Transcript Invasive plant and animal effects on the black

Invasive plant and animal effects on the blacknetted stilt (Himantopus mexicanus knudseni) and
the black-crowned night heron (Nycticorax hoatil of
Hawaii
By: Stephanie Woo

Hawaii is often referred to as the endangered
species capitol of the world and the extinction
capitol of the United States

After the introduction of non-native species of plants and
animals, many of Hawaii’s native species are being lost
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Although much of the loss of wetlands is caused by
human destruction, alien species of plants and animals
have caused many species of native birds and plants to
become endangered, and in some cases, extinct
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The alien red mangrove (Rhizophora mangle) and
pickleweed (Batis maritima) have altered the
environment for the native animal species, especially
already endangered bird species like black-netted stilt
(Himantopus mexicanus knudseni) and the indigenous
black-crowned night heron (Nycticorax hoatil).
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Red mangrove
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Pickleweed
 Exposing new, non-native plants and animals to new
environments can be dangerous because they usually
have no natural enemies and can quickly take over a
large area:

Pickleweed was
introduced in 1859 to
Hawaii from South
America
 Because of its high
tolerance for salt water,
pickleweed is not eaten
by many animals. One of
the only animals known to
feed on this plant is the
white-tailed deer, which is
not found in Hawaii, thus
explaining how the plant
was able to expand so
rapidly in Hawaii.
 Another
problem with pickleweed is
that they have short, dense strands,
which prevent important species like
shorebirds or waterbirds from nesting
on them.


Red mangroves were
introduced from Florida to
Hawaii in 1902 to
alleviate erosion after the
destruction of coastal
vegetation
Since the red mangrove
has only been living in
Hawaii for one hundred
years, Hawaiian marine
species have not been
able to exploit the
detritus-based food chain
 The
native and endangered black-netted
stilt has affected by invasive plant species
because it lays eggs on the ground, and
pickleweed is not a very good plant to nest
in.
 The
red mangroves had not been
completely invaluable to all species. The
black-crowned night-heron nests in the tall
tree tops of the mangroves, away from
predators
 BUT……there
is an animal species that
was introduced to Hawaii in 1883 to try
and control rats, insects, and other pest
species that fed on sugarcane…

Mongoose!
 After
hearing about this method of control,
Hawaiians imported the mongoose to
control their sugar cane crops as well.
 The plan didn't work out too well because
the mongoose slept all through the night
while the rats were busy eating the sugar
cane.

What the Hawaiians didn’t take into account was
the fact that the mongoose eats pretty much any
animal. It eats bugs, rats, snakes, lizards, birds,
etc.

The increased population of mongooses
(because of no natural predator on Hawaii) has
been linked to a direct cause of many
decreasing animal populations on the islands

Not true!

The pickleweed and mongoose populations
have been particularly detrimental to the blacknetted stilt populations because after laying
eggs on the ground, the mongoose can hide
under the think mats of pickleweed and hunt the
stilt chicks as prey.
 The
invasive pickleweed and mongoose
have caused stilt populations to greatly
decrease in numbers
 In 1975, the stilt bird count was 54 birds,
but after the management of pickleweed
plants, the stilt bird count reached a high
of 124 in 1985 (Drigot 2000).
How are the mangrove and
pickleweed controlled?
 The
marine corps helps by using the AAVs
to run over the pickleweed
 After rolling over the pickleweed, mud is
deposited on top of the weed, so it is
forced to grow in a new direction that
could take months to re-grow.
 These
“moats” made by the AAVs creates
nesting grounds for birds like the stilts
 But
how are mangroves removed?
 After
giving jurisdiction to the Marine
Corps and Nu’upia Ponds Wildlife
Management Area (WMA ) in 1980 to
control the pickleweed and mangrove
infestation on the island of Oahu,
increasing rates of stilt population and
night-heron population have been
observed.