Is there still hope for the American Avocet in this Rapidly Changing World?

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Is there still hope for the American Avocet in this Rapidly Changing World?

Ingrid Schoonover

The American Avocet (Recurvirostra
americana) is a beautiful North
American migratory shorebird that lives
in freshwater wetlands, marine intertidal
areas, salt marshes, and brackish

They are migratory in nature: traveling
northward to the breeding grounds
between February and May, returning
to their southern winter grounds
between June and December.

Despite their listing as a species of
Least Concern by the IUCN Red List,
the American Avocet faces numerous
threats to its survival. Unfortunately, in
a world that is being rapidly modified
and polluted by humans, most
migratory shorebirds are being exposed
to an ever-increasing variety of
environmental dangers.

Historically, American Avocet
populations have been negatively
affected by shooting and trapping, but
this has not been an issue since
hunting them has been criminalized
since the Migratory Bird Treaty Act of

The biggest threat to the
American Avocet today is reduced
breeding range due to the
massive wetland loss that has
occurred over the last 200 years
because of human development.
Climate-change in the form of
increasing sea levels, droughts,
and changing weather patterns
present another set of issues,
especially during incubation and
developmental periods.
Runoff and technology from the
agricultural industry has
contributed to the contamination
of wetlands with toxic elements
(such as selenium which causes
embryonic deformities). Similarly,
wetlands have been contaminated
by other industries including coal
burning, metal smelting, crude oil
processing, and mining.

Oil pits and gold-mining cyanide
leach ponds are another huge
danger because to the American
Avocet they appear as attractive
nesting grounds, but the metals
and elements at these sites are
toxic and will kill their eggs.

About the American
The American Avocet is easily
identified by their rusty-orange
head with a long upturned black
bill, and long blueish-gray legs
with webbed feet and black claws.
They are large birds that reach
17 to 18.5 inches (43-47 cm) in
length and weigh between 10 to
12 ounces (275-350 g). They
have large black wings with a
wingspan of 36 inches (91 cm),
that are contrasted with a white
‘V’ that runs down both wings
and connects along their lower
back. The dark wings stand out
against their white underparts.
The plumage on their head and
neck changes with seasons.
During the breeding season they
display alternate plumage, which
is characterized by a rusty head
and neck. During the non-breeding season, they display
basic plumage, distinctive due to
a light grey head and neck.

They are migratory birds, traveling
northward to the breeding
grounds between February and
early May. The breeding range is
expansive and includes the San
Francisco Bay area, to the east
of the Sierra Nevada and
Cascade mountain ranges, the
Southwestern United States, the
Central United States, and
Northward to Alberta and British
Colombia in Canada. They return
to the non-breeding winter ground
between the end of June and
beginning of December. Most
flocks overwinter along southern
California and southern Mexico,
occasionally overwintering on the
Atlantic Coast of the southern
United States between Florida
and South Carolina.

Disappearing Wetlands
Only half of original wetlands remain in the United States.
Wetland habitats are important
breeding sites for many species of
birds including the American Avocet,
but wetlands are destroyed and
degraded by processes of human
development including but not limited
to peat mining, drainage, damming,
logging, construction, runoff, dredging,
agricultural grazing, and damage from
invasive species.

At the beginning of the 19th century
there were 221 million acres of
wetlands in the geographic region
that today makes up the continental
United States, but today only 110
million acres remain, which is a 50%

The American Avocet form breeding
pairs before and during migration,
with over half of all migrating
breeding pairs stopping at wetland
sites to breed.

The massive wetland losses over the
last 200 have reduced the breeding
range of the American Avocet which
has led to population declines and
has forced birds to nest on less ideal
or even dangerous sites.

Many other species of waterbirds
have been declining in abundance in
areas of wetland loss, including the
American White Pelican, Snowy Plover,
Marbled Godwit, and Wilson’s
Phalarope. This negative trend is
especially true within the Great Basin
where populations of shorebirds have
declined by 70% since 1973.

Fortunately, the rate of wetland
decline has been slowing since the
early-2000s, this is the result of
wetland restoration projects, coastal
monitoring programs, public
education, enforcement of wetland
protections, and eliminating incentives
for wetland drainage.


Ecology of the American
American Avocet breeding pairs
will search for a nesting-site
together between early April and
mid-June. They nest on soft
ground, within 10 to 200 feet
(3-63 m) from waterlines, and
they build their nest by the
process of scraping, where the
pair use their breast and feet to
dig a small hole that is
surrounded by a mound that is
usually 1 to 4 inches tall (2-10
cm). Most nests are fully or
partially lined with grasses,
feathers, pebbles, and shells.

Pairs have one brood per
season (mid-April to late-June),
usually consisting of four eggs.
Pairs will incubate the eggs
together, alternating shifts during
the day and with the female
usually incubating alone at night.
The eggs hatch after 18 to 29
days of incubation. The newly
hatched chicks only have downy
feathers, and they leave the
nest within 24 hours of hatching.
Together the parents and the
chicks move to a nursery area
which has shallow water and low
vegetation to cover the chicks.
The chicks forage for their own
food while parents watch over
them closely. They quickly
develop juvenile plumage, which
is like breeding adult/Alternate
plumage, but all the colors are
washed out. They can fly at four
to five weeks old (27 days
approximately). They will migrate
to the winter ground and stay
for up to a year, and they
breed at one or two years of


Surviving a Changing Climate?
Dealing with floods, droughts, and a shifting climate.
Global climate change has resulted in
sea level rise, increased temperatures,
and changing weather patterns
including increased frequency of
storms, droughts, and floods, and
shifts in precipitation. In the coming
decades as the severity of climate-change worsens the American Avocet
will face significant obstacles to
survival and reproduction, and they
are in danger of losing half of their
range by 2050 due to climate change.

Within the range of the American
Avocet, shifts in precipitation have led
to a reduced water availability and in
some cases increased water salinity.

When salinity increases above an
optimal level then the invertebrate
prey that the Avocet feeds on will
suffer from smaller body size and
lower reproductive rates, which
reduces food availability for the birds.

Climate threats are the most
dangerous to Avocets during
incubation and development of their
young, because they build their nests
on the ground. Storms and fluctuating
water levels can flood nests causing
egg failure. Additionally, storm-related
cold weather events also lower the
rate of reproductive success.

American Avocets are restricted to
habitats with shallow water areas no
deeper than 8 inches (20 cm), these
areas are very drought-sensitive, so
when water levels drop due to
droughts the breeding range of the
Avocet is further restricted.

The odds of survival are already
rough without these added dangers,
within the year of hatching it is
predicted that 19% to 93% of
hatchlings survive, after that they have
an annual survival rate of 83% to
86%. On average they survive 8.7
years in the wild, but they can live at
least 15 years.

The Agricultural Impact on Wetlands
Selenium Poisoning Persists Across Generations of Avocet.
Selenium is an element that is essential to plants and
animals in trace amounts, but it is highly toxic at higher

Selenium is often added to fertilizers in agricultural
settings to improve crop productivity, but through
agricultural runoff it finds its way into wetlands and

Selenium bioaccumulates in these aquatic habitats
because it concentrates in the body of small
invertebrates and insects and then moves up the food
chain. So, when an American Avocet feeds on small
crustaceans, insects, and fish it receives a highly
concentrated dose of selenium which causes low
reproductive success, embryo deformities, and
congenital disorders.

Additionally, the nutrients and chemicals in agricultural
runoff increase algae blooms, decrease water oxygen
content, and decrease the abundance of invertebrates.
Other sources of selenium pollution include mining,
smelting of ore, coal burning, oil processing, industrial
manufacturing, and petrochemical operations.

A notable selenium bird poisoning event caused by
agricultural runoff occurred at the Kesterson National
Wildlife Refuge where thousands of birds and fish died.
Selenium poisoning can last for generations even after the
environment is cleaned because it is passed from the
parents to the offspring, and very high levels of selenium
have been found in avocet eggs.


Oil Pits and Cyanide Ponds
Nesting Sites or Graveyard?
Oil pits and gold-mining cyanide
leach ponds might not seem like the
place that you would want to raise a
family, but these are actually highly attractive nesting grounds for
breeding American Avocets,
especially as natural wetlands
disappear. Unfortunately, these sites
have metal and trace elements that
are toxic to Avocets and their eggs,
which results in nest failure.

Cyanide is used in mining processes
to extract gold from ore, where
cyanide solutions are sprayed onto
ore processing ponds. Cyanide is
highly toxic and can kill wildlife that
are attracted to the cyanide ponds.
Cyanide solutions often spill or are
discharged into waterways and
groundwater which contaminates
aquatic habitats, since the 1970s
billions of gallons have been spilled
and leaked into the environment.

Furthermore, when the mining
process is abandoned the ponds can
continue filling with water and may
form toxic lakes contaminated with
cyanide, arsenic, boron, copper,
fluoride, and zinc.

The process of producing oil
creates waste fluids that contain
salts, hydrocarbons, and toxic
metals. This waste is often stored
in open oil pits or large ponds that
resemble wetlands, and birds can
be poisoned or trapped in such

The US Fish and Wildlife Service
estimates that these oil pits are
responsible for up to a million bird
deaths annually.

One such example is Soda Lake, a
wastewater basin in Wyoming that
attracts nesting colonies of
American Avocets. An investigation
found that the concentration of
hydrocarbons, selenium, chromium,
copper, mercury, and zinc in the
bird livers and eggs was way above
the threshold that would cause
reproductive impairment and
deformities in the offspring.


What Comes Next for the American Avocet?
How we can save migratory shorebirds.
The American Avocet is listed as a Species of Least
Concern on the IUCN Red List as of a 2016 assessment,
and thus has no specific protection from state or federal
agencies. Although, they are protected by broad-sweeping
wildlife laws like the United States Migratory Bird Treaty
Act of 1918, which criminalized the hunting of the
American Avocet.

Populations of American Avocet have
been stable over the last forty years but there are
regional declines, and historically the Avocet population
has been negatively affected by shooting and trapping
prior to Migratory Bird Treaty Act of 1918. Despite being
listed as a species of Least Concern there are still many
threats for the American Avocet now and in the future, a
lot of effort and action is required to protect them and
other migratory shorebirds.

Wetland habitats must continue to be protected because
they are an important breeding and nesting ground for
the American Avocet and other migratory shorebirds, and
human-made wetlands can be constructed to counteract
the losses. Public education and outreach are necessary
to increase respect for protected areas and to prevent
trespassing on breeding grounds.

The chemical degradation of wetlands must also be
addressed and prevented by increasing the regulation of
agricultural and industrial processes that contaminate
waterways with toxic run-off. Consumers also have a role
to play in this battle for conservation by choosing to
support farmers that use sustainable agricultural
practices that prevent the accumulation of toxic
compounds in water or land.

New policies and regulations should also target cyanide
mining operations and petroleum waste fluids. Closed
containment systems should replace open pits to prevent
wildlife from having access. Solutions for open pits are
more limited and previous deterrents such as strobe
lights, flags, noisemakers, and reflectors have failed and
do not reduce bird deaths. Steel-framed netting can be
used to enclose an open pit and effectively exclude birds
where closed containment systems are not an option.
Innovative technology such as enzymes and microbes
can be used to breakdown selenium and other


• Ackerman, J. T., Hartman C. A., Herzog, M. P., Takekawa, J. Y., Robinson, J. A., Oring, L. W., Skorupa, J. P., Boettcher, R.
American Avocet (Recurvirostra americana), version 2.0. In The Birds of North America. Cornell Lab of Ornithology, Ithaca, NY,
USA. 2013.
• Kaufman, K. American Avocet. Audubon Guide to North American Birds. The National Audubon Society. n.d.
• Recurvirostra americana. The IUCN Red List of Threatened Species 2016: e.T22693717A93418724. BirdLife International 2016.


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