Tag Archives: Wildlife

Hungry Birds

Walking around the Apex Reservoir this afternoon I noticed a lone Double-crested cormorant paddling along. I kept an eye on him as I figured he’d soon be diving, and I was curious how far he’d go underwater. Sure enough he submerged, and I looked ahead five, ten yards to catch where he came up.

I stretched to see around trees that blocked my view, and noticed a Great blue heron standing tall and statue-like about three feet offshore. Then the cormorant surfaced, a white fish about 4 inches long wiggling in its beak. Before the first cormorant swallowed his catch, a second cormorant surfaced, also bearing white fish. As soon as the first cormorant downed his fish, he dove under and within seconds surfaced with another fish. Suddenly I noticed a third cormorant, also with white fish in its beak.

All this time the heron looked on, motionless, less than five yards away from the ongoing feast, beak empty.

The school of white fish under the surface continued to provide a late afternoon dinner for the trio of cormorants for another few minutes while the heron watched.

 

Advertisements

AIRSPACE CROWDING

As a general aviation pilot, a story about increasing conflicts among fliers sharing the skies overhead carries an intrinsic interest with a safety overtone. As a biologist and a birder, realizing the story is about wildlife-human aerial interactions awakens quite a different interest, still with a safety overtone.

Sergio Lambertucci, a wildlife ecologist at the National University of Comahue in Argentina, along with Emily Shepard, and Rory Wilson, wildlife scientists at Swansea University in the UK, outline the evidence in a thorough review of where and when human and wildlife uses of airspace can lead to problems (see Science magazine, 1 May 2015, 348(6234), pp. 502-504).

Lambertucci et al. include on the human side what you would expect, fixed-wing airplanes, helicopters, and of course, unmanned aerial vehicles (UAVs) or drones. But you may be surprised that human use of the near-surface airspace extends beyond aircraft. Buildings, wind turbines, power lines, and antennae also project well into the lowest hundred meters of airspace within which most flying animals operate.

Piper_wing
Piper Cherokee wing over West Virginia headed to Oshkosh

These three inclusive thinkers also remind their readers that less visible life forms exploit earth’s airspace; bacteria, algae, and fungi. I must admit, even wearing my biologist hat I never considered the impact of our use of airspace on microbial life. But aerial microorganisms can serve as condensation nuclei promoting cloud formation. Changes in the abundance and distribution of these organisms as a result of air pollution and wind flow patterns altered by tall buildings can impact precipitation and weather.
 
JordanLakeDam_2b
Bald eagle over Jordan Lake dam, North Carolina

Key to mitigating adverse impacts of human activities is a better understanding of just how and where and when wildlife use airspace. Beyond the obvious bird migration patterns that can extend across continental and oceanic boundaries, think about the more mundane, daily use of airspace by our avian friends to find food, mates, and nesting space. These smaller scale dynamics require understanding animal movements in the horizontal and vertical dimensions at scales from meters to kilometers, and how these uses change during the course of a 24-hour day.

HeronsPlus_13b
Great blue heron over the Apex Reservoir, North Carolina
 
Armed with better knowledge of wildlife habits of airspace utilization we can design and place buildings and other structures to minimize conflicts. Windows can include markers to alert flying animals, the newest technologies employing ultraviolet lights highly visible to birds. Radar can detect approaching flocks of birds and enable structural modifications to limit impacts, such as reducing wind turbine speeds. In selected instances, full-time or time-sensitive airspace reserves might provide the best alternatives.
 
With over 500 hours in the left seat of single engine aircraft, I’ve only come close to a vulture or other bird a handful of times, almost always in the landing or take-off pattern. But as Lambertucci et al. report, there have been over two hundred people killed by birds striking aircraft, and the cost of bird strikes in the U.S. alone exceeds $900 million per year. One year, 2013, saw 11,315 bird strikes. Better understanding of wildlife use of airspace at small and large scales should enable us to reduce these and the variety of more subtle human-wildlife conflicts in our skies.

DSCN0565
A student’s father took me up in his Christen Eagle!

 

The Evolution of Aerial Combat

Luna moth resting on a screen at the Len Foote Hike Inn in north GeorgiaIMG_3015

This was one of a few luna moths we saw while we were hiking this May in Amicalola Falls State Park in the north Georgia mountains. With apparently little to do in the daylight hours, these huge specimens mostly just hung around our lovely accommodations at the Len Foote Hike Inn. When nighttime comes, things might get a bit busier.

Luna moths, as large and impressive looking as they are, have little chance against the weight and teeth of a hungry bat. But as long ago as 1903 a published report suggested that the extended hindwing tails dragging behind the wings of saturniid moths, the family of moths that include luna moths, might serve to divert bat attacks away from crucial parts of the moth’s body. The hindwing tail may present an acoustic return of the bat’s sonar that proves more attractive than the main wings and body of these moths. Evidence of this was discovered by Jesse Barber and colleagues at Boise State University and the Florida Museum of Natural History.

The expendable hindwing tail does little to improve basic flight.IMG_3014

They presented luna moths with and without their hindwing tails to big brown bats in controlled settings and found that bats captured only 34% of moths with intact tails, but captured 81% of bats with their hindwing tails removed. Tail removal did not otherwise injure or significantly alter the flight characteristics of the moths.

The link below is infrared video of a big brown bat’s unsuccessful attack of a luna moth. The bat appears to aim for the hindwing tail, and even though the moth seems to lose part of its tail in the attack, it escapes.

BAT ATTACK VIDEO

Between 1937 and 1942, human technology, perhaps unknowingly, perhaps not, suggested imitating nature. British researchers thought that dropping strips of aluminum foil from aircraft might deflect German radar and allow British bombers to remain undetected as they approached targets over Germany during World War II. They called this dropped chaff, Window, and it appeared to work. German fighters could not be vectored to meet the approaching bombers, and ground-based anti-aircraft fire had to rely on visual sightings rather than advance alerts from radar.

Today, military aircraft flying in harm’s way fire flares behind them to distract enemy anti-aircraft missiles. The heat of the burning flare will attract the heat-seeking missile away from the vulnerable and slow-moving aircraft.

Seahawk helicopter firing anti-missile flares.chaff_Seahawk

——-

Jesse R. Barber, et al. 2015. Moth tails divert bat attack: Evolution of acoustic deflection. Proceedings of the National Academy of Sciences, Vol. 112 no. 9, p. 2812–2816, doi: 10.1073/pnas.1421926112 Continue reading

February’s Bird-of-the-Month

Sunset’s shadow fell about two-thirds of the way up the wall of tall pine trees lining the eastern shore of the lake. I thought it would be neat to get the rising shadow on video, but realized it would progress too slowly to enjoy in real time, perhaps a time-lapse would work. A blustery northwest wind pushed a few swells larger than I usually see on this three-quarter mile long, tree-shrouded lake. A rusty red-brown bird blew in on one gust, soaring down over the lake. Hawk. It pivoted in the winds, dark in the shadows below the sunset. Its swerve sent it streaking back up into the dying sun, shining pale yellow underwings bright against the darkened sky. Another gust and turn and it dived back into the shadows below, swiveling in a tight circle near the shoreline, searching for dinner? Then back up on the next bluster, seeming to enjoy playing the momentary meteor. Better than a time-lapse video of a slowly settling sun, this hawk swiftly banked around for one last flash of yellow before a few shallow beats of brown-red wings sent it up and over the treeline with the sunset. sunset021215 Sunset over the Apex Reservoir 5:45 PM on February 12, 2015

January’s bird-of-the-month

hawk2015jan_48
Heard this red-shouldered hawk somewhere in my backyard a couple days ago. Difficult to triangulate his location, but after a while I recalled these guys are often lower than you think, so I aimed closer to the ground and found him, only about 20 feet up on a branch, just biding his time. He looked so relaxed and comfortable I went back in the house, grabbed the camera, mounted the telephoto lens, and went back outside. Sure enough, he was waiting patiently. He posed for about 15 minutes. I was waiting for him to fly so I could get a good shot of his wings extended. From time to time I had to lower the camera from my eyes to rest my arms. Fingers were getting numb and feet were beginning to ache. I walked around, waved at him, talked to him. He sat and looked at me and looked all around. Finally I figured I would try to get him to fly, so I tossed a stick into the air under the branch on which he was perched. He stretched, which is the picture above, but didn’t fly right away. He waited another minute until I lowered the camera and glanced away for a second. By the time I could re-aim and shoot, he was 20 yards away and moving fast. I did manage to get his wings to show up in one frame, but it was not a good picture. This was the best of over 50 I took. Note he’s holding on with only his right claw. He’s stretching his left leg out, the left claw is below the branch. He appears to have been stretching his shoulder and wing or tail feathers as well, getting ready to fly.