Review
Seabird mortality induced by land-based artificial
lights
Airam Rodr
´
ıguez,
1 ∗
Nick D. Holmes,
2
Peter G. Ryan,
3
Kerry-Jayne Wilson,
4
Lucie Faulquier,
5
Yovana Murillo,
6
Andr
´
e F. Raine,
7
Jay F. Penniman,
8
Ver
´
onica Neves,
9
Beneharo Rodr
´
ıguez,
10
Juan J. Negro,
1
Andr
´
e Chiaradia,
11
Peter Dann,
11
Tracy Anderson,
12
Benjamin Metzger,
13
Masaki Shirai,
14
Lorna Deppe,
15
Jennifer Wheeler,
16
Peter Hodum,
17
Catia Gouveia,
18
Vanda Carmo,
19
Gilberto P. Carreira,
19
Luis Delgado-Alburqueque,
20
Carlos Guerra-Correa,
21
Franc¸ois-Xavier Couzi,
22
Marc Travers,
7
and Matthieu Le Corre
23
1
Department of Evolutionary Ecology, Estaci
´
on Biol
´
ogica de Do
˜
nana (CSIC), Avda. Am
´
erico Vespucio s/n, 41092 Seville, Spain
2
Island Conservation, 2100 Delaware Avenue, Suite 1, Santa Cruz, CA 95060, U.S.A.
3
Percy FitzPatrick Institute of African Ornithology, DST-NRF Centre of Excellence, University of Cape Town, Rondebosch 7701,
South Africa
4
West Coast Penguin Trust, P.O. Box 70, Charleston 7865, West Coast, New Zealand
5
Ornithological Society of French Polynesia, P.O. Box 7023, 98719 Taravao, Tahiti
6
Ringed Storm-Petrel Project, Joaqu
´
ın Sorolla 157, Lima 41, Peru
7
Kauai Endangered Seabird Recovery Project, P.O. Box 81, Hanapepe 96741, Kauai, HI, U.S.A.
8
Maui Nui Seabird Recovery Project, 4234 Hana Highway, Haiku, 96708-5404, HI, U.S.A.
9
Department of Oceanography & Fisheries ( DOP), University of the Azores, MARE (Marine and Environmental Sciences Centre),
IMAR (Institute of Marine Research), Rua Prof. Dr Frederico Machado 4, PT-9901-862 Horta, Azores, Portugal
10
Canary Islands’ Ornithology and Natural History Group (GOHNIC), La Malecita s/n, 38480 Buenavista del Norte, Tenerife, Canary
Islands, Spain
11
Research Department, Phillip Island Nature Parks, P.O. Box 97, Cowes, Phillip Island, Victoria, 3922, Australia
12
Save Our Shearwaters, P.O. Box 3330, Lihue, 96766, Kauai, HI, U.S.A.
13
BirdLife Malta, Flat 2, Xemxija Waterfront Apartments, Triq Is-Simar, Xemxija SPB9025, Malta
14
Environmental Science Research Laboratory, Central Research Institute of Electric Power Industry, 1646, Abiko, Abiko-shi, Chiba,
270-1194, Japan
15
The Hutton’s Shearwater Charitable Trust, P.O. Box 58 Kaik
¯
oura 7340, New Zealand
16
BirdsCaribbean, 4201 Wilson Blvd 110–174, Arlington, VA 22203, U.S.A.
17
Oikonos Ecosystem Knowledge, P.O. Box 1918, Kailua, HI 96734, U.S.A.
18
Portuguese Society for the Study of Birds, Travessa das Torres 2A, 1° andar, 9060–314 Funchal, Madeira, Portugal
19
Direc¸
˜
ao Regional dos Assuntos do Mar; Secretaria Regional do Mar, Ci
ˆ
encia e Tecnologia; Governo Regional dos Ac¸ores; Col
´
onia
Alem
˜
a - Apartado 9, 9900-014 Horta, Azores, Portugal
20
Ringed Storm-Petrel Project, Veterinary Science School, Ricardo Palma University, Av. Benavides 5440, Lima 33, Per
´
u
21
Centro Regional de Estudios y Educaci
´
on Ambiental, Universidad de Antofagasta (CREA-UA), 602 Angamos Av., Antofagasta, Chile
22
Soci
´
et
´
ed’
´
Etudes Ornithologiques de la R
´
eunion, 13, ruelle des Orchid
´
ees 97440 Saint Andr
´
e, La R
´
eunion, France
23
UMR ENTROPIE, Universit
´
edelaR
´
eunion 15, avenue Ren
´
e Cassin - CS 92003 97744 Saint Denis C
´
edex 9, La R
´
eunion, France
Abstract: Artificial lights at night cause high mortality of seabirds, one of the most endangered groups of
birds globally. Fledglings of burrow-nesting seabirds, and to a lesser extent adults, are attracted to and then
grounded (i.e., forced to land) by lights when they fly at night. We reviewed the current state of knowledge
of seabird attraction to light to identify information gaps and propose measures to address the problem.
Although species in families such as Alcidae and Anatidae can be grounded by artificial light, the most
affected seabirds are petrels and shearwaters (Procellariiformes). At least 56 species of Procellariiformes,
∗
email airamrguez@ebd.csic.es
Paper submitted July 11, 2016; revised manuscript accepted January 26, 2017.
1
Conservation Biology,Volume00,No.0,1–16
C
2017 Society for Conservation Biology
DOI: 10.1111/cobi.12900
2 Seabird Mortality and Artificial Lights
more than one-third of them (24) threatened, are subject to grounding by lights. Seabirds grounded by lights
have been found worldwide, mainly on oceanic islands but also at some continental locations. Petrel breeding
grounds confined to formerly uninhabited islands are particularly at risk from light pollution due to tourism
and urban sprawl. Where it is impractical to ban external lights, rescue programs of grounded birds offer the
most immediate and employed mitigation to reduce the rate of light-induced mortality and save thousands
of birds every year. These programs also provide useful information for seabird management. However, these
data are typically fragmentary, biased, and uncertain and can lead to inaccurate impact estimates and poor
understanding of the phenomenon of seabird attraction to lights. We believe the most urgently needed actions
to mitigate and understand light-induced mortality of seabirds are estimation of mortality and effects on
populations; determination of threshold light levels and safe distances from light sources; documentation of
the fate of rescued birds; improvement of rescue campaigns, particularly in terms of increasing recovery rates
and level of care; and research on seabird-friendly lights to reduce attraction.
Keywords: disorientation, illumination, light pollution, orientation, petrel, rescue campaign
Mortalidad de Aves Marinas Producida por Luces Artificiales Terrestres
Resumen: Las luces artificiales nocturnas causan una mortalidad alta de aves marinas, uno de los grupos de
aves en mayor peligro de extinci
´
on a nivel mundial. Los polluelos de aves marinas que anidan en madrigueras,
y en menor medida los adultos, son atra
´
ıdos y forzados a aterrizar por las luces cuando vuelan de noche.
Revisamos el estado actual del conocimiento sobre la atracci
´
on de las aves marinas por la luz para identificar
vac
´
ıos de informaci
´
on y proponer medidas para resolver el problema. Aunque las especies de familias como
Alcidae y Anatidae pueden ser forzadas a aterrizar por la luz artificial, las aves marinas m
´
as afectadas son
los petreles y las pardelas (Procellariiformes). Por lo menos 56 especies de Procellariiformes, m
´
as de un tercio
(24) de ellas amenazadas, son propensas al aterrizaje atra
´
ıdas por las luces. Las aves marinas forzadas a
aterrizar han sido halladas en todo el mundo, principalmente en islas oce
´
anicas, pero tambi
´
en en algunas
localidades continentales. Los sitios de anidaci
´
on de los petreles confinados anteriormente a islas deshabitadas
est
´
an particularmente en riesgo de sufrir contaminaci
´
on lum
´
ınica debido al turismo y al crecimiento urbano.
En donde no es pr
´
actico prohibir las luces externas, los programas de rescate de las aves accidentadas ofrecen
la mitigaci
´
on m
´
as inmediata y empleada para reducir la tasa de mortalidad inducida por la luz y salvar
a miles de aves cada a
˜
no. Estos programas tambi
´
en proporcionan informaci
´
on
´
util para el manejo de aves
marinas. Sin embargo, estos datos est
´
an t
´
ıpicamente fragmentados, sesgados y son inciertos, y pueden llevar
a estimaciones inexactas del impacto y a un entendimiento pobre del fen
´
omeno de la atracci
´
on de las aves
marinas por la luz. Creemos que las acciones necesarias de mayor urgencia para mitigar y entender la
mortalidad de aves marinas producida por la luz son: la estimaci
´
on de la mortalidad y los efectos sobre la
poblaci
´
on; la determinaci
´
on de umbrales de niveles de luz y de distancias seguras a las fuentes de luz; el
estudio del destino de las aves rescatadas; la mejora de las campa
˜
nas de rescate, particularmente en t
´
erminos
de incrementar las tasas de recogida y el nivel de cuidado; y la investigaci
´
on sobre las caracter
´
ısticas de la
luz para reducir la atracci
´
on de las aves marinas.
Palabras Clave: campa
˜
na de rescate, contaminaci
´
on lum
´
ınica, desorientaci
´
on, iluminaci
´
on, orientaci
´
on, petrel
Introduction
The alteration of n atural light levels in the environment,
or light pollution, has increased dramatically over the last
century and has led to the loss of natural nightscapes
worldwide (Bennie et al. 2015; Gaston et al. 2015a)
and affected, for example, individuals’ health, popula-
tions’ time partitioning, interspecific interactions, repro-
duction, movements, and community structure, thereby
causing cascade effects on ecosystem functioning (Long-
core & Rich 2004; Gaston et al. 2014, 2015b). Accord-
ingly, light pollution is recognized as a great threat to
biodiversity (H
¨
olker et al. 2010). One of the most se-
vere ecological consequences of light pollution is light-
induced mass fatality events.
Seabirds are among the most endangered groups of
birds globally, and Procelariiformes (hereafter petrels)
has one of the highest proportions of threatened species
(Croxall et al. 2012). The principal threats at sea are
commercial fishery operations (e.g., competition and by-
catch) and pollution (e.g., oil spills, marine-debris inges-
tion, and entanglement). On land introduced predators
and habitat loss can severely impact breeding colonies
(Croxall et al. 2012). The widespread and ever-growing
use of artificial light at night is an increasing threat to
seabirds. Burrow-nesting petrels are attracted to artifi-
cial lights at night, become disorientated, and are forced
to land (Imber 1975). This phenomenon, called fall-
out (Reed et al. 1985), can cause mass-mortality events
(Telfer et al. 1987; Ainley et al. 2001; Le Corre et al.
Conservation Biology
Volume 00, No. 0, 2017
Rodr
´
ıguez et al. 3
Figure 1. Locations where attraction of seabird fledglings to lights has been reported (numbers, number of species
affected; circle size, proportional to number of grounded birds; CR, c ritically endangered; EN, endangered; VU,
vulnerable; NT, near threatened; LC, least concern).
2002; Rodr
´
ıguez & Rodr
´
ıguez 2009; Rodr
´
ıguez et al.
2014). Light-induced grounding can be fatal due to col-
lisions with human-made structures (e.g. buildings, elec-
tric wires and pylons, fences, or posts) or the ground.
Even if uninjured, grounded birds may be unable to take
off again and are vulnerable to predation; vehicle colli-
sions (Rodr
´
ıguez et al. 2012b, 2014); starvation or de-
hydration (Rodr
´
ıguez et al. 2012b); and poaching (some
people eat grounded birds) (M.L-C., personal observa-
tion).
We reviewed the state of knowledge and the global
impact of seabird mortality induced by land-based arti-
ficial light. Specifically, we f ocused on the global distri-
bution and scale of impacts to seabird species; what is
known after four decades of seabird rescue and reha-
bilitation campaigns worldwide; and what information
is needed to better assess and mitigate this growing
threat.
Information Sources
To determine the taxonomic diversity of seabirds affected
by lights, we consulted the IUCN Red List of Threatened
Species website (IUCN 2016) and searched for species
affected by light pollution. We refined our search with
the terms Aves and light pollution (within excess energy,
pollution, and threats categories). We found 15 species
assessments: 13 petrels, 1 auklet, and 1 thrush (Support-
ing Information). We also searched Web of Science for
peer-reviewed literature on seabird attraction to light by
combining targeted keyword searches (light pollution,
artificial light
∗
, seabird
∗
, marine bird
∗
,light
∗
, mortality,
attraction, and disorientation). We classified publications
as of interest if they dealt with seabird mortality induced
by artificial lights and as terrestrial or marine, depend-
ing on whether mortality, attraction, or disorientation
was caused by land- or marine-based lights. Twenty-one
of the 100 publications that emerged from our search
at Web of Science dealt with light-induced mortality of
seabirds. Fourteen publications were classified as ter-
restrial and 7 as marine (Supporting Information). Our
list was not exhaustive, but it reflected the information
available for different taxa. To expand our search, we
examined the references in the publications of inter-
est, as well as their citations, and found 9 additional
publications.
Rescue efforts (defined as actions taken to recover
birds grounded by light attraction, mitigate threats associ-
ated with light-induced grounding [road kills, predation,
dehydration, starvation, or poaching], and release birds
to the ocean) constitute an information source because
data collection has been instituted for some projects. We
used the internet and social media (Google, Facebook,
and Twitter) to search for programs in which citizens
are encouraged to rescue and report on grounded birds.
We asked them for information on the number of species
and individuals, proportion of ages, proportion of the
population affected, and mortality rates.
Location, Species, and Age of Grounded Birds
We found that light-induced fatality of seabirds has been
recorded on at least 47 islands worldwide, on three
continental locations, and across all oceans (Fig. 1).
Conservation Biology
Volume 00, No. 0, 2017
4 Seabird Mortality and Artificial Lights
Figure 2. Threatened seabirds (IUCN 2014) affected by light-induced mortality on land (numbers on y-axis,
number of grounded birds dead and alive; question mark, species reported to be grounded by light but without
quantification).
This phenomenon affects mainly burrow-nesting petrel
species (Procellariidae, Hydrobatidae, and Oceanitidae),
although other seabirds such as auklets and puffins (Al-
cidae) and eiders (Anatidae) can also be affected (Dick
& Donalson 1978; Whitworth et al. 1997; Merkel &
Johansen 2011; Wilhelm et al. 2013). The disproportion-
ate effect on petrels was supported by the scant informa-
tion on other species. Only 1 of 14 publications classified
as terrestrial, and 2 of 15 IUCN species assessments dealt
with species other than petrels. Fifty-six of 113 burrow-
nesting petrel species have been recorded grounded by
lights, an estimate more than double the number reported
in previous publications (Reed et al. 1985) and four times
higher than the number of species for which this is
listed as a problem by IUCN. Twenty-four seabird species
subject to light-induced grounds are globally threatened
(Fig. 2 & Supporting Information). Attraction to and dis-
orientation by lights of seabirds at sea have also been
reported (7 studies report light mortality, attraction, or
disorientation at sea), primarily in association with lights
being used for fisheries purposes (Ryan 1991; Black 2005;
Merkel & Johansen 2011; Glass & Ryan 2013) but also
with lights on oil platforms (Wiese et al. 2001; Day
et al. 2015; Ronconi et al. 2015). Light-induced mortality
at sea is difficult to document (Montevecchi 2006); thus,
assessments may be underreported relative to estimates
of land-based mortality.
Of the 14 studies focused on light-induced fatali-
ties on land, all documented a greater number of fa-
talities of fledglings than of adults. Most seabirds af-
fected are fledglings grounded during their first flights
from their natal nests toward the ocean. The percent-
age of affected fledglings in relation to all grounded
birds (i.e., fledglings + adults) varies among species
from 68% to 99% (Table 1). Rescue programs that tar-
get fledglings and collect data on age probably under-
estimate the number of adults involved, but at most
sites it appears fewer adults are affected (Table 1).
Thus, presumably, the main functional consequence of
light-induced fatality on land is reduced survival after
fledging. However, rescue programs should ensure that
adults are not ignored by not restricting rescues to the
fledging season and by quantifying adult mortality. At
sea, light attraction may involve adults and juveniles
because some events occur outside fledging periods.
None of the 7 marine studies considered the age of
birds.
Reasons for Light-Induced Grounding
The reasons for seabird attraction to and disorientation by
lights are not well known. Three hypotheses have been
proposed. First, artificial light is perceived by birds as a
Conservation Biology
Volume 00, No. 0, 2017
Rodr
´
ıguez et al. 5
Table 1. Comparison of results of campaigns to rescue seabirds grounded by artificial light.
a
Island Species Fledglings (%)
b
Light-
grounded
fledglings (%)
c
Mortality of
grounded
birds (%)
d
Number of
birds rescued
e
Years
e
Source
Tenerife, Canary Is. Calonectris
borealis
96.4 45.4–60.5; 14 4.8 9,231 9 Rodr
´
ıguez & Rodr
´
ıguez
2009; Rodr
´
ıguez
et al. 2015b
Puffinus
lherminieri
90.3 20.9–46.9 4.9 144 9 Rodr
´
ıguez & Rodr
´
ıguez
2009
Bulweria
bulwerii
68 6.4–8.6 11.8 340 9 Rodr
´
ıguez & Rodr
´
ıguez
2009
Reunion Is. Pterodroma
baraui
98.9 20–40 10 1,643 4 Le Corre et al. 2002
Puffinus balloni 82.2; 95 10–17 7.9; 12 13,221 20 Le Corre et al. 2002;
Gineste et al. 2016
S
˜
ao Miguel, Azores Calonectris
borealis
n.a. 16.7 14 769 2 Rodrigues et al. 2012
Faial, Azores Calonectris
borealis
n.a. 19.7 4 1,236 1 Fontaine et al. 2011
Kauai, Hawaii Puffinus newelli 97 15 9; 43
g
11,767 8 Telfer et al. 1987;
Ainley et al. 2001
Pico, Azores Calonectris
borealis
n.a. 15.2 8 1,547 1 Fontaine et al. 2011
Robison Crusoe Is. Ardenna
creatopus
73.7 0.5–1.1 41 164 4 P. Hodum, personal
observation
Phillip Is., Australia Ardenna
tenuirostris
n.a. 0.39–0.70 39
g
8,871 15 Rodr
´
ıguez et al. 2014
Balearic Is. Puffinus
mauretanicus
n.a. 0.38–0.7 8.5 66 15 Rodr
´
ıguez et al. 2015a
Calonectris
diomedea
n.a. 0.26–0.49 8.5 199 15 Rodr
´
ıguez et al. 2015a
Hydrobates
pelagicus
n.a. 0.09–0.27 8.5 39 15 Rodr
´
ıguez et al. 2015a
Tahiti Pseudobulweria
rostrata
95 n.a. 9 981 11 L. Faulquier, personal
observation
Newfoundland Fratercula
arctica
f
n.a. n.a. 8.2 522 2 Wilhelm et al. 2013
Antofagasta region Hydrobates
hornbyi
n.a. n.a. 5 1,122 7 C. Guerra-Correa,
personal observation
a
Values separated by a semicolon are estimates of different studies listed at the end of the row.
b
Percentage of fledglings in relation to the total number of grounded birds (i.e., including adults and fledglings).
c
Percentage of fledglings grounded by lights in relation to the total of fledglings annually produced by the population. Ranges are given because of different breeding population size estimates
(maximum and minimum).
d
Reported as dead or dying during the rescue.
e
The number of birds and number of years of data collection are given to provide an idea of the reliability and robustness of the values in the table.
f
Not a petrel species.
g
Mortality rate based on systematic searches for grounded birds.
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Volume 00, No. 0, 2017
