a closer look (click on photo). You'll see that communications
towers are even a danger to the ultralight-led Whooping cranes.
Power Lines and Fences
can hit or get caught in fences, especially when fences are built
across wetlands. But the number one problem
fo migrating cranes is collision with power lines. Danger can be a huge
string of transmission lines high
in the air or simply a single wire running into a farm house or irrigation
system in an area where practically no one lives. The cranes
simply do not see the lines. Transmission
lines are hard to see when you are looking into the sun, late in the
the light is dim, or in bad weather such as blizzards or foggy days.
When we radio-banded six whooping cranes back in the early 1980's and
tracked them all the way to and from Canada, two of the six died hitting
lines. To make power lines more visible, red plastic balls or similar
devices are placed on the lines near airports so pilots can see any lines
as they come in to land. When power lines are built across wetlands,
U S Fish and Wildlife Service asks the companies to mark the lines. This
reduces bird strike mortality by 50 percent.
Whooping cranes potentially face increased predation rates
when they migrate. Every night they have to find a shallow pond that
clear from vegetation for them to roost (stand in as they sleep) throughout
the night. The shallow water helps them hear and flee any bobcat, coyote,
or fox that might be sneaking
up on them. But the cranes are unfamiliar with the places where they
stop. This increases the danger, and in some locations the cranes may
not be able to find an ideal place to stop.
Whooping cranes share wetlands with many kinds of migrating
birds. Ducks and geese, shorebirds, and other wading birds
as egrets and herons are among them. As wetlands are drained in this
country to make room for more farm land or housing, migrating birds are
forced to concentrate
whatever wetlands are left. These concentrations of birds greatly increase
the risk of spreading diseases such as botulism, cholera, or avian tuberculosis.
Cranes can also get shot by vandals or duck hunters. Fortunately,
we think shooting occurs only occasionally, but even once is too often.
The new Eastern flock's most
valuable adult female, #217, was shot to death while
at a fall migration stop in 2009.
habituated or accumstomed to humans is
one of the greatest dangers that Whooping cranes face. Being even a
little tame puts them
at greater risk from vehicle collisions, predation,
and illegal shooting.
The Toll from Human Activities