TRAVIS AIR FORCE BASE, Calif. – You get up and head out the door for work as you do pretty much every morning. Finally, fall is in the air and it seems cooler than it has been in a long time. As you get in your car, you see a flash of color in the hedges in front of your house. It’s just a glimpse but, no, wait, there it is again! A small bright yellow bird is flitting through the foliage, then it’s gone as quickly as it appeared. What you just witnessed is the beginning of one of the greatest wildlife spectacles to occur in the United States. It’s time once again for the fall bird migration.
As fall approaches and the weather begins to cool from the oppressive summer heat, birds begin to form flocks and start moving slowly away from their breeding grounds to warmer climates in the south. Many birds breed in the Canadian arctic and Alaska. They migrate to the lower 48 states in preparation for winter and many continue to Mexico, Central and South America. The same is true for birds that summer here.
According to the Cornell University School of Ornithology, the estimate of the number of birds that fly south from the United States into Mexico, the Caribbean or other points south is 4.3 billion. Sometimes, the flocks of birds are so dense during migration that they can show up on weather radar. This happens twice every year, when the spring migration repeats the process in the opposite direction.
Penn Craig, 60th Civil Engineer Squadron natural resources manager, is responsible for keeping track of resident threatened and endangered species, as well as all the flora and fauna found on the base. Travis Air Force Base, California, located well within the Pacific Flyway, is significantly impacted by bird migration activity.
“Currently, the major issues are the increase in flocks of birds moving across the airfield (e.g. blackbirds and Canada Geese) becoming a Bird Aircraft Strike Hazard,” said Craig.
The arrival of fall doesn’t only affect birds. Other animals that may not migrate have to start gathering food for the winter. Squirrels start building leaf nests high in trees that will withstand winter winds. They also store food by caching acorns and other nuts. Snakes start looking for a burrow to hibernate in during the winter. Turtles bury themselves in mud and go into a state of torpor where they don’t need to eat or drink and barely breathe at all until spring. Foxes, raccoons, opossums and skunks, although they do not hibernate, find safe, warm and dry places to spend the winter.
Other creatures become more active when the rains arrive in late fall and early winter.
“We are concerned about potential movement of adult California Tiger Salamanders from burrows to any of the 17 confirmed CTS breeding ponds on and around the installation,” said Craig.
“Rain and temperature are key conditions that trigger such movement. Adult CTS usually leave their burrows at night during a rain event and move to nearby CTS breeding ponds,” said Craig.
“Knowing adult CTS movement and the ponds that have being impacted by the CTS will provide essential information that will allow us to prevent CTS from moving across the airfield,” he continued.
“Natural Resources management is in the early stages of conducting studies under the Emergency Airfield Operation Biological Opinion which covers a 5-year period”.
It should also be noted that our Northern California climate during winter is relatively mild. At Travis, freezing temperatures seldom last more than a few days at a time. As a result, many animals that would disappear into a burrow during winter elsewhere may occasionally be seen out looking for food during the winter here.
What was that little yellow bird in your hedges? Well, chances are very good that it was either a Yellow Warbler or a Wilson’s Warbler. Both birds are predominantly yellow below and green above. They are similar in size but the Yellow Warbler is slightly larger and has yellow edging on its wing feathers. The adult male Wilson’s Warbler is unmistakable in that it has a black cap of feathers atop its head. These are just two of the migrating birds you can see around Travis during the fall. A close look around the Fishing Pond or the Eucalyptus grove north of the track could reveal many others.
For additional information contact the Animal and Plant Health Inspection Service at Matthew.J.Stevens@aphis.usda.gov or Matthew.R.Thomas@aphis.usda.gov or Penn Craig, natural resources manager, 60th Civil Engineer Squadron at 424-8354 or 424-5126.