Fall is the season when flora and fauna prepare for the upcoming winter. Most trees and plants lose their leaves and go into winter dormancy; cold-blooded creatures, such as snakes and frogs, hibernate in various hiding places. For some birds, a long trip is on order. We hear large flocks of migrating geese as they fly high overhead around this time of year. The large number of eagles that overwinter here is a direct result of their migrating from their breeding territories in Canada to our region in order to find unfrozen waterways to fish. Many other species of raptors, or birds of prey, migrate into or through our area during the fall as well. The autumn migration of raptors provides not only good bird watching opportunities, but also gives scientists an opportunity to keep track of the many species of raptors that traverse the area.

Raptors—hawks, falcons, eagles and vultures—all share traits that make them master aviators of the bird kingdom. In flight, all raptors take advantage of weather such as thermals and tail winds to conserve energy and stay aloft for long periods of time. A red-tailed hawk’s preferred method for spotting its prey, for example, is to “kite” along a ridge with its beak into the wind, appearing almost motionless; viewing through a locked-down spotting scope shows barely a couple of inches of movement. When the hawk spots prey using this method, it tucks in its wings and dives, or “stoops” at over 120 mph to catch its prey. During migration, raptors use all their flying tricks. They may start out thermaling to an altitude where a good tailwind exists and ride south on it. Raptors also heavily utilize ridge or orographic lift, riding the wind that is generated on the windward side of a ridge.

There are some places along ridges that channel many migrating raptors close enough to observe them, and these places are usually established hawk-counting sites. Observers man these sites during the fall and tally the number of each species they see. Count data is submitted to organizations like the Hawk Migration Association of North America (www.hmana.org). Scientists can use the data collected to gauge the population trends of raptors by comparing count data from year to year. This is the 40th year that HMANA has been collecting data. Non-raptor species are also tabulated at many sites. This year from October 1 to 20, 228 migrating monarch butterflies were counted at Scott’s Mountain, NJ. Comparing this year with 2011 when they counted 232 during the same time period would indicate some stabilization in the precipitous population decline of the monarch butterfly. This however is only one of many sites where monarchs are counted, and entomologists will be busy counting data from all the sites for trends.

You don’t have to be into counting to enjoy seeing some nice views of various raptors as they fly close to observers at various sites. Hawks and falcons you see high overhead during the summer might zip by just 50 feet away as they make their way south. Seldom seen birds, such as golden eagles and northern goshawks, are occasionally seen now at most sites, and kestrels, sharp-shinned hawks, as well as many other species abound. The best time to go is after a cold front with a northwest wind (and due to the wind, dress warmly). To find a good place to go, wherever you may be, check out hawkcount.org, and bring binoculars for an interesting outing. The images in this week’s column show but a few of the many species of raptors that can be seen.