http://www.digitaljournal.com/science/fall-is-the-time-for-foliage-tours-and-raptor-counts-in-virginia/article/409500

Fall is the time for foliage tours and raptor counts in Virginia

Posted Oct 18, 2014 by Karen Graham
When autumn comes to Virginia, the mountains and valleys don their coat of many colors, giving the countryside a patchwork quilt appearance. This is also the time of year for the annual raptor watch when birds-of-prey are counted as they migrate south .
Blue Ridge Parkway in Virginia
Blue Ridge Parkway in Virginia
DOT/GOV
For many Virginians a "Fall foliage trip" is a must-do event almost every year. It becomes a pilgrimage of sorts, an annual weekend event that might end up at a little restaurant at Mabry's Mill on the Blue Ridge Parkway. Visitors gorge themselves on homemade buckwheat cakes, made from flour ground at the mill outside.
Mabry s Mill was a working grist mill for years along the Blue Ridge Parkway.
Mabry's Mill was a working grist mill for years along the Blue Ridge Parkway.
Forestwander
But the real reason for the trip is to see the colors, of course. Here in Virginia, "the peak" is what most people wait for, and it can vary, depending on where in the three areas of the state you live. The intensity of the fall color and the time of the peak color is dependent on many factors. Most people don't realize there is a science behind all the profusion of color they see. It's actually a combination of environment, climate, weather and chemistry.
John Seller is a tree scientist at Virginia Tech in Blacksburg, Va. He teaches a class in Dendrology, the science of trees, woody plants and woody vines. He is also one of the creators of the leading tree identification smartphone app called VTree.
Autumn in Virginia. A visit to one of Virginia s many wineries in the Shenandoah Valley.
Autumn in Virginia. A visit to one of Virginia's many wineries in the Shenandoah Valley.
Karen Graham
Chemistry's role in fall foliage colors
Seller has a passion for trees, and has been studying them his entire life. He explains the chemistry behind the color of leaves by telling his students that leaves always contain the yellow color pigment. It is present even in the summer when the leaves are green, but the yellow is covered up by chlorophyll, and this makes them appear green.
Chlorophyll contains nutrients the tree needs to survive. The tree reabsorbs these nutrients as it gets ready for winter. As the chlorophyll is removed from the leaves, they turn yellow. But what about those red or orange leaves? For some trees, yellow is the only color they can produce. But for other trees, they have another chemical that turns leaves red.
Seller says there is a theory as to why some trees can produce a chemical that turns their leaves red. They are making a sunscreen that protects the plant as chlorophyll is reabsorbed. "Even on the same branch, leaves that are exposed to direct sunlight will turn red, while ones in the shade don’t need sunscreen, so they don’t put it on,” He says.
The intensity of autumn s colors are sometimes so vibrant they are blinding.
The intensity of autumn's colors are sometimes so vibrant they are blinding.
Forestwander
Weather and climate play a great role in fall colors
Weather plays a significant part in determining if an area will have a beautiful "peak" color array, or if the scenery is drab. Drought, for instance will cause leaves to produce less of the red chemical, and they will fall off the tree earlier. The length of the day has the greatest affect on the timing of the "peak" of the color, and the amount of sunshine as leaves begin to turn will determine the coloring.
Sunny, bright and clear days in the fall tends to make leaves produce more red coloring. But this is only for the red colors, says Seller. A lot of cloudy days will slow down the red color formation. In Virginia, this is most evident in Sugar Maples. The interior leaves will be a deep yellow, while the leaves on the outside of the tree will be a combination of oranges and reds.
Seller says that in Virginia, the timing of the peak of color production can vary a little, but it usually is the third week in October. The latest it has been is Nov. 1. Once the leaves start to turn, things happen quickly. They will brown and fall off in two weeks. Seller mentions that New England abounds in Sugar Maples. But Virginia had the highest diversity of trees in Eastern forests.
Flocking to Afton Mountain
Hawks, eagles and other birds of prey like fall in Virginia, but not because of the beautiful autumn colors.Virginia is part of the Atlantic Flyway, a winter migratory path for many raptors That leads them south along the Blue Ridge Mountains as they head further on their journey to their winter grounds.
Bird enthusiasts have been coming to Afton Mountain, or Rockfish Gap, Va. since 1976 to help in counting the different kinds of birds of prey during the winter migration. At an elevation of 1,903 feet, it is the perfect place to see and count the many different raptors flying on the updrafts from the valley floor. It is serious work, but a camaraderie has developed over the years as some groups make the journey time and time again, sitting in lawn chairs, their binoculars pointed skyward.
A red-shouldered hawk get counted during the hawk watch.
A red-shouldered hawk get counted during the hawk watch.
NASA Images
Merlins, American Kestrels, red-tailed hawks and eagles, among others get counted every year. According to the Daily Progress, watchers spotted 35,121 birds in 2010, a single-season record. They saw 11,783 broad-winged hawks on Sept. 16, 1986, a record for one species in a single day. The raptor count starts around mid-August and ends in late November. Some raptors, like golden eagles, migrate into December.
The little settlement on  top of Afton Mountain is called Rockfish Gap. People have been coming here...
The little settlement on top of Afton Mountain is called Rockfish Gap. People have been coming here for years to count the raptors in the winter migration.
Ben Shumin