Tennessee Warbler Dossier

by Carl Strang

The Tennessee warbler is one of our more abundant migrants, conspicuous more by sound than by sight in spring as it is well camouflaged and moves slowly, often high in the trees. It often works closer to the ground and more frenetically in the fall.

Warbler, Tennessee

Tennessee Warbler

Tennessee Warbler

Seen as migrant in many locations in the eastern U.S. Judging by songs, one of the most abundant warbler migrants. Not an easy bird to see; moves slowly and infrequently, and colors cryptic among tree leaves. Song loud and distinctive, and for a week or so every spring the trees of woods and residential areas ring with their songs. “Sebit, sebit, sebit, sebit, seteeteeteeteetee…” Initial part just like Nashville warbler’s, but last part very loud, rapid and energetic with no slurring of notes.

10MY87. First of season noted.

13MY87. At Willowbrook, one bird thoroughly working one small area, with much turning of its head, short reaches to probe nearby leaves, short hops between branches, relatively slow-moving for a warbler. Also does a lot of slow smooth stepping along a twig. Foraging in box elder, black willow.

13SE87. West DuPage Woods Forest Preserve. Several Tennessee warblers together in a mixed flock with a magnolia warbler, a red-eyed vireo, a female rose-breasted grosbeak, and several catbirds and robins. The warblers remained within 10 feet of the ground, active and acrobatic, probing, changing perches frequently (2-10 seconds), very chickadee-like and unlike last spring. 11MY88. First Tennessee warbler song of the year. Gone by May 20.

18MY90. Lots of Tennessee warblers at Willowbrook. Cold spring. The only warblers heard on the 24th.

4MY99. First migrant noted at Willowbrook. Last noted there on 25MY.

12MY99. Slow and deliberate, on 1 perch a long time as they look around.

31AU99. First migrant noted at Willowbrook. First-year Tennessee warbler very yellow, with yellow eye line, but white under tail. In contrast to spring birds, very frequent perch changes, actively pivoting and reaching. Last migrant at Willowbrook noted 17SE.

7MY00. Several Tennessees in a mixed flock at West DuPage Woods, high in canopy. One was moving steadily when I first saw it, foraging and singing, then was still for over a minute on a perch, apparently doing no foraging, but alternating singing with bouts of preening.

24SE00. Tennessees have been abundant, lately. Today, a couple in hedgelike borders of the Prairie Path at West Chicago Prairie just east of Industrial Drive.

8OC00. A couple Tennessee’s at West Chicago Prairie.

12OC02. A few at Fermilab in old field areas.

Mayslake Burns

by Carl Strang

Smoke rose in thick columns on Thursday as the Forest Preserve District’s controlled burn program reached Mayslake Forest Preserve. Mayslake has well-established restored prairies, and the burn cleared off the dead tops of last year’s growth. The fire released minerals back to the soil, opened the way for the living roots to send new, unimpeded shoots skyward, blackened the soil further to facilitate plant growth by soaking in solar heat, and knocked back undesirable, competing woody plants.

A prairie burn is an impressive thing to watch.

A prairie burn is an impressive thing to watch.

Goldilocks would appreciate the decision to burn on a given day. Everything has to be just right. There needs to be some wind, but not too much. The area has to be large enough but not too large, and bounded by mowed areas or other fire stoppers. The vegetation needs to be dry enough. Finally, the burn crews need to be sufficiently equipped and trained to manage the burn safely.

Ranger staff keep watch from all sides.

Ranger staff keep watch from all sides.

Sometimes burns are incomplete due to the plants being too wet, but this time the prairies burned well. A walk through a recently burned area is worth taking, as it reveals what was hidden by all that herbage: the microtopography of the land, which can help determine exactly which plants grow where; the networks of animal trails, large and small; skeletons of animals that lived their last moments there. No freshly killed animals, though. They have their ways of escaping the flames.

Tiny low spots can host a few plants that prefer slightly wetter soils.

Tiny low spots can host a few plants that prefer slightly wetter soils.

The day after the Mayslake burn I found a number of animals taking advantage of the change. Killdeers and robins ran unimpeded over the cleared ground. Migrating sandhill cranes took advantage of thermals rising from the blackened soil to gain altitude during their journey north. In a few days, the warming soil will release and activate insects, and eastern phoebes likely will congregate to feed on them.

A robin hunts on the newly opened ground.

A robin hunts on the newly opened ground.

Sandhill cranes on the thermal elevator above the burn site.

Sandhill cranes on the thermal elevator above the burn site.

Another month, and the ground will be thick with new green shoots. The prairie always grows better in a burn year. (Note: This post first appeared last week as a Nature Note in the Forest Preserve District of DuPage County’s Observe Your Preserve website. )

Rose-breasted Grosbeak Species Dossier

by Carl Strang

As usual, the dossier begins with the paragraph that established the file in the mid-1980’s. In this case I didn’t have much to say because my experience with the species was limited. Since then, dated notes have appended observations that I felt added to my understanding of the species.

Grosbeak, Rose-breasted

This species was relatively rare around my home town of Culver, Indiana. My first were a pair in my neighborhood in the town. The male sang from high in trees or TV aerials. His song began with a phrase much like the theme of the “Guestward Ho” TV series which was current then. That mnemonic has helped me recognize it elsewhere in Indiana as well as Pennsylvania and Illinois. They also have a loud “pick” call distinctive in quality from their close relative the cardinal. Foraging movements are slow, taking their time while visually searching for insects at mid to high elevations in trees. They are uncommon during the breeding season (though abundant in migration) in DuPage County, with occasional single pairs here and there in savannah-like forests. They are especially common for a couple of weeks during migration in May.

Adult male rose-breasted grosbeak

Adult male rose-breasted grosbeak

5MY87. First song of the year heard at Willowbrook Forest Preserve.

25JL87. Hartz Lake, Indiana: An adult male fed 10-15 feet up in saplings. Deliberate: about 10 seconds per perch, looking apparently over a radius of several feet, moving 2-5 feet between perches.

A male reaches for a food item. They can look very parrot-like in this maneuver.

A male reaches for a food item. They can look very parrot-like in this maneuver.

13SE87. A female was in a mixed flock with a red-eyed vireo, a Tennessee warbler, and several catbirds and robins.

7MY88. First song of the year, Culver, Indiana.

11MY88. A female was in Willowbrook Forest Preserve.

8MY89. I saw grosbeaks today and on May 6th at Willowbrook.

Singing posture

Singing posture

4MY99. First migrant noted at Willowbrook. Last observed there 14MY.

26AU99. First migrant noted at Willowbrook. Last one noted 29SE.

4SE99. A grosbeak in female plumage at Willowbrook produced “pick!” notes and bits of low-volume warbling song.

11JE00. Rose-breasted grosbeaks were in a diverse forest near Langlade, Wisconsin, associated with the Wolf River riparian edge and with savanna-like areas where trees were more scattered. Deciduous trees were abundant in those areas. Other birds in those habitats were least flycatcher, Baltimore oriole and black-throated blue warbler.

23-4SE00. Grosbeaks were numerous along the Prairie Path just east of Industrial Drive and bordering the West Chicago Prairie, in the hedge-like edges.

21MY08. Fullersburg Woods. A rose-breasted grosbeak nest was on Willow Island, midway along the east side. It was 10 feet up in the top of a buckthorn, 15 feet in from the trail, female incubating. The nest structure resembles that of the cardinal but thinner so you can see through it in places.

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.

On the Move

by Carl Strang

Yesterday morning as I parked my car at the Forest Preserve District’s Danada headquarters, a strikingly marked bird flew to the top of a shrub in front of me.

A northern shrike!

This always is an exciting bird to see, not only because they are uncommon winter visitors from the far North, but because of their dramatic behavior. When a shrike leaves its perch, it does not simply fly away, but rather drops and Accelerates! Going from a state of watchful rest to full speed in two wingbeats, the bird scribes a graceful line through the air as it rises to its next perch and instantly again is alert stillness.

Birds are on the move again, showing signs of shifting out of their winter patterns. This shrike probably had a winter territory somewhere else, or I would expect to have seen it sooner. The first red-winged blackbirds appeared a couple weeks ago. Dark-eyed juncos have moved out of their winter home ranges. Robins are showing up in small groups in places from which they were absent in recent months, and have begun to forage on the ground. The numbers remain small, but all these cases collectively signal the start of a season of change. Canada geese increasingly are in pairs rather than flocks. Great horned owls are well into incubation. Spring is coming.

Cicada Update

by Carl Strang

Periodical cicadas in small, scattered numbers have continued to appear in a large part of DuPage County. Steve Bailey, who conducts bird surveys for the state, also has heard them in parts of Grundy and southern Cook County. So far nearly all have been singing the cassini song type, except for one septendecim-like singer reported from Fullersburg Woods Forest Preserve by Naturalist Leslie Bertram.

There are so few that prospects for reproductive success are dim.

This is the expected fate for nearly all of these vulnerable individuals, to be eaten by birds, their wings plucked off and dropped to the ground.

I witnessed such a predation event myself at Mayslake Forest Preserve. A cicada got in maybe four songs before a robin flew straight to it. The insect got out an alarm squawk, then all was still.

In an earlier post I speculated about what was going on with these cicadas, which had been quiet the previous two years. A suggestion by WBEZ radio news director and nature enthusiast Brian O’Keefe reminded me of similar ideas expressed in the scientific literature when cicadas appear outside their brood’s normal area: perhaps these were transported from the southern brood XIX range in the root balls of nursery stock. That certainly could account for the ones in residential areas and in portions of forest preserves adjacent to private lands. I checked with the Forest Preserve District of DuPage County’s nursery staff, however, and none of our tree plantings in the past 13 years have come from so far south. Some of these cicadas are half a mile or more from the nearest preserve boundary. A little mystery therefore remains, but I have concluded that my time would be better spent in other directions.

Incidentally, while documenting these scattered emergences I was listening for green-winged cicadas (Diceroprocta vitripennis), another spring species which I believe emerged in small numbers in 2007. Their buzzings were largely covered by those of periodical cicadas, however, and the only hard evidence was a single wing, like the one in the photo above, but with green rather than red veins. Some of the literature suggests a 4-year periodicity for Diceroprocta, but I have encountered none in the places I thought I was hearing them in 2007.

Nesting Accelerates

by Carl Strang

Last week, Mayslake Forest Preserve’s restoration volunteers found a killdeer nest on one of the meadows that had been burned earlier in the season.

The burn removed dead vegetation tops in an area, rendering it suitable for the shorebirds’ nest.

Killdeers have been present for a few weeks, so this was not a big surprise.

Here one forages at the edge of May’s Lake.

I have seen a robin incubating, as well. The red-tailed hawks should be on eggs by now. One regularly hunts the preserve, but they did not nest there as I speculated they might, earlier. I suspect that the nest is in the residential neighborhood north of Mayslake.

Brown Creeper Species Dossier

by Carl Strang

This week I am sharing my species dossier for the brown creeper, a species which seems increasingly to be present in DuPage County through the winters in recent years. I wrote the initial paragraph in 1986 as I established the dossier, then added observations with their date codes.

Brown Creeper

Observed during migration in DuPage Co., sometimes all winter there and in Culver. Latest spring observation 13AP86 [April 13, 1986]. When foraging they commonly fly to the base of a tree and work their way up, climbing on and searching the bark. Often when changing trees they produce a high-pitched cheeping contact call as they fly.

1AP87. First of year seen at Pratts Wayne F.P.

12MR88. First of year at McDowell.

28AP88. Migrants still present.

14AP89. Creepers at Hartz Lake.

18AP90. Creeper on 6-inch box elder at Willowbrook.

31JA99. First of year at McDowell.

1AP99. Willowbrook’s first of year. Also seen there on 5AP.

1OC99. First fall migrant at Willowbrook.

26MR00. Several observed at West DuPage Woods Forest Preserve. All but 1 foraging selectively on white oaks, flying to within 3 feet of the ground on the main trunk and working up it, staying on the shaded side (sunny afternoon) and within an 8-inch width, mainly going straight up even over bumps. When up in crown, fly down to base of next tree. High-pitched contact calls similar in pitch and tonal quality to those of golden-crowned kinglets. One paused to preen body feathers on anterior part of body, remaining perched on vertical bark while doing so. The only one on another species of tree was on a black cherry. During the brief time I watched, it both came into the sun briefly and exceeded the 8-inch path width.

27MR00. Willowbrook. A number of golden‑crowned kinglets and 3 brown creepers observed. Kinglet contact notes usually more emphatic, in groups of 3 or 4. Creeper notes similar in pitch and tone, but a little fainter, more drawn out, and single notes evenly spaced as the bird flies between trees (spacing a little greater than the notes of the kinglets).

31MR00. Waterfall Glen. Brown creepers feeding along Sawmill Creek, with golden-crowned kinglets and a couple white-breasted nuthatches nearby (essentially a bird desert for more than half a mile until I reached this point). One feeding on a 6″dbh hackberry, going straight up the shaded side (sunny afternoon). Either the same bird on several similar sized hackberries, or several birds on same, always staying shaded side except for brief moments in the sun. When that happened, though, the creeper quickly returned to the shaded side of the stem. Once a creeper paused briefly, made a flycatcher-like sally from the bark into the air, reached with its head and beak at the turn-around point, then returned to the same point on the stem it had left. Flew out 3 feet or so. Another creeper was moving up the shaded side of an 18″ white oak, every few seconds reaching its bill to the bark and then making eating motions. Another creeper on a 12″ forked tree spent some time on the sun side (= side toward creek) of one fork, but the other larger fork was shading it.

1AP00. Morton Arboretum, Heritage Trail. A mixed flock with at least 1 brown creeper and 2-3 chickadees; juncos and robin nearby. Overcast day, no shaded side, but creeper still mainly going straight up the trunk. When defecating, lifts tail high, bending it well over back. When searching, doesn’t probe but rather peers, looking into crevices and going to different angles to do so as needed. Song “tsee-er-tser-tseree,” quick, high pitched like call but not as thin, sweet and musical tone. On a white oak, spiraled up a high 8″ branch.

13AP00. Willowbrook. 1 brown creeper observed.

13AP07. Brown creeper vocalizations include a rough call similar to that of cedar waxwing, faint thin high pitched notes given singly, and several such notes given in quick succession and similar to those of golden-crowned kinglet but a little fainter and more irregularly spaced.

2JA08. First creeper of the year, at Fullersburg (two stuck around for weeks afterward).

29AP08. Last creeper of the spring, at Fullersburg.

21OC08. Fullersburg. First creeper, fall migration.

29JA09. Mayslake. First creeper of the year.

25FE09. Mayslake. Another creeper, after a space of nearly a month, suggesting midwinter wandering.

25MR09. Mayslake. Another month between sightings.

21AP09. Mayslake. Final creeper of the spring at Mayslake (often present in past month)

29OC09. Mayslake. First creeper of the fall migration.

8JA10. Mayslake. Creepers seen in two locations.

1FE10. Mayslake. Another creeper, after a space of nearly a month.

19MR10. Mayslake. First spring migrant creeper.

13AP10. Mayslake. Last spring migrant creeper.

13OC10. Mayslake. First fall migrant creeper.

CBC 2009

by Carl Strang

One annual highlight as the end of the year approaches is the Christmas Bird Count. Last year I introduced the group to which I belong. Here our party proceeds along the Prairie Path in the 4-mile hike that filled Saturday morning.

Urs Geiser, our leader, is on the left. Behind him, Frank Padera converses with Marcia Nye (who walks behind a smiling Linda Padera). Lee Nye’s clipboard reveals that as recorder he had the challenge of keeping the data sheet dry. A very light snowfall was a constant through the day. Judy Morgan was with us, too, but doesn’t show in this photo. Chuck Drake couldn’t make it this year.

As you can see, the accumulated snow made the landscape beautiful.

The beauty had to compensate for a relative absence of birds. Nearly every species was down in numbers compared to last year, and to the area’s average. One species that was present in typical numbers was the American tree sparrow.

Among the 29 species we found were a few robins.

On the other hand, there were a few highlights. We saw our area’s first tufted titmouse in years (but no photo). Also, the area’s first-ever hooded merganser and coot (the latter shown below) cheered us in the afternoon.

I should clarify that when I refer to “area” I mean the bit of geography assigned to our little group. Our area was part of a much larger circle centering on Fermilab and covering significant parts of DuPage and Kane Counties. Ours was one of eight groups collectively covering that circle. Circles like this are one part of the continent-wide standard that allows CBC data to have some merit in long-term monitoring of birds across North America.

Cooper’s Hawk Dossier

by Carl Strang

It has been a while since I have shared one of my species dossiers. One of my practices is to keep records of what I have learned from my own observations of various species, as opposed to reading about them in other sources. Today I bring out my dossier on the Cooper’s hawk. In reviewing it I see that I have left out a lot of observations of this species, which has become common in the Chicago suburbs over the past decade or two, but those other observations would be much like the ones below. The observations begin with my date codes.

Cooper's hawk b

13SE85. Spring Valley Nature Center, Schaumburg. A Cooper’s Hawk pursued a frantic, cheeping young thrush in and out among the trees, in sharp twists, turns, and vertical climbs and plunges, for a good 15 seconds. Then the hawk broke off, and the thrush escaped. This took place in an old field between stands of trees. Could the cheeping have been a signal to the hawk that the thrush had plenty of wind? As soon as the hawk turned back into the woods, the thrush continued its flight over an open field.

2AP88. One passed through woods at Hartz Lake (in Indiana), occasionally calling “kip.” Flew and perched, flew and perched its way across woods.

12MR92, McDowell Forest Preserve. A Cooper’s 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.

18AP92. Hartz Lake. Pair of Cooper’s hawks hanging around a clearing in the woods, often calling: a wild-sounding, almost woodpecker-like “eh-eh-eh-…” (15-20 repeated syllables).

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

18MR99. An immature plumaged Coopers appeared, hung around the Willowbrook riparian area (SE corner of preserve) for the rest of March, calling frequently, but vanished in early April.

1SE99. Cooper’s hawk soared above Nature Trail area of Willowbrook, moving north to south. They soar from time to time.

15JE00. Morton Arboretum. Near Parking Lot 7, when I arrived around 8am, 3 robins were giving the high‑pitched thin call repeatedly, and the forest otherwise was relatively quiet. After 10 minutes, a Cooper’s hawk started calling nearby, then flew out away from the forest edge until an eastern kingbird started to chase it. It immediately turned around and flew back the way it had come, and kept going. The robins then were quiet.

16JE00. Willowbrook. In the afternoon, a Cooper’s hawk perched near the west edge of the prairie, drawing alarm calls from a robin (the hawk‑whistle warning call) and a cardinal, and a chorus of 7 loudly mobbing jays.

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.

26FE01. A Cooper’s called for a long time from the top of a tree near the islands in the river at McDowell Grove. A harrier was flying overhead, but the Cooper’s did not appear to be looking at it while calling.

14AP01. 2 Cooper’s, possibly a pair, at West DuPage Woods. One made an unusual flight through the open air, with exaggerated, moth-like wingbeats reminding me very much of a short-eared owl.

5MY01. A Cooper’s hawk incubating a stick nest high in a tree at Wayne Grove Forest Preserve. Tail visible from below.

10JA02. Two jays newly arrived at Willowbrook (for weeks there had been one, at most, and these were in addition to that one). They were mimicking crow caws, with lower volume and a brighter tone that made the mimicry clear, but an interesting sound. One of them also repeatedly imitated a Cooper’s hawk’s calls, both the string of notes and the isolated single notes. Again the volume was lower than in the hawk, but tonal fidelity was very good. They were in brush, low to the ground and close to me (the Cooper’s imitator was within 20 feet and clearly knew I was there). Before long I saw a Cooper’s hawk, almost certainly the same one that we saw hunting the day before by sitting and waiting on a tree branch for a minute or 2, then moving to a new perch. Today the hawk was perched about 100 yards from the jays.

12MR02. As 2 Cooper’s hawks began to call in the woods at Willowbrook, a jay flew to the treetops above them and began the bobbing “teakettle” call. Another jay arrived and began to “jay” call as the first continued on away in the direction it had been going.

26OC07. A Cooper’s hawk still calling at Fullersburg.

2006-2008. Cooper’s hawks nested at Fullersburg. The great horned owls there prefer to use a hawk nest from the previous year. In at least one year the Cooper’s were successful, as fledglings frequently were to be seen. In at least one year, and perhaps two, the hawks started to incubate but then abandoned. In one case this happened shortly after a pair of broad-winged hawks arrived and began to advertise their territory nearby.

24MR09. Mayslake. Scattered feathers of a Cooper’s hawk in the prairie south of the stream corridor marsh. The location, and nature of feather damage pointed to great horned owl as the predator.

Coopers kill 2b

 Late summer 09. Mayslake. One day a Cooper’s hawk caught a young-of-the-year robin in the woodland east of the mansion.

 Autumn 09, Mayslake. A Cooper’s hawk, flying low, could see through the windows of the library wing, and attempted to fly through as it would a space within a forest canopy. Unfortunately the windows were closed. It was not flying fast, and after bouncing off flew away, apparently unharmed.

With the winter’s slower season arriving, I expect to be sharing more dossiers. I encourage any student of natural history to be careful in separating what you know out of personal experience from what you have heard second hand.

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