These movements are largely a response to seasonal change in the availability of food. Some birds feed primarily on cold blooded prey and are forced to move across continents where the abundance of those food items has not been influenced by extremes of temperature. Broad-winged hawks, for example, feed largely on reptiles, amphibians, and insects. With the approach of winter in the Northeast, chemical codes within the brain of a Broad-winged hawk trigger a response to move south – as far south as Bolivia, where prey is active.
Some birds of prey feed on songbirds and shorebirds which also migrate to areas where food is plentiful. Frozen lakes and rivers force aquatic-feeding birds to move to open water. Other raptors are nomadic, wandering erratically in search of food. Red-tailed hawks may move just a short distance from their nesting grounds where food is abundant. If the food supplies dwindle there, they will move again.
With an elevation of only 330 feet, and no large body of water, Militia Hill has no geographic features of great importance to migration. But all sixteen species of east coast raptors have been seen at the Militia Hill Hawk Watch. Detailed records of raptor observation and weather conditions are reported daily to The Hawk Migration Association of North America. These records can be accessed at www.hawkcount.org.