loss, development, human activities and disturbance,
disease, toxic chemicals, plastics, invasive species, and
fisheries. Habitat loss is the primary factor affecting seabirds that nest along coasts because these regions are
highly developed, putting pressure on the cliffs, islands,
and bare ground where seabirds nest. In the long term,
climate change may pose a great risk by affecting
fisheries bycatch, spatial ecology, food sources, and prey
availability (Gremillet and Boulinier, 2009; Barbraud
et al., 2012).
Seabirds are exposed to a range of human activities that
disrupt their breeding, foraging, migrating, and
overwintering. Disruptions include direct disturbance,
such as people entering breeding colonies, scaring incubating adults from nests, destroying eggs, bringing in
predators (e.g., dogs), and disrupting foraging with boats,
Jet Skis, or other water-related activities. Indirect effects
include increases in native predators because of availability of food brought by humans (e.g., raccoons). Effects on
nesting and foraging seabirds can occur as a result of scientific investigators or others that visit colonies or monitor
seabird behavior. A meta-analysis of the effect of transmitters on avian behavior found significant effects – birds
with devices had greater energy expenditures and some
failed to nest (Barron et al., 2010). However, usually
devices are used on only a few individuals, and information gained from these is greater than the cost to these
individuals and any potential costs of alternative methods
of learning about movements and migration patterns
(Burger et al., 2012).
Fisheries are a special case of human activities; fisheries have a positive and a negative effect. Positive effects
include provision of food from offal, around factor ships,
or near processing plants. Negative effects include mortality from capture in fishing lines or equipment or being
entangled and drowning (called bycatch, Moore et al.,
2009) or because of competition with fisheries for fish.
Prey depletion can be a problem during breeding when
adults are limited to foraging distance around their nests.
Seabirds and fisheries have interacted for centuries with
little effect until the rapid enhancement of fishing capabilities and overexploitation of fish stocks that happened in
the last two centuries. However, the advent of large factory
ships and deployment of longlines that extend for kilometers increased overfishing of fish stocks and massive
increases in captures in nets, especially albatrosses and
petrels (Montevecchi, 2001).
Human activities are responsible for most of the toxic
chemicals in the environment, and where toxic elements
are present in soil or water (e.g., mercury in seawater),
organisms have adapted to natural levels. Pollution in
the ocean comes from dumping of wastes, dredging, runoff from towns and rivers, and point source pollution from
factories, urbanization, suburbanization, and coastal businesses and activities. Toxics and plastics threaten seabirds
because they spend so much time in water where they are
exposed externally, by inhalation and by ingestion of food
and water (Burger and Gochfeld, 2001). Both individuals
and populations can be affected, either acutely or by
chronic exposure. The chemicals that have been shown
to affect seabirds include lead, mercury and other metals,
oil, polychlorinated biphenyls (PCB), dichlorodiphenyltrichloroethane (DDT), and other organochlorine compounds (Burger and Gochfeld, 2001). Oil spills can
cause large-scale mortality (Kingston, 2002). DDT is
the classic case of toxic effects. Populations of several
fish-eating birds (e.g., Brown Pelican, Pelecanus
occidentalis; White Pelican, P. erythrorhynchos; and
Gannets) collapsed in the 1960s because DDT interfered
with calcium and eggshell development (Blue et al.,
1974). When adults sat to incubate, their thin-shelled eggs
broke. Plastics are synthetic organic polymers, and their
increase over the last two decades resulted in large quantities of plastics entering the oceans. Seabirds are mainly
affected by entanglement, exposure to PCBs from ingestion, and compromises to the digestive tract because of
ingestion of large quantities (Derraik, 2002). Many species of seabirds are endangered (Nettleship et al., 1994;
Schreiber and Burger, 2001a).
Summary
Seabirds, including penguins, albatrosses, petrels,
boobies, pelicans, gulls, and terns, spend most of their life
foraging at sea and breed on coastal or oceanic islands far
removed from mammalian predators. They are long-lived
and have delayed breeding, low clutch sizes, long incubation periods, and extended parental care. Most nest in colonies that are either monospecific or contain many
different species. Nesting in colonies allows for early
warning, groups defense, predator swamping that reduces
the chances of any individual being eaten, and information
transfer about food sources. The threats to seabirds include
habitat loss and degradation, overfishing, invasive predators, toxics, plastics, and climate change. The biggest
threat to nesting seabirds is nonnative mammalian predators, while fisheries provide the biggest threat to foraging
seabirds (both mortality and competition for prey). Many
species of seabirds are endangered.
Bibliography
Balance, L. T., Pitman, R. L., and Fiedler, P. C., 2006. Oceanographic influences on seabirds and cetaceans of the eastern tropical Pacific: a review. Progress in Oceanography, 69, 360–390.
Barbraud, C., Rolland, V., Jenouvrier, S., Nevous, M., Delord, K.,
and Weimerskirch, H., 2012. Effects of climate change and fisheries bycatch on Southern Ocean seabirds: a review. Marine
Ecology Progress Series, 454, 285–302.
Barron, D. G., Brawn, J. D., and Weatherhead, P. J., 2010. Metaanalysis of transmitter effects on avian behavior and ecology.
Methods in Ecology, 1, 180–187.
Blue, L. J., Neely, B. S., Jr., Belisle, A. E., and Prouty, R. M., 1974.
Organochlorine residues in Brown Pelicans: relation to reproductive success. Environmental Pollution, 7, 81–91.
Burger, J., 1982. An overview of factors affecting reproductive
success in colonial birds. Colonial Waterbirds, 5, 58–123.
Burger, J., and Gochfeld, M., 2001. Effects of chemicals and pollution on seabirds. In Schreiber, E. A., and Burger, J. (eds.),
SEABIRDS
541
disease, toxic chemicals, plastics, invasive species, and
fisheries. Habitat loss is the primary factor affecting seabirds that nest along coasts because these regions are
highly developed, putting pressure on the cliffs, islands,
and bare ground where seabirds nest. In the long term,
climate change may pose a great risk by affecting
fisheries bycatch, spatial ecology, food sources, and prey
availability (Gremillet and Boulinier, 2009; Barbraud
et al., 2012).
Seabirds are exposed to a range of human activities that
disrupt their breeding, foraging, migrating, and
overwintering. Disruptions include direct disturbance,
such as people entering breeding colonies, scaring incubating adults from nests, destroying eggs, bringing in
predators (e.g., dogs), and disrupting foraging with boats,
Jet Skis, or other water-related activities. Indirect effects
include increases in native predators because of availability of food brought by humans (e.g., raccoons). Effects on
nesting and foraging seabirds can occur as a result of scientific investigators or others that visit colonies or monitor
seabird behavior. A meta-analysis of the effect of transmitters on avian behavior found significant effects – birds
with devices had greater energy expenditures and some
failed to nest (Barron et al., 2010). However, usually
devices are used on only a few individuals, and information gained from these is greater than the cost to these
individuals and any potential costs of alternative methods
of learning about movements and migration patterns
(Burger et al., 2012).
Fisheries are a special case of human activities; fisheries have a positive and a negative effect. Positive effects
include provision of food from offal, around factor ships,
or near processing plants. Negative effects include mortality from capture in fishing lines or equipment or being
entangled and drowning (called bycatch, Moore et al.,
2009) or because of competition with fisheries for fish.
Prey depletion can be a problem during breeding when
adults are limited to foraging distance around their nests.
Seabirds and fisheries have interacted for centuries with
little effect until the rapid enhancement of fishing capabilities and overexploitation of fish stocks that happened in
the last two centuries. However, the advent of large factory
ships and deployment of longlines that extend for kilometers increased overfishing of fish stocks and massive
increases in captures in nets, especially albatrosses and
petrels (Montevecchi, 2001).
Human activities are responsible for most of the toxic
chemicals in the environment, and where toxic elements
are present in soil or water (e.g., mercury in seawater),
organisms have adapted to natural levels. Pollution in
the ocean comes from dumping of wastes, dredging, runoff from towns and rivers, and point source pollution from
factories, urbanization, suburbanization, and coastal businesses and activities. Toxics and plastics threaten seabirds
because they spend so much time in water where they are
exposed externally, by inhalation and by ingestion of food
and water (Burger and Gochfeld, 2001). Both individuals
and populations can be affected, either acutely or by
chronic exposure. The chemicals that have been shown
to affect seabirds include lead, mercury and other metals,
oil, polychlorinated biphenyls (PCB), dichlorodiphenyltrichloroethane (DDT), and other organochlorine compounds (Burger and Gochfeld, 2001). Oil spills can
cause large-scale mortality (Kingston, 2002). DDT is
the classic case of toxic effects. Populations of several
fish-eating birds (e.g., Brown Pelican, Pelecanus
occidentalis; White Pelican, P. erythrorhynchos; and
Gannets) collapsed in the 1960s because DDT interfered
with calcium and eggshell development (Blue et al.,
1974). When adults sat to incubate, their thin-shelled eggs
broke. Plastics are synthetic organic polymers, and their
increase over the last two decades resulted in large quantities of plastics entering the oceans. Seabirds are mainly
affected by entanglement, exposure to PCBs from ingestion, and compromises to the digestive tract because of
ingestion of large quantities (Derraik, 2002). Many species of seabirds are endangered (Nettleship et al., 1994;
Schreiber and Burger, 2001a).
Summary
Seabirds, including penguins, albatrosses, petrels,
boobies, pelicans, gulls, and terns, spend most of their life
foraging at sea and breed on coastal or oceanic islands far
removed from mammalian predators. They are long-lived
and have delayed breeding, low clutch sizes, long incubation periods, and extended parental care. Most nest in colonies that are either monospecific or contain many
different species. Nesting in colonies allows for early
warning, groups defense, predator swamping that reduces
the chances of any individual being eaten, and information
transfer about food sources. The threats to seabirds include
habitat loss and degradation, overfishing, invasive predators, toxics, plastics, and climate change. The biggest
threat to nesting seabirds is nonnative mammalian predators, while fisheries provide the biggest threat to foraging
seabirds (both mortality and competition for prey). Many
species of seabirds are endangered.
Bibliography
Balance, L. T., Pitman, R. L., and Fiedler, P. C., 2006. Oceanographic influences on seabirds and cetaceans of the eastern tropical Pacific: a review. Progress in Oceanography, 69, 360–390.
Barbraud, C., Rolland, V., Jenouvrier, S., Nevous, M., Delord, K.,
and Weimerskirch, H., 2012. Effects of climate change and fisheries bycatch on Southern Ocean seabirds: a review. Marine
Ecology Progress Series, 454, 285–302.
Barron, D. G., Brawn, J. D., and Weatherhead, P. J., 2010. Metaanalysis of transmitter effects on avian behavior and ecology.
Methods in Ecology, 1, 180–187.
Blue, L. J., Neely, B. S., Jr., Belisle, A. E., and Prouty, R. M., 1974.
Organochlorine residues in Brown Pelicans: relation to reproductive success. Environmental Pollution, 7, 81–91.
Burger, J., 1982. An overview of factors affecting reproductive
success in colonial birds. Colonial Waterbirds, 5, 58–123.
Burger, J., and Gochfeld, M., 2001. Effects of chemicals and pollution on seabirds. In Schreiber, E. A., and Burger, J. (eds.),
SEABIRDS
541