SJF February Summary

by Carl Strang

Beginning in the middle of the month, I went through all of St. James Farm Forest Preserve seeking the great horned owl nest. I did not find it, but did create an inventory of 25 large tree cavities where an incubating owl might not be visible from the ground. An additional possibility would be a hawk nest in the dense top of one of the spruces. Twice I saw an owl, presumably the male if they are nesting this year, in the same north central portion of the main forest. In past observations elsewhere, the male usually perched in the vicinity of the nest. I will continue to monitor the suspect cavities, but may need to see branched young later in the season to narrow down possibilities further.

I was able to eliminate this cavity, as it was otherwise occupied.

I was able to eliminate this cavity, as it was otherwise occupied.

Some photo processing in the computer makes the raccoon easier to see.

Some photo processing in the computer makes the raccoon easier to see.

I had not seen or heard a pileated woodpecker on the preserve for more than 6 weeks (though occasionally I heard suspicious loud, spaced tapping sounds), but in the second half of February heard or saw one on three different days. The one close sighting was of a male.

The pileated’s tongue-spear in action.

The pileated’s tongue-spear in action.

American coots and large numbers of mallards were a continuing presence on the stream. For much of the month the Canada geese roosting at Blackwell frequently passed over St. James Farm in large numbers, occasionally stopping to graze the lawns and meadow areas. Geese began to break off into pairs as ponds opened up during the last third of February. Interesting bird sightings included a bald eagle flying over, and a hermit thrush on February 16. Migrating sandhill crane flocks began to pass over beginning on the 21st. A small group of white-throated sparrows in the eastern part of the main forest were the first observed on the preserve this year. The first red-winged blackbirds arrived, and eastern bluebirds became a more consistent presence in the last part of February.

This male eastern bluebird seemed to be staking a claim in a corner of the grounds adjacent to a pair of bluebird houses.

This male eastern bluebird seemed to be staking a claim in a corner of the grounds adjacent to a pair of bluebird houses.

Fox squirrels fed heavily from Norway spruce cones in the south forest, and on tree buds elsewhere. Skunk and deer activity was much as described for January. The preserve’s deer minimally are a group of 3 does, a group of 2 deer which occasionally associate with those does, and a single buck. The snow was never deep enough to discourage raccoons. A mink used a den off the south edge of the pond in the preserve’s northwest corner.

Along the way during the owl nest search I found this curiosity.

Along the way during the owl nest search I found this curiosity.

The deer pelvic bone was well gnawed by rodents.

The deer pelvic bone was well gnawed by rodents.

The bone has been on this buckthorn twig long enough for the twig to grow several long branches.

The bone has been on this buckthorn twig long enough for the twig to grow several long branches.

The large area of restoration brush clearing in the main forest was expanded greatly by District staff, generally following the route of the new trail mapped in the preserve’s master plan. Among the more interesting plants encountered during the owl nest search were two of the most massive black walnuts I have ever seen, and a prickly-stemmed greenbrier (Smilax tamnoides).

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Gray Squirrel Species Dossier

by Carl Strang

For several winters, now, I have been sharing my notes on various species of our vertebrate wildlife. The main idea is to step away from the literature and other second-hand sources, and document what I know about each species from my own observations. At last I have reached the end of the list of dossiers which contain enough information to post here. There may be more in the future, as I add to the limited notes presently in unshared dossiers, but this will be the last for a while. I hope the main point has been clear: to remind you, as well as myself, to pay attention and learn from experience rather than rely on the sometimes limited or misleading second-hand reports (I shouldn’t need to point out that from your perspective, this dossier is itself a second-hand report!)

Squirrel, Gray

Gray squirrel

Gray squirrel

This species is more typical of larger forests and cities. Its relative the fox squirrel is the savanna and small woodlot species, though both can occur together (this one is not found around Culver, Indiana, however). Many notes from the fox squirrel dossier also apply to this one.

27JL77. Gray squirrels fed on unripe red oak acorns at Reineman Sanctuary, Perry County, Pennsylvania. The next day, one was eating Nyssa (black gum) seeds (discarding the fruit).

29JE86. One gray squirrel foraging on the ground in an old pine plantation at Waterfall Glen Forest Preserve, DuPage County, IL. It moved slowly (diagonal walk), nose to the ground, sometimes pushing the nose beneath the litter and walking several inches with the face thus submerged. Stopped and ate 3 small objects. Later investigation of the site revealed small oval shells with tough skins, possibly coccoons, flattened ovals viewed from side with a circular cross section, with one end neatly removed and empty inside.

20OC86. Squirrels in dense brushy old field of Willowbrook Back 40. Sounds, when alarmed, like 2-3 steps or jumps, the last louder, then quiet. Is squirrel getting to bigger shrub or a tree, jumping onto trunk then freezing and watching?

23FE87. Much renewal of nut-digging (removal) past few days (and continued next 10 days or so).

28FE87. Wayne Grove Forest Preserve. Gray squirrel stuffing itself with American elm buds in top of 8″dbh tree. Later another, also in a 5″dbh American elm. Much recent excavation of buried nuts. A third individual ate a few black cherry buds.

6MR87. Squirrel high in a black willow, cutting twigs 4-12 inches long and carrying them one at a time to the top of a major 3-branch crotch high in the tree, where it was stuffing or sewing them into a mass of them.

7AP87. A gray squirrel on the ground responded to chipmunk’s chip-trill at my approach, jumping onto low branch and looking alert.

28SE87. Lots of them on the ground in Willowbrook old field. Old and young of year, both.

23JA88. McDowell Forest Preserve. Gray squirrel dug up shallowly buried hickory nut, cutting a 1.5′-tall elm to get face in close for leverage in digging. Carried nut into tree, spent about 4-5 minutes consuming it, then ate snow off top of branch it was sitting on (about 1′ worth, a powdery, thin 0.5″ wide), went down tree and continued. Paused and looked back at me.

20MR88. A gray squirrel at Meacham Grove gathering dry leaves from ground, stuffing them into its mouth with its paws then taking them into cavity nest up in old white oak. Also gathering from among the few leaves still attached to the tree itself.

10AP88. Touched a squirrel at Hidden Lake Forest Preserve (tips of his tail hairs as he “hid” on the other side of a tree trunk barely too big for him to look around).

17AU88. A chase between squirrels, apparently not play. Gray squirrel pursuing a larger fox squirrel, which jumped out of trees twice from 15-20 feet up, landing hard, to escape (in the second jump it leaped out, seemed to sail a bit, and its fall was partly broken by a small shrub). The fox squirrel uttered a harsh call, short and sharp, like part of a mobbing call, on 2 occasions. There was an un-play-like seriousness about the pursuer.

27MY89. Young gray squirrels very curious, approach when you hold still (yesterday in the park at the Newberry Library in Chicago, today in Maple Grove Forest Preserve). They have a buzzing call, precursor of the adult’s bark.

22JE89. 2 gray squirrels eating red (not quite ripe) mulberries at Willowbrook. The berries began to ripen the previous weeks, so many other ripe ones were available.

29AU89. Many twig ends, some more than 1 foot long, cut from a sugar maple in Back Yards exhibit by Sciurus sp. The twigs were laden with developing new seeds, but only a few of these were eaten. Happened in last 24 hours (lawn mowed yesterday). No nest visible in nearby trees, and this tree 25 feet from edge of lawn, similar distance from nearest other tree.

3SE89. Gray squirrel youngster (from spring litter) passing through yard, east to west (not a neighborhood where squirrels lived).

20MR90. Gray squirrel chased fox squirrel away from Willowbrook crow cage area, then came back (note: squirrels often enter Willowbrook cages to take food from dishes. A squirrel nest has been found in the bullwinkle in that cage).

22AP90. Winfield Mounds Forest Preserve. 2 gray squirrels eating enlarged cottonwood buds high in the tree. They ascended together, the larger almost seeming to pursue, certainly to follow, the smaller. The smaller climbed in 2-foot spurts, the larger following, beginning its move as soon as the smaller’s ended. Larger flicked tail in rippling pattern reminiscent of fish or salamander courtship. The smaller may have done so once or twice, but less forcefully. Slow and deliberate, not a rapid play chase. When they were high up, it appeared the smaller would leap to another branch to escape. Larger broke off chase, and they fed. Didn’t take every bud, examined many without taking. Later, larger followed smaller to ground, then up another tree, same way. Larger sometimes sniffed where smaller had been. Larger got ahead of smaller and turned to face it, flicking tail. Smaller turned away. Etc.

1JL90. Gray squirrel in mulberry tree, feeding on ripe berries, West DuPage Woods.

26JA92. Hidden Lake Forest Preserve. Lots of nut digging by squirrels, last 24 hours. Fresh snow, overnight low 20F.

21SE97. Gray squirrel eating gilled mushroom cap, Petoskey State Park, MI. Both gray and black individuals common. One chased by red squirrel briefly.

4MR99. At mid-day a gray squirrel emerged from a hole in a large, dead willow across from the Safari Trail/Glen Crest Creek junction at Willowbrook to drive away an approaching fox squirrel. The gray immediately returned to the hole.

27OC99. Fox and gray squirrels active. Former have been eating nuts in recent days, one this morning in a box elder eating seeds, another appearing to work on a broken down old nest. Gray squirrels on ground this morning, some in woods, at least one in base of savanna finger at Willowbrook.

28OC99. Gray squirrel with nut, fox squirrel eating box elder seeds.

17NO99. A gray squirrel (young) and a fox squirrel both eating box elder seeds at Willowbrook.

2DE99. Several gray squirrels and 1 fox squirrel foraging on ground.

9FE00. Gray squirrel using an exposed (though low) leaf nest at Willowbrook.

14FE00. Many gray and fox squirrels this winter in nests only 12‑14 inches outer diameter at Willowbrook.

4MR00. A gray and 2 fox squirrels feeding on the expanding buds of an American elm near the Joy Path of Morton Arboretum. As I left the path to approach the tree to ID it, the gray squirrel immediately left and ran to other trees. As I walked up to the trunk, the lower of the fox squirrels finally left, but the higher one remained.

15MR00. Willowbrook. A gray squirrel carrying a walnut, in vicinity of trail willow den (have seen a squirrel eating a walnut near there recently).

11JE00. In a morning’s hiking south of Langlade, WI, 1 gray squirrel seen.

21OC05. Willowbrook. Gray squirrel, tail curled over its head, giving its growling-snarling-whining call with an education raptor volunteer holding a red-tailed hawk on a glove nearby. Squirrel holding still, oriented so that its right side is toward the hawk.

25JA06. Fullersburg. 2 pairs gray squirrels chasing one another, probably courtship.

10JL06. Gray squirrel eating ripening hackberries, Fullersburg’s Willow Island.

5OC10. Mayslake. A fox squirrel chased a gray squirrel on the ground in the south savanna.

Fox Squirrel Dossier

by Carl Strang

This week’s species dossier is one of my larger ones.

Fox Squirrel

Fox squirrels are distinguished from our other common tree squirrel, the gray squirrel, by the reddish tones in the tail and belly.

This is a squirrel of woodlands and residential areas with trees. The fox squirrel is the only large tree squirrel of the Culver, Indiana, area. They nest in tree cavities or in leaf nests; some used leaf nests all winter at Willowbrook Forest Preserve, Illinois. Nest building involves cutting of leafy branch-ends. A leaf nest in cross section is made of those leafy twigs, woven into a framework of thicker sticks, with a fresh leafy lining. Overall it has a very thick wall with small insulated cavity within.

Squirrel nests are approximately the diameter of a basketball.

Fox squirrels feed on the ground and in trees. They begin to eat acorns and hickory nuts in August when those still are green. Hickory nuts and acorns are consumed in treetops, especially early in morning and late in afternoon, resulting in a distinctive rain of fragments as hulls are gnawed away. Squirrels (gray squirrels?) also ate black gum fruits in Pennsylvania on Reineman Sanctuary in late fall. Generally they open large nuts (hickory, walnuts) neatly, prying them open on the seams.

Fox squirrel with a pair of shagbark hickory nuts.

They also bury individual acorns, nuts, black cherry pits, etc., in the fall. Distinctive burying site goes into earth at a 45 degree angle or a little shallower, producing an oval shaped bare soil excavation site about 1×2 inches (wider than tall) in soft soil, smaller in hard soil. Mushrooms also are on the fall food list near Culver. Diet in early winter emphasizes excavated nuts buried earlier.

Squirrel tracks, right, follow a winding course as the animal sniffed for a buried nut. On the left is the hole where it excavated one.

Twigs and bark, e.g. of elm, eaten occasionally in mid- and late winter. Buds, e.g. of maple, are added as those expand in spring. Developing elm seeds are heavily consumed in May in DuPage County, generally twigs are cut and seeds eaten from them. Occasionally they gnaw bones.

Fox squirrel eating buds in spring.

Fox squirrels have two breeding seasons, typically, in spring and fall, with 2-5 young per litter. Young began to appear at the Willowbrook Wildlife Center hospital in mid-March (born mid-late February) and mid-August (born late July or early August). Young normally begin to emerge from the nest in May or late September. Young play in vigorous chasing and hiding games on tree trunks and in branches, occasionally extended onto the ground. Adults sometimes play as well, also tease dogs. Leap between trees. They use suspended wires as tightropes between trees and over roads.

These could be fox or gray squirrel footprints.

Tree squirrel tracks are distinctive, the 5-toed hind footprints about 1.25 inches long, with 3 parallel middle toes close together, pointing forward, and outer toes pointing out at angles. The 4-toed front footprints show more spread and independence of toes. The traveling gait typically is a gallop, with front feet leaving ground before back feet land. The back feet are side by side, as are the front feet. Slowing down causes front feet to get closer and closer to back footprints, until one or both front footprints are in front of the back feet. Acceleration also begins with a set of footprints showing the bound gait. Squirrels sniffing slowly over the ground sometimes use the diagonal walk. Fox squirrels show considerable ingenuity and acrobatic ability in overcoming bird feeder protections.

Early spring 1986, Taft Campus of Northern Illinois University, north central IL, with snow still on ground. A fox squirrel, opportunistically foraging in a temporary meltwater stream, looked much healthier than the many gray squirrels fastidiously foraging on the wet-snow-covered hillside nearby.

24NO86. Squirrel began to go onto a branch with 2 great horned owls. The squirrel stopped, tail twitching, sat still for a while, then backed and started to go on a branch over the owls’ heads. They were watching it. Finally it turned around and ran down the tree.

12DE86. Puffer Lake, Morton Arboretum, IL. Fox or gray squirrel tracks in snow that fell yesterday afternoon, on ice among cattails at edge of lake. The tracks were made early this morning. Diagonal walk first 7 feet onto ice, then slow gallop gait.

Fox squirrel, winter.

14MR87. Fox squirrel eating cherry and elm buds at Maple Grove Forest Preserve.

30AP87. Fox squirrel feeding heavily, frenetically, on large green silver maple fruits (seeds only; dropping wings). Also on 1MY, 8:30 a.m. both days.

4MY87. Squirrel-cut elm twigs with fragments of seeds on ground.

6MY87. Early evening, a fox squirrel feeding in an elm top at Willowbrook. Mostly clipped twigs first, then stripped them of seeds, and finally dropped them. The squirrel removed more foliage in 3 minutes than a noctuid caterpillar would in its entire life.

18DE87. 4 days after an abrupt 1-foot snowfall, little but rabbit and squirrel tracks can be seen in the Willowbrook Back 40. The latter are relatively few, restricted to woods.

25MY88. A squirrel when being stealthy carries his tail behind him like the cloak on a figure in an old novel.

This one looks pregnant.

29MY88. Fox squirrel numbers at Hartz Lake (in Indiana) appear limited by hickories. The few squirrels I’ve seen to date have been in parts of woods where hickories are (may simply be a preference, if hunters are keeping numbers low).

20SE88. A fox squirrel nest came into Willowbrook from Lombard with 3 young. The nest was made of leafy elm twigs, with grasses and a work glove toward the center. Overall shape was like an urn, with branches interwoven to nearly cover the entrance. Couldn’t tell for sure whether the entrance was on top or side. Nest blown out of tree by storm.

27JL89. Fox squirrel still feeding heavily on red half-ripe mulberries at Willowbrook after purple ripe ones have been available more than 1 month.

10MR90. Warrenville Grove Forest Preserve. Fox squirrel lunges up tree when climbing, pushing with all four feet at once. Toes catch in cracks, don’t appear to slip although a slight adjustment with a foot may be made now and then before the next lunge.

24JL90. Fox squirrel still eating mulberries.

15NO90. Willowbrook. A fox squirrel eating catalpa seeds right out of the pod, and letting the wings fall.

13JA92. Fox squirrel eating box elder buds, Willowbrook.

22AP95. Midafternoon, Warrenville Grove Forest Preserve. 2 fox squirrels feeding heavily on American elm buds in a 6″dbh tree.

13OC96. 3 fox squirrels in full bark, simultaneously, in Mom and Dad’s Culver front yard. A large cat was their target. They were turned so their bodies pointed in its direction and they were focused, looking straight at the cat.

Not a hibernator, the fox squirrel remains active all winter.

19FE99. Fox squirrel eating expanding silver maple buds, Willowbrook.

4MR99. At mid-day a gray squirrel emerged from a hole in a large, dead willow at Willowbrook to drive away an approaching fox squirrel. The gray immediately returned to the hole.

20AP99. Fox squirrel feeding on buds or expanding leaves of a black cherry tree with leaves much more expanded than those of other cherries at Willowbrook.

28AP99. Willowbrook. Fox squirrel eating silver maple seeds.

13OC99. Willowbrook. Young fox squirrel out of nest. Another fox squirrel eating box elder seeds.

21OC99. Willowbrook. Several fox squirrels gathering walnuts.

Synchronized acorn-eating team, Mayslake savanna.

27OC99. Fox and gray squirrels both are active. The former have been eating nuts in recent days, one this morning in a box elder eating seeds, another appearing to work on a broken down old nest.

28OC99. Gray squirrel with nut, fox squirrel eating box elder seeds.

1NO99. Willowbrook again. Fox squirrel eating box elder seeds.

17NO99. A gray squirrel (young) and a fox squirrel both eating box elder seeds at Willowbrook.

2DE99. Several gray squirrels and 1 fox squirrel foraging on the ground.

30DE99. Fox squirrel at Willowbrook building leaf nest 15 feet up in a buckthorn in a tall-brush area. Taking leaves from nearby small oak that had not dropped many of them.

2FE00. A fox squirrel carried a ball of snow up onto a branch and ate from it.

14FE00. Many gray and fox squirrels this winter in nests only 12‑14 inches outer diameter at Willowbrook.

25FE00. Willowbrook, afternoon. 2 fox squirrels eating buds from a mulberry tree rich in witches’ brooms. Temperature 70F.

2MR00. Willowbrook. 2 fox squirrels sharing a hole in the trunk of a large willow, 1 of them adding leaves picked up from the ground.

Grooming the fur.

4MR00. A gray and 2 fox squirrels feeding on the expanding buds of an American elm near the Joy Path of Morton Arboretum. As I left the path to approach the tree to identify it, the gray squirrel immediately left and ran to other trees. As I walked up to the trunk, the lower of the fox squirrels finally left, but the higher one remained.

15MR00. Willowbrook. Fox squirrel nest high in the very top of a red oak across the exhibit trail from the eagle cage (occupant barked at another fox squirrel lower in tree). A fox squirrel eating expanding sugar maple buds.

13AP00. A fox squirrel feeding on expanding sugar maple buds, Willowbrook.

19AP00. Willowbrook. 2 fox squirrels eating expanding sugar maple buds.

7MY00. West DuPage Woods F.P. 2 fox squirrels clipping American elm twig ends and eating the nearly ripened seeds, then dropping the twigs with leaves.

1JA02. A fox squirrel at the Arboretum eating honey locust seeds from a thornless tree on a very cold day. Sometimes it ate individual seeds from the pod attached to the tree, sometimes removed entire pods and took the seeds from them.

This fox squirrel was mobbed by a pair of Baltimore Orioles in June of 2009 until it left their nest tree.

5OC10. Mayslake. A fox squirrel chased a gray squirrel on the ground in the south savanna.

27JA11. Mayslake. Fox squirrels feeding in thornless honey locust in south (former) friary grounds, presumably getting seeds from pods.

1DE11. Fox squirrel eating honey locust seeds from pod on ground.

Worth the Effort?

by Carl Strang

On Saturday I went to Les Arends Forest Preserve in Kane County to watch a high school regional cross country meet.

The boys’ race, half a mile in.

While waiting between the girls’ and boys’ races, I sat and had lunch at a beautiful wooded edge.

Something caught my eye.

In the top of a spindly sapling 15 feet or so tall, there was a lump.

See it, near the top?

It proved to be a walnut, wedged in a fork of branches.

The sapling was not the source of the nut.

A walnut is a good bundle of calories for a tree squirrel, and one such rodent (probably a fox squirrel) had gone to the effort to grab a nut, husk and all, haul it out into the secondary growth perhaps 20 yards from the source tree, and carry it to the top of the sapling, wedging it well enough that recent storms have not dislodged it. Now, if that squirrel can just remember that the nut is there, and is not pre-empted by another sharp-eyed bushytail, the effort will have been worthwhile.

Mast Year

by Carl Strang

Mast is a collective term referring to nuts and acorns. Trees do not produce these in the same amounts each year. In some years very few nuts or acorns develop in a given species, and in other years prodigious numbers appear. High production seasons are called mast years. 2009 is proving to be a mast year for bur oaks and white oaks at Mayslake Forest Preserve, where the trails in places are littered with the fallen acorns. Here is an example for bur oak.

Bur oak mast b

Here, white oak acorns abound.

White oak mast b

Though elsewhere I am seeing lots of walnuts, this does not seem true for that species at Mayslake, which also is having an unremarkable year for hickory nuts. Nearby, at Fullersburg Woods Forest Preserve, I noted in 2007 that walnuts, hickories and red oaks had a mast year. It is common for members of the white oak group and red oak group of species to be decoupled from one another in their mast years.

Fox squirrel 1b

As you might imagine, animals such as tree squirrels are impacted by mast years. Mayslake’s gray and fox squirrels will have an easy winter with so much food available. They help their cause by biting acorns before burying them in an effort to kill them. The acorns, in a countermeasure, are quick to sprout when they fall to the ground. A study published in 2006 in Science (314:1928) found that red squirrels (which live north and south of us, but not in DuPage County) themselves reproduce more heavily in mast years (perhaps responding to an increase in flowering or other advance cue). Such adaptive interactions between species are referred to as coevolution. The phenomenon of the mast year itself likely is, at least in part, an evolutionary tactic by the trees. By coordinating their mast production they can limit their seed-predators’ survival in some years, overwhelm them in others. Such an episodic mass reproduction is reminiscent of the periodical cicadas.

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