Archive for the ‘Ornithology’ Category

Ice Age Western Lakes and Altered Bird Migrations

April 9, 2017

I photographed a lesser yellowlegs (Tringa flavipes) at Woodbridge Lake, Evans, Georgia last weekend.  I was thrilled to see this transient species in such an unexpected locality.  Lesser yellowlegs and many other species of sandpipers spend the winter in South America, Florida, and the coasts of Georgia and South Carolina, but they migrate to their summer breeding grounds in western Canada during spring.  The present day breeding grounds of 22 American species of sandpipers, plovers, curlews, and dowitchers were mostly or completely under glacial ice during Ice Ages.  One might ask where these species bred during Ice Age summers.  Weather patterns were much different then.  Today, much of the west is arid desert, but during Ice Ages the region enjoyed a cooler and much wetter climate.  Many large lakes existed in western North America, and they provided beach, reedy marsh, and open water habitats for aquatic birds.  A large prehistoric body of water, known as Pleistocene Lake Manix, covered what today is the Mojave Desert, and Pleistocene Fossil Lake inundated the modern day site of a desert in central Oregon.  Both of these sites yield abundant remains of the aquatic bird species that formerly spent all or part of their lives there.

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Map of western North America during the Ice Age.  More precipitation and cooler weather patterns resulted in large lakes in place of present day arid landscapes.

Image may contain: bird, outdoor, nature and water

Lesser yellowlegs in Evans, Georgia.  This species is a transient here.  It spends winters in South America, Florida, and the southeastern Atlantic Coast, but breeds during summer in western Canada.

Lesser Yellowlegs Range Map

Range map for a lesser yellowlegs.  Many species of sandpipers have similar ranges.  Almost their entire breeding range was under glacial ice during Ice Ages.  They shifted their breeding ranges to the lakes in western North America that no longer exist and are deserts today.

The entire breeding range of the white fronted goose, the blue goose, and 10 species of ducks was also under glacial ice during the late Pleistocene.  The geese and some species of ducks shifted their breeding ranges to these western lakes.  However, harlequin, eider, king eider, and the extinct Labrador duck have/had more easterly distributions and likely bred near the Atlantic coast south of the ice sheet.  Other migratory species of birds that bred on western lakes during Ice Ages include whooping cranes, northern skuas, and arctic loons.

Many species of aquatic birds that breed in western Canada during summer still breed in western states as well wherever wetlands still exist.  Instead of shifting their breeding ground migration north, these species expanded their summer breeding grounds but still also nest within their Pleistocene range.  This list of species includes 2 loons, 2 grebes, white pelicans, 2 swans, 10 ducks, sandhill cranes, Virginia rails, Hudsonian godwits, American avocets, 3 phalaropes, and 3 jaegers.

The abundant large lakes of Pleistocene western North America attracted some species of non-migratory birds that no longer occur in the region.  Anhingas are fish-eating birds confined to southeastern North America today, but fossil evidence shows they lived in Oregon during the Ice Age.  The beautiful scarlet ibis no longer occurs north of Central America but ranged to Oregon then also.

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The scarlet ibis no longer occurs north of Central America but did live as far north as Oregon during Ice Ages.

Western lakes evaporated and turned into desert following the end of the Ice Age.  A number of species failed to adapt by shifting their ranges to newly available Canadian habitat, and they became extinct.  The extinct species include a flamingo, 2 gulls, a jaeger, a cormorant, a grebe, a swan, a goose, and a shelduck.

Breeding colonies of aquatic birds attract predatory species such as bald eagles and great horned owls.  Fossil evidence of both these species is found at most of the sites of these former Pleistocene lakes.

The extinct western lakes would have been a birder’s paradise. Paleo-indians saw the wealth of avifauna as a food source.  Paleo-indians had no television, radio, and little in the way of entertainment, so perhaps bird-watching was a leisure activity for them after they filled their bellies with spit-roasted duck.

Reference:

Jefferson, George

“Remains of the Late Pleistocene Avifauna from Lake Manix, Central Mojave Desert, California”

Bulletin of the Natural History Museum of Los Angeles County June 1985

The Disappearance of the Dickcissel (Spiza americana) from the Mid-Atlantic States

April 4, 2017

The dickcissel is a cyclically abundant grassland bird that spends its summers in North America and flies to South America during winter.  They feed upon grass seeds, though they give their young high protein insects in spring.  Their nests are hidden in tall grass.  Dickcissels are found associated with other grassland species of birds such as meadowlarks, red-winged blackbirds, vesper sparrows, grasshopper sparrows, and savannah sparrows.  Dickcissels prefer clover and alfalfa pastures and old abandoned fields, but they don’t like suburban habitat.  The heart of dickcissel range is the agricultural Midwest.  Migrating stragglers may occur on the Atlantic coast today, but mysteriously, large breeding populations of dickcissels invaded the mid-Atlantic during the middle of the 19th century and just as mysteriously they disappeared from this part of their range by 1900.  Maybe farmers in this region planted more corn and less wheat and clover fields.  Corn rows don’t offer usable habitat for dickcissels.

Summer range map of the dickcissel.  It breeds in the dark red area but vagrants are found within the dotted lines.  They formerly bred in the mid-Atlantic states from South Carolina to Massachusetts.  Stragglers migrate south along the Atlantic coast.

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A pair of dickcissels.  They are a type of finch.

Dickcissels likely were cyclically abundant during the Pleistocene as well with widely changing geographic ranges.  Studies show dickcissels are eliminated from ranges that are burned, and their numbers decline in areas where bison graze.  This suggests they bred on grasslands temporarily abandoned by grazing megafauna herds and left untouched by fire for at least a year.  Lightning-ignited wild fires were less frequent during colder climate phases of Ice Ages.

As far as I can determine, dickcissel remains have been excavated from only 1 Pleistocene-aged fossil site–Little Box Elder Cave in Wyoming, a site just outside the periphery of their modern day range.  (Little Box Elder deserves a blog entry of its own.  Remains of at least 62 mammalian species were recovered here including horse and the only known association of grizzly and short-faced bears south of the former ice sheet.)  Although dickcissels are known from just this 1 fossil site, they may have been common during some climatic stages of the Pleistocene.  I believe they are rare in the fossil records because they inhabit open grassy areas where their remains are not likely to be preserved.

Little is known abut the dickcissel’s past.  Scientists could use genetic analysis to determine historic and pre-historic population dynamics and their evolutionary relationships to other members of the Cardinalidae family which includes cardinals, grosbeaks, finches, and buntings.  Maybe some day, they will be able to explain why the dickcissel disappeared from mid-Atlantic sites.

A Pleistocene-age Carolina Parakeet (Conuropsis carolinensis) Fossil Finally Discovered

December 29, 2016

The Carolina parakeet was a common species living in old growth bottomland forests until Europeans settled eastern North America.  Overhunting and deforestation doomed this only temperate species of parakeet. The colorful noisy birds were an agricultural pest that destroyed ripening fruit when they fed upon the seeds inside the pulp.  Orchardists wiped out entire flocks.  Though parakeets are supposed to be intelligent, they were not well adapted to avoiding patient men with guns.  A farmer firing his weapon into a flock (the birds routinely congregated in flocks of 200-300) caused the survivors to fly in a wide circle and return to the same place where their feathered comrades had just been killed.  A farmer could slaughter the entire flock in an afternoon without moving from the same spot.  Carolina parakeets nested in large hollow trees, but lumbering operations during the late 19th century eliminated their homes as well.  The last population of Carolina parakeets was probably rubbed out by market hunters seeking red and green and yellow feathers, then fashionable in women’s hats.  The last wild specimen was taken near Lake Okeechobee, Florida in 1904, and the last captive specimen died in the Cincinnati Zoo in 1918, coincidentally the same place and year where the last passenger pigeon died.

Until recently, the only North American fossil remains of a parakeet was a specimen found in Nebraska, dating to the mid-Miocene (about 16 million years BP).  Scientists are uncertain if this specimen represents a species ancestral to the Carolina parakeet, the same species, or a different lineage.  In any case no fossil remains of a parakeet dating to the Pleistocene age (~2 million years BP-11,000 years BP) had ever been found in North America.  Carolina parakeets lived in habitat where preservational processes don’t often occur.  Most bird remains are found in caves where they were carried by roosting owls or hawks.  There aren’t many caves in the lowland habitats favored by parakeets.  Moreover, the flesh of parakeets was toxic to many predators because they fed on poisonous cocklebur seeds.  Their colorful plumage may have worked as a deterrent to predators who learned to avoid the well-marked prey that may have sickened them previously.  Although preservational bias was the probable reason why remains of this species had never been found, it was possible Carolina parakeets were a recently evolved species that colonized North America, following the end of the most recent glacial-interglacial transition.  But finally, just a few years ago, the remains of a Pleistocene-age Carolina parakeet were unearthed at the Dickerson Coquina sand pit in St. Lucie County, Florida.  Fossils found at this site are estimated to be somewhat younger than 730,000 years BP-430,000 years BP, proving that Carolina parakeets had a very long history in North America.

Map of Florida highlighting St. Lucie County

St. Lucie County, Florida.  The Dickerson Coquina Pit fossil site, located in this county, yielded the first known Pleistocene-age remains of a Carolina parakeet.

The extinct Carolina parakeet.

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Range map of the formerly widespread Carolina parakeet.  It was doomed by overhunting and deforestation.

Sand is mined from the Dickerson Coquina sand pit to replace sand lost on Hutchinson Island to erosion.  Hutchinson Island is located in the same county as the sand pit.  Pleistocene-age fossils have been found in the sand pit and on the sand dumped on Hutchinson Island Beach.  Electron spin resonance dating determined the specimens excavated from the sand pit were above a layer dated to 730,000 years BP-430,000 years BP.  The species found are consistent with this dating and were common during the late Pleistocene including giant tortoise ( Hesperostestudo crassicutata ), box turtle, snakes, sharks, rays, fish, mammoth, paleollama, tapir, horse, pampathere, dire wolf, and jaguar.  No bison fossils were found.  Bison didn’t colonize North America until 300,000 years ago, so the absence of this species is consistent with an estimated date of 400,000 years BP for the fossils found here.

The remains of at least 24 species of birds have been excavated from these sands including a number of interesting extinct or extralimital species aside from the Carolina parakeet.  (The complete list of species found is described in the paper linked below as a reference).  Ornithologists have identified the remains of great auk ( Pinguinus impennis ), short-tailed albatross (  Phoebastrea albatrus ), northern gannet ( Morus bassanus ), an extinct stork ( Ciconia maltha ), and an unnamed extinct crane ( Grus sp. ).

Today, the short-tailed albatross nests on just 4 islands in the North Pacific between Hawaii and Japan (including Midway near where the famous WWII battle took place). But the presence of their bones in Florida means this species formerly ranged throughout the North Atlantic Ocean.  They probably nested on islands that were inundated by rising sea levels about 400,000 years ago, causing their extirpation here, but they didn’t necessarily nest in Florida.  Storms may have blown flocks inland.

Short tailed Albatross1.jpg

Today, the short-tailed albatross is a rare bird that nests on 4 islands in the North Pacific, but it also lived in the Atlantic Ocean during the middle Pleistocene.

The great auk was a denizen of rocky islands off the coast of Maine and Canada until 1852 when it was overhunted to extinction.  I hypothesize they nested on a rocky island off the coast of South Carolina, known as Bulls Scarp, that was above sea level during Glacial Maximums.  This possible nesting site may explain why they were close enough to have fished waters off the coast of Florida.  It’s likely storms blew this species inland as well.

A large, stuffed bird with a black back, white belly, heavy bill, and white eye patch stands, amongst display cases and an orange wall.

The great auk was overhunted to extinction by 1852.  Remains of this species were also found at this site.  I hypothesize that during Glacial Maximums this species may have nested as far south as South Carolina.

Northern gannets nest on subarctic islands in the North Atlantic but range throughout most of the Atlantic when seeking fish.  They too may have nested on Bulls Scarp.  The extinct species of stork probably ate carrion and depended upon the existence of large herds of megafauna for a major part of its food supply.  Not enough skeletal material has been found here from the large extinct species of crane to officially name it.  The fossil bone recovered from the sand pit resembles that from an extinct flightless crane that formerly lived in Cuba, but it is not an exact match.  This species was probably not flightless, like its Cuban cousin, because there were too many predators on the mainland.

Reference:

Kilmer, John; and David Steadman

“A Middle Pleistocene Bird Community from Saint Lucie County, Florida”

Bulletin of the Florida Museum of Natural History 2016

http://www.flmnh.ufl.edu/files/2514/8113/2040/Vol55No1_archival.pdf

Forest Succession and Changing Song Bird Species Composition in Central Georgia

November 13, 2016

Cotton and corn cultivation were important in central Georgia until the boll weevil struck in the 1920’s.  Then the depression bankrupted many farmers who tried to persevere, despite this agricultural pest.  This economic calamity gave ecologists the opportunity to study forest succession as fallow fields eventually were transformed into climax forests.  In less than a year bare soil becomes covered in grass and weeds 2 feet tall.  Ragweed, asters, and broomsedge (a type of bunch grass) take over in the 2nd year, and by the 3rd year broomsedge and pine saplings up to 3 feet tall predominate.  These 1st three years are known as the “grassland stage.”

If left unmodified, years 3-10 are known as the “grass and shrub stage.”  Broomsedge and pine saplings are joined by blackberry, blueberry, sumac, greenbrier, and persimmon often covered by grape vines, Virginia creeper, Carolina jessamine, and honeysuckle–all plants that thrive in the sun.  Eventually, pine trees emerge above this tangled mess.  During years 11-30 the landscape is known as a “young pine forest.”  An “old pine forest,” years 31-60, hosts tall pine trees but with a dense oak understory.  This mixed pine/oak forest is habitat for more species of birds than any other stage.  Lightning strikes, red heart disease, and pine beetles kill many pine trees during this stage, opening up the forest canopy and creating uneven-aged stands of trees beneficial for many different species of birds.  After 60 years left fallow the land becomes a climax oak/hickory forest.

Below is a chart interspersed with photos showing the association of bird species with each stage of forest succession.

Years 1-3 (Grassland Stage)–grasshopper sparrow, field sparrow, song sparrow, meadowlark, killdeer plover, quail, junco, horned lark.

Female grasshopper sparrow returning to nest with prey in beak

Grasshopper sparrows (Ammodramus summurum) are abundant in old fields.

Years 3-10 (Grass and Shrub Stage)–Add white-throated sparrow, rufus-sided towhee, cardinal, catbird, mockingbird, mourning dove, Carolina wren, and brown thrasher.

bobwhite quail covey

 

 

 

 

 

 

 

 

 

 

 

Covey of quail.  This species becomes most abundant 3-5 years after cleared land is left fallow.

Years 11-30 (Young Pine Forest)–Subtract most of the grassland species but add flicker, blue jay, chickadee, titmice, pine warbler, and white-eyed vireo.

Eastern Towhee

 

 

 

 

 

 

 

 

 

 

 

 

 

Rufus sided towhees move into young pine forests.

Years 31-60 (Old Pine Forest Stage)–Subtract mourning dove, catbird, mockingbird, brown thrasher, and white-eyed vireo, but add summer tanager, woodpeckers, yellow-throated warbler, black and white warbler, wood thrush, flycatchers, red-eyed vireo, and kinglets.

Carolina Wren Photo

Carolina wrens are abundant in old pine forests with an hardwood understory.

> 60 years (Climax Oak/Hickory Forest) Subtract towhee, pine warbler, and tanager, but add white breasted nuthatch.

White-breasted nuthatch foraging in tree

White breasted nuthatches won’t move into a forest until it is at least 50 years old.  Last time I saw this species was when I visited Marshall Forest in Rome, Georgia which is a virgin forest.

Forest succession from bare soil to climax forest has occurred in Georgia ever since Indians began cultivating the land here over 1000 years ago.  However, habitat including each successional stage is much older than this because our present day species of song birds, especially habitat specialists, have existed for over 1 million years.  Before man impacted the environment, changes in the landscape depended upon natural disturbances.  Heavy acorn consumption by megafauna along with trampling and bark-stripping suppressed tree recruitment and growth.  Lightning-ignited fires thinned forest into open woodlands.  Tornadoes and downbursts flattened wide swaths of trees.  Drought, ice storms, floods, and fluctuating climate cycles also changed forest structure and tree species composition.  Landscapes are never eternally permanent.

References:

Johnson and Odum

“Breeding Bird Populations in Relation to Plant Succession on the Piedmont of Georgia”

Ecology 37 1956

Meyers, J.M. and A.S. Johnson

“Bird Communities Associated with Succession and Management of Loblolly-Shortleaf Pine Forests”

U.S. Forest Service General Technical Report

 

Pleistocene Roadrunners (Geococcyx californianus)

August 5, 2016

Roadrunners are neotropical invaders that spread across North America, probably no earlier than the late Pleistocene.  Fossil remains of roadrunners dating to this time period have been excavated from sites in Arizona, New Mexico, and California.  Roadrunners are ground foraging birds in the cuckoo (Cuculidae) family.  All other members of this family prefer the tree canopy.  There are just 2 species of roadrunner–Geococcyx californianus ranges from central Mexico west to California and east to Arkansas and Louisiana and G. velox occurs in tropical deciduous forests from southern Mexico to Nicaragua.  The ancestor of these species likely diverged during an arid climate cycle of the Pleistocene.  G. californianus evolved a preference for desert scrub and cactus environments and moved north across the Rio Grande.  I think they are a fairly recent colonizer of this region because desert grassland and scrub habitat was widespread across southeastern North America during the late Pliocene/early Pleistocene about 2 million years ago, yet there is no fossil evidence of roadrunners in this region from that time period.    If roadrunners lived in southwestern North America during this early time period when their ideal habitat was so widespread, I believe they would have colonized the southeast.  And they would still persist in some areas of the southeast where favorable habitat exists.  There’s no shortage of thickets mixed with clearings in the southeast.  In Arkansas, the easternmost part of their modern range, roadrunners occur in farms and clearings, cedar glades, scrubby woods, and rocky outcroppings.  Currently, the Mississippi river appears to be a barrier that prevents them from expanding their range east.  They haven’t crossed the river yet because they are weak flyers and prefer to run in zigzag patterns between thickets.  They are the fastest runners among birds capable of flight, reaching speeds of 25 mph–about the speed of an Olympic male sprinter.

Roadrunner and Snake

 

 

 

 

 

 

 

 

Roadrunner killing snake.  They kill their prey by bashing it against the ground until it is senseless.

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Roadrunner range map.  I believe the Mississippi River is the barrier that keeps them from expanding their range east.

Video of a roadrunner ambushing an hummingbird at a feeder.

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Real life roadrunners are smart like their cartoon imitation.

Pleistocene roadrunners were slightly larger than modern roadrunners but are considered to be the same species.  Scientists believe they grew to a larger size due to cooler Ice Age summers.  The modern smaller birds have more endurance in warmer conditions than larger birds and can chase down their favored prey (lizards, snakes, mice, scorpions, insects, and other birds) for longer periods.

Roadrunners are poorly studied.  I searched The Auk and The Condor, 2 ornithology journals, for more information about them and found very few articles..  They are an intelligent bird, not unlike their cartoon counterpart, and this makes them hard to study because they are smart enough to avoid traps.  This is 1 case when the cartoon imitation of an animal matches its real personality.

 

Passenger Pigeons (Ectopistes migratorius) and Forest Succession

August 1, 2016

The former abundance of the now extinct passenger pigeon amazed all of the pioneers who witnessed their migration and roosts.  Some researchers estimate passenger pigeons composed 25% of the total bird population in eastern North America during colonial times.  Their migrations consisted of billions of birds that could eclipse the sun for as long as 14 hours.  Pigeon dung fell like “snowflakes” underneath this eclipse.  They nested in enormous colonies, covering many square miles.  Their survival strategy was predator satiation.  With synchronized hatching there were billions of squabs on the forest floor during the week they left the nest and were learning how to fly.  There were just too many for predators to eat all at once. They nested and reproduced in the great deciduous and coniferous forests of the Midwest, then migrated to the middle south during the winter where they still roosted in large colonies.  Passenger pigeon roosts destroyed vast areas of the forest.  The weight of all those birds broke limbs off trees and even busted thick tree trunks in half.  The armies of pigeons vacuumed all the acorns, beechnuts, and chestnuts off the forest floor, leaving no mast for other animals.  But their dung was the most detrimental element of their roosts–overfertilizing the soil and killing all the trees in the vicinity.  Yet, ecologists believe passenger pigeons played a critical role in creating habitat diversity across the landscape.

Illustration showing how passenger pigeons created more diverse habitats.

Flocks of migrating passenger pigeons could eclipse the sun for as long as 14 hours.  Areas of the forest where they roosted were devastated.

Stuffed specimen of a male passenger pigeon.

The response of the environment following the aftermath of a cataclysmic pigeon occupation would have been interesting to study.  Unfortunately, passenger pigeons were overhunted to extinction before scientific studies of their ecological impact could be conducted.  However, we can safely assume the environment recovered in stages.  First, plants; such as ginseng, pokeberry, and Virginia creeper; that thrive in soils rich in nitrogen were the initial species to grow in the open conditions strewn with fallen dead trees and limbs.  Second, as rain reduced the concentration of nitrogen in the soil over the years; ragweed, grasses, sedges, and composites returned.  A shrubby stage with pioneer trees including cedar and pine gradually replaced the grassy stage.  Acorns carried by jays and squirrels sprouted into oaks that grew with the pioneer trees before eventually outcompeting them.  If undisturbed for centuries, shade tolerant species such as maple and beech took over from the oaks. The dead wood from the original pigeon roosts was flammable during dry weather, and wild fires were likely more common, explaining why fire-tolerant species of oaks (burr, white, and black) predominated in the Midwest.

In many areas of the Midwest some species of oaks are in decline, especially white oak, while red oak is increasing.  White oak germinates during the fall when passenger pigeons were absent in this region.  But the pigeons were able to consume spring-germinating red oak acorns after the snow melted.  Moreover, red oaks are less fire tolerant than white oaks.  Oaks are also shade-intolerant and are being replaced by shade tolerant maples.  Ecologists think white oaks are missing the passenger pigeon invasions that created the natural disturbance they need and reduced the competition they now face from red oaks.

Scientists with the Revive and Restore Project hope to genetically engineer the passenger pigeon by cutting and pasting their genes into the embryos of their closest living relative, the band-tailed pigeon.  I doubt they will successfully be able to re-establish passenger pigeons in the wild.  Passenger pigeons fail to breed unless they live in enormous colonies.  To survive predation, they must exist in large numbers…the sheer size of their population was the survival mechanism they required.  Researchers would need to release at least 10,000 birds to establish a successful breeding population in the wild.  Passenger pigeons evolved their survival strategy millions of years ago.  Though 1 genetic study suggests their overall numbers fluctuated with changes in climate phases, I am convinced they always occurred in large colonies. The task of re-establishing these numbers is probably an impossible one.

See also: https://markgelbart.wordpress.com/2010/08/27/pleistocene-passenger-pigeon-populations/

Pleistocene chickens (Gallus sp.)

July 4, 2016

Some of my wife’s relatives are chicken farmers.  Modern day poultry farmers raise chickens in long metal warehouses containing as many as 30,000 birds.  The warehouses smell like the inside of a toilet bowl that hasn’t been flushed or cleaned in a year.  Chicken farmers have to walk through each of their warehouses twice a day to collect and dispose of dead chicks.  This task prevents the spread of infectious diseases.  Agricultural catalogues sell Israeli gas masks for poultry farmers, so they won’t get sick from working inside their warehouses.  Wild chickens have a better quality of life than the birds that spend their entire lives inside these awful concentration camps.  At least they get to breathe fresh air and live naturally.

According to the paleobiology database, chickens formerly lived all across Eurasia.  The bones of extinct species of chickens have been unearthed at 8 sites in Europe.  These extinct species lived from the late Miocene to the early Pleistocene.  But when Ice Ages began occurring, the range of the chicken was reduced to southeast Asia.  Now, there are 4 or 5 species of chickens, but many additional species existed when earth’s overall climate was warmer.  Chickens require warm tropical/semi-tropical river valley forests where they can forage for seeds, fruits, and insects on the ground.  They can’t endure harsh temperatures.  Curiously, there are no known Pleistocene-aged fossils of chickens from their current range, though they undoubtedly abounded in the region then.  Bone preservation is uncommon in lowland tropical forests because of the acid soils.

Distribution map of the red jungle fowl, 1 of the ancestors of the domesticated chicken.

Research of the origin of chicken domestication is confused and contradictory.  Zooarchaeological and genetic evidence suggests chickens were first domesticated in northern China about 8,000 years ago.  However, some scientists re-examined the zooarchaeological evidence and determined the chicken bones were misidentified.  Instead, these supposed chicken remains are actually pheasant bones.  They also note that chickens are and were not native to northern China, a temperate zone region.  The fauna associated with the pheasant bones consisted of temperate species such as red deer, sika deer, and wild boar.  The species of mammals that co-occur with wild chickens including rhesus macaques, Asian elephants, and rhinos were absent from this region.  Northern China is just too cold for chickens, and it’s far more likely they were first domesticated in their native range of southern China.  By 3000 BP chicken farming had spread to northern China where the birds could survive winter with human help.

The modern farm-raised chicken is a hybrid cross between 2 species–the red jungle fowl (Gallus gallus) and the gray jungle fowl (G. sonneratii). Genetic evidence suggests the yellow skin pigment descends from the latter species.  Feral chickens occur locally in many towns and cities across southeastern North America including Miami, Key West, St. Augustine, Houston, New Orleans, and Fitzgerald, Georgia.  Chickens living in Fitzgerald descend from a population released along the Ocmulgee River.  The Georgia State Fish and Game Department hoped the birds would become a popular target for hunters.  Instead, the chickens abandoned the river bottomland forest and moved into suburban areas of the nearby town where they have thrived for decades.  Their preference for human-modified habitats may mirror their close ties to habitats modified by elephant foraging in their native range.  Elephants expand and maintain open areas, and they knock fruit to the ground.  Their manure attracts insects and contains undigested seeds.  Wild chickens benefit from the presence of elephants.  In suburbs humans maintain the open areas and accidentally provide food for chickens.

Feral chickens in Fitzgerald, Georgia.

Some people love suburban wild chickens, while others (the get-off-my-lawn assholes) resent the crowing and droppings.  I like free-ranging chickens better than grouchy old people.

References:

Eriksson, J; and et. al.

“Identification of the Yellow Skin Gene Reveals a Hybrid Origin of the Domestic Chicken”

PLOS Genetics 2008

Peter, Joris; and Ophelia Librasseum, Hai Deng, and Gregor Larsh

“Holocene Cultural History of Red Jungle Fowl (Gallus gallus) and its Domestic Descendent in East Asia”

Quaternary Science Reviews   June 2016

Pleistocene Chickadees

March 27, 2016

It is difficult to discern the difference between a black-capped chickadee (Poecile atricapillus) and a Carolina chickadee (P. carolinensis).  The former has a longer tail and is a little heavier on average, but as the below photos show, they are hard to distinguish, even if examined side-by-side.  Moreover, the 2 species hybridize in regions where their ranges overlap.  The hybrid zone extends from New Jersey to Kansas with an outlying zone in the Appalachian Mountains.  In captivity male Carolina chickadees outcompete black-capped chickadees for mates, and scientists know female black-capped chickadees will choose male Carolina chickadees in the wild, often as “extra pair sires.”  Supposedly Carolina chickadees have a 4 note song, while black-capped chickadees have a 2 note song.  (See: https://www.allaboutbirds.org/search/?q=chickadee ) In the hybrid zone chickadees use both songs.  However, I live in Augusta, Georgia; far from the hybrid zone, and I discovered Carolina chickadees here use both the 2 note and the 4 note song.  I conclude the 2 species can’t be distinguished by which song they use.

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Partial range map for Carolina and Black-capped Chickadees.  

Black-capped chickadee

Black-capped chickadee.

Carolina Chickadee

Carolina chickadee.

 

The chickadees are tough Pleistocene survivors.  They are a year round resident of forest and woodland, capable of enduring harsh winters because they stash caches of seeds utilized during lean times.  Chickadees belong to the Paridae family that also includes tits and titmice.  Genetic evidence suggests the ancestors of all American Paridae originated in Asia and then colonized North America about 3.5 million years ago.  Cyclical climate change caused corresponding changes in the environment over time.  The founding population of these forest-dwelling birds became isolated into different populations by expanding desert grassland or in some cases by glaciers, resulting in the evolution of different species.

I was surprised to learn Carolina chickadees and black-capped chickadees are not sister species, even though they appear so similar and hybridize.  (Sister species are organisms that most recently evolved from the same common ancestor.  The official definition is “taxa derived from a common ancestral node.”)  Instead, the genetic evidence suggests the black-capped chickadee is a sister species of the mountain chickadee (P. gambeli), a bird that ranges throughout the Rocky Mountains, and the Carolina chickadee is a sister species of the Mexican chickadee (P. sclateri).  The chestnut-backed chickadee (P. rufescens) of the Pacific northwest, the boreal chickadee (P. hudsonicus) of Canada, and the gray-backed chickadee (P. cinctus) of Alaska and Scandinavia are sister species with each other.  Genetic evidence also shows black-capped chickadees and boreal chickadees have greatly expanded their ranges from single source populations, since the end of the last Ice Ages after the massive glaciers that covered their present day ranges melted.

Chickadees have likely been a common bird in southeastern North America for over 2 million years.  Yet, I’m aware of just a single specimen found in this region dating to the Pleistocene.  This specimen belongs to the University of Florida Museum of Natural History and was found at the Inglis fossil site in Florida.  It is early Pleistocene/late Pliocene in age (~1.9 million years old).  It was identified as a boreal chickadee, a species restricted to Canada today.  I can’t find the scientific journal within which this specimen was described.  Considering how hard it is to distinguish between species of chickadees, I’m uncertain how accurate this species diagnosis is.  However, boreal chickadees may have once been more widespread in North America before other chickadees, such as the Carolina, evolved and outcompeted them in various regions. The rarity in the fossil record of a species that was probably abundant for millions of years shows how fleeting evidence of an organism’s existence is.

References:

Gill, FB; B. Slikas and F.H. Shulde

“Phylogeny of titmice (Paridae): 11 Species Relationships Based on Sequences of the Mitochondrial Cytochrome Gene”

The Auk 122 Jan 2005

Reudink, Matthew; et. al.

“Structure and Dynamics of the Hybrid Zone between Black-Capped Chickadee (Poecile atricapullus) and Carolina Chickadee (P. carolinensis) in Southeastern Pennsylvania”

The Auk 124 (2) 2007

The First Ever Ornithological Expedition to the Okefenokee Swamp in 1912

February 6, 2016

In 1912 an expedition composed of 4 Cornell University professors, 2 graduate assistants, the principle of Ithaca High School, 2 Georgia state entomologists, and 4 local guides conducted an ornithological survey of the Okefenokee Swamp.  The expedition lasted from May 6th-July 13th.  They found 75 species of birds, and 19 species were added to their list based on descriptions of the local guides who were considered reliable sources.  At the time of the expedition the Okefenokee was still a vast wilderness of cypress swamps, flooded marshes, hardwood hammocks, and larger islands topped by open pine savannahs.  River bottomland forests grew along the Suwanee River.  A few families lived on the edges of the swamp and within it, but a lumber company was making inroads at the time because they were felling much of the best timber.  The expedition wrongly assumed the swamp was going to be destroyed, like so many other remnants of wilderness left in North America then.  They did not know Franklin Roosevelt would eventually make it a protected wildlife refuge.

The most abundant bird in the swamp was the red-bellied woodpecker followed closely by the crested flycatcher.  Old growth forests provide plenty of food for woodpeckers.  Bobwhite quail were abundant on the larger islands where “pine barrens” prevailed.   Prothonotory warblers were also considered abundant.  The expedition found a rookery consisting of 500 little blue heron nests with eggs.  However, they saw just a few egrets because a recent fashion craze for egret feathers on women’s hats had led to the decimation of this species.  Georgia outlawed egret hunting in 1910.

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The information for this blog entry comes from an article published in The Auk from October 1913.  I purchased this vintage scientific journal from paleopublications.com .

The red-bellied woodpecker was the most abundant bird in the Okefenokee Swamp during Frances Harper’s survey of 1912.

The crested flycatcher was the 2nd most abundant bird during his survey.

File:Everglades Little Blue Heron.jpg

Harper found an active rookery of 500 little blue heron nests in the Okefenokee during his 1912 survey.

The expedition saw 150-200 wood storks feeding in shallow water, and 1 day a flock of 40 bobolinks flew over their heads.  Carolina wrens and brown-headed nuthatches were also considered very common/abundant in the swamp.

Woodpeckers in order of abundance were; 1. red-bellied, 2. pileated, 3. red-cockaded.  Hairy, downy, and red-headed woodpeckers were present but considered uncommon.  Ivory-billed woodpeckers, extinct since ~1945, still occurred in the northwestern part of the swamp on Minne Island then.  A guide heard an ivory-billed call during the expedition, and they found some recently used nests.  Red-cockaded woodpeckers, rare and endangered today, were still common here in 1912.

Ivory-billed woodpecker and nest.  Frances Harper found ivory-billed woodpecker nests in the Okefenokee that had been in use within 3 years of his survey.  One of his guides heard the call of an ivory-billed woodpecker during the survey, but Harper did not see or hear any.

Swainson’s warbler, considered uncommon now, were reported to be “not uncommon” in the swamp during the expedition.  Chimney swifts were a common bird seen hunting for mosquitoes over the water.  Evidentally, large colonies of this bird nested in hollow cypress trees for the local guides said they did not nest in their homestead chimneys.  Other common song birds included grackles, yellow-billed cuckoos, yellow throats, pine warblers, bluebirds, tufted titmice, eastern meadowlarks, and cardinals.

Red-shouldered hawks were the most common bird of prey during the day, while barred owls dominated the night.  Turkey vultures and black vultures were both common and made quick work of skinned alligators killed by hunters.  The expedition found 15 osprey nests.  They also often enjoyed seeing the aerial acrobatics of swallow-tailed kites.

Swallow-tailed Kites

Harper saw flocks of swallow-tailed kites summersaulting above the tree line.

Wood ducks were common year round residents, but the expedition came at the wrong time of the year to see winter migrants.  However, the local guides informed them that hooded mergansers, mallards, and coots commonly wintered in the swamp.  Shy sand hill cranes were  more often heard than seen because the local people hunted the delicious birds whenever they could.  The locals also relished wood ducks.  Oddly enough, white ibises were on the local menu.  I would suppose a fish-eating bird would taste too strong.

Anhingas could be found along the Suwanee River and in some of the larger bodies of water.  One of the guides was blind in 1 eye because his pet anhinga had stabbed it with its bill.

A single loggerhead shrike was seen chasing a bluebird.  A dead bluebird impaled by a shrike was further evidence of this species.

The only species the expedition was surprised to find was the spotted sandpiper.  This bird prefers open shore type habitat, but apparently some individuals were content to forage around fallen logs adjacent to marshes.  Spotted sandpipers winter south of this region and spend summers to the north.  The birds the expedition saw were probably in the process of migrating north.

Remarkably, not a single common crow was seen in the swamp.  The crow is 1 of the most common birds in my neighborhood in Augusta, Georgia, and I always see them wherever a travel.  This demonstrates just how attached crows are to the neighborhoods of man.  They thrive in manmade environments but avoid deep wilderness.  They like to eat human agricultural waste and garbage–a rich source of food compared to what they can forage in deep wilderness.  The expedition did identify a few fish crows along the Suwannee River.

Carolina parakeets became extinct in 1914.  Sadly, this species had been gone for so long from the Okefenokee that none of the old-timers were able to give any personal accounts of their encounters with them.

Reference:

Wright, Albert; and Frances Harper

“A Biological Reconnaissance of the Okefinokee Swamp: the birds”

The Auk 30 (4) October 1913

Pleistocene Pastures and Loggerhead Shrikes (Lanius ludovicianus)

January 18, 2016

The habitat requirements of the loggerhead shrike suggest a long interrelationship with extinct Pleistocene megafauna.  Shrikes prefer grazed grasslands with nearby thickets of short trees for nesting and isolated taller trees for perching.  A cow pasture adjacent to a large yard landscaped with trees and bushes is ideal habitat for a shrike.  Shrikes use the isolated trees as observation posts where they search for prey.  A grazed pasture maintains just the right height of grass so a shrike can find their favorite foods–grasshoppers, mice, lizards, small snakes, and other song birds.  Grass that gets too tall could also conceal a predator such as a fox or cat not averse to making a meal of shrike.  Thickets provide good places for shrikes to hide their nests.  During the Pleistocene mammoths, bison, and horses maintained the range of habitats required by shrikes, the haphazard mix of grazed pasture, isolated tall trees, and thickets.  Despite the unlikelihood that a predatory songbird could become preserved in the fossil record, shrike remains dating to the Pleistocene have been excavated from 2 fossil sites in Florida at Arredondo and Reddick.  Shrikes were probably common in the southeast for millions of years, and they surely witnessed herds of megafauna stirring up prey.  The ancestor of the loggerhead shrike diverged from a Holarctic population of northern shrikes (Lanius excubitor) when Ice Ages began occurring, and glaciers isolated the founding population.

A great grey shrike with an impaled mouse. Photo courtesy of Marek Szczepanek. Source.

A great gray shrike with a mouse it impaled.  They kill their prey by snipping the spine behind the head.  Their claws are too weak to hold on to their prey when feeding and tearing with their bill, so they impale them on thorns or barbed wire.

Following the extinction of the megafauna, shrikes remained common in the southeast.  Fire and Native American agricultural practices maintained favorable shrike habitat.  The characteristics of sand hills with widely spaced pines, scrubby thickets, and sparse ground cover were always a preferred habitat for shrikes.  When William Bartram traveled through the Florida sand hills in 1776 he noted that shrikes (or butcher birds as he called them), along with rufous-sided towhees and Florida scrub jays, were “very numerous.”  He described this landscape as an open pine and palm savannah interspersed with thickets of magnolia, dwarf oaks, devilwood, blueberry, pawpaw, and buckthorn.  In 1939 John May wrote in his classic A Natural History of North American BirdsThe Loggerhead Shrike is an extremely common bird along the roadsides of Florida, where in winter every third or fourth telephone pole seems to serve as an outlook point for either a Mockingbird, a Sparrow Hawk, or a Loggerhead Shrike.”

Unfortunately, loggerhead shrike populations have drastically declined over the past 60 years. I’ve never seen one.  A century ago, before the adoption of the car, horse pastures were abundant across the southeast.  Farmers still raised cattle on all this excess pastureland for decades after cars replaced horse and buggies.  Cotton and corn fields left fallow covered much of the south as well.  Fallow fields rank 2nd to pasture as good shrike habitat.  Much of this favorable shrike habitat has been converted to pine plantations, a type of environment that supports no wildlife.  This ecological disaster also explains declines in the populations of eastern meadowlarks, vesper sparrows, grasshopper sparrows, and bobwhite quail.  In Louisiana and Texas the conversion of cow pastures to rice plantations has caused a decline in shrike populations there.  Invasive fire ants colonize the bare earth left after the rice is harvested, and they compete for the same prey items.

Shrikes are permanent residents in the south.  Shrikes that breed in the Midwest migrate south during the winter.  These migratory populations are suffering an even worse decline.  Territorial shrikes that permanently reside in the south drive away migratory pairs from the remaining suitable habitat.  Migratory shrikes have become extirpated from many areas where they formerly ranged.  One study of shrikes in the North Carolina sand hills region determined that shrikes are disappearing from the periphery of their range, but core populations living in good shrike habitat are stable.  I hope they remain so.  The loggerhead shrike is on my birding wish list.

References:

Lynn, Nadine; and Stanley Temple

“Land Use Changes in the Gulf Coast Region: Links to Decline in Midwestern Shrike Population”

The Passenger Pigeon 1991

McNair, Douglas

“Breeding Distribution and Population Persistence of Loggerhead Shrikes in a Portion of the North Carolina Sandhills”

The Southeastern Naturalist 4 (14) 2015