October is a month of change. By the end of the month, our eastern deciduous forests will transform from a green jungle of activity to a quiet world of gray bark and brown leaf litter. Certainly for me, this month marks the end of another season and along with it, and the beginning of a little melancholy.
If you’re out this month, look for mating masses of walking sticks; often found in large numbers on leafless branches or cedar trees with the smaller male (or males) trying to mount the larger female. These wingless plant eaters make up one family in the Order Orthoptera, which includes other insect families of grasshoppers, katydids, crickets, praying mantis and cockroaches. The Order Orthoptera is one of many that constitute the Class Insecta (Remember the mnemonic, Kings Play Chess On Fine Green Silk, for Kingdom, Phylum, Class, Order, Family, Genus, Species).
Speaking of insects, fall is also the time to find large populations of daddy-long-legs. Also known as harvestmen, due to their congregations at harvest time, these saprophytes (eating dead organic matter of leaves or animals) are not insects at all. Surprisingly, they are not insects, but rather arachnids, in the Class Arachnida, which includes spiders, scorpions, mites and ticks ( insects have three pair of legs; arachnids have four pair of legs).
But if there is anything to look forward to in October, it is the neotropical bird migration. Birds are the only warm-blooded class of animals other than mammals. And, like mammals, it takes a lot of energy to maintain body temperature in winter. Thus, with the luxury of wings to enable such an alternative, many bird species have opted for migration to warmer climates. There is an abundance of food (especially for insect eaters) in warmer climes that isn’t available in colder habitats. Other reasons for migration include longer daylight hours, greater area over which the birds can spread, and, possibly, fewer predators. In fact, I’ve read that the winter territory vacated in spring is not taken over by the resident bird populations during the bird’s summer absence. The implication here is that, just like our summer birds will return to their same breeding site year after year, they also have ‘site fidelity’ in their wintering territory.
Such a long migration is certainly a risky venture. For those birds that survive their first summer, statistics suggest that over their lifetimes, 80% of the bird population will die during migration versus at their winter or summer grounds. Despite this figure, ultimately, the reason why migration persists is because it increases breeding success.
Not all birds migrate. In Virginia, of the 245 species that can be seen in the State, 60 are permanent residents (75 are summer residents, 67 are winter residents and 43 are transients passing through the State).
Neotropical migratory birds are birds that breed in North America and Canada and winter in Mexico, Central or South America. Songbirds constitute a majority of the 200 known migrants (including warblers, thrushes, tanagers and vireos), although many shorebirds, waterfowl and raptors are also known to migrate.
It is interesting to compare our songbird migration with that of the birds of prey, or raptors. Most noteworthy, is that songbirds tend to be nocturnal migrants while raptors are diurnal migrants. Songbirds, shorebirds and some waterfowl migrate at night when conditions are more favorable (cooler temperatures and calmer air and less predators). Birds of prey, however, take advantage of the rising currents of air, which enable them to soar during the day as the sun heats the earth’s surface. Swallows, swifts, and nighthawks are also diurnal migrants because they feed on flying insects that are active only by day.
Another difference between the songbird and raptor migration is that songbirds tend to travel along the lower elevations of the coastal plain or the Ohio/Mississippi River valley corridor while the majority of raptors stick to the mountain ridgelines.
In general, nocturnal migrants travel at higher altitudes than diurnal migrants. For example, songbirds will tend to migrate from 500 – 6,000’ while raptors will be found between 700 – 4,000’. Songbirds also travel at a slower rate than raptors, with an average speed of 10-30 mph compared to 20-45 mph respectively.
These fall migrations may take four weeks to four months, depending on species. The fall migration tends to be a little less frenetic than the spring migration, with warblers migrating 25 – 100 miles per day and hawks covering 60 – 300 mpd. Typically, migration is accomplished in a series of flights lasting from several hours to several days. Between flights, birds make pit stops for resting and “re-fueling” which last anywhere from a day to a few weeks.
Beginning in early September extending through November, hawks and other birds of prey can be seen migrating along Appalachian ridges from the northeast to the southwest to winter in Mexico, Central America, and South America.
The mountain updrafts permit the soaring hawks to travel long distances with little effort. The late naturalist Edwin Way Teale (1899-1980) once rented a plane to fly with the migrating hawks. He was astonished to find that the birds use the updrafts so efficiently that they occasionally travel hundreds of miles without a single wing beat.
As the accompanying table shows, the various species migrate at different times throughout the fall. Broad-winged and American Kestrels have already peaked in September. By the first week in October, Sharp-shinned and Cooper’s Hawks are at their peak. Merlins and Peregrine Falcons are also most likely to be seen at this time. After mid-October, you can look for the ‘big birds’; Red-tailed and Red-shouldered Hawks, Northern Goshawks, and Rough-legged Hawks. On a good day, hundreds of these large buteos can be seen. This is also the time to see migrating Golden Eagles.
The number of migrating hawks that travel the mountain flyway can be enormous. On September 15th 1985 spectators estimated that upwards of 10,000 broad-winged hawks passed by Rockfish Gap at milepost 0 on the Blue Ridge Parkway. In a single day, during the third week of September, birders counted more than 17,000 broad-wings passing by Linden Fire Tower in northern Virginia.
Virginia has about 10 established hawk lookouts where volunteers sit all day and attempt to count the birds going by in September and October. Most lookouts are in the mountains where ridges run northeast to southwest, the direction the birds are headed. Two are staffed throughout the Fall season (mid-August to mid-November), with records kept by the Hawk Migration Association of North America (HNABA). The closest is at Snickers Gap, where the Appalachian Trail crosses Route 7, near Round Hill, VA. This, and other sites in VA and other states can be found at http://www.hmana.org/watches.php?stateprov=Virginia&country=USA
The second site is at Rockfish Gap (at the southern end of the Shenandoah National Park where US 250 crosses the Blue Ridge). You can read about this site, including seasonal and daily counts, at http://home.ntelos.net/~btkin/rockfish_gap_hawk_watch/
Other good sites for observation include the Tri-County Towers on top of the G. Richard Thompson WMA (known for it’s spring trillium), and Hawksbill Mountain, Mary’s Rock, and Stony Man; all in the Shenandoah National Park.
If you want the best, you will have to go to Hawk Mountain, PA. This is the center of the universe for Hawk watchers along the Appalachian flyway in the eastern U.S., bringing on average more than 24,000 raptors of 16 species over it's North Lookout. A five-hour drive and $7 dollar fee from here, you can read about their counts and much more at http://www.hawkmountain.org/default.shtml
Your best odds of seeing great numbers of hawks is by being in place from 10 a.m. to noon and 2 p.m. to 4 p.m.—after the sun warms the air currents. The largest numbers will typically be seen just after a low pressure system passes through.
Finally, HawkCount.org facilitates the tracking and reporting of raptor migrations. As part of HMANA's Raptors Online effort, many North American hawk watch sites report their daily raptor counts here. Reach them at http://hawkcount.org/index.php
And, if you get up to these sites this fall, be sure to keep an eye out for the other migrators that also use these flyways, namely monarch butterflies and dragonflies!