Collisions with electrical powerlines are a well-known documented cause of avian mortality (Avian Power Line Interaction Committee [APLIC] 1994, Savereno et al. 1996). Mortality caused by collisions with powerlines can be an important concern for many bird species, but is a serious conservation problem for threatened and endangered species because any mortality can have biological and legal ramifications (Janss 2000). Loss of individuals, particularly breeding adults, from an already small population may impede a species’ recovery by reducing reproduction and recruitment into the breeding population. The death of an individual from a threatened or endangered species as a result of a collision may constitute “take” as defined by the federal Endangered Species Act (1973; 16 U.S.C. 1531–1544.) and the federal Migratory Bird Treaty Act (1918; 16 U.S.C. 703–712). Companies and/or individuals may be prosecuted when powerline collisions occur, particularly if recommendations intended to reduce the risk of collision, provided by the United States Fish and Wildlife Service (USFWS) regarding the placement of the powerlines, have not been followed

Brown, Mary Bomberger

Dinan, Lauren R.

Jorgensen, Joel G.

English

Collisions with electrical powerlines are a well-known documented cause of avian mortality (Avian Power Line Interaction Committee [APLIC] 1994, Savereno et al. 1996). Mortality caused by collisions with powerlines can be an important concern for many bird species, but is a serious conservation problem for threatened and endangered species because any mortality can have biological and legal ramifications (Janss 2000). Loss of individuals, particularly breeding adults, from an already small population may impede a species’ recovery by reducing reproduction and recruitment into the breeding population. The death of an individual from a threatened or endangered species as a result of a collision may constitute “take” as defined by the federal Endangered Species Act (1973; 16 U.S.C. 1531–1544.) and the federal Migratory Bird Treaty Act (1918; 16 U.S.C. 703–712). Companies and/or individuals may be prosecuted when powerline collisions occur, particularly if recommendations intended to reduce the risk of collision, provided by the United States Fish and Wildlife Service (USFWS) regarding the placement of the powerlines, have not been followed.
The interior least tern (Sternula antillarum athalassos) is a federally endangered species (50 Federal Register 21784–21792) that breeds on and along the Mississippi and Missouri rivers and their tributaries (Thompson et al. 1997). The species’ principal nesting habitat includes sparsely vegetated sandbars within main river channels, but in some cases birds will nest on human-created habitats such as waste sand from dredging or mining operations (Thompson et al. 1997). Interior least terns are small and agile flyers able to readily avoid powerline collisions. In fact, collisions with powerlines were not identified as a potential threat to recovery in the interior least terns’ recovery plan (United States Fish and Wildlife Service [USFWS] 1990). Here, we provide the first documented report of an interior least tern mortality that we are aware of, caused by a collision with a powerline, and comment on the conservation implications of the incident

DigitalCommons@University of Nebraska

University of Nebraska - LincolnDigitalCommons@University of Nebraska - LincolnPapers in Natural Resources Natural Resources, School of2012INTERIOR LEAST TERN POWERLINECOLLISION ON THE LOWER PLATTERIVERLauren R. DinanNebraska Game and Parks Commission, lauren.dinan@yahoo.comJoel G. JorgensenNebraska Game and Parks Commission, joel.jorgensen@nebraska.govMary Bomberger BrownUniversity of Nebraska-Lincoln, mbrown9@unl.eduFollow this and additional works at: https://digitalcommons.unl.edu/natrespapersPart of the Natural Resources and Conservation Commons, Natural Resources Management andPolicy Commons, and the Other Environmental Sciences CommonsThis Article is brought to you for free and open access by the Natural Resources, School of at DigitalCommons@University of Nebraska - Lincoln. Ithas been accepted for inclusion in Papers in Natural Resources by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln.Dinan, Lauren R.; Jorgensen, Joel G.; and Brown, Mary Bomberger, "INTERIOR LEAST TERN POWERLINE COLLISION ONTHE LOWER PLATTE RIVER" (2012). Papers in Natural Resources. 639.https://digitalcommons.unl.edu/natrespapers/639The Prairie Naturalist 44:109-110; 2012INTERIOR LEAST TERN POWERLINE COLLISION ON THE LOWER PLATTE RIVER—Collisions with electrical powerlines are a well-known documented cause of avian mortality (Avian Power Line Interaction Committee [APLIC] 1994, Savereno et al. 1996). Mortality caused by collisions with powerlines can be an important concern for many bird species, but is a serious conservation problem for threatened and endangered species because any mortality can have biological and legal ramifications (Janss 2000). Loss of individuals, particularly breeding adults, from an already small population may impede a species’ recovery by reduc-ing reproduction and recruitment into the breeding popula-tion. The death of an individual from a threatened or endan-gered species as a result of a collision may constitute “take” as defined by the federal Endangered Species Act (1973; 16 U.S.C. 1531–1544.) and the federal Migratory Bird Treaty Act (1918; 16 U.S.C. 703–712). Companies and/or individu-als may be prosecuted when powerline collisions occur, par-ticularly if recommendations intended to reduce the risk of collision, provided by the United States Fish and Wildlife Service (USFWS) regarding the placement of the powerlines, have not been followed.  The interior least tern (Sternula antillarum athalassos) is a federally endangered species (50 Federal Register 21784–21792) that breeds on and along the Mississippi and Mis-souri rivers and their tributaries (Thompson et al. 1997). The species’ principal nesting habitat includes sparsely vegetated sandbars within main river channels, but in some cases birds will nest on human-created habitats such as waste sand from dredging or mining operations (Thompson et al. 1997).  Inte-rior least terns are small and agile flyers able to readily avoid powerline collisions. In fact, collisions with powerlines were not identified as a potential threat to recovery in the interior least terns’ recovery plan (United States Fish and Wildlife Service [USFWS] 1990). Here, we provide the first docu-mented report of an interior least tern mortality that we are aware of, caused by a collision with a powerline, and com-ment on the conservation implications of the incident.On 7 June 2012, we recovered a dead male adult inte-rior least tern on a lower Platte River sandbar in Saunders County, Nebraska. We found the tern lying on the sand di-rectly below a set of transmission lines mounted on tall steel H-frame structures; the set included five individual lines. The transmission lines crossed the river and a large midstream sandbar (Fig. 1). We discovered the tern’s carcass in a colony that included approximately 30 adult terns associated with 13 nests, all early in the incubation period. All five transmission lines were marked with yellow, spiral bird flight diverters (APLIC 1994). These diverters were spaced approximately 15 m apart in a staggered pattern over the entire 485 m wide river crossing. The bird flight diverters were placed on the transmission lines following the recovery of a dead black tern (Chlidonias niger) at the same location in 2009, out of con-cern that the line could present risks to the legally protected interior least tern, piping plover (Charadrius melodus), and bald eagle (Haliaeetus leucocephalus) which regularly occur in the area. The transmission lines also were marked with nine yellow, white, and orange aerial marker spheres which are traditionally intended to alert aircrafts to the presence of the lines, but have occasionally been installed in an attempt to reduce bird collisions (APLIC 1994).The interior least tern carcass was fresh and in relatively good condition. Immediately after collection, the Nebraska Game and Parks Commission (NGPC) sent the carcass to the United States Geological Survey (USGS) National Wildlife Health Center in Madison, Wisconsin, where a necropsy was conducted. The results from the diagnostic evaluation indi-cated the tern was well nourished with no puncture wounds. The necropsy showed extensive hemorrhaging into the left lung and a blood clot in the left lobe of the liver; the suspect-ed cause of death was blunt force trauma to the left side of the body (J. L. Buckner, USGS National Wildlife Health Cen-ter, unpublished data). The results exclude possible causes of death such as emaciation, disease, or predation. Other than the transmission lines, no other vertical structures were within 150 m of where the tern carcass was found. Thus, the mortality is consistent with collision with a transmission line and all other explanations have been satisfactorily excluded. To our knowledge, this is the first report documenting powerline collisions as a source of interior least tern mortal-ity. Henderson el al. (1996) noted that terns are at a lower risk of powerline collisions due to their small size and agile flight. However, size and flight agility may not be the only factors that influence a species’ susceptibility to powerline collisions. Behavior, habitat use, time of day, wind speed, weather conditions, and age may influence a species’ suscep-tibility to powerline collisions. Interior least terns’ courting and pair-bonding behavior may increase their susceptibly to powerline collisions. When interior least terns are forming pairs, they engage in aerial chases with other terns (Thomp-son et al. 1997), such behaviors may make interior least terns more susceptible to collisions. The mortality we observed oc-curred early in the nesting season, shortly after birds arrived at breeding sites, and at a time when pairs were being formed and nests were initiated. Henderson et al. (1996) reported that adult common terns (Sterna hirundo) were more susceptible to powerline collisions during chick rearing when the fre-quency of adult tern flights to and from the colony increased >3 times. Additionally, adult terns flew closer to the electri-cal wires during the nestling and fledgling phases than dur-ing the courtship and incubation phases, due to the increased frequency of foraging flights necessary to feed their chicks (Henderson et al. 1996). This increase in a species suscepti-bility to powerline collisions also may be true for other tern species. The location of a powerline is an important determinant of whether collisions occur or can be avoided (APLIC 1994, Henderson et al. 1996). Powerlines located in habitats that are regularly frequented by species obviously have an in-creased probability of being encountered (Janss 2000).  In 110 The Prairie Naturalist  •  44(2): December 2012the case of interior least terns, powerlines that cross rivers, especially those that cross directly over large midstream sandbars or other traditional nesting sites, present higher risk (Henderson et al. 1996). Sandbar location, size and elevation can be dynamic, however there are static variables known to influence tern nesting habitat selection that can be used to predict the location of tern colonies (Jorgensen et al. 2012). For example, Jorgensen et al. (2012) documented that inte-rior least tern nesting incidence increased with increasing river channel width, and that interior least terns avoid nesting on sandbars located in narrow river channels. The location where this collision and mortality occurred was in one of the widest channels (84th percentile) in the lower Platte River (J. G. Jorgensen, NGPC, unpublished data), indicating that this area is likely to be more attractive to interior least terns than other narrower sections of the river. The mortality incident summarized here indicates in-terior least terns are vulnerable, albeit rarely, to powerline collisions that can result in mortality. This mortality incident shows that marking powerlines that are placed in areas com-monly used as a feeding, nesting, or roosting site, or divid-ing a habitat, with bird flight diverters or other types of line markers does not completely eliminate collision risk. The problem of bird mortality resulting from powerline colli-sions has become more important as the growing demand for electrical power increases and the number of kilometers of powerlines needed to distribute that power increases (APLIC 1994). This increase requires utility companies and state and federal agencies to be even more conscious of environmental factors when choosing locations for new transmission lines. Entities hoping to avoid or reduce avian collision risks should use information about habitat use when making powerline placement decisions.  Major funding was provided by the Nebraska Wildlife Conservation Fund and the State Wildlife Grant Program. We thank Jennifer L. Buckner with the USGS National Wildlife Health Center in Madison, Wisconsin for conducting the nec-ropsy and diagnostic tests. We also thank the two anonymous reviewers that provided useful comments that improved the manuscript.—Lauren R. Dinan1, Joel G. Jorgensen, and Mary Bomberger Brown. Nongame Bird Program, Ne-braska Game and Parks Commission, Lincoln, NE 68503, USA (LRD, JGJ). School of Natural Resources, University of Nebraska-Lincoln, Lincoln, NE 68583, USA (MBB). 1Cor-responding author email address:ngpc.nongamebird.temp@nebraska.gov.LITERATURE CITEDAvian Power Line Interaction Committee [APLIC]. 1994. Mitigating bird collisions with power lines: the state of art in 1994. Edison Electric Institute, Washington, D.C., USA.Henderson, I. G., R. H. W. Landgston, and N. A. Clark. 1996. The response of common terns Sterna hirundo to power lines: an assessment of risk in relation to breeding com-mitment, age and wind speed. Biological Conservation 77:185–192.Janss, G. F. E. 2000. Avian mortality from power lines: a morphologic approach of a species-specific mortality. Biological Conservation 95:353–359.Jorgensen, J. G., M. B. Brown, and A. J. Tyre. 2012. Chan-nel width and interior least tern and piping plover nest-ing incidence on the lower Platte River, Nebraska. Great Plains Research 22:59–67.Savereno, A. J., L. A. Savereno, R. Boettcher, and S. M. Haig. 1996. Avian behavior and mortalities at power lines in coastal South Carolina. Wildlife Society Bulletin 24:636–648. Thompson, B. C., J. A. Jackson, J. Burger, L. A. Hill, E. M. Kirsch, and J. L. Atwood. 1997. Least tern (Sterna an-tillarum) in A Poole and F. Gill, editors. The Birds of North America, No. 290. The Academy of Natural Sci-ence, Philadelphia, PA, and the American Ornithologist’ Union, Washington, D.C., USA.U.S. Fish and Wildlife Service [USFWS]. 1990. Recovery plan for the interior population of least tern (Sterna an-tillarum). U.S. Fish and Wildlife Service, Twin Cities, Minnesota, USA.Submitted 11 November 2012. Accepted 19 December 2012. Associate Editor was Chadwick P. Lehman.Figure 1. Dead adult interior least tern (Sternula antillarum athalassos) photographed on 7 June 2012 on a lower Platte River sandbar near Ashland, Saunders County, Nebraska. Photograph by Joel G. Jorgensen.

INTERIOR LEAST TERN POWERLINE COLLISION ON THE LOWER PLATTE RIVER

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Interior Least Tern Powerline Collision on the Lower Platte River

University of Nebraska - Lincoln
DigitalCommons@University of Nebraska - Lincoln
Papers in Natural Resources Natural Resources, School of
2012
INTERIOR LEAST TERN POWERLINE
COLLISION ON THE LOWER PLATTE
RIVER
Lauren R. Dinan
Nebraska Game and Parks Commission, lauren.dinan@yahoo.com
Joel G. Jorgensen
Nebraska Game and Parks Commission, joel.jorgensen@nebraska.gov
Mary Bomberger Brown
University of Nebraska-Lincoln, mbrown9@unl.edu
Follow this and additional works at: https://digitalcommons.unl.edu/natrespapers
Part of the Natural Resources and Conservation Commons, Natural Resources Management and
Policy Commons, and the Other Environmental Sciences Commons
This Article is brought to you for free and open access by the Natural Resources, School of at DigitalCommons@University of Nebraska - Lincoln. It
has been accepted for inclusion in Papers in Natural Resources by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln.
Dinan, Lauren R.; Jorgensen, Joel G.; and Brown, Mary Bomberger, "INTERIOR LEAST TERN POWERLINE COLLISION ON
THE LOWER PLATTE RIVER" (2012). Papers in Natural Resources. 639.
https://digitalcommons.unl.edu/natrespapers/639
The Prairie Naturalist 44:109-110; 2012
INTERIOR LEAST TERN POWERLINE COLLISION 
ON THE LOWER PLATTE RIVER—Collisions with 
electrical powerlines are a well-known documented cause 
of avian mortality (Avian Power Line Interaction Committee 
[APLIC] 1994, Savereno et al. 1996). Mortality caused by 
collisions with powerlines can be an important concern for 
many bird species, but is a serious conservation problem for 
threatened and endangered species because any mortality can 
have biological and legal ramifications (Janss 2000). Loss 
of individuals, particularly breeding adults, from an already 
small population may impede a species’ recovery by reduc-
ing reproduction and recruitment into the breeding popula-
tion. The death of an individual from a threatened or endan-
gered species as a result of a collision may constitute “take” 
as defined by the federal Endangered Species Act (1973; 16 
U.S.C. 1531–1544.) and the federal Migratory Bird Treaty 
Act (1918; 16 U.S.C. 703–712). Companies and/or individu-
als may be prosecuted when powerline collisions occur, par-
ticularly if recommendations intended to reduce the risk of 
collision, provided by the United States Fish and Wildlife 
Service (USFWS) regarding the placement of the powerlines, 
have not been followed. 
 The interior least tern (Sternula antillarum athalassos) is 
a federally endangered species (50 Federal Register 21784–
21792) that breeds on and along the Mississippi and Mis-
souri rivers and their tributaries (Thompson et al. 1997). The 
species’ principal nesting habitat includes sparsely vegetated 
sandbars within main river channels, but in some cases birds 
will nest on human-created habitats such as waste sand from 
dredging or mining operations (Thompson et al. 1997).  Inte-
rior least terns are small and agile flyers able to readily avoid 
powerline collisions. In fact, collisions with powerlines were 
not identified as a potential threat to recovery in the interior 
least terns’ recovery plan (United States Fish and Wildlife 
Service [USFWS] 1990). Here, we provide the first docu-
mented report of an interior least tern mortality that we are 
aware of, caused by a collision with a powerline, and com-
ment on the conservation implications of the incident.
On 7 June 2012, we recovered a dead male adult inte-
rior least tern on a lower Platte River sandbar in Saunders 
County, Nebraska. We found the tern lying on the sand di-
rectly below a set of transmission lines mounted on tall steel 
H-frame structures; the set included five individual lines. The 
transmission lines crossed the river and a large midstream 
sandbar (Fig. 1). We discovered the tern’s carcass in a colony 
that included approximately 30 adult terns associated with 13 
nests, all early in the incubation period. All five transmission 
lines were marked with yellow, spiral bird flight diverters 
(APLIC 1994). These diverters were spaced approximately 
15 m apart in a staggered pattern over the entire 485 m wide 
river crossing. The bird flight diverters were placed on the 
transmission lines following the recovery of a dead black tern 
(Chlidonias niger) at the same location in 2009, out of con-
cern that the line could present risks to the legally protected 
interior least tern, piping plover (Charadrius melodus), and 
bald eagle (Haliaeetus leucocephalus) which regularly occur 
in the area. The transmission lines also were marked with 
nine yellow, white, and orange aerial marker spheres which 
are traditionally intended to alert aircrafts to the presence of 
the lines, but have occasionally been installed in an attempt 
to reduce bird collisions (APLIC 1994).
The interior least tern carcass was fresh and in relatively 
good condition. Immediately after collection, the Nebraska 
Game and Parks Commission (NGPC) sent the carcass to the 
United States Geological Survey (USGS) National Wildlife 
Health Center in Madison, Wisconsin, where a necropsy was 
conducted. The results from the diagnostic evaluation indi-
cated the tern was well nourished with no puncture wounds. 
The necropsy showed extensive hemorrhaging into the left 
lung and a blood clot in the left lobe of the liver; the suspect-
ed cause of death was blunt force trauma to the left side of the 
body (J. L. Buckner, USGS National Wildlife Health Cen-
ter, unpublished data). The results exclude possible causes 
of death such as emaciation, disease, or predation. Other 
than the transmission lines, no other vertical structures were 
within 150 m of where the tern carcass was found. Thus, the 
mortality is consistent with collision with a transmission line 
and all other explanations have been satisfactorily excluded. 
To our knowledge, this is the first report documenting 
powerline collisions as a source of interior least tern mortal-
ity. Henderson el al. (1996) noted that terns are at a lower 
risk of powerline collisions due to their small size and agile 
flight. However, size and flight agility may not be the only 
factors that influence a species’ susceptibility to powerline 
collisions. Behavior, habitat use, time of day, wind speed, 
weather conditions, and age may influence a species’ suscep-
tibility to powerline collisions. Interior least terns’ courting 
and pair-bonding behavior may increase their susceptibly to 
powerline collisions. When interior least terns are forming 
pairs, they engage in aerial chases with other terns (Thomp-
son et al. 1997), such behaviors may make interior least terns 
more susceptible to collisions. The mortality we observed oc-
curred early in the nesting season, shortly after birds arrived 
at breeding sites, and at a time when pairs were being formed 
and nests were initiated. Henderson et al. (1996) reported that 
adult common terns (Sterna hirundo) were more susceptible 
to powerline collisions during chick rearing when the fre-
quency of adult tern flights to and from the colony increased 
>3 times. Additionally, adult terns flew closer to the electri-
cal wires during the nestling and fledgling phases than dur-
ing the courtship and incubation phases, due to the increased 
frequency of foraging flights necessary to feed their chicks 
(Henderson et al. 1996). This increase in a species suscepti-
bility to powerline collisions also may be true for other tern 
species. 
The location of a powerline is an important determinant 
of whether collisions occur or can be avoided (APLIC 1994, 
Henderson et al. 1996). Powerlines located in habitats that 
are regularly frequented by species obviously have an in-
creased probability of being encountered (Janss 2000).  In 
110 The Prairie Naturalist  •  44(2): December 2012
the case of interior least terns, powerlines that cross rivers, 
especially those that cross directly over large midstream 
sandbars or other traditional nesting sites, present higher risk 
(Henderson et al. 1996). Sandbar location, size and elevation 
can be dynamic, however there are static variables known to 
influence tern nesting habitat selection that can be used to 
predict the location of tern colonies (Jorgensen et al. 2012). 
For example, Jorgensen et al. (2012) documented that inte-
rior least tern nesting incidence increased with increasing 
river channel width, and that interior least terns avoid nesting 
on sandbars located in narrow river channels. The location 
where this collision and mortality occurred was in one of the 
widest channels (84th percentile) in the lower Platte River (J. 
G. Jorgensen, NGPC, unpublished data), indicating that this 
area is likely to be more attractive to interior least terns than 
other narrower sections of the river. 
The mortality incident summarized here indicates in-
terior least terns are vulnerable, albeit rarely, to powerline 
collisions that can result in mortality. This mortality incident 
shows that marking powerlines that are placed in areas com-
monly used as a feeding, nesting, or roosting site, or divid-
ing a habitat, with bird flight diverters or other types of line 
markers does not completely eliminate collision risk. The 
problem of bird mortality resulting from powerline colli-
sions has become more important as the growing demand for 
electrical power increases and the number of kilometers of 
powerlines needed to distribute that power increases (APLIC 
1994). This increase requires utility companies and state and 
federal agencies to be even more conscious of environmental 
factors when choosing locations for new transmission lines. 
Entities hoping to avoid or reduce avian collision risks should 
use information about habitat use when making powerline 
placement decisions.  
Major funding was provided by the Nebraska Wildlife 
Conservation Fund and the State Wildlife Grant Program. We 
thank Jennifer L. Buckner with the USGS National Wildlife 
Health Center in Madison, Wisconsin for conducting the nec-
ropsy and diagnostic tests. We also thank the two anonymous 
reviewers that provided useful comments that improved 
the manuscript.—Lauren R. Dinan1, Joel G. Jorgensen, 
and Mary Bomberger Brown. Nongame Bird Program, Ne-
braska Game and Parks Commission, Lincoln, NE 68503, 
USA (LRD, JGJ). School of Natural Resources, University 
of Nebraska-Lincoln, Lincoln, NE 68583, USA (MBB). 1Cor-
responding author email address:ngpc.nongamebird.temp@
nebraska.gov.
LITERATURE CITED
Avian Power Line Interaction Committee [APLIC]. 1994. 
Mitigating bird collisions with power lines: the state of 
art in 1994. Edison Electric Institute, Washington, D.C., 
USA.
Henderson, I. G., R. H. W. Landgston, and N. A. Clark. 1996. 
The response of common terns Sterna hirundo to power 
lines: an assessment of risk in relation to breeding com-
mitment, age and wind speed. Biological Conservation 
77:185–192.
Janss, G. F. E. 2000. Avian mortality from power lines: a 
morphologic approach of a species-specific mortality. 
Biological Conservation 95:353–359.
Jorgensen, J. G., M. B. Brown, and A. J. Tyre. 2012. Chan-
nel width and interior least tern and piping plover nest-
ing incidence on the lower Platte River, Nebraska. Great 
Plains Research 22:59–67.
Savereno, A. J., L. A. Savereno, R. Boettcher, and S. M. 
Haig. 1996. Avian behavior and mortalities at power 
lines in coastal South Carolina. Wildlife Society Bulletin 
24:636–648. 
Thompson, B. C., J. A. Jackson, J. Burger, L. A. Hill, E. M. 
Kirsch, and J. L. Atwood. 1997. Least tern (Sterna an-
tillarum) in A Poole and F. Gill, editors. The Birds of 
North America, No. 290. The Academy of Natural Sci-
ence, Philadelphia, PA, and the American Ornithologist’ 
Union, Washington, D.C., USA.
U.S. Fish and Wildlife Service [USFWS]. 1990. Recovery 
plan for the interior population of least tern (Sterna an-
tillarum). U.S. Fish and Wildlife Service, Twin Cities, 
Minnesota, USA.
Submitted 11 November 2012. Accepted 19 December 2012. 
Associate Editor was Chadwick P. Lehman.
Figure 1. Dead adult interior least tern (Sternula antillarum 
athalassos) photographed on 7 June 2012 on a lower Platte 
River sandbar near Ashland, Saunders County, Nebraska. 
Photograph by Joel G. Jorgensen.


University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln The Prairie Naturalist Great Plains Natural Science Society 12-2012 Interior Least Tern Powerline Collision on the Lower Platte River Lauren R. Dinan Nebraska Game and Parks Commission, ngpc.nongamebird.temp@nebraska.gov Joel G. Jorgensen Nebraska Game and Parks Commission Mary Bomberger Brown University of Nebraska-Lincoln Follow this and additional works at: https://digitalcommons.unl.edu/tpn  Part of the Biodiversity Commons, Botany Commons, Ecology and Evolutionary Biology Commons, Natural Resources and Conservation Commons, Systems Biology Commons, and the Weed Science Commons Dinan, Lauren R.; Jorgensen, Joel G.; and Brown, Mary Bomberger, "Interior Least Tern Powerline Collision on the Lower Platte River" (2012). The Prairie Naturalist. 48. https://digitalcommons.unl.edu/tpn/48 This Article is brought to you for free and open access by the Great Plains Natural Science Society at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in The Prairie Naturalist by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. The Prairie Naturalist 44:109-110; 2012INTERIOR LEAST TERN POWERLINE COLLISION ON THE LOWER PLATTE RIVER—Collisions with electrical powerlines are a well-known documented cause of avian mortality (Avian Power Line Interaction Committee [APLIC] 1994, Savereno et al. 1996). Mortality caused by collisions with powerlines can be an important concern for many bird species, but is a serious conservation problem for threatened and endangered species because any mortality can have biological and legal ramifications (Janss 2000). Loss of individuals, particularly breeding adults, from an already small population may impede a species’ recovery by reduc-ing reproduction and recruitment into the breeding popula-tion. The death of an individual from a threatened or endan-gered species as a result of a collision may constitute “take” as defined by the federal Endangered Species Act (1973; 16 U.S.C. 1531–1544.) and the federal Migratory Bird Treaty Act (1918; 16 U.S.C. 703–712). Companies and/or individu-als may be prosecuted when powerline collisions occur, par-ticularly if recommendations intended to reduce the risk of collision, provided by the United States Fish and Wildlife Service (USFWS) regarding the placement of the powerlines, have not been followed.  The interior least tern (Sternula antillarum athalassos) is a federally endangered species (50 Federal Register 21784–21792) that breeds on and along the Mississippi and Mis-souri rivers and their tributaries (Thompson et al. 1997). The species’ principal nesting habitat includes sparsely vegetated sandbars within main river channels, but in some cases birds will nest on human-created habitats such as waste sand from dredging or mining operations (Thompson et al. 1997).  Inte-rior least terns are small and agile flyers able to readily avoid powerline collisions. In fact, collisions with powerlines were not identified as a potential threat to recovery in the interior least terns’ recovery plan (United States Fish and Wildlife Service [USFWS] 1990). Here, we provide the first docu-mented report of an interior least tern mortality that we are aware of, caused by a collision with a powerline, and com-ment on the conservation implications of the incident.On 7 June 2012, we recovered a dead male adult inte-rior least tern on a lower Platte River sandbar in Saunders County, Nebraska. We found the tern lying on the sand di-rectly below a set of transmission lines mounted on tall steel H-frame structures; the set included five individual lines. The transmission lines crossed the river and a large midstream sandbar (Fig. 1). We discovered the tern’s carcass in a colony that included approximately 30 adult terns associated with 13 nests, all early in the incubation period. All five transmission lines were marked with yellow, spiral bird flight diverters (APLIC 1994). These diverters were spaced approximately 15 m apart in a staggered pattern over the entire 485 m wide river crossing. The bird flight diverters were placed on the transmission lines following the recovery of a dead black tern (Chlidonias niger) at the same location in 2009, out of con-cern that the line could present risks to the legally protected interior least tern, piping plover (Charadrius melodus), and bald eagle (Haliaeetus leucocephalus) which regularly occur in the area. The transmission lines also were marked with nine yellow, white, and orange aerial marker spheres which are traditionally intended to alert aircrafts to the presence of the lines, but have occasionally been installed in an attempt to reduce bird collisions (APLIC 1994).The interior least tern carcass was fresh and in relatively good condition. Immediately after collection, the Nebraska Game and Parks Commission (NGPC) sent the carcass to the United States Geological Survey (USGS) National Wildlife Health Center in Madison, Wisconsin, where a necropsy was conducted. The results from the diagnostic evaluation indi-cated the tern was well nourished with no puncture wounds. The necropsy showed extensive hemorrhaging into the left lung and a blood clot in the left lobe of the liver; the suspect-ed cause of death was blunt force trauma to the left side of the body (J. L. Buckner, USGS National Wildlife Health Cen-ter, unpublished data). The results exclude possible causes of death such as emaciation, disease, or predation. Other than the transmission lines, no other vertical structures were within 150 m of where the tern carcass was found. Thus, the mortality is consistent with collision with a transmission line and all other explanations have been satisfactorily excluded. To our knowledge, this is the first report documenting powerline collisions as a source of interior least tern mortal-ity. Henderson el al. (1996) noted that terns are at a lower risk of powerline collisions due to their small size and agile flight. However, size and flight agility may not be the only factors that influence a species’ susceptibility to powerline collisions. Behavior, habitat use, time of day, wind speed, weather conditions, and age may influence a species’ suscep-tibility to powerline collisions. Interior least terns’ courting and pair-bonding behavior may increase their susceptibly to powerline collisions. When interior least terns are forming pairs, they engage in aerial chases with other terns (Thomp-son et al. 1997), such behaviors may make interior least terns more susceptible to collisions. The mortality we observed oc-curred early in the nesting season, shortly after birds arrived at breeding sites, and at a time when pairs were being formed and nests were initiated. Henderson et al. (1996) reported that adult common terns (Sterna hirundo) were more susceptible to powerline collisions during chick rearing when the fre-quency of adult tern flights to and from the colony increased >3 times. Additionally, adult terns flew closer to the electri-cal wires during the nestling and fledgling phases than dur-ing the courtship and incubation phases, due to the increased frequency of foraging flights necessary to feed their chicks (Henderson et al. 1996). This increase in a species suscepti-bility to powerline collisions also may be true for other tern species. The location of a powerline is an important determinant of whether collisions occur or can be avoided (APLIC 1994, Henderson et al. 1996). Powerlines located in habitats that are regularly frequented by species obviously have an in-creased probability of being encountered (Janss 2000).  In 110 The Prairie Naturalist  •  44(2): December 2012the case of interior least terns, powerlines that cross rivers, especially those that cross directly over large midstream sandbars or other traditional nesting sites, present higher risk (Henderson et al. 1996). Sandbar location, size and elevation can be dynamic, however there are static variables known to influence tern nesting habitat selection that can be used to predict the location of tern colonies (Jorgensen et al. 2012). For example, Jorgensen et al. (2012) documented that inte-rior least tern nesting incidence increased with increasing river channel width, and that interior least terns avoid nesting on sandbars located in narrow river channels. The location where this collision and mortality occurred was in one of the widest channels (84th percentile) in the lower Platte River (J. G. Jorgensen, NGPC, unpublished data), indicating that this area is likely to be more attractive to interior least terns than other narrower sections of the river. The mortality incident summarized here indicates in-terior least terns are vulnerable, albeit rarely, to powerline collisions that can result in mortality. This mortality incident shows that marking powerlines that are placed in areas com-monly used as a feeding, nesting, or roosting site, or divid-ing a habitat, with bird flight diverters or other types of line markers does not completely eliminate collision risk. The problem of bird mortality resulting from powerline colli-sions has become more important as the growing demand for electrical power increases and the number of kilometers of powerlines needed to distribute that power increases (APLIC 1994). This increase requires utility companies and state and federal agencies to be even more conscious of environmental factors when choosing locations for new transmission lines. Entities hoping to avoid or reduce avian collision risks should use information about habitat use when making powerline placement decisions.  Major funding was provided by the Nebraska Wildlife Conservation Fund and the State Wildlife Grant Program. We thank Jennifer L. Buckner with the USGS National Wildlife Health Center in Madison, Wisconsin for conducting the nec-ropsy and diagnostic tests. We also thank the two anonymous reviewers that provided useful comments that improved the manuscript.—Lauren R. Dinan1, Joel G. Jorgensen, and Mary Bomberger Brown. Nongame Bird Program, Ne-braska Game and Parks Commission, Lincoln, NE 68503, USA (LRD, JGJ). School of Natural Resources, University of Nebraska-Lincoln, Lincoln, NE 68583, USA (MBB). 1Cor-responding author email address:ngpc.nongamebird.temp@nebraska.gov.LITERATURE CITEDAvian Power Line Interaction Committee [APLIC]. 1994. Mitigating bird collisions with power lines: the state of art in 1994. Edison Electric Institute, Washington, D.C., USA.Henderson, I. G., R. H. W. Landgston, and N. A. Clark. 1996. The response of common terns Sterna hirundo to power lines: an assessment of risk in relation to breeding com-mitment, age and wind speed. Biological Conservation 77:185–192.Janss, G. F. E. 2000. Avian mortality from power lines: a morphologic approach of a species-specific mortality. Biological Conservation 95:353–359.Jorgensen, J. G., M. B. Brown, and A. J. Tyre. 2012. Chan-nel width and interior least tern and piping plover nest-ing incidence on the lower Platte River, Nebraska. Great Plains Research 22:59–67.Savereno, A. J., L. A. Savereno, R. Boettcher, and S. M. Haig. 1996. Avian behavior and mortalities at power lines in coastal South Carolina. Wildlife Society Bulletin 24:636–648. Thompson, B. C., J. A. Jackson, J. Burger, L. A. Hill, E. M. Kirsch, and J. L. Atwood. 1997. Least tern (Sterna an-tillarum) in A Poole and F. Gill, editors. The Birds of North America, No. 290. The Academy of Natural Sci-ence, Philadelphia, PA, and the American Ornithologist’ Union, Washington, D.C., USA.U.S. Fish and Wildlife Service [USFWS]. 1990. Recovery plan for the interior population of least tern (Sterna an-tillarum). U.S. Fish and Wildlife Service, Twin Cities, Minnesota, USA.Submitted 11 November 2012. Accepted 19 December 2012. Associate Editor was Chadwick P. Lehman.Figure 1. Dead adult interior least tern (Sternula antillarum athalassos) photographed on 7 June 2012 on a lower Platte River sandbar near Ashland, Saunders County, Nebraska. Photograph by Joel G. Jorgensen.

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Interior Least Tern Powerline Collision on the Lower Platte River

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