You are here

Airborne

This turkey, no doubt, is squarely on the ground. But you'll see the reason for the blog title shortly.

I hope everyone had a nice Thanksgiving. We have so much to be thankful for, don't we? As a gesture of thanks, please consider giving to your favorite local charity or nonprofit on Giving Tuesday, 11/27. Consider making a donation to the Elizabeth River Project, and help it restore the Elizabeth River.

Thanksgiving Day, 2018

My wife and I spent the day in Smithfield, VA. On the way there, it seemed as if every home had at least 2 pickups, 3 sedans and a motorbike in the driveway. That's not counting the vehicles in the front yard. After Thanksgiving dinner, we walked some of the meal off at Windsor Castle Park (a great park and an eBird Hotspot like Paradise Creek Nature Park in Portsmouth).

While driving home, we passed Dennis' Auto Sales in Suffolk. It appears Dennis uses the AP Stylebook. I would have spelled it: "Dennis's Auto Sales."

Here--cars were parked everywhere. I said to my wife, "Honey, look at all the people visiting there." She responded by giving me one of those looks. We had a great time. And I hope you did too.

A Little Review

Please keep in mind that you can click on and enlarge any blog photo except the feature photo.

In "Flight School," our last blog and the third blog in our bird flight series, we began to explore "lift." It's interesting. We easily grasp other flight forces, or forces working on birds' bodies as they fly. We understand gravity, which birds overcome. Drag (air resistance) is easy to figure out. And thrust is a familiar concept as well. We've noted that it's produced when birds jump from high places, (see "Flight Shots") or flap like crazy (same section). Some birds also create thrust by running across the ground or the surface of the water. But lift isn't quite as easy to understand.

"A Study in Lift"

So before we go on, why don't we illustrate it? That may help. And we need a photo anyway. So here again is Vic Laubach's Bald Eagle flight shot. As I look at it, I imagine Vic in a glider alongside the eagle and firing his Sony Cyber-shot through the window. This bird is unquestionably in the air, isn't it?

 

Much as our female Mallard is "a study in aerodynamics," this eagle, to me, is "a study in lift"--especially if we consider the backstory. According to Vic, the eagle was "dropping while approaching a branch that it was going to land on, but then at the last second, just as it touched the branch, it changed its mind and pulled up. It came in slowly from about a half-mile away and a higher elevation."

This photo is a great one for our purposes. Enlarge it and take a closer look. Notice the airfoil shape, the "teardrop shape," of the wings and the body. Lift is generated when air moves around an airfoil. Remember the airfoil examples we referenced in the last blog (see Birds' Wings and Lift): a sail, a wind turbine blade, and an airplane wing? We could say that a bird's wings and body are prototypical examples. Note the fanned tail here, too, helping the bird manuever and "brake."

A Bird's Wings

A bird's wings and body, then, help to create lift. A bird's tail helps to create lift as well. But the most important lift generator of the 3 is the wings. Let's examine that further.

As a bird flies, oncoming air moves around a bird's wings. Some of the air is deflected upward, reducing the air pressure above the wings. The higher pressure below the wings then exerts an upward force on the wings, creating lift. Lift is also created when some of the air hitting the wings is deflected downward. That downward directed force creates an opposing upward force. Think: Newton's third law (and what happens when you stick your arm out of a window of a fast-moving car). Flapping flight also helps to generate lift. And as we have seen, flapping flight helps to generate thrust as well (see "Flight Shots).

A Bird's Tail

Here's another airborne bird, again courtesy of Dr. Laubach. This is an immature Red-tailed Hawk, North America's most common hawk. FYI, Red-tailed Hawks and Bald Eagles are members of the same bird family.

Vic sent this to me as another example of a bird in flight. But it's also a great example of a bird using its tail--in this case to achieve level flight. I like to think of a bird's tail as its rudder, helping it to maneuver. Here again, as above, we see that "rudder" in action.

And This Just In

Wintering birds continue in good numbers both at Money Point in Chesapeake and at Paradise Creek Nature Park in Portsmouth. Savannah Sparrows, like this one, spend the winter at Money Point. They breed both north of us and west of us. This is a species of special concern as the open habitat they prefer is disappearing. They showed up at Money Point in mid-October, before they showed up anywhere else in the watershed. Here's a little-known fact about them: The Savannah Sparrow was named for Savannah, Georgia, and not because it is a grassland species. Who knew?

Swamp Sparrows arrived at Money Point on 11/4. That was the first documented sighting this fall in Chesapeake. This species breeds as far north as the Northwest Territories in Canada and just about up to the tree line there. I can see why so many Swamp Sparrows winter here. Winters up there must be brutal. I was talking with my wife on the phone while observing one at Money Point recently. The bird came so close to me as it hopped around in the underbrush, that I thought it might be trying to listen in on the conversation.

Soon to be Ph.D., Nick Flanders, observed a small flock of Pine Siskins on 11/3 at Paradise Creek. His was the first and so far the only sighting of this species this fall in Portsmouth. This is a species whose breeding range is also far north of us, yet many occasionally, but not reliably, winter here and points south.

Quip, Question, Quote

This has nothing to do with birding--like our vignette at the beginning. And this is directed to an older audience. Have you ever heard something or read something that made you consider your age? Well, consider this question that I came across recently: "Do you remember when we used to buy our music on CDs?" If that doesn't give you pause, I'm not sure what will.

Click here to email Dave or leave your public comment below.