Excerpted from Finding a Safe Place to Rest and Refuel, which first appeared in the Spring 1998 GCBO newsletter.
What types of habitat are most
important to migrating songbirds? Where do they occur, and how is their
distribution and abundance changing as a result of development and land
conversion? The movement of birds across the Gulf of Mexico each spring
and fall is a prominent feature of the Nearctic-Neotropical bird migration
system. The coastal woodlands and narrow barrier islands that lie scattered
along the northern coast
of the Gulf of Mexico probably provide important stopover habitat for
Neotropical landbird migrants.They represent the last possible stopover
before fall migrants make a nonstop flight (18-24 hr) of greaterthan 1,000
km, and the first possible landfall for birds returning north in the spring.
Some of the birds that stop to rest and forage
in coastal habitats will avoid predators, find food, replenish fat stores
and get on with their northward journey; others will be less successful.
Visualize a red-eyed vireo gleaning small caterpillars from the edge of
hackberry leaves in the middle of the long, narrow chenier near Johnson's
Bayou, Louisiana. Now consider the many "decisions" she must
make in response to the problems encountered en route. Besides the energetic
cost of transport, she must adjust to unfamiliar surroundings, balance
conflicting demands between predator avoidance and food acquisition, compete
with other migrants and resident birds for limited resources, cope with
unfavorable weather, and correct for orientation errors. How well she
solves those problems will determine the success of her migration, while
a successful migration is ultimately measured in terms of her survival
and reproductive success.
Migrating birds are likely to solve en route
problems if they settle in high quality habitat. Coastal woodlands of
SE Texas, Louisiana, Mississippi and Alabama are good places to stop over
following a trans-Gulf flight. Yet, the northern coast of the Gulf of
Mexico, arguably the most important migratory stopover area for songbirds
in North America, is expected to see significant human population increases.
Between 1960 and 1985, the population living within 50 miles of the US
coast increased from 92.7 million people to 125 million people-52 percent
of the population in the coterminous United States (US Department of Commerce
1988). The southward migration of industry coupled with changing demographics
will increase development pressure on stopover habitats in the decades
ahead. As stopover habitat is transformed or degraded, the cost of migration
increases and the potential for a successful migration is jeopardized.
Some coastal habitats spared from development are threatened by accelerating
rates of coastal erosion. The combined effects of coastal subsidence,
the disruption of sediment supplies, and sea level rise will add further
to the loss of important stopover habitats. As coastal areas are developed,
there is a commensurate increase in the value of unaltered habitat to
migratory birds, which makes the creation of new habitats to replace those
lost to coastal development a major conservation challenge in the next
Dr. Frank Moore is an avian
biologist at the University of Southern Mississippi, and a member of the GCBO Scientific Advisory Committee