Some Mayslake Migrants

by Carl Strang

This has been a good spring for migrant birds at Mayslake Forest Preserve. Some are species that nest in DuPage County, but use Mayslake only for day stops.

The savanna sparrow is one of these, though as Mayslake’s prairies continue to expand, the day may come when one or more pairs nest on the preserve.

The savanna sparrow is one of these, though as Mayslake’s prairies continue to expand, the day may come when one or more pairs nest on the preserve.

Scarlet tanagers prefer forests to Mayslake’s more open woodlands.

Scarlet tanagers prefer forests to Mayslake’s more open woodlands.

One morning my walk across the mansion grounds was arrested by a distinctive, repeated “pick-a-tuck.”

Sure enough, a summer tanager, an immature male.

Sure enough, a summer tanager, an immature male.

Summer tanagers are among the southern birds that increasingly are appearing in the Chicago region. The point of all these birds stopping for the day is illustrated in the next photo.

A Philadelphia vireo refuels.

A Philadelphia vireo refuels.

Caterpillars and other herbivorous insects start early in the season so as to take advantage of the newly opened leaves’ relative lack of defensive chemicals. The caterpillars themselves have only camouflage for defense, and birds like the vireo have sharp eyes.

Species Dossier: Brown-headed Cowbird

by Carl Strang

Cowbirds haven’t arrived in our area yet this spring, but it won’t be too long. The following represents my limited knowledge of this, our main local nest parasite.

Cowbird, Brown-headed

Male brown-headed cowbird

This blackbird has been common essentially everywhere in the eastern U.S. I’ve gone. They feed in and around open areas and fields. Females lay eggs in other birds’ nests, early examples observed in warbler nests of a few species. They sometimes stayed around Culver, Indiana, in winter, taking seeds from feeders.

31MR99. First of season noted at Willowbrook.

29MR00. Willowbrook. Cowbird males displaying in high, bare tree tops: a group of 5, and a group of 3 (one of the latter had left the first group). No females were present with the group, but a female was present elsewhere on the preserve. The display consisted of fanning the wings out to the side, fanning the tail and lifting it above back level, then bowing or leaning forward to the point of sometimes losing balance. While performing the display, the bird at least sometimes gave its high‑pitched call. (I call this the falling-down-drunk display.)

Falling-down-drunk display, closely watched by a female.

1JL00. A female yellow warbler fed a cowbird fledgling near the south end of Silver Lake at Blackwell. Earlier this week a pair of scarlet tanagers fed a cowbird at Willowbrook, and half a dozen times this spring I have seen male cardinals feeding them (some were the same pair, but at least 3 different broods were involved), also at Willowbrook.

12OC02. After not seeing many in recent weeks, a couple individual cowbirds appeared earlier in the week at Willowbrook, and today, a number of them, especially young ones, were at Fermilab.

19JE08. A pair of gnatcatchers fed a cowbird fledgling at Fullersburg.

20JE09. Last year I also saw song sparrows feeding a cowbird at Fullersburg. This year at Mayslake I have seen cowbirds fledged by phoebes and Baltimore orioles.

Fledgling cowbird being fed by a female Baltimore oriole.

15JL09. Mayslake. Yesterday in the south savanna a cowbird fledgling was being attended by a song sparrow. Today another fledgling was in the north savanna being fed by a phoebe, clearly a different brood or pair than the earlier one (last observed 3 July).

Scarlet Tanager Dossier

by Carl Strang

It has been a while since I have posted one of my species dossiers. This is an awareness support method I developed in the 1980’s, when I realized that for most animal species, including the common ones, there was little that I could say I knew about them from direct experience. I wrote starting paragraphs based entirely on memories of my own observations, then added notes as I noticed new things over time. This helped me to focus, to pay more attention when out in the field. As time went on there was less to add from casual observation, but I continue to expand the dossiers as I continue to learn. Today’s example is a species that is good at staying out of sight in the upper canopy during the breeding season, and heads to the tropics for the winter, so my dossier on it remains relatively brief. (Date codes begin with a number representing the day of the month, followed by a unique 2-letter code for the month, ending with the year.)

Scarlet Tanager

Scarlet tanagers often forage closer to the ground in the spring migration, and are easiest to see then. There also is less obstruction as leaves still are expanding.

This bird lives in larger forest areas in summer, though sometimes they can be seen in smaller woodlands during migration. They mainly stay in the upper canopy in the breeding season, though often they are lower when migrating. Sometimes migrants occur in fairly large numbers for a week or so in mid-May in DuPage County. This was a fairly common breeder in the larger forests of south central Pennsylvania. They are more thinly scattered in DuPage County’s smaller forest islands. They are occasional in riparian strips in northern Indiana. This is a fairly deliberate, leaf-searching forager. The song is similar to the robin’s in its phrasing, speed and rhythm, but with occasional distinctive fuzzy or burry notes.

This male was rolled by the wake of a car as he flew over a road in Pennsylvania. He quickly recovered and went on his way.

10MY87. First tanager of the year heard singing at north Blackwell Forest Preserve.

13MY87. Willowbrook. A tanager in a willow top foraged by sitting for several seconds at a time, and hopping or flying 5 inches to 2 feet between perches. When it sighted prey, it hopped to a perch nearby, then reached for it.

Though she lacks the male’s brilliant breeding plumage, the female’s olive-yellow feathers, as well as the balanced symmetry of her shape, lend beauty to her appearance.

7MY88. First tanager of the year singing, Culver Indian Trails.

12MY99. First migrant noted at Willowbrook. Last spring migrant noted there 18MY.

13MY99. Tanagers were common today, low in the canopy, at Willowbrook.

5OC99. A late migrant at Willowbrook.

28JE00. A pair of tanagers fed a cowbird fledgling at Willowbrook, in the riparian zone midway along the Nature Trail’s west leg. A tanager could be heard singing east of the Nature Trail late into the spring, as recently as a couple weeks ago.

2JL00. A male tanager was singing in southern Waterfall Glen, in the topmost branch of a large dead tree, 10 feet from the nearest foliage, just perched and singing.

I don’t recall whether this bird was singing, or just stretching his mouth.

22JL00. Tanagers still are singing at Waterfall Glen. The one at Willowbrook has not been singing since the first week of July.

16JE01. A male scarlet tanager fed a cowbird fledgling in the savanna area of the Morton Arboretum’s Heritage Trail.

Tanager at Fullersburg Woods.

25MY02. Groups of scarlet tanagers moved together low in the forest today at Meacham Grove, and yesterday at Willowbrook. They all seemed to be males yesterday, but there were both genders today.

Northern Cardinal Dossier

by Carl Strang

This time I share my dossier for a common and beloved species. As usual, it begins with the general account I wrote when I established the file in the 1980’s, then additional entries begin with my date codes.

Cardinal, Northern

The cardinal is the first bird I studied with any intensity, as a child mapping song perches of males in my neighborhood and connecting them into “territories.” Generally they selected highly exposed perches in treetops and on television antennas. The song is highly variable, but tonal qualities of voice and type of song pattern are distinctive. The alarm note is a sharp “teek,” again of a distinctive tonal quality and pitch. The female also sings, the songs following the same pattern as the male’s but sometimes lower in volume.

They nest usually in thick bushes within 10 feet of the ground. A nest at Boiling Springs, PA, was in a rain gutter closely overarched by spruce branches. Young birds in a brood observed in Lombard, IL, were kept together and off the ground by the parents.

Both sexes have bright red beaks surrounded by black feathers. When viewed head-on this has an imposing effect, the bird’s weapon thus being highlighted. No doubt this is of significance in agonistic display. Field guides, with their emphasis on lateral views, lead us away from this kind of discovery.

Cardinals feed in bushes, in trees, and on the ground. They are not acrobatic foragers. They consume large seeds at feeders in winter. Cardinals appear to show some territoriality through winter.

Songs vary among locations, individuals, and times. Each male has more than one song. Some rendered songs are: “chibone, chibone, chibone, chibone;” “What-cheer, wheet wheet wheet wheet;” they beging singing in late January (as early as 23JA83 in DuPage); “pul’see pul’see …” (~7 reps).

17JL84. Male foraging in black cherry tree spent 5-8 sec. on a perch, moving head to look at nearby leaves and twigs in small turning movements, moving 0.5-1m between perches (Willowbrook Back 40).

NO84 they were often feeding on ground, scratching in leaves.

12FE87. Heard first song of year.

5MY87. Nest with 3 eggs, of twigs (slightly loose structure) beside trail in riparian strip at Willowbrook. In honeysuckle, 5 feet up, in fork of branches. Deep cup. Eggs bluish with brown mottling. By a few days later only one egg left, nest apparently abandoned (too close to trail?).

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

19JA89. First Cardinal song, on Willowbrook early morn. In an unusually warm January.

9MR89. Cardinals all singing today through midday (first warm day, 40 degrees F, after a long cold spell). There seem to be too many Cardinals singing, and I see 3 males chasing each other. In this year with such a mild January and no super-severe weather, unusually high survival?

17AP89. A cool, cloudy day. Cardinals all over the Back 40 are giving constant series of “alarm” (?) notes.

29JA90. First cardinal song of year, Willowbrook.

1990. The year of the 17-year cicadas, I caught some at Fullersburg and released them at Willowbrook. One of these flew across a small forest clearing, and a cardinal flew out and caught it with its beak, in mid-air.

26JA99. First cardinal song of year, Willowbrook.

4MR99. Many cardinals singing at Willowbrook, including a female near the Nature Trail head.

3MY99. Cardinals fighting in area of white cedars at Willowbrook.

13MY99. Cardinal nest at Willowbrook in honeysuckle shrub overhanging creek. May still be under construction, though birds agitated when someone is nearby. Female incubating 17MY, 27MY.

10AU99. Cardinal songs distinctly reduced in number, length. Only a few weak, partial songs this morning.

25AU99. Last cardinal song of year noted at Willowbrook.

26AU99. Cardinal fledgling, with rapid notes, similar in pitch to adult’s note but not as sharp, and rapidly repeated rather than separate.

1NO99. Cardinal eating buckthorn berries. 

14JA00. Cardinal sang a half song in afternoon, Willowbrook.

2FE00. First full cardinal song of year, Willowbrook.

21FE00. McKee Marsh, north Blackwell Forest Preserve. A male cardinal singing from a very exposed perch at the top of a 25-foot-tall cottonwood. Doesn’t change posture much when singing. Thrusts face forward a little, but keeps bill level. Sang back and forth with other audible cardinals, answering with full songs, “What-cheer, wheet wheet wheet wheet.” The others stopped singing, it paused for some seconds, then gave a “what-cheer,” paused, did so again, and gradually added “wheet” syllables until it was singing full songs again, even in the others’ absence. When not singing, turned head to look all around.

25FE00. Willowbrook. Several juncos and cardinals singing this morning. A display by a male cardinal that was singing at the service road junction with the Nature Trail. A female was in the same tree, and for a minute or two the male faced her, occasionally adopted an extended, stretched out body posture unlike the normal singing pose, moved with body held rigidly, and emitted a chattering dry trill between some of the songs, all the while facing the female. She stayed in place, he never approached within less than 5 feet, and he then turned away from her and resumed singing normally.

1JL00. A female yellow warbler feeding a cowbird fledgling near the south end of Silver Lake, Blackwell. Earlier this week a pair of scarlet tanagers were feeding a cowbird at Willowbrook, and half a dozen times this spring I have seen male cardinals feeding them (some were the same pair, but at least 3 different broods involved) also at Willowbrook.

2SE05. Had to re-learn fledgling call of rapid high notes lacking sharpness of adult alarm. May have been contact call rather than alarm, though adult nearby gave very occasional alarm, too.

7JA08. Fullersburg. A cardinal sang, briefly and uncertainly, but definitely. My earliest noted song (previous earliest 14JA00). Temperatures in the 50’sF past couple days.

15JA10. Culver. First cardinal song of the year.

5OC10. Mayslake. Singing: white-crowned sparrow, phoebe, cardinal, song sparrow.

7DE10. Mayslake. A cardinal singing, full strong song repeated a couple times. Sunny day but cold, teens F. (I have heard cardinals singing on occasion all through the middle of this winter, the first time I have observed such an extended singing period).

Another observation in recent years is that cardinals in our area seem to raise mainly cowbirds early in the season, but a final August nest nearly always produces only cardinals. If this is correct, it implies a strong selective pressure, at least locally, for shifting the nesting season later.

Mayslake Update

by Carl Strang

Today I want to share some miscellaneous notes on what has been happening at Mayslake Forest Preserve. Most of these are reflective of the season. For instance, thousands of migrating dragonflies have been passing through in recent weeks. Most of these have been green darners, with some black saddlebags and wandering gliders. I also saw the preserve’s first swamp darners (but was frustrated in my attempt to photograph them as they patrolled the stream). Some of the green darners paused to mate and lay eggs.

Birds also have been migrating. A good mix of warblers and others, including this scarlet tanager, have been refueling on Mayslake’s insects and berries.

Some insects appear late in the season. An example is this adult locust borer, the preserve’s first record of the species.

Of course, our year-round residents continued their activities, with signs of preparation for winter. For example, I have been seeing more skunk tracks than usual, in one case accompanied by scats.

The season’s progress makes this a time of daily change, and time spent outdoors inevitably brings its rewards.

Cowbird Fledglings

by Carl Strang

Over the past 2-3 weeks I have been noticing cowbird fledglings at Mayslake Forest Preserve. These are the offspring of obligate nest parasites: brown-headed cowbirds cannot nest themselves, but rather lay their eggs in the nests of other birds. Foster parents that fail to recognize the foreign egg will raise the baby cowbird, often at the expense of their own young. The cowbird develops rapidly, and begs vigorously, gaining an advantage. Here is a fledgling cowbird raised by Mayslake’s eastern phoebes earlier this year.

Cowbird fledgling 2b

I saw no phoebe fledglings. The cowbird’s begging call is distinctive. It sounds like a chorus of baby birds, and probably qualifies as a supernormal releaser. That term refers to an exaggerated stimulus that produces a particular instinctive response by an animal. In this case, the call draws disproportionate attention, in the form of food, from the foster parents. If you hear a chorus of baby birds that all start at once and all pause for breath at once, you probably are hearing a single cowbird youngster.

I heard this call coming from the cottonwood tree bearing the south savanna Baltimore oriole nest . As I like to do, I found the cowbird and waited to see what would come to feed it. The foster parents were the orioles. Here the female feeds the cowbird.

Baltimore oriole feeds cowbird b

I watched for a few minutes, during which the female fed the cowbird three times, the male oriole fed the cowbird once, and he fed the baby orioles (still in the nest) once. A period of rain and work duties kept me from checking for a couple days, by which time there was no sign of any of these birds near the nest.

Over the years I have seen cowbird fledglings being fed by yellow warblers, song sparrows, scarlet tanagers, blue-gray gnatcatchers and cardinals. Cardinals are common at Willowbrook Forest Preserve, but for several years the only time I saw cardinal fledglings was late in the season, after the cowbirds were done. All early products of cardinal nests were cowbirds. This kind of selective pressure is what has led many birds to evolve the capacity to recognize and reject cowbird eggs. Obviously such an ability remains to emerge in many others. Incidentally, once the cowbird becomes independent, it instinctively seeks out other young cowbirds and behaves as a cowbird from then on.

Spring Bird Count

by Carl Strang

Saturday was the Spring Bird Count in DuPage County. I explained the principle in my description of last December’s Christmas Count . I have less to show you on the spring count. The area was much the same, and again was led by Urs Geiser. There were enough of us to split into two subgroups. I was joined in my subgroup by Michael Marlow and Bruce Struckman. We covered Kline Creek Farm and the nearby North Woods subdivision, a beautifully wooded area surrounded on all sides by forest preserves. The only bird photo I managed to get was of our first scarlet tanager.

Scarlet tanager b

Other highlights were a vesper sparrow, a bald eagle, and three golden-winged warblers, plus a variety of other beautiful birds briefly glimpsed or heard through the dense vegetation in the gusting winds that impaired us that day.

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