Birds in Transition

by Carl Strang

Soon the first wave of birds that overwintered in the tropics will reach northern Illinois. April has brought a transition from wintry weather to the warmth, plant growth and insects that make the trip worthwhile for the many species whose ancestors were content with tropical conditions.

For most of the month we see birds that are year-round residents or are newly arrived from their wintering grounds in the southern states. They have to deal with the season’s variability, though. Early in April a cold spell brought a thin snowfall. There still were insects to be found, but they were on or close to the ground. A selection of species foraged on the banks of the stream at St. James Farm Forest Preserve.

These included an eastern bluebird that abandoned his practice of hunting from tree branches, and shifted to hopping around in the open.

These included an eastern bluebird that abandoned his practice of hunting from tree branches, and shifted to hopping around in the open.

The preserve’s first yellow-rumped warbler of the year also searched for prey there, though such bank foraging is a common practice for that versatile species.

The preserve’s first yellow-rumped warbler of the year also searched for prey there, though such bank foraging is a common practice for that versatile species.

Even an eastern phoebe was forced to a ground-foraging interval.

Even an eastern phoebe was forced to a ground-foraging interval.

On other days, getting set for the nesting season was a priority.

Cooper’s hawks occasionally called in wooded areas, considering whether to nest at St. James Farm.

Cooper’s hawks occasionally called in wooded areas, considering whether to nest at St. James Farm.

Song sparrows sang as they began to sort out their territories.

Song sparrows sang as they began to sort out their territories.

Cardinals have been singing since January, as they are the songbirds most sensitive to day length change.

Cardinals have been singing since January, as they are the songbirds most sensitive to day length change.

Pairs of hooded mergansers hung out on ponds where there are wood duck boxes.

Pairs of hooded mergansers hung out on ponds where there are nest boxes.

The preserve’s red-tailed hawks completed their nest and were good to go.

The preserve’s red-tailed hawks completed their nest and were good to go.

A second pair of geese chose St. James Farm for nesting, but their site is a risky ridge beside the stream, with water on each side but reachable from either end by a coyote.

A second pair of geese chose St. James Farm for nesting, but their site is a risky ridge beside the stream, with water on each side but reachable from either end by a coyote.

April 21 was warm enough that the great horned owl young did not need brooding. This was my first look, and I could not be certain there was more than one.

April 21 was warm enough that the great horned owl young did not need brooding. This was my first look, and I could not be certain there was more than one baby.

And now, with the warm days forecast ahead, the big push of migrants soon will diversify the preserve’s avian picture.

 

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Mayslake Birds

by Carl Strang

Bird action at Mayslake Forest Preserve has sped up to the point of being hard to follow. Migrants have been stopping by in good numbers.

Baltimore orioles are scattered through all the woodlands. Some will stay and nest.

Baltimore orioles are scattered through all the woodlands. Some will stay and nest.

Warbling vireos are another recent arrival.

Warbling vireos are another recent arrival.

Savannah sparrows haven’t nested at Mayslake yet, but one day last week the meadows and prairies were full of them.

Savannah sparrows haven’t nested at Mayslake yet, but one day last week the meadows and prairies were full of them.

I know this is a broken-record theme for me (for those of you old enough to know what that expression means), but note how in the face-on view all those head stripes converge on the bill, accentuating it for rival intimidation (maybe). I’m reminded of Maori facial tattoos.

I know this is a broken-record theme for me (for those of you old enough to know what that expression means), but note how in the face-on view all those head stripes converge on the bill, accentuating it for rival intimidation (maybe). I’m reminded of Maori facial tattoos.

This Canada goose brood appeared on Mays’ Lake.

This Canada goose brood appeared on Mays’ Lake.

On the same day, the nest in the nearby stream corridor marsh was empty, with open eggshells, almost certainly that brood’s origin.

On the same day, the nest in the nearby stream corridor marsh was empty, with open eggshells, almost certainly that brood’s origin.

The other nest, in the parking lot marsh, has been abandoned. Three unhatched eggs are visible. The highest water levels in recent rains may have reached their undersides.

The Cooper’s hawk nest is under incubation just off the preserve in a neighbor’s yard.

The Cooper’s hawk nest is under incubation just off the preserve in a neighbor’s yard.

The nest was found by Vicky S., a former student of mine who went on to mentor with some of the area’s top birders and should be regarded as one of their number at this point. There’s some satisfaction to be had in being surpassed by one’s student. She pointed out that this is an unconventional structure, the hawks having added a layer of sticks to the top of a squirrel nest.

Mayslake Vertebrate Action

by Carl Strang

The season’s progress can be measured in many ways. One is through vertebrate activities.

A fox squirrel feeding on flowers

A fox squirrel feeding on flowers

Song sparrows, among other birds, have been singing like crazy.

Song sparrows, among other birds, have been singing like crazy.

Migration is accelerating. This unusually pale savannah sparrow stopped by Mayslake Forest Preserve a couple weeks ago.

Migration is accelerating. This unusually pale savannah sparrow stopped by Mayslake Forest Preserve a couple weeks ago.

Pied-billed grebes have been regulars on Mays’ Lake.

Pied-billed grebes have been regulars on Mays’ Lake.

And the Cooper’s hawks are happy to exploit the stopovers of migrants who don’t know the territory.

And the Cooper’s hawks are happy to exploit the stopovers of migrants who don’t know the territory.

Seasonal Transition

by Carl Strang

We have long been waiting for spring, and the seasonal transition at last is under way. Soon the snow birds will be heading back north.

Dark-eyed juncos have begun to sing and to chase each other.

Dark-eyed juncos have begun to sing and to chase each other.

The earliest migrants have begun to come through, or to pass over.

A flock of sandhill cranes flies over Mayslake Forest Preserve.

A flock of sandhill cranes flies over Mayslake Forest Preserve.

They hit a thermal, break formation and use its rising air to gain altitude.

They hit a thermal, break formation and use its rising air to gain altitude.

Breeders have begun to arrive and set up shop.

Great blue herons at the Danada colony

Great blue herons at the Danada colony

A recent arrival at Mayslake Forest Preserve has the smaller birds nervous.

The Cooper’s hawk pauses in its patrol…

The Cooper’s hawk pauses in its patrol…

…then resumes.

…then resumes.

The next mini-stage of migrant birds has begun.

Ruby-crowned kinglet at Fermilab, Sunday

Ruby-crowned kinglet at Fermilab, Sunday

Soon I expect to reach my personal criterion for the arrival of spring and the end of winter.

 

One Less Red-bellied

by Carl Strang

Birds don’t molt feathers in clumps. When you find a bunch of feathers together, you can take it as a sign of predation.

This group of feathers on the mansion lawn at Mayslake Forest Preserve last week is an example.

The black and white barring all across the feathers, and their size, identify the vic as a red-bellied woodpecker. The perp? My vote goes to one of the preserve’s great horned owls. The feathers appeared plucked rather than pulled out and mangled as teeth would have done. Red-tailed hawks can take birds of this size, but woodpeckers are so nervous and alert that a nighttime hit seems more likely. A migrating Cooper’s hawk is another possibility to consider. They are predators of birds, and have a variety of sneaky tactics that might catch even a woodpecker off guard. In any case there is one less red-bellied on the preserve, but others still are around. This year’s resident pair at Mayslake raised two broods successfully, for example, so even if one of those adults was the prey, there will be a new generation ready to take its place.

Red-tailed Hawk Species Dossier

by Carl Strang

I have heard reports that red-tailed hawks are starting to carry sticks, and March is the month when they begin to nest in DuPage County, so today I am sharing my species dossier on that raptor. As usual, the rule is that the dossier is limited to what I have observed personally rather than second-hand reports or through the literature.

Hawk, Red-tailed

Red-tailed hawk

This hawk is common in the eastern U.S. They nest in treetops in woodlots, sometimes on utility poles, and forage over nearby fields, soaring, or perching on trees or poles. Unless winter weather is severe, they remain all year round.

28MR87. Hawk carried a snake by the head, body dangling beneath, to treetop.

16JA88. McDowell. A great horned owl flew to a tree on the west bank of the river, just north of where trees thin to a thread of willows, and where a housing development comes down to the river. There’s a top-blown tree nearby, also several large oaks. Then crows began raising a ruckus nearby in another direction, as though pestering a great horned owl. From that direction a red-tailed hawk soared, but they paid it no heed. It circled an adjacent riparian strip, but when the owl finally broke and flew with a flock of 10 crows in pursuit, the hawk fell in between, and also began to chase the owl. Once it got above the owl and swooped at it, brushing the owl’s back with its feet, but about then the crows caught up and chased both raptors down toward where I had seen the first owl perched, now out of my sight.

1MY88. Call a wheezing “preeyarrrr.”

7FE89. A red-tail “visited” Willowbrook’s outdoor animal exhibit. The captive red-tails called, caged crows gave short, uninflected (flat) caws with somewhat sharp beginnings but open ends. These were fairly rapid, but not chattering, and not clearly strung together.

Soaring red-tails usually seem to be patrolling territory rather than hunting.

12JA92. Hidden Lake Forest Preserve. A soaring red-tail gave the k-yer call, over woods. Moments later a second passed over, going in the same direction. Is that call given only when another hawk is in sight?

2DE95. West DuPage Woods. A red-tail called frequently. After 10 minutes I saw a second one, also flying. It seems likely that if one calls, another is in its view.

27JA97. Morning. Snow fairly deep. A red-tail flew over the College of DuPage parking lot with something in its talons, pursued by half a dozen crows. The hawk perched on a flat-topped, wooden light pole, and began plucking its prey while crows sporadically left nearby perches and swooped at it. After 10-15 minutes the hawk flew away, and I checked the feathers, which were scattered in singles and small clumps over a 20×30-foot area: mourning dove. The crow calls resembled the ones they use in owl mobbing, but there were fewer birds and the mobbing was less sustained.

Red-tail fledgling at Mayslake, July 2011.

9DE99. Crows pursued a red-tailed hawk in the northeast part of Willowbrook preserve.

18JL00. Willowbrook. In the early afternoon, a Cooper’s hawk soared low above the marsh and areas east and west of it, while 3 red‑tails soared high. One of the visiting red‑tails called once, but the Cooper’s, which has been resident all summer, called repeatedly.

22AU04. Canadian side of Lake Superior. On a driving journey around the lake I passed through an area where there had been a big fire, and saw there both the first kestrel and the first red-tail of the trip, showing them to be associated with relatively early successional, extensive areas in this part of the northern forest.

20NO09. Mayslake. A pair of adult red-tails circled the west end of the savanna calling frequently, and a third call was coming from within the canopy. Eventually one of the adults flushed out a young red-tail, perched in one of the oaks, and it flew low out of the savanna and south across the lake. This could be the same bird that was perched near the dog parking lot yesterday. Clearly this was a defense of winter territory by the pair. It was not clear whether the young bird called, or whether that was mimicry by a blue jay that was nearby. Last winter a pair of adult red-tails stayed around Mayslake the entire season. They seemed to be investigating nesting possibilities, but ultimately vanished for the summer.

The 2010 red-tail nest at Mayslake

16MR10. A red-tail pair is building a nest at Mayslake, in the stream corridor woods adjacent to the parking lot marsh. They carried small sticks in their beaks while flying. (This pair fledged one youngster from this nest, and it stayed around the mansion grounds area for some weeks in the summer, calling loudly and frequently. In 2011 they did not nest on the preserve; their 2010 nest was used by the great horned owl pair. Apparently they nested nearby, however, as a fledgling came onto the preserve occasionally in the summer, and displayed the same loud calling behavior. The pair has been present on the preserve through February of this year, and I will be watching for nesting activity.)

The noisy fledgling from 2010

19JA11. Mayslake. A red-tail flushed from one of the trees near the chapel was carrying a dead gray squirrel and accompanied by its mate. They flew toward the S stream corridor.

Great Horned Owl Species Dossier

by Carl Strang

Today’s species dossier is one of my largest. Great horned owls simply attract my attention and interest more than most other animals, and so I have accumulated more notes on them. Great horned owls haven’t been as easy to follow in the years since West Nile virus came into our area. Formerly the crows were reliable blabbermouths as to where the owls were. If our local crows develop resistance to the disease, those days will return.

Owl, Great Horned

Great horned owl

My earliest memory of young great horned owls was in a forest near Purdue, after they had branched one spring [branching is the term for owlets leaving the nest; it is different from fledging, because they reportedly climb down to the ground, walk to another tree, and climb up it]. I know this species primarily from observations in DuPage County, IL, where it is the common large owl, occurring in forests, even small ones. A pair nested annually in the Willowbrook riparian strip for many years, staying as year-round residents. They nested in large willows, 20-30 feet up, first in a nest on branches, then after a storm dislodged the nest, on a provided platform until that tree fell. Incubation begins January or February. The non-incubating male bird usually perches nearby in the daytime, flying away apparently to draw off people or mobbing crows. Owlets (usually 2) branch in May as trees are leafing out, can fly between trees by late May. Young have a distinctive begging call, a rising squeaky-scraping or -grating loud “scaip!” Young disperse usually by the end of October. Before then, they fly all over their parents’ territory, usually staying fairly close together. Branched young mostly sit still, observing all that goes on around them. November brings frequent late afternoon and evening territorial calls: the female’s call is a higher-pitched “WHO-whowhowho-whowhowho-who.” The male’s call has fewer syllables and a lower pitch.  Deep, booming voice. Willowbrook’s territorial birds had a running, never-ending conflict with the caged birds. I also heard calls during childhood campouts on the Tippecanoe River, Indiana, in summer, and later in the woods near the Boiling Springs, Pennsylvania, house in spring.

Pellets and food remains in late winter 1986 at Willowbrook were heavy in rabbit fur and bones in February, meadow voles in March. There were feathers of a gull in May. They covered a territory that included Willowbrook, adjacent residential neighborhoods, and much of the College of DuPage campus, for a total of perhaps 100 acres.

In the Basin of the Chisos Mountains, Big Bend National Park in Texas, they were calling around 5:30am in late July. We saw others there on the road in early evening in the upper desert. They were a bit paler than Midwestern birds.

Some contents of owl pellets at Mayslake, 2009. Prey species are meadow voles, white-footed mice, and a short-tailed shrew.

12FE87. Lots of recently molted breast feathers in Willowbrook Back 40.

8AP87. Photos of branching young owls.

Great horned owl, soon after leaving the nest.

29AP87. Crow remains found under nest area.

5MY87. The pair’s own nestlings now branching, in a willow 50m from nest tree.

6MY87. Remains of a consumed pigeon.

7MY87. The young are in another willow, closer to the nest tree, the one used most by last year’s young when branching. The third (foster, added by Willowbrook staff) youngster is on another branch of the same tree.

8MY87. Another tree change.

1JE87. The young are flying.

5OC87. Adult male beginning to hoot, in afternoon, Willowbrook Back 40.

9JA88. McDowell. Owl flushed from pine grove at south end of north field.

16JA88. McDowell. A great horned owl flew to tree on the west bank of the river, just north of where trees thin to a thread of willows, and where a housing development comes down to the river. There’s a top-blown tree nearby, also several large oaks. Then crows began raising a ruckus nearby in another direction, as though pestering a great horned owl. From that direction a red-tailed hawk soared, but they paid it no heed. It circled an adjacent riparian strip, but when the owl finally broke and flew with a flock of 10 crows in pursuit, the hawk fell in between, and also began to chase the owl. Once it got above the owl and swooped at it, brushing the owl’s back with its feet, but about then the crows caught up and chased both raptors down toward where I had seen the first owl perched, now out of my sight.

30MR88. Willowbrook. Fresh pellet with remains of 2 meadow voles.

25AP88. Both great horned owls off the nest, though in nearby trees.

17MY88. I hadn’t seen great horned owls of Willowbrook Back 40, or heard harassment by crows, in some days. Today I saw 2, upstream of their nest. Crows didn’t harass them for long or in numbers (2-3), apparently too occupied with their own nesting activity.

18JE88. Harassment of owls by crows gradually has increased this month at Willowbrook. Today I observed heavy harassment of a great horned owl by a large number of crows at McDowell Grove F.P. Owls branch at the same time crows are starting to nest, and becoming too busy to harass owls.

22FE89. Owl on a nest at Willowbrook (started incubating within the past 10 days).

26AP89. For the first day since February, there is no adult owl in the nest tree at Willowbrook (have been brooding several days, then a few days of adult perched beside nest with a youngster visible. 2 young. A fox squirrel climbed the nest tree. When it was just below the nest, the adult female flew from a nearby willow, and landed on the nest. The squirrel turned around and began to climb down as she flew in, but was not panicked.

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

30NO89. Great horned owl flying, viewed from behind. Wingbeat of remarkably little amplitude, compensated by its more rapid rate. A fluttering sort of appearance. Wings kept straight. (A behavioral quieting of flight?)

14DE89. Willowbrook nature trail. The owl caught a mouse, according to tracks. Slight blood drops in snow. Many steps trampled snow just beyond the mouse burrow. Then the owl walked, either having swallowed mouse or transferred it to bill. Tracks: landed on mouse tunnel, then walked 5m. Noticeable straddle, up to 1 inch. Track 4 inches long, 3.5 wide, right angle toe pointing to outside distinctive for species. 8 inches center to center for length of step between tracks.

Sketch of great horned owl tracks.

3JA90. The Willowbrook owl pair perching near nest platform.

29JA95. Following a tip, I found a great horned owl on a nest at Maple Grove F.P. Stick nest was built last year by Cooper’s Hawks, according to informant. Nest solidly based in a main crotch 15-20 feet up. Owl had head and ear-tufts up, very noticeable but only from the front. Nest tree right beside a regularly used trail, but not a main trail, less than 200 yards from Maple Ave. and less than 100 yd. from the private school on the east border of the preserve. The owl reportedly has been on the nest less than a week.

18FE99. At Willowbrook, I found this year’s great horned owl nest (they probably have used this site before; not easy to find) in the top of a dead tree trunk, with most of branches gone, a large hollow with little in the way of a roof. Only part of the owl’s head is visible, and only from certain angles. A single fuzzy feather tuft was the give-away. Once while I watched, the bird appeared to stand and turn or shift eggs by moving feet, stepping from one to the other. The owls had been advertising consistently in the area around this tree in the early winter. Crows mobbing nearby earlier in the day (presumably after the non-incubating bird nearby) drew my attention to this area. Only one other candidate tree is nearby.

A sketch I made after finding the nest on February 18.

11MR99. The great horned owl was standing in the Willowbrook nest in the morning.

15MR99. A young bird was seen on the afternoon of the 12th. Today at least 2 young are visible. They were being fed between 3 and 3:30pm.

18MR99. The 2 young owls frequently are standing in the sun in the nest.

12AP99. The Willowbrook great horned young have branched.

A pair of branched young.

16AP99. One of the owl young somehow crossed the rain-swollen Glen Crest Creek to perch between it and the Nature Trail. Flew?

4MY99. At mid-day, a flock of 8 crows pursuing an adult great horned owl over much of Willowbrook Preserve.

27MY99. Both Willowbrook owl young still alive.

11AU99. Only one of the Willowbrook owl young remains.

18AU99. The young owl calling at mid-morning.

8MR00. A neighbor near the north edge of the Willowbrook preserve reported that the pair of great horned owls have been calling in his yard nightly since late January. He gave us permission to look for a nest, and we found it, in the top of a large blue spruce, built on an old crow or squirrel nest. 20 minutes were required to find a small hole through which to confirm the bird’s presence. The tree, perhaps 40 feet tall, is close to a dead‑end side street, in between his house and garage (the 2 buildings less than 20 feet apart), with no other tall trees right there though several others were in the yard. The bird appeared still to be incubating, occasionally turning eggs. We did not see the non‑incubating owl, but numerous potential roosting sites are nearby.

30MR00. We checked the nest again. After a few minutes the brooding bird flew away (sunny, warm afternoon). We could see one young bird clearly; there may have been more. Development seems behind last year at this date by at least a week. Still all white down, as far as we could see.

14AP00. In central Kane County, in a bur oak woodlot of perhaps 10 acres, a great horned owl nest. The nest is an appropriated crow or hawk nest in the top of a large oak. At least one young bird still is inside. The presence of the owls was made clear when the adult male flew past us, pursued by crows. He was small, appearing no larger than the crows. Later I found the nest when walking through the woods. The female flew a short distance, and a few crows called, but she settled in against the trunk of an oak, well camouflaged, and they left her alone.

17JL00. No sounds of great horned owl adults or young at Willowbrook in the evening.

2001: No signs of nest or young around Willowbrook this year, though in the spring an adult seemed to be decoying crows.

Great horned owl tracks. Owl tracks are distinctive in having one of the toes protruding out to the side at an odd angle.

14SE01. An owl called several times in the early dusk at Herrick Lake, south of the former youth campground. I see that this is my earliest record of territorial behavior, by about 3 weeks.

3NO01. Saw an owl, probably a male, at Herrick Lake F.P. in the forest behind a house, north of the big trail loop and south of the former youth group camp. That was in the morning. In the late afternoon, heard one hooting along the Fox River somewhere around Red Oak NC.

27SE02. While walking after a run at Herrick Lake, heard both members of the pair duetting strongly for at least 5 minutes (same area as previous 2 entries).

13FE07. At mid-day in the middle of a winter storm with heavy blowing snow, a great horned owl at Fullersburg holding a recently caught gray squirrel.

3AU08. Great horneds called for a long period, early morning, in my neighborhood. This continued into the dawn hour and overlapped with a cardinal’s singing, past 5 a.m.

21JA09. Mayslake. An elm branch, apparently broken from tree by storm, with bark being consumed by cottontails. Near there, one of the rabbits caught and consumed on the spot last night by a great horned owl (impressions of wing and tail feathers in the snow). Head, feet, a couple bones, and fur all that remain.

29JA09. Mayslake. I found where a great horned owl had walked on the frozen stream surface, heading S out of the woods, taking off before reaching the bridge. The tracks led back to a feeding site, with much cottontail fur and a bone, but no rabbit tracks. Continuing downstream 20 yards I found another area against the bank with fur and blood, and a couple great horned owl footprints again from last night, but again no rabbit tracks. On downstream another 30 yards I found yet a third such site, but again no rabbit tracks. Here there was no feeding, mainly just the impression of the rabbit in the snow. As the owl had walked a few steps before that impression, it must have had the rabbit in its beak. The owl had come from the N or NW. I searched all around but did not find a clear kill site. All of this was under trees with moderately thick brush that makes it seem unlikely the owl would carry prey in there from outside. The shift of location twice would seem to reflect a sense of vulnerability. I wonder if the owl would have removed the head and feet at the actual kill site. The body impression where it first landed on the stream ice was bloody.

Here is one of the stops made by the great horned owl described in the January 29 entry. There is an oval depression where the rabbit’s body was placed.

14FE09. Fullersburg. This year the great horned owls are nesting in last year’s Coopers hawk nest, just west of the Amphitheater. That nest has been available both the past two years, but the owls have chosen to use other hawk nests close to 31st Street in all of the previous 4 years but 1. In that year there were reports of a nest well south of the preserve, but I could not find one on the preserve.

19FE09 Mayslake. I found the great horned owl nest in a hollow willow near the west boundary of the preserve close to May’s Lake. It is not high up, and exposed thanks to the brush clearing, but facing away from the lake may limit its discovery by fishermen.

Great horned owl incubating nest in tree cavity, Mayslake, February 2009.

6MR09. Mayslake. Great horned owl is standing in the nest cavity, apparently brooding.

13MR09. Mayslake. The great horned owl nest tree snapped off at the point of the nest cavity, presumably in the wind storm 3 nights ago (gusts reached 45mph). A dead owlet at the base of the tree, none others nor adult seen, no sign of hurt adult but nest apparently abandoned (cold enough today that an adult would be brooding). There has been enough time that scavengers could have removed other young.

Dead nestling beneath storm-broken nest tree.

10DE10. Neighborhood. I heard a great horned owl calling early this morning.

27JA11. Mayslake. Great horned owl incubating on last year’s red-tailed hawk nest. It was not there yesterday.

Great horned owl incubating nest, Mayslake, January 2011.

10MR11. Mayslake. The owls have abandoned the nest. No sign of disturbance or dead nestling beneath, best guess is the eggs didn’t hatch, either infertile or perhaps the female was forced to abandon during the fierce blizzard at the beginning of February.

18MR11. Mayslake. At a bright mid-day, the great horned owl pair duetted for more than 15 minutes, the male in the west end and the female in the east end of the area 9 hilltop pines.

29MR11. Mayslake. A single hoot from GHO in pines, mid-day, the first I’ve heard since the 20th.  (In September I heard the pair duetting at Mayslake, so they remain at the preserve.)

Starling Species Dossier

by Carl Strang

The European starling was one of the species that prompted me to begin my species dossiers. The first short paragraph contained everything I could say I knew about the species from personal experience when I set up the dossiers in 1985-86. It was embarrassing, and prompted me to pay more attention. Notes added later begin with date codes.

Starling

Starlings usually are associated with human structures.

A year-round resident throughout Indiana and Illinois, as well as southern Pennsylvania. Usually they are seen around human constructs, nesting in buildings, street lights, etc. They also nest in tree cavities and bird houses, even in open woods well away from people. In late winter they become vocal, mixing squeaky “querk” and “joo” notes with mimicries that are realistic but low in volume. Frequently they perch in and around tops of chimneys on cold winter days. Their plumage adds abundant white spots to feather tips in winter. Observations of a nest in a hollow catalpa on the Purdue campus, spring 1976, impressed me with the frequency of feeding trips and the domination of the diet with large caterpillars. They forage mostly on the ground in short grass. The young are very noisy, especially when a parent returns with food. Eggs are pale blue. The young are a uniform gray in color, forming into flocks of their own after leaving their parents. In fall, starlings often form large flocks, sometimes mixed with assorted blackbirds.

15JE86. A pair of starlings chased a broad-winged hawk in Maple Grove. It had paused briefly in the tree where they were, but I could not see if it carried anything. They uttered rattling calls throughout.

Starlings mobbing red-tailed hawk at Mayslake.

29MR87. Starlings on a road after rain, apparently eating worms.

6AP87. Starling at Willowbrook mimicking spotted sandpiper.

14MY87. Bird on horizontal branch of dead tree performing a display: bill pointed up, neck only stretched a little, wings lowered and fluttering more or less in coordination with a continuous calling, a mix of rattles, whistles and gurgles that continued for over a minute.

5MR88. Starlings imitating pewees, McKee Marsh.

21MR88. Starlings imitating purple martins, Willowbrook.

2MY88. Gathering nest material.

5MY88. First thin, high begging cries heard from a nest.

Older starling nestlings.

6JE88. First independent starling youngster seen, and the harsh “jeer” begging notes are not nearly as ubiquitous as during the past 10 or so days. First brood done.

4AU88. Youngster (independent) in Willowbrook Back 40 eating fruit from black cherry tree, spitting out seeds.

22MR89. Starling at Willowbrook loudly and accurately imitating the sound of a squirrel chewing on a nut.

24MR89. At Winfield Mounds Forest Preserve, starling imitations of nighthawk, meadowlark.

4JL89. Second brood of starling young chattering in nests, Myers Grove, near Jeffersonville, Indiana.

Starling pauses during a frigid mid-winter bath.

24JA90. Extended (at least 2 minutes) fight between starlings. They locked bills and beat one another with their wings, each trying to force the other onto its back. When beak grip lost, they sought it again. Finally one broke free and flew away. The other flew up to the top of an adjacent building and sang, with slight lifting of wings at 1-2-second intervals.

1NO99. Starlings mimicking killdeers at Willowbrook.

30JL00. Large flock of starlings, many or most of them immature, in trees on south side of McKee Marsh.

Starling flock on an early December morning.

9MR01. On 3 occasions this week, I have seen an interesting reaction by the flock of starlings hanging around the outdoor cages at Willowbrook to a hawk passing through. On 3 different days there were low flying hawks, an adult red-tail, a Cooper’s, and a young red-tail. Each time, the starlings all took off and flew in a tight flock. At first it reminded me of a mobbing flight, or a shielding as the red-necked phalaropes do, but soon it became clear that the flock was not pacing the hawk but adopting a course oblique to its path. The remarkable features were the flock’s tightness, which was a little greater and with no outliers in contrast to the usual, and the coincidence in their taking flight with the arrival of the hawk. They landed as soon as the hawk was gone.

1JA02. Starlings at the Morton Arboretum are feeding heavily on a bumper crop of red cedar fruit.

American Crow Dossier

by Carl Strang

Here is another, relatively long, entry in my series of species dossiers, accounts of what I have learned of various species from my own experience. In sharing these I am less interested in transmitting information than in encouraging you to think about what you know about these animals from what you have observed. When I started these records in the 1980’s I was embarrassed by how little I could say, and developing them was a good exercise in paying better attention when in the field.

Crow, American

Abundant around Culver, Indiana, in Cumberland County, PA, and [formerly] in DuPage County, IL. Strictly rural in the Culver area when I was a child, staying out of town [though this no longer is the case]. In PA, occurred in and out of town, but more typical of drier uplands and agricultural areas (the fish crow was more common in town and around rivers). In DuPage County, IL, American crows were abundant in both town and rural areas. They spend times in all habitats, though they stay up in trees when in the forest, usually. They spend more time in open, drier habitats than in others.

Their diet is equally diverse. I’ve seen them take corn sprouts, insects, young birds and rabbits, and carrion. In DuPage County they were the principal avian scavengers; vultures are practically nonexistent except during migration. Road kills are the most commonly observed food there. In late winter 1986 I saw a group of crows feeding on smooth sumac fruits, along the road at Warrenville, IL.

Crows nest solitarily, in the highest levels of forest trees. Vocalizations include a feeding call of young, a whining sound with somewhat the quality of a played sawblade: ree ree ree reereereereeree. This call accelerates and becomes slightly higher pitched and squeakier toward the end. Adults’ single “caws” appear to be contact calls. Harsher, sharper rapid clusters of caws are signals that rally crows to mob hawks or owls. This is a social, flocking species for most of the year, though spreading out when foraging for widely scattered foods like insects in short grass.

In DuPage County, crows mob great horned owls most frequently. Usually a mobbing begins with a single crow spotting the perched owl, and giving the rallying call. As more crows gather and add their voices, they perch all around the owl and the noise gets very loud. Usually the owl just sits stoically, but if it flies the crows give chase, sometimes one or two so bold as to peck the owl on the back. Eventually they lose interest, and silently fly off in one’s and two’s. Crows themselves are the objects of aerial harassment attacks by red-winged blackbirds.

Tall dead treetops with many branches in woods often are congregation sites.

10JA80. Boiling Springs, PA. In the afternoon I watched a crow chasing a kestrel. The birds flew high, and the crow stayed right with the little falcon’s twists, turns and dives. Finally, the crow broke off after the chase had carried the two a couple of hundred meters from the starting point. The crow flew back there, and the Kestrel flew a parallel course 50m away, but continued out of my field of view.

22FE87. Flock of 15 crows, flying. Cawing a lot, caws a little short though they aren’t chasing anything. Occasionally one utters a low, dry rattle. Later a loose group of four flew, taking turns making sets of 3-4 connected sharp caws. When calling, an individual folded his wings slightly and glided at a slight angle downwards.

14MR87. Signs of breeding. One, after cawing as though after an owl (none right there) broke off a twig from a treetop and flew away with it. Later a crow closely chased another out of that part of the woods. The chase went for at least 100m.

15MR87. Crow flying with beakful of soft material.

29AP87. Remains of a crow beneath great horned owl nest area.

16JA88. (McDowell?) Great horned owl flew to tree on west bank, just north of where trees thin to a thread of willows, where a housing development comes down. There’s a top-blown tree nearby, also several large oaks. Crows raising a ruckus, as though pestering a g.h. owl. From that direction a red-tailed hawk soared, but they paid it no heed. It circled an adjacent riparian strip, but when the owl finally broke and flew with a flock of 10 crows in pursuit, the hawk fell in between, and began to chase the owl, itself. Once it got above the owl and swooped at it, brushing the owl’s back with its feet, but about then the crows caught up and chased both raptors down toward where I had seen another owl perched, now out of my sight.

21MR88. Crows have been molting wing and tail feathers. Still chasing each other.

10AP88. 3-5 harsh, medium-fast caws apparently means “human here.” Several circled me at Hidden Lake F.P. woods, some perched in treetops above me and peered down, making that signal.

14AP88. Spotted 2 crow nests along Butterfield Rd., one beside construction site in a small grove of 30-40-foot-tall trees, the other well up in one of a grove of large oaks.

7MY88. Culver, IN. 2 nests high in oaks of “Indian Trails” area between town and Culver Military Academy. Adults flew off silently.

17MY88. I hadn’t seen the great horned owls of Willowbrook’s Back 40, or heard harassment by crows, since the restorational clearing of the marsh and fill area. Finally I saw 2, upstream of nest. Crows didn’t harass them for long or in numbers (2-3), apparently too occupied with their own nesting activity.

Harassment picked up, gradually, in June. On 18JE88 I observed heavy harassment of a great horned owl by a large number of crows at McDowell Grove F.P. Owl’s branching comes at the same time crows are starting to nest, and becoming too busy to harass owls.

18AP(MY?)88. The notes of a crow’s “human” call may be uttered rapidly when given as a warning. I walked into a riparian strip, one crow gave that fast version as I approached, and another immediately flew up from the streambed where it could not have seen me.

23MY88. Crow carrying medium-sized ear of dried corn, with about half of corn still attached, in beak.

29JA89. The crow mobbing call is a drawn out, often slurred, slightly burred caw, but retaining the abrupt start. (Another crow flying in, when still at a distance, gave a single note of this type but lazier, more drawled sounding, because it lacked the abrupt start and because it was more drawn out.)

7FE89. Permanently disabled crows in the exhibit cage at Willowbrook Wildlife Center responded to a “visiting” red-tail with short, uninflected (flat) caws with somewhat sharp beginnings but open ends. Fairly rapid, but not chattering-like, not clearly strung together. Many notes, long-continuing.

12MR89. A crow near Hartz Lake (Indiana) carrying a twig.

13MR89. DuPage County. Crow nest, same cluster of trees but farther back from busy Butterfield Road, as last year.

21AP89. A crow nest in downtown Chicago, in the little park across from the Newberry Library. I seldom have seen crows in the city. One bird visited the nest while I watched, but did not switch with the incubating crow.

25AP89. At end of a brief chase between 2 crows, one (I believe the pursued) gave a rattle-call. But I’ve recently heard the call from a bird perched for a long time.

10MR90. Crow with twig in beak, flying straight and parallel to road at 25mph.

30AP90. Crow chasing crow: a rattle call by the pursuing bird, with an emphatic inflection within.

12MR92, McDowell Forest Preserve. A Cooper’s hawk flew, northerly, high above woods. Pursued by a crow that occasionally swooped at it, but the hawk itself was nearly crow-sized, and it often turned and flew at the crow. Flight faster and more twisty then, but the crow turned to pursue the hawk when the latter resumed its path. Three such cycles observed.

20AU92. Cooper’s chased a couple crows at Herrick Lake F.P., not seriously. They rattle-called afterwards.

24JA93. Warrenville Grove Forest Preserve, IL. In late morning on a cold, sunny day, a goshawk flew past as I crossed a brushy opening in the forest. The bird was low, perhaps 10 feet up, and abruptly dipped, then flew up to a 15-20-foot-high perch on a large branch of a tree at the edge of the clearing. I came within 40 yards or so; the bird watched me but did not fly as I turned and skirted its position. Crows passing over gave several sets of quick, paired caws: “caw-caw, caw-caw, caw-caw,” merging in some cases into a fairly rapid series of cawing notes. This was not a response to me. Long after I left the site, I heard the same paired caws and looked back to see that the crows emitting them were circling above the goshawk’s position. The crows stayed at an altitude of ~1.5 tree-heights; the hawk was perched between 1/3 and ½ the trees’ height.

27JA97. Morning. Snow fairly deep. A red-tailed hawk flew over the College of DuPage parking lot with something in its talons, pursued by half a dozen crows. The hawk perched on a flat-topped, wooden light pole, began plucking prey while crows sporadically left nearby perches and swooped at it. After 10-15 minutes it flew away, and I checked the feathers, which were scattered in singles and small clumps over a 20×30 foot area: mourning dove. Crow calls resembled owl mobbing, but smaller number of birds and less sustained.

1997-98. I occasionally see a white crow as I drive to work at Willowbrook Forest Preserve, the bird on either side of Park Boulevard a short distance north of Butterfield Road.

15MR99. Crow flew across Butterfield Road near Naperville Road crossing, north to south, with sticks.

14AP99. Willowbrook. Crows seen chasing one another several times.

4MY99. At mid-day, a flock of 8 crows pursuing an adult great horned owl over much of Willowbrook Preserve.

25MY99. Blue jay mobbing a perched crow in top of dead willow, Willowbrook.

9DE99. Crows pursuing a red-tailed hawk in NE part of Willowbrook preserve.

2010. In recent years, crows have become scarce in DuPage County, apparently because of a lack of immunological resistance to West Nile Virus. The pattern seems to be that new birds disperse into the area in winter, and may attempt to nest (but this isn’t common as far as I can tell, supporting the idea that these are young, dispersing individuals). When conditions support the emergence of West-Nile-carrying mosquitoes in late summer, the crows vanish, apparently victims of the disease. Supporting this notion is the observation that in the cooler wetter summer of 2009, more crows persisted into the fall.

Mayslake Ecology

by Carl Strang

I’ll conclude the summary of my first year at Mayslake Forest Preserve with an ecological sketch. The preserve has diverse plant communities, some high in quality thanks to the restoration efforts I described yesterday. There are lakes, a stream, savannas, prairies, a couple small marshes, European meadows undergoing succession, a degraded former garden at the friary and brushland areas dominated by Eurasian species of shrubs, as well as lawn areas around the mansion and friary grounds.

Mayslake dog meadow to savanna b

This habitat variety leads to the diversity of plants and animals I mentioned a couple posts ago. Strongly reproducing populations of cottontails, squirrels and other small mammals, as well as various small birds, support a suite of predators somewhat surprising for such a small preserve: a pair of great horned owls, a pair of coyotes, a couple mink, Cooper’s hawks and, in winter, red-tails.

Red-tail Mayslake 1b

Of course, these predators do not limit their activities to the preserve’s borders. White-tailed deer pass through the preserve regularly, but Mayslake is not quite large enough at 90 acres to hold many or to be more than an occasional center of activity.

This summary of course hides a lot of detail, some of which I observed and reported here over the past year. I will continue to do so as the details and patterns of that place change over time, keeping it refreshingly interesting.

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