Yellow-rumped Warbler Dossier

by Carl Strang

Today’s species dossier selection focuses on the yellow-rumped warbler, the species in its family that winters the farthest north, with a few sometimes staying through the winter in northern Illinois. Mainly we see them in migration, however, as they nest in the North Woods.

Warbler, Yellow-rumped

Yellow-rumped warbler

Yellow-rumped warbler

This is a very abundant warbler, observed around Culver and Lafayette in Indiana, DuPage County, Illinois, and Cumberland and Perry Counties, Pennsylvania. Usually they travel in flocks, foraging from the low understory to the canopy top. Many stay late in fall, and some appear early in spring. They retain the yellow rump patch (an obvious “follow-me” signal) year-’round. Call of fall birds “tseeet,” slight slur down in pitch early in call, then up at end, again slightly.

21AP87. Has appeared at McKee Marsh, Blackwell Forest Preserve.

26AP87. Song “tsew, tsew, tsew, tli-tli-tli-tli” (short I’s). In late morning at North Blackwell, these are sitting on perches and looking, as palm warblers did, but traveling farther between perches, working higher (mostly mid tree canopy) and not hover gleaning so much as flycatching.

29AP87. Some have songs composed entirely of the “tli” syllables, others place “tsew” syllables in the middle, others have more “tsew’s” than “tli’s.” Any combination of those two syllables seems possible, 8-15 syllables total in a song.

1MY87. Still a predominantly sit-and-wait foraging style.

4OC87. First fall migrants observed at Maple Grove.

12OC87. A yellow-rumped warbler foraged on the ground, hopping, probing, and peering under the leaves of the plants. It moved slowly, less than 1 foot per minute, turning all around.

13OC87. I observed 2 in Willowbrook’s Back 40, and on the 16th, several in the old field there.

17AP88. A couple at Blackwell Forest Preserve.

29AP88. One observed foraging in trees, spending 1-5 seconds per perch scanning, and moving 3-several feet between perches. It pursued prey once, and also tore apart a cottonwood flower. Then it sally-foraged a while. Later, it switched to reaching and probing in the flowers, moving shorter distances (mostly 1 inch-1 foot). The song was relatively weak for a warbler, accelerating through its 2-3 second duration.

7MY88. Indian Trails, Culver. One flycatching.

8OC88. Hidden Lake Forest Preserve. Abundant in woods, and in fields.

11OC88. Observed in Willowbrook Back 40.

18OC88. Observed at Hartz Lake, foraging with or at least near chickadees and golden-crowned kinglets.

17AP89. First of year seen, Willowbrook Back 40. Next mentioned 30AP, McDowell.

9MY89. One at Willowbrook, flycatching low beside stream.

21OC89. Lots of them in West DuPage Woods Forest Preserve. Foraging mainly by flycatching and hover-gleaning. Air cool, 50F or less, sunny, breezy.

Male breeding colors are much brighter, but I have yet to photograph one.

Male breeding colors are much brighter, but I have yet to photograph one.

17AP90. First of year seen, Willowbrook Back 40.

23AP90. One foraging in silver poplars at Willowbrook, probing etc. in canopies, with song: “we-see’-we-see -we-see -we-see -we-see” very fast, with slight emphasis on 2nd syllable and 20-30 seconds between songs. Afternoon.

19AP99. First of season noted at Willowbrook. Last spring migrant there 13MY.

30SE99. First yellow-rumped warblers of the fall, many at Willowbrook, 2 eating poison ivy berries. Also seen eating them on 5OC, 12OC.

20AP00. First spring migrants at Willowbrook. (I saw my first of the year 18AP while running near Warrenville).

22AP00. East Woods Trail, Morton Arboretum. Several yellow-rumps feeding high in forest canopy. One observed in crown of a sugar maple in flower. The bird was mainly sitting still, reaching into flower clusters for insects. They are singing the weak sounding song that alternates between two notes, beginning weakly, crescendo and decrescendo into a trailing, weak ending. Also calling: a harsh, “pick” sound, dull and flat in tonal quality but a sharply pronounced, sparrow-like note.

7AP01. First yellow-rumps of the season at Greene Valley Forest Preserve, feeding in trees in chickadee style, with much searching of twigs and bark, and a flush-and-pursuit seen.

30SE01. Many yellow-rumped warblers along the Fox River and on Island Park, Batavia. Spread out all over, some hover-gleaning, some flycatching, others getting poison ivy berries.

27DE01: Yellow-rumped warbler at Willowbrook, foraging at the edge of the open stream, seen to catch a small worm prey.

19DE03. A yellow-rumped warbler at Willowbrook feeding on poison ivy berries and calling, the first seen there in weeks.

28SE10. Mayslake. Some yellow-rumps eating cedar berries.

26OC10. Mayslake. In recent days I have found that yellow-rumped warblers can produce the common warbler call-note (high pitched, briefer) in addition to their lower species specific note.

10DE10. Mayslake. Yellow-rumped warbler eating cedar berries near the mansion.

Yellow-rumped warbler eating a red cedar berry

Yellow-rumped warbler eating a red cedar berry

25AP11. Mayslake. A yellow-rump singing a patterned song repeatedly, very similar to Nashville warbler song but ending just different enough to distinguish.

29AP11. Mayslake. Another distinctive yellow-rump song, this one ending like the one earlier in the week but beginning with a rising sequence of notes as in a scale.

Literature Review: Leaf Mine Diversity

by Carl Strang

This week’s literature focus is on a paper that provided information suggesting why leaf miners produce such diverse mine structures.

Leaf miners are larval insects so tiny that they fit between the upper and lower leaf surfaces, feeding on the tissues in between. This example is a twisting linear mine on Heracleum.

Leaf miners are larval insects so tiny that they fit between the upper and lower leaf surfaces, feeding on the tissues in between. This example is a twisting linear mine on Heracleum.

Ayabe Y, Ueno T (2012) Complex Feeding Tracks of the Sessile Herbivorous Insect Ophiomyia maura as a Function of the Defense against Insect Parasitoids. PLoS ONE 7(2): e32594. doi:10.1371/journal.pone.0032594

They looked at linear mines in a fly that develops in a French aster. In their review they mention research that has been done on various mine forms and how they may deter parasitoids. Parasitoids focus mainly on the upper leaf surface, so lower surface mines (including tentiform mines of Phyllonorycter moth caterpillars in some of our local plants) provide some protection, and upper surface miners sometimes shift to the lower surface to pupate. Blotch mines provide more escape space for their occupants. In this study they found that complex linear mines, especially ones that have branches and crossing tunnels, reduce parasitoid effectiveness.

We can see a wide range of leaf mine types on our local plants.

Expanded blotch-type mine on poison ivy (the leaves aren’t always 3 leafleted!).

Expanded blotch-type mines on poison ivy (the leaves aren’t always 3 leafleted!).

The outline of a tentiform mine shows on this maple leaf. The mine is on the underside of the leaf, not readily reached from above.

The outline of a tentiform mine shows on this maple leaf. The mine is on the underside of the leaf, not readily reached from above.

According to this research, it boils down to a game of hide-and-seek. If a leaf miner can make its mine complex enough, or in a place where it is difficult to reach, or expand the mine to the point where finding the miner is somewhat needle-in-haystackish, it gains an advantage over the insects that would parasitize and kill it. Furthermore, the diversity of mine types provides a more complex evolutionary puzzle for the parasites as a whole to solve.

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.

Maple Leaf Miners: Canopy Data

by Carl Strang

Last week I returned to Maple Grove and Meacham Grove Forest Preserves to collect leaf miner data from fallen sugar maple/black maple leaves. Fallen leaves mainly represent what happened in the canopy, and data from them allow me to make comparisons between preserves, between years, and between the understory and the canopy (I had collected understory data earlier in the season).

This year all the leaves had fallen by the time I did the survey.

It was a pleasant day, and I dressed warmly enough that the November weather was no distraction.

In fact, a number of male linden looper moths were flying at Maple Grove. Also known as winter moths, they wait until November to seek mates.

Though the main purpose of the venture was to count leaf mines, I also kept my eyes and ears open for anything else of interest.

I don’t remember noticing this small concrete foundation at Maple Grove before now. It appears to be an old latrine site.

With the leaves largely changed from yellow to brown, leaf mines were easy to see.

Typical leaf litter scene.

I counted 30 leaves at each of 10 randomly selected points on each preserve. Comparisons between canopy and understory counts this year revealed no statistically significant differences at either preserve, except that there were more Phyllonorycter clemensella tent mines in the Maple Grove understory than in the canopy. This species seems more tied to the understory, and seems to be more affected by controlled fall burns of leaf litter. There were no successful burns at either preserve last year, and I suspect that accounts for the statistically significant increase in this species in the understory at Meacham Grove this year. There were no differences between 2010 and 2011 in the canopy for any of the four mine types at either preserve, and there were no differences between the preserves in canopy counts.

Leaf Miners in the Understory

by Carl Strang

Yesterday I reported on one of my herbivory studies at Maple and Meacham Grove Forest Preserves. Today I have the data for the first part of the other study, a decades-long following of 4 leaf miner  genera in sugar and black maples in the understories of the two forests. While attempting to photograph confused ground crickets at Warrenville Grove, I had noticed a high incidence of tent mines, produced by the micro moth Phyllonorycter clemensella.

This photo from Warrenville Grove shows many leaves with one or more Phyllonorycter mines.

Consequently I was wondering if I would find a lot of mines at my study preserves this year. In fact, Phyllonorycter incidences were relatively high in both forests, in 15 percent of understory leaves at Maple Grove and 4 percent at Meacham. Statistically there were more at Maple than at Meacham, which has been true over the years, probably because of more intensive management at the latter site (controlled burning, and culling of maple saplings). Numbers were not different from last year at Maple Grove, but there was a statistically significant increase at Meacham for this species, possibly because there was no burn last year.

The other leaf miners were present in lower numbers that were indistinguishable from last year’s values. The two species of moths in genus Caloptilia, which leave their mines early and construct little cones or boxes in the leaf lobe tips for most of their development, were more abundant at Maple Grove (8 percent incidence) than at Meacham Grove (2 percent of leaves had them). While 3 percent of leaves at Maple Grove had blotch mines of Cameraria saccharella (another tiny moth), none of the 300 leaves in the Meacham Grove sample had any (only one had a mine last year). The fourth mine is distinctive in having a winding linear form.

The linear mine is visible in the lower part of this maple leaf at Warrenville Grove. I have not reared this one; it probably is produced by a caterpillar of the non-native moth Stigmella aceris.

This one was present in low numbers that statistically were indistinguishable between the preserves (8 leaves at Maple, 1 at Meacham). In November I’ll return to assess canopy incidence of these moths.

Literature Review: Cicadas and Trees

by Carl Strang

The phenomenon of the periodical cicadas raises a lot of questions. Some of these questions are ecological. Millions of the insects emerge at once every 13 or 17 years, depending on the area, and their sheer biomass suggests that they must influence the ecology of the forest as a whole. Their nymphs grow by drawing sap from tree roots. The adults damage twigs when they cut them to insert their eggs. When the masses of cicadas die, their decomposition releases nutrients into the soil. Thus, from a tree’s standpoint some of the effects are potentially beneficial, others harmful. This was the background for the paper I am reviewing today (Speer, James H., Keith Clay, Graham Bishop and Michelle Creech. 2010. The effect of periodical cicadas on growth of five tree species in Midwestern deciduous forests. American Midland Naturalist 164:173-186).

Periodical cicadas also occasionally feed on tree sap during their brief time in the adult stage. These are sitting very still, and their beaks are piercing the bark.

This research group used dendrochronology methods in southern Indiana, measuring growth ring widths in several tree species. They first factored out climatic influences, ruling out the effects of relatively good or bad growing seasons. Then they tested the effect of feeding by cicada nymphs, oviposition damage and the nutrient pulse following emergence.

Periodical cicada nymph emerging from the ground. Did the nymphs’ diet of tree sap impact tree growth?

Cicada nymphs start out very small, and grow to be relatively large, so if their numbers are impacting tree growth, the trees should grow progressively slowly through the insects’ 17-year cycle. Speer and associates could find no nymphal feeding effect in any of the 5 tree species they examined.

Periodical cicada egg slits in a redbud twig. Typically the twig end dies as a result of this damage.

Sassafras, pin oak and black oak showed some growth loss from oviposition (egg-laying) damage, but these plants are less preferred for oviposition than sugar maple and white ash. The latter appeared to be hit harder, but growth rings showed no effect.

Dead cicadas litter the ground as an emergence ends. Does the pulse of nutrients from their decomposition benefit the trees?

There was a nutrient pulse effect for black oak, pin oak and sugar maple, but it happened 5 years after emergence. The authors suggest that trees may need time to absorb the nutrients and produce extra wood after the adult cicada mortality event. Alternatively, this effect may result from a pulse of mortality in cicada nymphs of that age.

Maple Leaf Miners, Canopy

by Carl Strang

On Saturday I returned to Maple Grove and Meacham Grove Forest Preserves to complete this year’s measurements of leaf miners in black and sugar maples. Earlier I reported the results for the understory. This time I was looking at fallen leaves to index leaf miner abundance in the forest as a whole. This can be regarded as a measure of these tiny caterpillars in the canopy, in part because the vast majority of leaves grow there and in part because saplings still are holding many of their leaves at this point in the season.

I went to 10 randomly selected points at each preserve and examined 30 leaves per point. The sunny, calm day was good for this as mines can be difficult to see after the fallen leaves have turned brown. I can hold the leaf so the sun shines on each surface, then hold it up so light shines through it.

In the five years that I have taken this measurement I have found few differences between canopy and understory leaf miner abundances. The most common difference is a lower incidence of Phyllonorycter tent mines in the canopy than in the understory, and such was the case this year at Maple Grove. Also at Maple Grove, Caloptilia boxfolds were less common in the canopy than in the understory this year.

All four genera of these tiny moths were in low numbers in the canopies of both preserves. The most abundant were Phyllonorycter at Maple Grove, where I found tent mines on 15 of 300 leaves, or 5%. That was the only species which produced a statistically significant difference between the preserves. In general, populations have been low since I began measuring canopy leaves, so I have yet to see a consistent pattern of differences. The only complete miss this year in understory and canopy combined was an absence of linear mines (probably produced by the non-native moth Stigmella aceris) at Meacham Grove (one turned up in the canopy sample there last year).

I have been interested in the effect of the more intensive management at Meacham Grove on insects and plants I am studying in these preserves. On Saturday I noticed that a burn had been attempted yet again at Meacham.

As you can see, the line of burning fuel dripped along the edge of the trail (which serves as a firebreak) did not take. There still is time for another attempt this fall.

Maple Leaf Miners, Understory

by Carl Strang

In addition to the trailing strawberry bush (reviewed yesterday), I looked at leaf miners on understory sugar and black maples at Maple Grove and Meacham Grove forest preserves last week. As was the case with the other study, I was interested in the potential impact of controlled burning on the populations of the tiny moths whose caterpillars mine the leaves. Even after a year, the burned areas still had essentially no leaf litter.

Unburned areas at Maple Grove, and in a separate, off-study-area forest in Meacham Grove Forest Preserve, had plenty of litter remaining.

The upshot, though, is that I cannot identify any impact of that fire on leaf miner populations. This is not because they are all high, but rather because the four genera of miners have been consistently low at Meacham Grove for 15 years, now. This year, likewise, maple leaves were very clean at Meacham.

That result, I suspect, is more from the sustained intensive management at Meacham Grove over the years, with greater removal of understory maple saplings and more frequent and extensive burning. This is consistent with Meacham Grove’s forest having more of an oak component, a sign that it was exposed more to fire in its early days, fire that would have limited maple reproduction and dominance. The differences I have observed between the two forests in understory leaf miner populations thus may reflect a historically significant difference in the ecologies of the two preserves. Certainly the management at Meacham has produced an increase in botanical diversity of forest floor plants there.

In three of the four leaf miner genera, understory populations were higher this year at Maple Grove than at Meacham Grove. At Maple Grove, Caloptilia were present on 8% of understory leaves (2% at Meacham), probable Stigmella were on 3% (0% at Meacham), and Phyllonorycter were on a whopping 19% of understory leaves (0% at Meacham). The difference in Cameraria blotch mines, on 2% of Maple Grove leaves and 0% of Meacham Grove leaves, was not statistically significant (for more on these insects, go here). Though I did not take measurements, Phyllonorycter tent mines to the eye were much more abundant in the unburned, less managed forest block at Meacham Grove, and thus resembled Maple Grove.

At Maple Grove, two of the four insect groups increased over last year. That 19% figure for Phyllonorycter in fact is the highest since before 1996, and it is the fifth time that population has occurred on more than 10% of leaves in that period. The median annual value in those 15 years has been a healthy 6%. Caloptilia likewise have stayed strong, with a median matching this year’s value of 8%. This year’s frequency of 3% likewise is the median value for Maple Grove (probable) Stigmella. Cameraria has stayed low, with a median of 2% (also this year’s Maple Grove value). The respective medians for Meacham Grove have been 1%, 4%, 1%, and 0%. All of this discussion has been about the understory. The forest canopy may produce different results, which I’ll investigate in November.

Canopy Leaf Miners 2009

by Carl Strang

Recently I reported the results of my survey of black/sugar maple leaves in the forest understory at Maple Grove and Meacham Grove Forest Preserves. Each year I measure the incidence of four groups of leaf miners on those trees at those preserves, continuing a study I began in the 1980’s. Having found very few leaf miners of any type on the low saplings in September, I returned in November to gather data from fallen leaves, nearly all of which come from the canopies of mature trees.

Linear mine on a fallen leaf

As in the understory, canopy leaves had relatively few leaf miners. The highest incidence in any 300-leaf sample was 11 leaves bearing blotch mines of Cameraria caterpillars at Maple Grove. In comparisons between canopy and understory incidences, none were statistically significant. Comparisons between canopies of the two study areas likewise revealed no differences.

I also compared leaf miner incidences between 2009 and 2008. The only statistically significant changes were decreases in Caloptilia boxfolds at Maple Grove, both in the understory (a drop from 42 to 9) and in the canopy (a similar drop from 32 to 9).

It is worth noting that I found low numbers of all four mine types at both preserves this year.

Cameraria mine in a fallen leaf

This is the first time since 2006 that the sample included Cameraria at Meacham Grove.

Understory Leaf Miners 2009

by Carl Strang

In a series of posts last winter I outlined my results to date in a study of several species of leaf mining moth caterpillars that occur on black/sugar maples at Maple Grove and Meacham Grove Forest Preserves. This study, begun in the 1980’s, continues to be worth pursuing; I put in a total of about one full field day per year.

ACNI tent mine b

Tent mine formed by Phyllonorycter larva

One aspect of the study is a comparison of leaf miner occurrence in the canopy versus the understory. Today I’ll report this year’s results for the understory, having gathered those data in September. The story can be told simply, as I found very few leaf miners of any kind at either study area. Out of the 300-leaf samples from each preserve, the greatest number of leaves bearing a leaf mine type was 9 (Caloptilia boxfolds at Maple Grove). That number itself represented the only statistically significant change from 2008, having dropped from 42 leaves in last year’s Maple Grove sample. In comparisons between study areas, only the linear mines which I believe are produced by Stigmella showed a difference. Technically, however, the 8 leaves at Maple Grove versus 0 leaves at Meacham do not meet the criteria for the statistical test I use.

Maple leaves 19SEb

So in the understory the maple leaves were about as clean as I have ever found them. I’ll go out to collect the canopy data soon.

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