Monday, January 31, 2011

Carcass-cam: scavengers at a roadkill cafe

Revealing images of winter scavengers

Red-tailed Hawks proved to be the most consistent scavengers of a roadkill button buck. This small white-tailed deer fell to vehicle hit injuries in a secluded corner of our back acre near a large brush pile beside a small stream. Scavengers arrived the next day to begin eating frozen venison. Images speak for themselves.

Red-tailed Hawks spend much more time scavenging than other species imaged.

Infrared illuminated mice (Peromyscus sp.) were first on the scene the first night, returning several times. Additional images show mice entering the skin opening at base of jaw and apparently gleaning the jaw of tissue tatters.

A mink is a regular customer at this roadkill cafe, day and night. 
Red-tailed Hawks squabbling over abundance.
Uneasy truce between scavenging rivals.
At least two, probably three red-tailed's spend a lot of time scavenging.
Opossums take a break from threatening each other to take a few mouthfuls of meat.
About 26,000 white-tailed deer are hit by vehicles annually in Ohio. Additional carcasses are left by errant hunters each autumn and winter. More than 260,000 deer are expected to be harvested and checked-in  during the 2010-2011 hunting season (that's 260,000 gut piles left in woods and fields): uncounted numbers are mortally wounded and lost. Countless quadrupeds; raccoons, skunks, opossums, and dozens more species of wildlife are killed by vehicles. The ecological impact of carcasses supplied by human causes must be huge.

The camera is a Reconyx HC600, a research quality day-night trail camera. The camera is cable-locked to the base of a tree very near the carcass. Set to collect a motion-triggered image each second, the collected images viewed sequentially are like a movie clip of scavenger motion. Time-date-weather stamped digital images, many thousands, tell the whole story of scavengers, day and night.

Friday, January 28, 2011

Emerald ash borers create woodpecker wonderland

Green ash swamp infested with emerald ash borer (EAB)
Update: EAB continues to ravage ash tree populations in many states. See our more recent post here for details and to find links to treatment options for protecting landscape trees.

Invasive emerald ash borer (EAB) has found an ash bonanza in the impounded swampland east of Delaware Reservoir. The infestation is no surprise for Delaware County, Ohio residents. Complete destruction of ash trees may be inevitable in central Ohio and beyond. Just a few years from now there may be no large ash trees left living.

Optimistic ecologists hope that infestations will not cause complete destruction of large ash trees within natural woodland ecosystems. This area offers a window of insight into this hypothesis. The outcome does not appear promising, here.

Dying green ash twins. Advanced EAB infestation is is killing this green ash tree.
The twin green ash above may not live through this winter. The dozens of scraggly-looking twigs are "epicormic sprouts" indicating that the tree's essential inner bark was disrupted by wood borers a year ago. The sprouts are the trees last defense. Light gray patches indicate woodpecker activity a year ago, fresh yellow exposures are very recent. Woodpeckers don't kill the trees, they respond to fatal EAB infestations wherever destructive larvae are abundant. This tree was infested at least two years ago.

Dozens of green ash trees harbor emerald ash borer larvae in this impounded swamp. Woodpeckers chip away bark to reach the large larvae in heavily infested trees.

These large serpentine galleries are diagnostic for emerald ash borer. Woodpeckers have exposed galleries under the bark of this green ash tree to get to the larvae.

Friday, January 7, 2011

Green Canyon Peregrines

Did peregrines ply the skies of riparian canyons between green canopied flanks of major Midwestern river valleys before European settlement? How common were green canyon peregrines?

Peregrine Falcons are familiarly characterized as big sky raptors of towering landscapes where stony heights offer vast vistas of prey filled sky and isolated rock ledges where falcons nest on protected eyrie's. They are modern heat-island denizens, too. They kite and flap and "kak-kak-kak" through windy gray urban canyons between monolithic buildings of urban heat-islands. Modern urban peregrines are descendant from a mix of hacked (hand-raised and released) exotic subspecies from North America, Europe and beyond. A huge effort through three decades brought these breeding peregrines to our Eastern cities. The reintroduction effort was necessary and successful, they are here to stay. Will they expand beyond urban canyons to reoccupy native haunts some day? Will they once again occupy green canyons?

Our native Eastern United States breeding peregrine form is extinct. The robust eastern form of Falco peregrinus anatum disappeared, a victim of excessive DDT used for mosquito control and "better living through chemistry" during the post-war boom years. We are still paying unforeseen cleanup and recovery costs for that era's bravado and careless economic growth, today.

Let's go back in time, back before the big wars, all of them: Imagine North America's Midwestern landscape before European settlement, visualize. A view from Space reveals Illinois' western prairie fringe blending with forest cover increasing eastward. Forest tentacles follow river valleys westward into vast prairie. From stationary satellite view, our fat green planet spinning westward under our cosmic perch reveals closing forest canopy as gathering trees coalesce. The earth turns and the landscape quickly transitions to nearly unbroken green forest canopy in eastern Indiana. Our original vast Eastern Deciduous Forest is passing under our cosmic gaze and already, irregularities are apparent. Zoom in just a little..., our view changes a lot. Green summertime canopy is imperfect at closer inspection, now we see hairlike ribbons coursing through green valleys, zoom in a little more, islands of irregular canopy appear where prairie openings pattern the sea of green. Prairie openings pockmark the glacial plains and beyond, even the eastern hills are broken by pigeon balds and rocky gorges. Ohio, for example, was ranked 95% forest before settlement, yet, prairie openings, in western Ohio, mainly, were many, some quite large. As far east as central Ohio, in Pickaway County, a six-thousand acre prairie known as the Pickaway Plains occupied the broad glacial terrace along the green canyon of the Scioto River, the green canyon and plains easily seen from high in space, even today.

Major and minor river valleys dissecting Midwestern landscapes formed permanent corridors through Eastern Deciduous Forest landscapes. These green canyons offered corridors of open sky filled with waterfowl and frequent canyon dashes by crossing passerine (perching) birds like flocks of noisy showy Carolina Parakeets, now extinct. Did peregrines hunt ribbons of open sky along river valleys?

We have few records for Duck Hawks (peregrines) nesting away from stony eyries, in the east. My home state, Ohio, has no accepted record of native nesting peregrine falcons at all. Of course, early settlement records of bird observations are few and far between anywhere you look.

I speculate that peregrines regularly occurred in green canyons of riparian corridors throughout the Midwest. Indiana records may suggest a pattern of occurrence repeated along major river valleys.

Green canyon falcons along the Wabash River...

Birds of Indiana, by Amos W. Butler, Indiana Department of Geology and Natural Resources, Twenty-second Annual Report, 1897, page 795 (italics, mine):

"Nest, in cavity in trees, and on cliffs, eggs, 3-5; pale creamy white, sometimes overlaid with light chocolate, irregularly blotched, streaked and spotted with brown or reddish-brown; 2.10 by 1.68.
Resident, not rare, in Lower Wabash Valley. Throughout the remainder of the State, rare. Migrant. Breeds. In the spring of 1878, Mr. Robert Ridgway discovered that this was by no means a rare bird in the heavy timber in the bottoms of the Wabash River, in the vicinity of Mt. Carmel, Illinois. Three nests were found there. All were placed in cavities in the top of very large sycamore trees, and were inaccessible. One of these trees was  felled, and measurements with a tapeline showed the nest had been eighty nine feet from the ground. It was placed in a shallow cavity, caused by breaking off of the main limb, the upper part of which projected
sufficiently to protect it. Four fully feathered young were taken from the nest (B. N. 0. C, 1878, pp. 163, 164).
Mr. Ridgway also informs me it breeds in Knox and Gibson counties, Ind. The Duck Hawk usually nests on the projections of cliffs, and the foregoing sites are unusual."