to Native Birds
Major threats affecting bird populations
Habitat Loss and Degradation
By far the largest threat to birds is loss and/or
degradation of habitat due to human development
and agriculture. In some regions the loss of
habitat is extreme. For example, more than 95% of
Tallgrass Prairie habitat in the U.S. has been
destroyed since the 1800s. Aquatic habitats are
drained, plowed, filled in, and channelized,
while terrestrial habitats are clearcut,
overbrowsed, and fire-suppressed. Natural
disturbance regimes are changed by water and
forest management practices. Habitat is also
degraded by the introduction of invasive plant
and animal species that can alter the nesting,
foraging, and roosting habitats for birds.
Increased Numbers of Competitors
Competition with abundant and exotic species
makes it harder for native species to survive.
Example: Snow Goose populations tripled in size
between 1969 and 1993. Their foraging behaviors
leave the arctic tundra denuded of vegetation,
which will probably take hundreds of years to
regrow. As a result, shorebirds that breed on the
tundra are now declining.
Birds are targeted for activities such as hunting
and capture for pets. Each year, tens of
thousands of migratory birds, including Baltimore
Orioles and Painted Buntings, are captured for
the caged bird trade on their wintering grounds
in Mexico, Cuba, and Central America. Painted
Buntings have declined 60% during the last 30
years, according to Breeding Bird Survey data.
Introduced predators are especially problematic
on islands where, in the historic absence of
predators, birds have evolved to nest on the
ground. Hawaii and Guam are well-known examples
where many of the native birds have gone extinct
due to predation by introduced cats, dogs, rats,
mongoose, ferrets, brown tree snake, monitor
lizards, sheep, goats, pigs, and more.
Birds can become sick or die from eating toxins,
or absorbing them through their skin. Examples of
such toxins include DDT, pesticides, metals, oil
spills, and bilge discharges. A recent connection
has been made between herbicide spraying on lawns
and bird kills.
Indirect Chemical Pollution
Acid rain has recently been linked to population
declines in forest birds. Acid rain washes
calcium out of the soil and decreases the amount
of calcium-rich prey for birds like thrushes,
which require a calcium source to produce eggs.
Eutrophication, excessive plant growth resulting
from an influx of nutrients, changes the water
quality and species composition of lakes and
ponds. This can deprive birds of their food
source, or even make the water body unsuitable as
Avian diseases, including avian malaria, pox,
House Finch disease, and West Nile virus, are
leading causes of death among some bird
populations. Many of Hawaii's native birds
suffered drastic population declines once
introduced mosquitoes began transmitting avian
malaria between birds.
Human disturbance of nesting, feeding, and
roosting areas. Disturbance can come from kayaks,
jet skis, low flying aircraft, pets and feral
animals, off-road vehicles, and other outdoor
Many seabirds suffer from the longline and gill
net fisheries when they become entangled and
Diminished food supply through fisheries,
eutrophication (see above), habitat alteration
that reduces prey (salinity changes in estuaries,
forest structure), and replacement of food
sources with invasive species. Shorebirds
migrating along the Atlantic coast rely on
horseshoe crab eggs to increase their body weight
before continuing their flight to their Arctic
breeding grounds. Horseshoe crabs are harvested
for bait, and their populations take many years
to recover. Therefore, shorebirds that rely on
horseshoe crab eggs have declined in numbers and
often have insufficient weight for breeding.
Degraded quality of foraging habitat by the
invasion of introduced species or by fisheries
that trawl the sea bottom.
Public dislike for some species, such as colonial
waterbirds that nest or roost in urban and
suburban areas, may be a barrier to long-term
conservation. Examples include Double-crested
Cormorant, Ring-billed Gull, or vultures.
Increased human populations bring communication
towers, wind power development, domestic cats,
lighted buildings along migration corridors, nest
parasitism, and competition with exotic species
such as European Starlings and House Sparrows.
Creek Bird Supply and see our
selection of Bird
Feeders & Heated
Bird Baths .