill cranes at
a greater distance, even to small flocks. Increased
visibility may be achieved by incorporating materials
with brighter and longer lasting glow-in-the-dark char-
acteristics. Reduced spacing of glowing markers may
help birds avoid a wire suspended between markers
either through illumination of the wire itself or through
avoidance of flying between markers. Although these
approaches seem intuitive, three potential concerns
exist. First, very prominent glowing power line markers
suspended on wires may be disagreeable to the public.
Second, reduced spacing between power line markers
would add weight and loading to power lines, particu-
larly during high winds and ice storms. Third, birds can
be attracted to nocturnally lit structures (Jones and
Francis 2003; Poot et al. 2008), so bird’s reactions to
markers with increased illumination may not be entirely
as desired. Consequently, the relative effectiveness of
increasing power line marker prominence should be
quantitatively evaluated within the context of a study
designed to consider negative impacts.
Avian collision risk can be exacerbated during poor
weather (Brown et al. 1987; Jones and Francis 2003; Kirsh
et al. 2015). Our study did not report weather effects in
reaction distances because we had too few days with
weather-obscured power lines to draw statistically
meaningful comparisons. However, Brown et al. (1987)
also recorded reaction behaviors of sandhill cranes
approaching a power line, and they were able to
consider weather effects. In their study, sandhill cranes’
maneuverability and control were impaired by high
winds, and 69% of sandhill crane mortality occurred on
days with high winds, fog, or precipitation. Kirsch et al.
(2015) also found that sandhill crane flight behavior
differed when fog covered roost sites, leading to reduced
flight distances and increased circling. If a power line
exists in or near a roost, then increased circling during
fog may increase collision risk. Future study should
include weather data in multivariate analyses of the
effectiveness of power line markers.
Martin and Shaw (2010) postulated that the field of view
of some bird species during flight may preclude detection
of suspended obstacles directly ahead, a reasonable
hypothesis given that birds did not evolve in the presence
of suspended obstacles. Evaluation of this hypothesis is
critical, because if correct, then power line marking may
not be effective mitigation measure regardless of type,
glow, or spacing. Martin and Shaw (2010) specifically
identified the field of view of blue cranes Anthropoides
paradiseus as extending from 158below the bill to 608
above the bill. A blue crane rotating its head .608
downward during flight could lose sight of suspended
obstacles within its flight path (Martin and Shaw 2010).
Following this logic, blue cranes, and presumably similarly
structured sandhill cranes and whooping cranes, could
hypothetically approach and collide with a power line
without the power line ever entering the blue crane’s field
of view. Our finding that reactions of sandhill cranes to
marked power lines in proportion to the level of marking
(none, aviation balls, power line markers) refutes this
hypothesis, at least with respect to drawing inference
beyond blue cranes to sandhill cranes. Future research
could compare studies of collision mortality among various
crane species, including at-risk whooping cranes, sarus
cranes, and free-flying blue cranes to identify whether
solutions implemented to protect some might also protect
others. Future research also should include other migratory
stopover locations, such as the San Luis Valley in southern
Colorado, where sandhill cranes and whooping cranes also
experience collision mortality (Brown et al. 1987; Brown
1993; Brown and Drewien 1995), but where roost sites are
distributed through scattered wetlands rather than along a
linear river feature.
Management Implications
Our study provides a novel behavior-based approach to
evaluating avian collision risk that may be useful
elsewhere. Resource managers with concerns about the
occurrence of avian collisions may not need to rely on a
carcass survey that can be a time- and labor-intensive task;
yield low sample sizes; and be fundamentally reactive
because first a mortality has to be detected. Rather,
managers may be able to evaluate flight reaction behavior
to identify whether proactive collision mitigation may be
warranted. This could be a particularly important surro-
gate for mortality monitoring if the species hypothesized
to be involved are small bodied, because small-bodied
carcasses can be quickly removed by scavengers (Rogers
et al. 2014). The approach could be coupled with Bird
Strike Indicators (EDM International, Inc.; Murphy et al.
2016) in areas where power lines of concern traverse
water, preventing effective carcass surveys.
Supplemental Material
Please note: The Journal of Fish and Wildlife Management
is not responsible for the content or functionality of any
supplemental material. Queries should be directed to the
corresponding author for the article.
Table S1. Counts of reaction distances and reaction
behaviors by flocks of sandhill cranes Antigone canaden-
sis in flight toward a marked transmission power line
bisecting the National Audubon Society’s Lillian Rowe
Sanctuary in Gibbon, Nebraska, from 4 March to 8 April
2009. Small flocks were composed of one to three
individuals; large flocks were composed of four or more
individuals (Morkill and Anderson 1991).
Found at DOI: http://dx.doi.org/10.3996/052016-
JFWM-037.S1 (31 KB XLSX).
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1987. Mortality of cranes and waterfowl from power line
collisions in the San Luis Valley, Colorado. Pages 128–136
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American Crane Workshop. Platte River Whooping Crane
Journal of Fish and Wildlife Management | www.fwspubs.org December 2016 | Volume 7 | Issue 2 | 486
Sandhill Crane Reactions to a Power Line R.K. Murphy et al.
Maintenance Trust, Grand Island, Nebraska, and U.S. Fish
and Wildlife Service, Washington, D.C.
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JFWM-037.S2 (430 KB PDF); also available at http://
www.nacwg.org/proceedings4.html.
Reference S2. Faanes CA. 1987. Bird behavior and
mortality in relation to power lines in prairie habitats.
Washington, D.C: U.S. Fish and Wildlife Service Technical
Report 7.
Found at DOI: http://dx.doi.org/10.3996/052016-
JFWM-037.S3 (2119 KB PDF); also available at https://
pubs.er.usgs.gov/publication/2000102.
Reference S3. Hurst N. 2004. Corona testing devices
used to mitigate bird collisions. California Energy Com-
mission, PIER energy-related environmental research 500-
04-086F. EDM International, Inc., Fort Collins, Colorado.
Found at DOI: http://dx.doi.org/10.3996/052016-
JFWM-037.S4 (1198 KB PDF); also available at http://
www.energy.ca.gov/reports/CEC-500-2004-086F.PDF.
Reference S4. Miller JL, Spalding MG, Folk MJ. 2010.
Leg problems and power line interactions in the Florida
resident flock of whooping cranes. Pages 156–165 in
Hartup, BK, editor. Proceedings of the Eleventh North
American Crane Workshop. North American Crane
Working Group, Wisconsin Dells, Wisconsin.
Found at DOI: http://dx.doi.org/10.3996/052016-
JFWM-037.S5 (510 KB PDF); also available at https://
www.savingcranes.org/proceedings-of-the-eleventh-
north-american-crane-workshop/. (September 2016).
Reference S5. Murphy RK, McPherron SM, Wright GD,
Serbousek KL. 2009. Effectiveness of avian collision
averters in preventing migratory bird mortality from
powerline strikes in the central Platte River, Nebraska.
2008–2009 Final Report. Nebraska Game and Parks
Commission (NGPC) via US Fish and Wildlife Service
Section 6 Program.
Found at DOI: http://dx.doi.org/10.3996/052016-
JFWM-037.S6 (1069 KB PDF); also available at http://
www.thesis.com/data/literature/effectiveness%20of%
20avian%20collision%20averters%20in%20preventing%
20migratory%20bird%20mortality%20from%20powerline%
20strikes.pdf.
Reference S6. Nesbitt SA, Schwikert ST, Spalding MG.
2008. Survival and sources of mortality in Florida sandhill
crane chicks – hatching to fledging. Pages 86–89 in
Hartup BK, editor. Proceedings of the Eleventh North
American Crane Workshop. North American Crane
Working Group, Grand Island, Nebraska.
Found at DOI: http://dx.doi.org/10.3996/052016-
JFWM-037.S7 (236 KB PDF); also available at http://
digitalcommons.unl.edu/cgi/viewcontent.cgi?article¼1190&
context¼nacwgproc.
Reference S7. Pandey AK, Harness RE, Schriner MK.
2008. Bird strike indicator field deployment at the
Audubon National Wildlife Refuge in North Dakota:
phase two. California Energy Commission, Public Interest
Energy Research energy-related environmental research
program, CEC-500-2008-020, Sacramento, California.
Found at DOI: http://dx.doi.org/10.3996/052016-
JFWM-037.S8 (2241 KB PDF); also available at http://
www.energy.ca.gov/2008publications/CEC-500-2008-
020/CEC-500-2008-020.PDF.
Reference S8. Stehn TV, Haralson-Strobel C. 2014. An
update on mortality of fledged whooping cranes in the
Aransas/Wood Buffalo population. Pages 43–50 in
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Workshop. North American Crane Working Group, Grand
Island, Nebraska.
Found at DOI: http://dx.doi.org/10.3996/052016-
JFWM-037.S9 (936 KB PDF); also available at http://
www.nacwg.org/proceedings12.html.
Acknowledgments
We thank C. Kemper, W. Brown, and two anonymous
reviewers for comments that greatly improved this
writing. Funding from the Nebraska Game and Parks
Commission through the U.S. Fish and Wildlife Service’s
Section 6 program supported our fieldwork. Dawson
Public Power District installed spiral vibration dampers
and FireFlys. We thank Nebraska Game and Parks
Commission, Nebraska Rural Electric Association, Nation-
al Audubon Society’s Lillian Rowe Sanctuary, and the U.S.
Fish and Wildlife Service for additional support. We are
grateful to University of Nebraska–Kearney students C.
Fickel, M. Morten, and K. Serbousek for field assistance
and to G. Wright for laying much of the groundwork for
this study. M. Fritz, B. Taddicken, R. Harms, and J. Runge
facilitated study implementation.
Any use of trade, product, or firm names is for
descriptive purposes only and does not imply endorse-
ment by the U.S. Government.
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