Back in late August, John and I traveled to Platteville, Colorado, to work with Xcel Energy employees Bill Heston, Tina Lopez, and Naresh Dahagama on an upgrade to the Fort St. Vrain Eagle cam. Over three days, we took down and re-positioned the existing cam, added a new PTZ cam, cleaned up the solar panel area, added two radios and a couple of networked video recorders so plant staff could watch their eagles from the lunchroom again, threw in a couple of network switches to tie everything together, and got an IP camera configured for the Fort St. Vrain owl nest. One of the eagle cameras is currently up here: http://www.raptorresource.org/birdcams/xcel-energy-cams/ and we hope to have both available soon! We did the best we could to position all of the cameras out of poop range!
So what does the area look like? The Fort St. Vrain bald eagles are nesting in a large cottonwood near the junction of the St. Vrain and Platte rivers. A variety of animals drink at the waterhole just below their nest, western painted turtles sun themselves on logs, fish swim in both rivers, and prairie dogs squeal and dig at a large colony roughly 1,000 feet away. Their grove is populated by cottonwood trees with an abundance of perches, which provide great places to sun and shade while searching for potential prey. Like many grassland groves, it is located on the east or leeward side of a river, which serves as a natural firebreak against fires driven by western winds. While life is not always easy here, the eagles’ grove is a small oasis in the dry landscape around them.
|A look at the nest area. The plant is about 1/2 mile from the nest.|
The nest itself measures eight feet, one inch by six feet, seven inches by nine feet, ten inches. The total area is a bit tough to calculate since it sits somewhere between a triangle and an oval, but if I calculate for both and average them, I come up with around 30 square feet. It is about 6.5 feet high, constructed almost entirely out of cottonwood sticks – far and away the dominant tree here – and contains at least three other bird nests. It has excellent flyways – perhaps due in part to stick-snapping and nest-building activities – and favorite perches as indicated by well-worn spots on branches right next to the nest.
What does the nest weigh? Using the method outlined here
for calculating a cone – the closest shape I could come up with – yielded a total volume of 103 cubic feet (note that I calculated the radius by averaging the three measurements I had). Cottonwood weighs about 28 pounds per cubic foot, which yields a weight of 2,884 pounds…if the nest were constructed of solid wood. But it isn’t, since the eagles weave branches together in a rough spiral. Once the solid weight is multiplied by the fibonacci ratio of 61.8%, we get an estimated weight of around 1,700 pounds. 61.8%, which is also referred to as the golden ratio, or the golden mean, turns up quite a bit in natural series, especially ones that involve spirals. Don’t believe it? Check this out: The Golden Ratio In Nature
. The Fort St. Vrain nest is larger but, thanks to its cottonwood construction, probably lighter than N2B in Decorah.