Blue Jay Species Dossier

by Carl Strang

This week’s species dossier contains my observations of the blue jay, a bird I regard as the Forest Crier, who lets everybody know what is going on.

Blue jay

Blue jay

Jay, Blue

Lives in forests and old, tree-filled residential areas. Nested in the yard at Culver (15′ up in silver maple), riparian strip at Willowbrook Forest Preserve, IL (8′ up in small tree) and Maple Grove F.P. (10′ up in hawthorn at forest edge, incubating 31MY86). Bird reluctant to move when on nest. Eats mainly insects in summer, a lot of nuts and seeds in fall and winter. Forages from ground to top of canopy. Very vocal. “Eeth! Eeth!” sharp alarm call; rising, accelerating “a-a-a-ee-ee-ee-ee” (long a’s and ee’s) begging/feeding call of young (much like crows’); “ool-ool” and “teekle-teekle” calls accompanied by peculiar bobbing of body. Captive reared birds at the Willowbrook Wildlife Center often used this latter movement in concert with vocal mimicries (whistles, telephone ringing). Low, highly musical, conversation-like vocalizations among Willowbrook’s caged birds. Wild birds mimic calls of various hawks. They travel in loosely organized flocks much of the year. Mob crows in spring. Courtship feeding observed in a treetop at Maple Grove F.P. on 10MY86. Tend to take over feeders, other birds stay away until they leave.

15JE86. As a broad-winged hawk flew past, pursued by a couple of starlings at Maple Grove, a blue jay uttered a single “eeth!” call.

Late summer 86. As a flock of ground-feeding grackles flushed at the approach of people, jays and downy woodpeckers at Meacham Grove emitted contact calls, apparently as a final check of location and status before possible flight.

11MY88. Responded to deer breaking twig loudly with “thief” call, Hartz Lake.

12MY88. Jay on nest in 20′ box elder, nest 15′ up, riparian strip of Willowbrook Back 40.

5JE88. In the middle of Geneva I stood under a tree in which a pair of cardinals suddenly began to alarm-call rapidly. They were close to me, but not paying attention to me. The calls were directed at a blue jay which the cardinals chased from the isolated street-side tree to a clump of trees and brush, and continued the alarm calling and chasing until the jay left. The jay resisted some, was not driven off easily.

29MY88. Hartz Lake, in woods. A chipmunk saw me move my arm laterally, gave 3 chips increasing in speed, and ran. Immediately 2 jays feeding on the ground flew up. They were 40-50 feet away.

13JL88. Blue jay young still following, begging from parent, though they look full grown.

18OC88. Cactus Camp, IN. A blue jay yelling at me with repeated, energetic “jay jay” (“thief thief,” “eeth eeth”) calls.

24DE88. Cactus Camp. Jays doing a lot of “jay” mobbing; information about animals moving away from me?

4JE89. Elsen’s Hill Forest Preserve, IL. Teekettle call used as a warning to an intruding jay, given as the intruder landed. After several repetitions the intruder hadn’t left, and so the calling bird flew into the same oak and began to displace it (flights of 10-20 feet). It “jay”ed once, then resumed “teakettles,” continuing displacements and increasing their frequency, until the intruder left.

11JE89. Cactus Camp. Pair of jays mobbed me with loud “jay” calls.

17JE89. A broad-wing called repeatedly, in north end of Maple Grove. Jays, flickers and grackles highly agitated, flickers the most continuously vocal with “keels” every 2 seconds (2 birds). Grackles gacking frequently, too. A great crested flycatcher near, also vocal, but not clearly in response to the hawk; same with chickadees. Robins definitely disturbed, with nervous dee-dee-dee’s every 20 seconds or so. Jays in bursts, with several birds mobbing.

18AU89. Willowbrook marsh. Kestrel and jays. Latter making a strange, harsh, parrot-like call. Chasing, mobbing. Kestrel seemed to stoop at the jays a couple times, but the jays kept mobbing until the kestrel left.

31AU89. Jays vigorously “jay”-ing at a great horned owl well hidden among leaves in a willow top. Chipmunks chucking nearby, below.

3SE89. Jays maintain contacts with a-a calls (long a’s) and a variety of squeaky notes.

14OC89. Cactus Camp. Jays “jay”ing at a hawk, landing on branches nearby. Hawk appeared to be a red-tail, but was down inside forest. Jays stayed with it as it flew.

Late MY90. Cactus Camp. Jays foraged in accumulated oak leaves in the open among short brush by perching on tree or sapling branches, searching the ground, and making short flights out.



Mayslake Notes

by Carl Strang

Last Friday a doe and her newly spot-free fawn appeared at the edge of the prairie at Mayslake Forest Preserve.

The fawn was noticeably smaller, more skittish, and shorter of body in proportion to leg length than its mother.

The fawn was noticeably smaller, more skittish, and shorter of body in proportion to leg length than its mother.

I am guessing that this is the fawn that was so successfully hidden on the preserve through the summer, though it is possible that this pair came onto the preserve to find respite from the frantic nuttiness of the rut.

Another mammalian development was the sudden appearance of a new muskrat house in the parking lot marsh.

This den was built in less than a week.

This den was built in less than a week.

The other main marsh, in the stream corridor, had dried out earlier in the fall, but did not remain so for long.

Some heavy rains in recent weeks have built the central pool back up to nearly a third of its normal full size.

Some heavy rains in recent weeks have built the central pool back up to nearly a third of its normal full size.

For the most part otherwise, the routine shutting down into winter has characterized the state of the preserve in the past month.

Mayslake Update

by Carl Strang

Between trips to Indiana for parental care, and vacation days for research, I haven’t spent as much time as usual in Mayslake Forest Preserve. Life goes on there, of course, and I have some glimpses to share.

This summer’s deer have been more secretive than usual. This doe, photographed at the beginning of July, showed no signs of nursing.

This summer’s deer have been more secretive than usual. This doe, photographed at the beginning of July, showed no signs of nursing.

However, she sometimes has accompanied another doe, and this week I saw tracks of a fawn, which I expect to encounter at some point.

There have been a few tawny edged skippers this year, a species I have seen at Mayslake before but not in most years.

There have been a few tawny edged skippers this year, a species I have seen at Mayslake before but not in most years.

A new species for the preserve list was Mydas tibialis, a large and impressive, flower-visiting fly discovered at Mayslake by Nikki Dahlin.

A new species for the preserve list was Mydas tibialis, a large and impressive, flower-visiting fly discovered at Mayslake by Nikki Dahlin.

The rains of spring and early summer, along with the prairie burns, have resulted in Mayslake’s prairies blooming with unprecedented beauty.

The first swamp rose mallow I have seen blooming on the preserve.

The first swamp rose mallow I have seen blooming on the preserve.

Prairie blazing stars are just now peaking.

Prairie blazing stars are just now peaking.

Banks of yellow coneflowers and wild bergamot are providing gorgeous backdrops.

Banks of yellow coneflowers and wild bergamot are providing gorgeous backdrops.

Buck Fawn? Apparently Not

by Carl Strang

Deer have not been a consistent presence at Mayslake Forest Preserve this year. Signs indicated that two or three were present intermittently through the first half of the summer, but then were gone. This suggests that the few were bucks, as does generally select a place to raise their fawns, and stay there. Last week I got a glimpse of a single deer, and then on Tuesday a clear look at one.

With just tiny bumps on his head, I was inclined to label him a male fawn. Note the ears oriented to hear from all directions.

But then as I looked at the photos, I had doubts. I went back to pictures I remembered taking at Fullersburg Woods in 2007.

That fawn had barely discernible head bumps, a rounder face, and a smaller body that was shorter in proportion.

With larger body size, a more adult body length in proportion to height, longer nose, and bigger head bumps, Tuesday’s deer must have been an unusual yearling, with practically no antler development. In retrospect he was much more alert and ready for flight than I would expect from a newly independent fawn. With a relatively easy winter and early spring this past year, perhaps the good conditions helped an otherwise marginal animal to survive. He seems strong now, and perhaps will continue to follow a more typical development pattern, just a year behind his cohort.

Gentle Herbivores…Not!

by Carl Strang

Crickets and katydids are largely vegetarians, but they are not above adding some meat to the diet. I saw an example of this while sweeping for meadow katydid nymphs at Mayslake Forest Preserve early last week.

This female nymph caught a small beetle that the net also had picked up, and systematically munched it down.

Protein, good for a growing katydid. Incidentally, I have learned from bird banders that they dare not leave birds in a mist net for long or the deer will eat them. So much for the Bambi image!


by Carl Strang

Midewin National Tallgrass Prairie is a former military base that has been nearly all transferred to the U.S. Forest Service. A few remaining parcels are being cleared of old munitions and other hazards, and ultimately will be added to the Forest Service site. The historical connection between the Forest Service and the great conservationist, wildlife biologist and wilderness advocate Aldo Leopold has led to a number of interpretive efforts celebrating Leopold’s life and accomplishments. They worked with the Aldo Leopold Foundation to produce a documentary film, Green Fire, and Midewin educator Wendy Tresouthick asked me to give a first person interpretive presentation as Leopold, who died in 1948. At some point I will elaborate on that, but for today I want to share some images and impressions of the site. Thinking that if Leopold had come down to give a talk he would have wanted to see the site, I asked for a tour of Midewin’s restoration effort, and it was my good fortune to be taken around by Bill Glass, Midewin staff ecologist.

Bill Glass, standing in one of his favorite restored areas.

Midewin is huge, a 20,000 acre property, and has not been under Forest Service management for many years, so only about a tenth of it is being actively restored so far. Its history as a munitions storage site still is evident in the now empty bunkers, widely spaced so that if one went up it wouldn’t trigger others to explode.

Ammunition storage bunker.

The bunkers gradually are being removed, but they were solidly built and so their demolition is expensive and the process has to be gradual.

If you study this photo closely you will see a large number of bunkers dimpling the landscape. In the foreground is the top of a gravelly ridge, which provides some significant ecological relief to a largely flat and often wet outwash plain.

In the meantime, the bunkers provide nice, elevated vantage points for surveying the landscape.

A large area has been seeded, planted with plugs, and placed into various regimes of mowing and burning. There are prairies and wetlands covering an impressive range of types.

There is even a federally endangered plant on the site, the leafy prairie clover (Petalostemum foliosum, in the same genus as the familiar white and purple prairie clovers). The bunkers also provide elevated bedding sites for some of the local white-tailed deer.

A deer bed is in the foreground, at the lip of the bunker’s steep side.

I am looking forward to getting back there in the summer to do some singing insect survey work.

Trailing Strawberry Bush 2011

by Carl Strang

One of my autumn rituals is to visit Meacham Grove and Maple Grove forest preserves to continue a study I began in the 1980’s, of two plants and their herbivores. One of these, which occurs only at Meacham Grove, is the trailing strawberry bush.

Trailing strawberry bush is a low, sprawling member of genus Euonymus.

Once an abundant understory plant, this species was reduced to a minor component of the forest community by the colonial caterpillars of the ermine moth, which defoliated the plants repeatedly in the 1980’s. Though I have not seen signs of that moth in years, the trailing strawberry bush has not grown much, in part because of browsing by deer, and in part because of scorching by controlled burns. No new fruits have been produced since 2000.

This year, herbivory again was minimal though a couple study patches had been browsed a little by deer. There was no burn last year, and two of the 16 study patches showed some growth, but 5 were smaller, probably because of overtopping by other plants. One of these apparently is gone as I could find no trace beneath the Virginia creeper and other plants. Mean and median measures of patch size were close to last year’s, but these are very small (median ground coverage by patches is 0.1 square meter).

There is no question that the overall floristic quality of this forest has improved thanks to the burning and other management measures, but such good work has its casualties as well. The trailing strawberry bush is not endangered there yet, but at best it is holding on.

Deer Make Camp

by Carl Strang

In May I mentioned white-tailed deer tracks that were the first signs of that species on the Mayslake Forest Preserve in about a year. Deer have been present consistently since then, though the numbers have dropped to two. I got a glimpse of them last week. As expected from the timing and clues in the footprints, they were bucks, a big older individual already with significant antlers, and a yearling with buttons at best. On Friday I ran across a bed.

This was a well-placed resting spot, away from people and close to both food and a wooded travel corridor.

They may or may not stay for the summer. Bucks wander more than does, though sometimes not so much in summer when food is easy to find.

Prehistoric Life 19

by Carl Strang

This year’s winter series has been a review of the prehistoric life and geologic history of northeast Illinois. Each chapter has summarized current understanding, gleaned from the literature, of what was going on with life on Earth in a particular span of time, what we know about the local landscape, and what we can say about local life. I include some references, particularly to papers published in the journal Science which commonly is available at public libraries. Contact me if you need sources for other items. The Earth is so old that every imaginable environment was here at some point, from ocean depths to mountaintops, from equatorial tropics to tundra, and from wetlands to desert. Today’s chapter concludes the series.

At last we reach the most recent times. This mastodon and its kind lived in our area in the recent past.

Pleistocene Epoch (1.64 million years ago to the present day)

The Pleistocene Epoch (named 1839), literally “most recent,” marks the latest series of continental glacial times. We are in an interglacial interval, regarded as part of the Pleistocene by some, by others named separately the Holocene (1885) or Recent (1833) Epoch.

Life on Earth. This is the time when our human species Homo sapiens evolved, along with the rest of the modern species. Our species originated in Africa around 200,000 years ago as it separated from its earlier hominid precursors, then began to migrate out of Africa around 100,000 years ago, fanning out into Europe, Asia, Polynesia-Australia and ultimately North America. Homo erectus earlier (1.5 million to 770,000 years ago) ranged from Kenya to China (Science 323:1197, 1419). Shaped tools and red ochre use suggest modern-like behavior had begun to appear by 164,000 years ago (Science 318:777). Genetic studies indicate that the Neandertals were a separate species, though they shared with us a gene for speech communication (Science 318:546). Skin color may have diversified in our species much more recently, with pale skins in some races developing only within the past 5300-12,000 years (Science 316:364).

Reconstructed giant ground sloth, Mastodon State Historic Site, Missouri.

There were new arrivals in North America from South America: 2 sloth genera (Nothrotheriops and Eremotherium), opossum, anteaters. And, from Eurasia, mammoths, bison, saiga, musk oxen, and humans. The polar bear evolved away from brown bear ancestors of the southeast Alaska area around 150,000 years ago. Many large birds and mammals became extinct, in many areas (including North America) because of human hunting (Science 300:885; 306:70).

Local landscape. This was a time of ice ages, more than 20 periods of continental glaciation alternating with periods when the glaciers retreated (only 4 of these reached as far as the Mississippi River drainage basin). The dominant theory ties the growth and ebbing of glaciers to regular cycles in the Earth’s orbit, tilt, and precession. Up until 1 million years ago, the glacial cycles were 41,000 years long, corresponding to the cycling of the Earth’s tilt. For the past million years the cycle has become 100,000 years long, for reasons that are unexplained but may be connected to a change in atmospheric carbon dioxide.

Rotten or weathered rock had formed at the surface; most of this was removed by Pleistocene glaciers. Glaciers don’t remove much thickness of bedrock, however, carrying mostly fractured pieces. In the DuPage County area, the glaciers scoured the Silurian dolomite bedrock clean of any sediments, except for the Devonian or Mississippian marine clays in cracks on the upper surface (this is why there are no pre-Pleistocene terrestrial fossils in much of northeast Illinois).

If we could clear the glacial deposits from our bedrock we might see something like this, grooves scratched on the surface by the glacier as it pushed southwest out of the Lake Michigan basin. Rock Point, Ontario.

Dolomite bedrock escarpments such as the one tracing the western and southern boundary of the Lake Michigan basin, and other highlands such as the northern Wisconsin Arch, played a significant role in channeling glacial flow. Lake Michigan started as a south-flowing stream. The sequence and timing of events: the Nebraskan glacial advance 1.8mya (million years ago), then the Aftonian interglacial stage, then the Kansan advance 900-600kya (thousand years ago), then the Yarmouthian interglacial, then the Illinoian advance 400-300kya, then the Sangamon interglacial, then the Wisconsinan glacial advance began 100kya and ended 18kya. Within the Wisconsinan there was an Altonian advance 70-30kya that reached northeast Illinois, a retreat 30-22kya called Farmdalian time, and the largest final advance 22-18kya called the Woodfordian.

A continental glacier was not a single body, but rather several rivers of ice, or lobes, flowing side by side. The Silurian escarpment divided the Lake Michigan lobe from the Green Bay lobe. Kettle Moraine in Wisconsin is a glacial deposit left between those lobes. The Lake Michigan Lobe had to climb (be pushed) several hundred feet to overtop the escarpment and enter northeast Illinois.

As the glacier advanced, the Straits of Mackinac outlet became blocked, and Lake Michigan drained south through the Chicago and Des Plaines Rivers. The Glenwood phase of Glacial Lake Chicago, as it is called, was followed by alternating advances and retreats that blocked and opened the Mackinac Straits and further eroded the Des Plaines valley. Because the weight of the glacier had depressed the crust, for a time after the last glacial retreat the river through the Straits lowered Lake Michigan (in that incarnation called Lake Chippewa) to the point where it was much smaller and occupied only part of its current area. Crustal rebound later raised the northern end of the lake to the point where the current basin filled. When the Upper Peninsula of Michigan, Lake Huron and part of Lake Superior were cleared of retreating glacial ice but other outlets still were blocked, the Des Plaines became the major drainage for all three lakes.

In 2007-2008 Mastodon Camp, a partnership between the Forest Preserve District of DuPage County and the Field Museum of Natural History, gave high school teachers and students an opportunity to participate in a dig. Bits of mastodon bone and tusk, as well as buried black spruce trees and cones, were the main physical product from the site at Pratts Wayne Woods Forest Preserve.

During the latest, Wisconsin glaciation, the permafrost (tundra) zone was 50-120 miles wide beyond the glacial margin, and the mean annual temperature was about 5 degrees C cooler than today. Most of our familiar prairie and forest species were restricted to rather small refuges in the South during the glacial maximum, though oaks and hickories occupied a large part of the southern U.S. Species occurred in unfamiliar combinations, which changed as environmental conditions shifted (i.e., distributed themselves according to individual species tolerances rather than in community clusters of species).

According to recent work with cores from Nelson Lake in Kane County and Brewster Creek in DuPage, our landscape originated 18,000 years ago as the Wisconsin glacier melted away. By 17,000 years ago the glacier locally had shrunk back to the Lake Michigan basin. Open sedge tundra with some spruce trees invaded the zone nearest the glacier (18,000-16,000 years ago), then white spruces filled in to form a recognizable northern coniferous forest until around 15,000 years ago. The climate was dry and windy, piling a layer of loess (silty material) on top of the glacial till and outwash. The wind diminished and the climate became wet around 15,000 years ago because of the collision of warm air from the Gulf with polar air from the glacier north of us. White spruce declined, with black spruce becoming important in low wet areas, and black ash and fir along with a variety of deciduous trees invading the uplands. The glacier retreated to Canada by 13,000 years ago, then advanced in a new cool period as far as northern Wisconsin and the U.P. of Michigan (this may have been a Northern-Hemisphere-only cooling: Science 318:86), and began its final retreat 11,650 years ago. Then alder, birch, jack pine, ironwoods and elms increased locally, and additional trees invaded until a mix of deciduous species, including lots of oaks, was achieved. Beginning around 10,000 years ago there was a drying period, which led to the spread of prairie through our area. The prairie then retreated a little, so that by 6200 years ago our area became a prairie with islands of woodlands.

Local life. After the Wisconsin glacier retreated, first there was tundra, home of woolly mammoths (grazers), musk oxen, caribou, collared lemmings and other animals now extinct or found only in arctic Canada and Alaska. People arrived at this time, hunting with spears (one of the earliest human sites in North America, with butchered mammoth bones dated at 12,500 years ago, has been discovered just north of here near Kenosha; Science 305:590). As the forest filled in the warming landscape, additional mammals included moose, stag moose, scimitar cats, dire wolves, giant beavers, snowshoe hares, Jefferson’s ground sloths and mastodons (unlike mammoths these were browsers which also ate walnuts, spruce cones and other seeds; some species such as Kentucky coffee tree and osage orange are thought to be relatively uncommon today because they have lost mastodons and other large herbivores as seed dispersers). During the time of deciduous forest, local mammals included mountain lion, bobcat, red wolf, elk, white-tailed deer, raccoon, gray fox, porcupine, black bear, flying squirrel and gray squirrel. The prairie and mixed prairie savanna of historical times included today’s familiar animals, along with black bears, badgers, mountain lions, red wolves, elk and bison.

Imagined Paleoindians, Mastodon State Historic Site, Missouri.

Clovis points have been found in DuPage County, indicating that some of those early big animal hunters (known as Paleoindians) were here. The largest animals became extinct, thanks in large part to the Paleoindians’ killing them faster than they could reproduce (Science 326: 1100). Subsequent human cultures wandered less, and shifted to more of a hunting-gathering economy in the several thousands of years of the Archaic Period. Thrust spears and spear-throwers did not give way to bow and arrow in North America until later, during the Woodland Period that began with early signs of agriculture about 2000 years ago. Agriculture did not become an important part of the local economy until the most recent 1500-1000 years. The Woodland people were even more sedentary than Archaic people, and used pottery. Mississippian and Oneota cultural influences, centered in west central Illinois and Wisconsin, respectively, were characterized by increasing social-political complexity made possible by corn-based agriculture. Ultimately the familiar tribes emerged, in northeastern Illinois the Miami followed by the Potawatomi.

For a time in recent years, a group of researchers attempted to make the case that a comet or other extraterrestrial object exploded over North America, causing a climatic cooling (the Younger Dryas time), ending the Clovis culture and resulting in the extinction of the North American megafauna. By the end of 2010 a number of studies had invalidated the supposed evidence for this idea and shown that the Younger Dryas was the result of a sudden influx of cold, fresh glacial meltwater into the northern oceans that for a time shut down the Gulf Stream current.

Prehistoric Life 18

by Carl Strang

This year’s winter series is a review of the prehistoric life and geologic history of northeast Illinois. Each chapter will summarize current understanding, gleaned from the literature, of what was going on with life on Earth in a particular span of time, what we know about the local landscape, and what we can say about local life. I include some references, particularly to papers published in the journal Science which commonly is available at public libraries. Contact me if you need sources for other items. The Earth is so old that every imaginable environment was here at some point, from ocean depths to mountaintops, from equatorial tropics to tundra, and from wetlands to desert.

Pliocene Epoch (5.2-1.64 million years ago)

The Pliocene Epoch, literally “more recent,” originally was defined (1833) by the percentage of then known fossil mollusk species still living (35-95%). Its end is marked by the beginning of the glacial times.

Life on Earth. In the Pliocene, grazers became largely supplanted by more generalist herbivores as savannas became widespread in Eurasia and North America. The dominant groups were camels, antilocaprids (e.g., pronghorn “antelope”), and Equus horses (which, like most horses, originated in North America). Opossums diversified in South America, mammoths appeared in Africa (early Pliocene), the North American rhinoceroses vanished (middle Pliocene), and Sorex shrews appeared in the late Pliocene.

Sorex shrews like our short-tailed shrew of today made their evolutionary appearance in the Pliocene Epoch.

Land bridges finally allowed camels to spread into South America and Asia in the Pliocene (a camel survived in North America into late Pleistocene times). In the middle Pliocene, continued connection to Asia brought immigration of more carnivores, deer, and the elephant Stegomastodon. From North America to Eurasia went a rabbit, a squirrel, the beaver, and Equus.

The world’s lynx and cheetahs first appeared in North America, crossing to the Old World via the Bering Sea land connection.

In the late Pliocene, new appearances were pocket gophers, the white-tailed deer genus Odocoileus, raccoons, the giant beaver, bobcat (Old World lynxes, and also cheetahs, trace their ancestry to the New World where their groups first appeared), the New World porcupine family, eastern mole, and masked shrew.

Modern deer made their appearance in the Pliocene.

In the meantime, the first hominids were beginning to walk upright in Africa 3.8-4 mya (million years ago; Science 307:1545). Upright walking may have begun in the trees, as a hand-assisted way of negotiating thin, flexible branches (Science 316:1328 ). “Lucy,” Australopithecus afarensis (3-3.6my ago), regarded as a human ancestor or close to it, has been tied to the older A. anamensis (4mya), which in turn may have come from the still older Ardipithecus ramidus (4.4mya). Fossils of all three species were found in the same African river valley (Science 312:178). Ardipithecus significantly was a woodland dweller; apparently upright walking was not a product of a grassland habitat (Science 326: 64). Genus Homo had evolved by the late Pliocene, with species from Africa to Asia. Homo habilis and H. erectus are two earlier species which apparently overlapped considerably in time, so that it is uncertain whether the latter descended from the former (Science 317:733). Examination of limb structure points to habilis being arboreal while erectus was terrestrial, so a connection by descent is unlikely (Science 320:609).

The New World chickadees evolved from a single species that emigrated from Eurasia in the Pliocene.

Birds also were dispersing, and our modern species began to emerge. At least some modern songbirds had evolved by the early Pliocene (Auk 124:85). The chickadees and titmice, which had appeared in Eurasia originally, came over to North America in the Pliocene. The first crested species (titmouse) came over around 4 mya, and a single non-crested (chickadee) founder species around 3.5 mya. Subsequent evolution led to the 3 modern titmouse species and about 7 chickadees in the Americas. One terror bird species, in genus Titanis, reached North America from South America 2-3 million years ago, but was extinct by the end of the Pliocene.

Local landscape. Cooling and increased seasonality continued in the Pliocene (the middle Pliocene was the last time that Earth temperatures were warmer than at present).  Climate in the early Pliocene was significantly warmer than today; the major difference apparently was that the El Niño pattern of Pacific Ocean currents was permanent rather than episodic as it is today. The re-establishment of such a pattern is a possible outcome of global warming (Science 312:1485). Woodlands were more open in the Pliocene, perhaps savanna-like in places in our area. Elsewhere in North America, the continent developed its first near-modern boreal forest, as well as the first deserts, tundra and permafrost areas.

The Pliocene brought increasing seasonality, and extensive savannas replaced much of the Miocene grasslands.

The nearest Pliocene deposits are tiny areas in southern Indiana, and extensive areas in eastern Nebraska. By the Pliocene, much of northeast Illinois was draining eastward into the river that ultimately was enlarged by Pleistocene glaciation to become Lake Michigan. This happened when the relatively erosion-resistant and eastward-sloping Niagaran dolomite beneath us was brought close to the surface. Today, surface waters are directed by much more recent glacial deposits on top of that bedrock, and all ultimately flow into the Des Plaines-Illinois River system, ending up in the Gulf of Mexico rather than the North Atlantic.

Local life.  There is a likelihood that the camels, antilocaprids and horses (including Equus, the genus that includes modern horses) were represented locally. Deer, rabbits, beavers, raccoons, sabertooth cats (including Meganteron, an ancestor of the famous Smilodon), bears, the scavenging “hyaenoid dog” Borophagus, otters, and skunks are other likely species at that time.

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