Mayslake Birds Update

by Carl Strang

We have entered the time when most birds are focused on raising young. It is much quieter at Mayslake Forest Preserve now that territories are established and the effort of feeding nestlings occupies the parents’ time and energy.

This Baltimore oriole’s nest hangs above the trail near the northeast corner of Mays’ Lake.

This Baltimore oriole’s nest hangs above the trail near the northeast corner of Mays’ Lake.

The nest is sufficiently concealed by black cherry leaves that its composition is difficult to read, but I would be surprised if it is not constructed largely of fishing line, as has been the case for all recent oriole nests there.

Red-winged blackbirds are ever-ready to cuss out any person who comes anywhere near their nests.

Red-winged blackbirds are ever-ready to cuss out any person who comes anywhere near their nests.

The preserve’s pair of eastern kingbirds is much quieter than they were before nesting.

The preserve’s pair of eastern kingbirds is much quieter than they were before nesting.

Some broods already have fledged.

Yesterday this tree swallow brood occupied a dead tree at the stream corridor marsh.

Yesterday this tree swallow brood occupied a dead tree at the stream corridor marsh.

A final, sad note was the find of a dead chimney swift in Mayslake Hall.

It’s not clear how the swift got inside, or how a bird that nests in dark chimneys could have met its end in a room as spacious as the Event Hall.

It’s not clear how the swift got inside, or how a bird that nests in dark chimneys could have met its end in a room as spacious as the Event Hall.

Swifts have stiff tail feathers, which they use to prop themselves against interior chimney walls.

Swifts have stiff tail feathers, which they use to prop themselves against interior chimney walls.

I took the swift to Willowbrook, which periodically delivers specimens to the bird department at the Field Museum of Natural History in Chicago.

Mayslake Avian Update

by Carl Strang

With the frantic migration season fading away, birds have entered the frantic breeding season. Indeed, some birds already are on their second brood.

I took this photo of a robin fledgling back on May 22, and saw some second nests under incubation last week.

Birds continue to wander, however, and unexpected individuals pop up from time to time.

This coot showed up on May’s Lake one day last week, for example.

There always is something new to learn. On Thursday of last week I saw a female orchard oriole in the north savanna. She seemed to be at home, and so I returned there on Friday, mixing plant survey work with a wish to gain more information on the orioles’ presence.

It didn’t take long to find the male.

He was fairly vocal, but his song and call were more similar to those of the Baltimore oriole than other orchard orioles I have observed in the past (though lacking the loudly whistled “hey batter batter batter” call of that baseball-oriented bird). I had no record of this species at Mayslake last year, but now I wonder if I was hearing this male and labeling him a Baltimore oriole. There always is something new to learn.

Nesting Update

by Carl Strang

Earlier this spring I reported on a failed Canada goose nest, coyotes having reached the vulnerable site chosen by a pair that evidently was young and inexperienced. Soon after, I noticed another nest under incubation in Mayslake Forest Preserve’s parking lot marsh.

They chose one of the lower muskrat houses, well buried in cattails off shore.

Late last week I found the nest empty. When my back is healed I will be able to wade out and confirm what appears from a distance to be a successful nest. I will be interested in the number of eggshells, because the next day I spotted two Canada goose broods on May’s Lake, one with 3 and one with 6 small goslings.

Yesterday the broods were still together, but one appeared to be down to two goslings, one in the frame here.

Apparently one gosling jumped ship, for the other brood was up to 7.

On the other hand, with the two families hanging together there could be shifting back and forth.

Meanwhile, I have kept an eye on the great horned owl nest. Over the past three weeks only one owlet has been visible.

In this first photo the baby clearly is bigger than it was when the platform was installed.

I didn’t give up hope that both survived. On cooler or windy days no owlet could be seen, so they can hide beneath the platform’s sides.

Here, a little larger, the owlet strikes a Kilroy Was Here pose.

I will be happy to be proven wrong, but I suspect that one of the two babies didn’t make it.

In this photo from Friday, the still larger youngster sports developing head tufts.

On Monday the owlet had left the nest and was perched a couple branches above it. Yesterday I could find no owlet, which probably means it hiked to a distant tree and climbed up. From this point I will be able to track it only by encountering it happenstance, or by hearing its distinctive calls in the evening.

Are Siskins Nesting at Mayslake?

by Carl Strang

This past winter brought good numbers of winter finches down from the North. The last time that happened, Mayslake was a beneficiary with pine siskins all winter and occasional visits by groups of white-winged crossbills to the assorted conifers around the mansion. This year I was disappointed that such visitations were not repeated. Then, in early spring, siskins began to appear.

Pine siskins are close relatives of goldfinches, with many similar vocalizations, but browner and streaked down the front.

The siskins haven’t left. They have hung around in some past springs, too, and though I haven’t seen any young, again I am suspicious that they may be nesting. Last week I saw a squabble between a couple pairs that looked territorial. Their nests are small (4 inches in diameter according to my references), and won’t be easy to spot in the dense foliage of a conifer. If they are neatniks, there won’t be telltale bits of grass hanging down. Still, every time I walk past those conifers I am looking up, trying to spot a nest. If I find one I’ll let you know. Siskins are mainly birds of the North, but they are known to nest in Illinois.

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.

Ready and Waiting

by Carl Strang

The parking lot marsh at Mayslake Forest Preserve holds many muskrat mound houses this winter.

Two large mounds are plainly visible in the north end.

In each of the past two breeding seasons the only Canada goose nest on the preserve has been on a muskrat mound in this marsh. Thanks to presence and absence of leg bands, I know that it has been a different pair each year. Both nests were successful. Three seasons ago the muskrats had only bank dens, the water was shallower, a pair of geese nested on a low, exposed island, and the preserve’s pair of coyotes waded out and killed the incubating female and got her eggs.

Here are 3 more mounds in the center of the marsh.

With so many potential platforms this year, there is the possibility that more than one pair will nest there.

Add one more in the south end.

It’s not a big marsh, though, and an aggressive pair of geese may be able to keep others out. I’ll be interested in seeing what develops.

For the moment, Canada geese still are in their winter pattern. I have not followed them as closely this winter as in past years, but clearly more roosts have stayed active and more birds have hung around in this milder season. I checked out the Blackwell roost earlier this week, and found that though the geese continue to use it, the water has been drawn down.

Most of the roost area is in mudflats.

This is not simply the result of low precipitation.

The gate has been removed from the dam. There are plans to enlarge the zone of marsh-edge vegetation.

This could be a good place to see migrant shorebirds later in the spring.

Great Horned…On Watch?

by Carl Strang

For over a decade, now, one of my February rituals is to search for the great horned owl nest on whichever forest preserve I am stationed. It started at Willowbrook in 1999 when I saw a single feather tuft in an old willow cavity that gave away the incubating bird. The search in later years shifted to Fullersburg Woods, a much larger preserve but not so large as to contain more than one pair. Great horneds are big enough, and sufficiently constrained in their choices (either a large tree cavity or a previous year’s hawk nest), that with some experience and knowledge of the area one usually can find the local nest.

In recent years I have followed the tragic story of the pair at Mayslake Forest Preserve. The first winter I was there, they nested in a large cavity in a dead willow. A March storm snapped off the tree at the nest cavity, killing the young. The next winter they either nested off preserve or skipped a year. In any case there were no youngsters screeching their feed-me calls that summer. Last year they tried a red-tailed hawk nest, starting incubation just a few days before the “snowmageddon” blizzard that apparently drove the female off the nest and killed the eggs, for they did not hatch.

This year was not promising. I heard the owls duetting in October, but the only sign of them on the preserve after that was a killed duck in December. Nevertheless, I searched. And one day last week, I saw an owl.

The bird looked small, like a male.

He was perched not far from two tree cavities that might be big enough to hold a nest. The closest, in fact, I knew had been a raccoon den a couple springs before. The problem is that both cavities are too deep to look into. I will have to hope that, if one contains a nest, the growing young will force the brooding mother high enough for me to see one of those telltale feather tufts. In any case, I hope that this year they succeed. It would be nice to have some young owls to watch this summer.

Common Grackle Dossier

by Carl Strang

In anticipation of spring, this week’s choice of species dossier features a bird that winters not so far to our south, and so is one of the first to arrive in spring.

Grackle, Common

Courting group of grackles in a quiet moment.

Typically this is a colonial nester in tall trees, although I have seen low nests (e.g., at Purdue gravel pit). Birds radiate out from the colony to feed, traveling at least up to ½ mile. They feed mostly on the ground, in tall (at least 6″) grass in summer in Pennsylvania, in forests in early to mid-spring in Illinois. Latter birds feed in groups, noisily throwing leaves aside with beaks as they walked. Former ones fed more commonly as individuals.

Squeaky, rusty-hinge voice. In early May 1986, at West DuPage Woods Forest Preserve, Illinois: A large male grackle, perched on a bare branch beside the river, periodically gave his squeaky “erlik-geck” call. Each call was accompanied by elevation of the feathers of the head, neck and upper back and chest. Feather elevation began slightly before vocalization. Alarm call is a series of rapid “geck” notes.

Migrates south for winter, forming large flocks mixed with other blackbirds (especially red-winged) in fall, disappearing in November from northern Illinois and Indiana, reappearing in March. The male holds his long, wedge-shaped tail vertically in long straight flight. That tail also can be held in a V-shape.

Migrant grackle flock, foraging on Mayslake mansion lawn.

Both parents participate in feeding. Nestling grackles at Willowbrook’s hospital were unusual in their lack of aggressiveness in taking food. They would not bite food off its holder (implying regurgitation by parents into the nestling’s throat?). The inside of the mouth is dark red on older youngsters.

7MR87. First arrival of year noted at McKee Marsh, Blackwell Forest Preserve.

7MY87. Grackle caught moth it flushed from lawn, removed wings before eating.

4JE87. Broods out of nest, not strong fliers, still begging hard.

11JE87. Mother grackle fed youngster several items, apparently brought up from her crop although some she picked up nearby on the ground. After she flew off, the fledgling pecked at the ground, picking up dropped bits, and also did some close looking of its own into the grass.

14SE87. Migrants in Willowbrook Back 40, also one on 28th.

6MR88. Numbers of grackles are back.

2AP88. Grackles flying in pairs and showing much courtship activity in past week.

8AP89. Grackles mostly in pairs.

17JE89. A broad-winged hawk calling 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.

18JE89. Grackles foraging in forest litter, Maple Grove and Meacham Grove Forest Preserves.

Grackles perched near a nesting colony.

30JE96. As I paddled my sea kayak on Lake Michigan, just north of the IL-WI border, I saw many grackles along that 2-mile stretch foraging over the surface of the water. Both genders. The birds flew pretty much straight out from shore, 100-200 yards, and then flew back and forth until they saw something on the water to pick up. Then the bird dropped down and reached for the item with its bill. There were lots of dead and dying small fish, and on at least 2 occasions these clearly were what the grackles picked up. At other times the objects appeared to be too small or the wrong shape. Sometimes a grackle dropped down and appeared to miss, or not even quite reach the surface, but it seemed that after a single try, successful or not, the bird headed straight back to shore (sometimes dropping down to the water on the return trip, though). They flew along as high as 30 feet, usually 10-15, and when seeing objects they spun on a wing and often hovered, looking surprisingly tern-like. They minimized contact with the water, though one that dropped down close to me, where I could see clearly, plunged its head into the water, and its tail tip dipped in as well. Their fluttering flight appeared clumsy and energy-gobbling when compared to the purple martins, gulls and terns also cruising those waters.

22FE99. First of year noted at Willowbrook.

12AU99. 2 grackles hunting up in trees.

2NO99. Last of season at Willowbrook.

31OC01. Flocks of red-wings and grackles remain (Nelson Marsh, Kane Co.)

4NO01. An enormous flock of red-wings and grackles along Kirk Road in eastern Kane County. The species were staying apart, on the whole, and there were mainly grackles, but there were hundreds of each. They were landing in a harvested corn field.

18MR09. Both red-wing and grackle include tail fanning and wing spreading in their displays. In the red-wing, these movements accompany the song but are expressed in a range from not at all or nearly so, to slight fanning of tail, slight tail fanning and spreading of wings, and finally much tail fanning and wing spreading.

Grackle courtship flock, displaying

1JE09. Mayslake. First grackle fledglings.

18MR11. Mayslake. Most grackles still are males, but a female often is among them from the start (when a pair forms do they leave, so males always outnumber females?).

29MR11. Mayslake. Displaying grackle group. Often there is only one female with the several males. In the past week or two I frequently have noted trios of flying grackles, one female with 2 males.

Lessons from Travels: Migrants Elsewhere

by Carl Strang

When we are at home in Illinois, we categorize our birds with respect to their status when we see them here. They may be year-round residents, breeders that migrate south for the winter, winter residents, or migrants that breed north of us and pass through in the spring and fall. Those categories do not define the birds from their own perspective, however, and we can get some sense of this when we see them perfectly at home in other places. When we think of yellow-throated warblers, for instance, we typically associate them with sycamores, not with palm trees.

Yellow-throated warbler in Belize.

Still, there is a consistency in the open canopies of sycamores and palms that makes sense from the bird’s perspective. Though we commonly think of our breeding birds as being northern animals that head south to escape the winter, it might be better to regard them instead as tropical birds that travel north to take advantage of high summer productivity and fewer predators.

Travel also allows us to broaden our perspective on migrants, when we see them on their breeding grounds. This was one of the side benefits of the summers I spent in western Alaska. On the rare occasions when we see long-tailed ducks in northeast Illinois they are quiet, placid, unobtrusive. They are quite the opposite on their breeding grounds.

Male long-tailed duck, Kokechik Bay study area.

When courtship commences they become very noisy with un-duck-like tenor voices, chasing each other at rocket speeds and coming very close, apparently using people as picks. The females incubate large clutches of eggs, producing tiny dark ducklings.

In those days we called them oldsquaws. Here a mother and ducklings share a pond with red-necked phalaropes, which then were known as northern phalaropes.

Tundra swans have extraordinary courtship and territorial displays, and make huge nest mounds. Biologists can count eggs from the air. The young are placid.

Nonbreeders gather into flocks of 30 or more.

In the treeless tundra, dunlins advertise by hovering 10 feet above the ground, trilling a song that is almost identical to that of American toads. They have well camouflaged ground nests with 4 eggs.

When we see them as migrants in Illinois, dunlins are traveling in small flocks and behaving as shorebirds.

Jaegers are rarely encountered seabirds in Illinois, sought along the edge of Lake Michigan especially during the fall migration. On the breeding grounds they are predators.

Long-tailed jaegers are beautiful and graceful, hovering like kestrels in their hunt for tundra voles and bird eggs.

Two species nested there, the other being the parasitic jaeger.

Parasitic jaegers are larger than long-taileds. Once I saw one chase down and swallow whole an adult red-necked phalarope.

Such experiences sit in my mind, reminding me to think of these animals in terms of their entire lives rather than the more limited glimpses we see in Illinois.

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.)

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