GeorgiaBeforePeople

I was jogging on Piney Grove Road, located in Richmond County Georgia last summer and saw a flock of crows mobbing a bald eagle and a red-tailed hawk. I sprinted inside my house, grabbed my camera, and took a decent photo of the eagle. I don’t often see eagles and was excited to document my sighting. The eagle was near the red-tailed hawk, and I was able to make a direct size comparison. I never realized how much larger eagles are compared to hawks.

Crows were mobbing this hawk and a nearby eagle.

I was excited to get this photo of the eagle. I was surprised how much bigger it was than the hawk. Nevertheless, crows were tormenting both.

This incident inspired my investigation into genetic studies of bald eagles. Bald eagles belong to the sea eagle genus (Haliaeetus) which includes 9 species with a near worldwide distribution, excepting deep ocean and polar regions. Genetic studies suggest bald eagles are more closely related to species of sea eagles found in the Northern Hemisphere. All sea eagles occupy the same ecological niche, feeding upon fish, waterfowl, carrion, and small animals.

Another genetic study determined bald eagles living in Alaska belonged to a different clade than those living in Florida. The study found significant genetic differences between boreal populations and Florida populations. Eagles found near Florida bay located in the southern part of the state are sedentary populations living in a resource rich region, but they are genetically similar to eagles found in the central and northern part of the state. The differences between boreal and Florida populations are probably due to geographical distance. Southern bald eagles may be more resistant to malaria.

Despite a sudden population decline following DDT exposure during the middle of the 20th century, scientists have not found any genetic bottlenecks in eagle populations. This is probably because it is such a widespread species.

I found an error in general information about bald eagles on google. According to more than 1 website in a basic google search, bald eagles supposedly appear suddenly in the fossil record during the late Pleistocene about 125,000 years ago. However, I looked at the University of Florida museum database and learned an eagle fossil identified as belonging to the Haliaeetus genus dating to the early Pliocene was excavated from the Chicory Mine (a phosphate mine) located in Polk County Florida. Fossils from this site date to the early Pliocene (5.3 million years ago-3.6 million years ago). It seems likely bald eagles and closely related ancestors have lived in North America for millions of years. Eagles belong to the Accipitridae Family which includes the Buteo and Accipiter hawks and the kites. The ancestors of eagles diverged from the ancestors of kites about 36 million years ago.

References:

Helnick, E.

“Genetic Differentiation Among Populations of Bald Eagles, Haliaeetus leucocephalus”

Masters Thesis for Florida Atlantic 2011

Nadeau, A.

“A Genetic Analysis of Bald Eagles in the Pacific Northwest: Retained Genetic Diversity Following a Large Scale Population Bottleneck”

Masters Thesis for Boise State August 2012

Wink, M. ; P. Heidrich, C. Fentcliff

“A mtDNA Phylogency of Sea Eagles (genus Haliaeetus) Based on Nucleotide Sequences on the Cytochorme b Gene”

Biochemical Systematics and Ecology 24 (18) 1996

The only time I have ever seen a woodcock I was driving 60 miles per hour on a state highway and almost drove into it. The bird appeared suddenly from between rows of corn, carrying a large earthworm while flying 6 inches above the ground. At the last instant the bird wisely lightened its load and dropped the worm, thus avoiding catastrophe by less than a second. I checked the rear-view mirror and was glad to see I missed it. I have heard the “peenting” call of woodcocks while I was taking a stroll at dusk, but I mistakenly thought it was a migrating flock. Woodcocks are year-round residents in southeastern North America and during Ice Ages this region was their stronghold. The diet of the woodcock is largely earthworms, though they eat other invertebrates as well. During Ice Ages areas covered in glacial ice had no earthworms and no woodcocks. Even after Ice Ages ended, earthworms did not recolonize most of New England and Canada until after Europeans introduced non-native species of earthworms there. Europeans brought earthworms in dirt used as ship’s ballast and in fruit tree root balls encased in dirt. Woodcocks rapidly extended their summer breeding ranges to these regions in response to the new source of food.

Woodcocks belong to the Scolopacidae family which includes the sandpipers. They are also known as timberdoodles. They use their long bills to hunt for earthworms, usually at night when worms burrow closer to the surface. During mating season male woodcocks attempt to attract females by making a “peent” call, then flying in a spiral pattern high in the sky before returning to the ground. Females lay eggs on the ground and carry their slow-developing young between their legs. Woodcocks can decimate earthworm populations in certain locations, and this forces them to move to other territories. They require a varied habitat of moist woodlands and meadows, habitats that apparently occurred throughout the Pleistocene in southeastern North America. Woodcock fossil remains dating to the Pleistocene have been found at 3 sites in Florida, 3 sites in Virginia, and 1 each in Georgia, Alabama, Tennessee, and New Mexico. Southwestern North America enjoyed more precipitation during Ice Ages.

Most species of earthworms people find in North American gardens are non-native, but there are about 100 species of native worms from 5 families. 2 families have just 1 species each. The largest North American family of earthworms is the Megescolescidae with 76 species, 40 of which are found in the east.

Reference:

Krementz, D; and J. Jackson

“Woodcock in the Southeast: Natural History and Management for Landowners”

UGA Department of Agriculture and Environmental Services Cooperative Extension Service

More fossil feathers of Cretaceous Age have been found in the state of Alabama than in any other state. 14 fossil feathers, encased in shale, were found in a lens located in the Eutaw Formation, the site of an ancient shoreline. Shale is basically fossilized mud, and ocean currents rapidly buried the feathers in mud which eventually turned to shale. The fossilized feathers are impressions of the original objects. The Cretaceous Age lasted from 145 million years BP to 66 million years BP, and these feathers probably date to about 80 million years ago. Fossilized feathers have also been found in Kansas, New Jersey, New Mexico, and Alberta; but none of these states or provinces have yielded as many as Alabama.

The feathers include 2 different sizes. Scientists believe the smaller ones come from extinct species of shorebirds. The larger feathers may be from the tails of either a species of hesperornthid or a dromaeosaur. Hesperornthids were an aquatic fish-eating dinosaur that occupied a niche similar to modern day penguins. They were related to the ancestors of birds, and they lived in lakes, rivers, and oceans. Dromaeosaurs include dozens of families of carnivorous dinosaurs ranging in size from 2 feet long to 20 feet long. Some species hunted in packs, though paleontologists are unsure whether they were organized hunters or disorganized mobs like modern Komodo dragons and crocodilians. Some species had a large retractable claw on their 2nd toe that could inflict devastating damage on their prey or each other. Carnivorous dinosaurs were cannibalistic, and the number of carnivorous predators in ratio to herbivorous prey was higher than in modern day ecosystems. For example today in a pristine environment there may be 1 large predator per 40 deer, but during the Cretaceous there may have been 1 predator per 5 large herbivores. Dromaeosaurids were related to the ancestors of birds, and some species may be directly ancestral to birds. Paleontologists don’t agree with each other about the exact evolutionary relationship between birds and dromaeosaurs. Nevertheless, I catalogued this blog entry under ornithology.

Scientists looked at these fossil feathers under a microscope and found structures that look similar to the bacteria involved in feather decay. However, these structures also look like melanosomes responsible for the color in feathers. The feathers from the shorebirds were likely gray, brown, or black. Whether these structures are feather-consuming bacteria or melanosomes is yet another point of contention between paleontologists. Fossils are a vague clue compared to a live organism.

Reference:

Knight, T.; S. Bingham, R. Lewis, C. Saurda

“Feathers of the Ingersoll Shale, Eutaw Formation (Upper Cretaceous) Eastern Alabama: The Largest Collection of Feathers from the North American Mesozoic”

Palaios V. 28 N. 51 May/June 2011