Ice, Snow, and Geese

by Carl Strang

 

Since the initial impressions of DuPage County’s wintering Canada geese that I reported at the beginning of December, we have experienced some cold weather and a period when a few inches of snow covered the ground. The cold was sufficient to freeze some of the lakes and ponds where geese were roosting. In some cases this led to at least a temporary abandonment, for instance of roosts at Rice Lake (Danada Forest Preserve) and Herrick Lake. The number at the South Blackwell roost at least doubled from its November count of approximately 1000, presumably through the addition of birds from abandoned roosts such as those noted.

 

cg-herrick-2b

 

Earlier the geese had no trouble finding food (those in the above photo simply walked up from their then roost on Herrick Lake into the picnic ground to graze), but when the snow was deep there were fewer choices. All the geese I had observed prior to the snow were grazing the mowed lawns of open areas, and had seeming limitless places to go. Increasingly, easy grazing was limited to south facing slopes and hilltops where the snow was thinner and melted away first. The South Blackwell geese, now numbering at least 2-3,000, poured into the harvested agricultural fields of nearby St. James Farm.

 

I have been driving around the county seeking additional roosts, and my next entry in this series will list the ones I have found.

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Alphabet of Tracking 3: Other Toe Counts

by Carl Strang

 

I’ll conclude the alphabet portion of this abbreviated tracking primer with species which typically show two toes, and those which register four toes on the front feet and five on the hind feet.

 

Two-toed feet mean white-tailed deer in the wild fauna of today’s northeast Illinois. In the photo, a hind footprint partly overlaps a front footprint.

 

White-tailed Deer

White-tailed Deer

 

 

The four-five combination indicates members of the rodent family. Three examples follow. Our largest rodent is the beaver. Here is its four-toed front footprint.

 

Beaver front footprint

Beaver front footprint

 

 

In muskrat tracks the hind footprint is much larger than the front footprint. Can you find all five toes belonging to the hind print to the left in the photo, and all four toes on the front foot to the right?

 

Muskrat tracks

Muskrat tracks

 

 

This set of squirrel tracks has four footprints. The outer prints are the hind feet, the inner ones are front feet. Some study may be required to find all the toes, but they all are showing.

 

Squirrel tracks

Squirrel tracks

 

 

The next lesson when I return to this topic will introduce typical footprint arrangements, or gaits, of these animals.

Alphabet of Tracking: 5 Toes Front and Hind Feet

by Carl Strang

 

Today I continue my tracking primer with a focus on mammals whose feet typically show 5 toes on the front and hind feet of complete tracks (but remember that in the field you often have only partial footprints; this is where dirt time comes in, as mentioned in the last post). Local animals in today’s category are raccoons, opossums, members of the weasel family, and shrews. Bears also are in this category, though they are even less likely than mountain lions to show up in northeast Illinois.

 

Black bear track

Black bear track

 

 

Raccoon tracks have long, round-tipped toes and are among the most frequent footprints we notice, because these are common animals, they often are passing through muddy areas, and they are heavy enough in body to sink into the surface.

 

Raccoon track

Raccoon track

 

 

Opossum tracks are, like the animals themselves, amazing and odd. Typically the hind foot is rotated so that it is oriented sideways, wrapping around the heel of the front foot with the big toe pointing in and the other four pointing out. The toes on the front foot are spread so widely that the overall effect reminds me of a star.

 

Opossum tracks

Opossum tracks

 

 

Our most common local weasel family representatives are the mink and the striped skunk, but I remain alert for otters as well. Mink tracks have a round appearance overall. Though primarily aquatic animals, their footprints often turn up away from water (in DuPage County it is not possible for them ever to be truly distant from water, however).

 

Mink tracks

Mink tracks

 

 

Otters likewise are aquatic. Their tracks are bigger, and they likewise can travel distances over land between water bodies. (I am deliberately not including size measurements. I have to leave something for your own inquiry!). I have not encountered an otter in DuPage County yet, but given the success of the program re-introducing them to the state I regard this as simply a matter of time.

 

Otter track

Otter track

 

 

Striped skunk tracks at first glance often remind me of domestic cat tracks, except that five smaller toes are crowded into the space of the cat’s four. Skunk tracks have toenail marks, with the longer toenails of this digging animal’s front feet prominently in front of the ends of the toes.

 

Striped Skunk tracks

Striped Skunk tracks

 

 

Shrews are tiny animals. Most of their tracks you encounter will be in snow, and so will not show the individual toes. Masked shrews are much smaller than mice, and so their sets of tracks will be smaller (quarter coin provides scale; the photo includes an entire set of four footprints to the left, and another to the right of the coin).

 

Masked Shrew tracks

Masked Shrew tracks

 

 

Least shrews likewise are tiny, but these are much rarer than masked shrews. Short-tailed shrews often show a diagonal walk gait pattern (to be explained once we reach the “word” level of this introduction).

 

(probable) Short-tailed Shrew tracks

(probable) Short-tailed Shrew tracks

 

Alphabet of Tracking: 4 Toes Front and Hind

by Carl Strang

 

To set the stage for future posts, I am beginning a series on basics of tracking, with an initial emphasis on mammal footprints. Tracking is a language. It has an alphabet, words, sentences, and these build to tell a story. The completeness of that story is limited mainly by the experience and skill of the tracker. Experience and skill are built only by what Tom Brown, Jr., calls “dirt time.” The more you study, the better you will be. Books and Internet postings like this one can provide hints to get you started, but you have to practice, and train your eye.

 

Reading any language begins with a mastery of its alphabet. The alphabet in tracking, as I learned it and teach it, is the identification of the species of animal which made the track. We’ll begin with animals whose feet typically register four toes on both the front and hind feet when leaving a footprint, and in our area of northeast Illinois this means members of the dog, cat and rabbit families.

 

Cat tracks are distinct in typically showing four toes per foot, with no toenail marks, and generally a circular shape to the track as a whole. The example usually encountered is the domestic cat.

 

Domestic cat

Domestic cat

 

 

I certainly keep my eyes out for bobcat tracks, but so far have found none in northeast Illinois. The photos are from other parts of the country. Note the lobed heel.

 

Bobcat track, Nevada

Bobcat track, Nevada

 

 

Bobcat track New Jersey

Bobcat track New Jersey

 

 

Mountain lion tracks have the same properties as other cat tracks, but are much larger and of course are not usually to be expected in our area.

 

Mountain lion track, Texas

Mountain lion track, Texas

 

 

Dog family members in our area include dogs, coyotes and foxes. In coyote and fox tracks the toes fit together so as to form an egg shape, with the middle two toes farther in front of the outer two toes. Coyotes have slightly larger footprints and a longer stride than foxes.

 

Coyote track

Coyote track

 

 

Coyote muddy foot on concrete

Coyote muddy foot on concrete

 

 

When the substrate is fine enough to register them, red fox tracks show ridges protruding through the fur in the heel and toe pads. In gray foxes, coyotes and dogs the pads are not so furry.

Red fox on the beach

Red fox on the beach

 

 

Red fox track, clay

Red fox track, clay

 

 

Red fox track, snow

Red fox track, snow

 

 

Dog tracks are relatively spread out, forming more a maple leaf shape, and the middle toes are not so far in front of the outer toes. This is a matter of degree which requires dirt (or snow!) time to learn.

 

Dog tracks

Dog tracks

 

 

Our local rabbit is the eastern cottontail. They are smaller animals, and their feet are furry, so unless they pass through soft mud or snow you will have to look for the 4 toenail marks of each foot.

 

Rabbit faced left, hind feet top and bottom, front feet center

Rabbit faced left, hind feet top and bottom, front feet center

 

Can you find the four toenails of this cottontail track?

Can you find the four toenails of this cottontail track?

 

 

 

I am providing just a starting sketch here. More will come later. If you want references, the best tracking books I have seen are by Tom Brown, Jr. (Tom Brown’s Field Guide to Nature Observation and Tracking; and, for more advanced study, The Science and Art of Tracking, both published by Berkley Books), and Mark Elbroch (Mammal Tracks & Sign, and Bird Tracks & Sign, both by Stackpole Books).

Predator Peregrinations

By Carl Strang

 

After marveling over the crowd of goldfinches and pine siskins described in yesterday’s post, I took a looping route through Mayslake Forest Preserve. Almost right away I found where a mink had crossed the mansion grounds the previous night.

 

mink-4-10deb

 

On one of my early exploratory walks at Mayslake in November I saw a rock in the little stream that had what appeared to be mink droppings on it. Mink like to leave these calling cards on distinctive elevated landmarks, no doubt to make it easy for other mink to find them. In this case the droppings appeared to be composed mainly of invertebrate exoskeleton material.

 

mayslake-mink-maybe-b

 

I didn’t have time to follow the mink tracks through all of their wanderings. The animal had gone back and forth over the north mansion grounds and around the chapel with the occasional hieroglyphics that distinguish an active, hunting weasel like the mink.

 

mink-6-10deb

 

The mink appeared to have come and gone from the direction of the little stream that flows north out of Mays Lake. I also found mink tracks, perhaps by the same animal, around the origin of that stream and along the eastern shore of that lake, with a side trip up onto the adjacent ridge. It’s tempting to think of mink as water animals, but I often have found their tracks well away from water.

 

Near Mays Lake the mink trail crossed that of two coyotes.

 

mink-coyote-10deb

 

Up until then I had seen only one set of coyote tracks at a time but here were two, possibly members of a pair, hunting together. While the two stayed together all the way from the south part of the preserve, along the main trail to the mansion grounds and on north and west, there were occasional side trips by one or both. Sometimes one stepped in the tracks of the other, presumably to save energy, and sometimes they walked apart.

 

coyote-pair-10deb

 

Tracking is a valuable tool in mammal inquiries, especially in winter. I have begun to write a primer on tracking for this blog, and I think I had better start it tomorrow.

The Birch Birds Came Back

by Carl Strang

 

Two days ago I described how the Mayslake paper birch had opened its cones and dropped some seeds. Yesterday morning that tree was the focus of attention for around 30 goldfinches and 30 pine siskins, all busily digging into the opening cones for dinner.

 

birch-goldfinches-siskins-b

 

Goldfinches and siskins are close relatives, with goldfinches abundant DuPage County residents, and siskins mainly winter visitors from the North, though the odd pair has been known to nest locally. At this time of year, goldfinches are pale greenish yellow and white with darker wings, the males having molted out of their bright yellow summer plumage.

 

birch-goldfinch-b

 

Pine siskins have bits of yellow here and there, but are distinctive with their dark stripes. The voices of these two finch species are different from one another as well, but I don’t believe I can describe the difference adequately in words. Seek out reference CD’s or a website with recordings of their calls, if you are interested.

 

birch-siskin-b

 

The sudden appearance of so many of these birds brings out an observation I have made about Mayslake. The birds I encounter there have been highly variable from day to day. Yesterday I also saw the first American tree sparrows I have observed at that preserve. In both of my two previous office locations, Willowbrook and Fullersburg Woods Forest Preserves, tree sparrows have come and gone at widely spaced intervals through the winters. Tree sparrows do not make use of bird feeders as consistently as many other species. I am beginning to wonder if the variability of small winter birds at Mayslake is connected to the lack of bird feeders there. Willowbrook and Fullersburg both have feeders, and both have a more consistent presence of birds through the winter than I have observed at Mayslake so far. I resist drawing conclusions so soon, but I find myself asking whether birds undisturbed by human influences are inclined to wander over wider areas, so they appear in a given location less frequently.

 

There is more to report from yesterday at Mayslake. I’ll share the rest tomorrow.

African Bird

by Carl Strang

 

I’m not a huge TV watcher, but “Survivor” is one of my guilty pleasures. The current series, taking place in Africa, occasionally shows a passing shot of a species of bird I have seen a number of times despite never having visited that continent. It’s also a species which nests in northeast Illinois. I’m talking about the osprey.

 

Osprey nest, Maryland Eastern Shore

Osprey nest, Maryland Eastern Shore

 

 

Ospreys occur all around the world. I saw them in Australia. Though there are no recent known nests in DuPage County, for the past two seasons there has been one a stone’s throw from the county’s northwest corner. I should say “baseball’s throw,” because this nest is built on one of the light poles in a complex of ball diamonds. It’s tempting to say the birds must be baseball fans.

 

For one species (and there is only one) to have become so cosmopolitan is testimony to the success of its complex of adaptations. Freshwater fish that stay close enough to the surface to be susceptible to a plunge-and-grasp are found on all the warm continents. Ospreys’ feet are wonders. The long curved talons are supplemented by hard sharp protruding scales on the undersides of the toes that grip the slippery prey.

 

Osprey carries fish head forward

Osprey carries fish head forward

 

 

My best opportunity to watch ospreys in action came during my sea kayak circumnavigation of Isle Royale a few years ago. I camped a couple days at a site called Hay Bay, which is accessible only by boat or bushwacking. There I had an excellent opportunity to watch ospreys, cormorants and gulls as they hunted for the abundant lake herring. The ospreys plummeted from spectacular heights, and when it was calm I could hear their collisions with the water from most of a mile away. Often they rose with fish that were at least a third of their own length.

 

Recent nesting success of ospreys in northeast Illinois bodes well for their return as a more familiar part of our fauna.

Seeds on Snow

By Carl Strang

 

There is a magnificent paper birch near the entrance of Mayslake Hall which has managed to evade the bronze birch borers long enough to become robust and beautiful.

 

paper-birch-2b

 

Yesterday I noticed that the birch had dropped seeds onto the snow.

 

paper-birch-seeds-2b

 

For a moment I was a little surprised that there were any seeds left. A couple weeks ago that tree was filled with goldfinches, juncos and pine siskins pigging out on seeds they were digging out of the tree’s cones. Obviously they missed some, for the snow was covered with yellow-brown seeds and shed cone scales.

 

paper-birch-1b

 

After taking some photos, I thought about the timing. Now, with leaves dropped from deciduous trees, the little winged seeds have their best chance of being carried away on the wind. Furthermore, if there happens to be snow on the ground, the wind can further push the seeds, increasing the area over which they are spread. This might improve the possibility that some will find suitable places to grow.

 

That thought brought out a memory, of a presentation decades ago at an Ecological Society meeting. Someone had studied Queen Anne’s lace and found that its seeds are contained within the closed umbrella of its flower/fruit support struts.

 

qa-lace-closed-b

 

The struts remain closed when the air’s humidity is high, but open as humidity drops, so that seeds are released in the dry air of winter when there is a good chance the ground will be snow-covered, allowing the seeds to be wind dispersed over a smooth surface.

 

qa-lace-open-2b

 

Later during my lunchtime walk I found some Queen Anne’s lace, and sure enough, though some were closed, others had opened and begun to drop their seeds onto the snow.

 

qa-lace-and-unknown-seeds-2b

Do the Leaf Miners Avoid One Another?

By Carl Strang

 

Yesterday I described several species of tiny moths whose caterpillars mine the leaves of black/sugar maples in DuPage County, Illinois. Today I want to review some of the results of my inquiries into this system (by “system” I mean a group of interacting species in a particular environment) since 1983.

 

In the mid-1980’s these species all were abundant, and collectively they were removing a significant portion (in 1984 more than 20%) of the maples’ photosynthetic tissue in understory plants. We might expect that in such a situation it might benefit them to avoid one another. There are mathematical methods, called statistical tests, that allow us to say whether the co-occurrence of these herbivores on leaves is taking place randomly (no interaction evident), whether they may be avoiding one another (co-ocurrence on leaves is less than one would find in a random situation), or whether they are attracted to one another or at least to the same leaves (co-occurrence greater than in the random case).

 

acer-leaf-miners-b

 

I made these comparisons in 1984, 1985, and 1986. If there are any interactions between these leaf miner species, we would expect to see the same result showing that to be the case in each year. With four mine types, there are 6 ways any two of them can form a pair for comparison in a given year. That makes 18 statistical tests over the three years. Out of these 18, only four showed a statistically significant departure from random co-occurrence. However, only two of the four involved the same two species, Caloptilia and presumed Stigmella in 1985 and 1986. Those same two species gave a random result, however, in 1984, the year when leaf tissue loss was highest and presumably there would be the greatest benefit from avoidance. On the whole I had to conclude that these species are interacting weakly if at all.

 

This seems puzzling, but I have a guess as to why it’s the case. When I returned to this system in 1996 I found the populations of leaf miners very low compared to the 1980’s. Only in the case of Caloptilia at Meacham Grove did more than 10% of the leaves have one or more of these insects. Populations have remained at or below these levels ever since. It’s beginning to look like the high numbers of the mid-1980’s were unusual, so that there has not been selective pressure to benefit individuals with avoidance behavior.

Maple Leaf Miners: Introduction

by Carl Strang

 

Leaf miners are amazing insects, so tiny that they live between the upper and lower surfaces of leaves. They eat the succulent interior leaf tissues, and as they grow, the area they have depleted of these tissues expands to form a shape that is easy to see and is distinctive according to the insect species. Here are two common forms, linear mines in a cow parsnip (Heracleum) leaf, and blotch mines in a leaf for you to identify (note: this is a trick question! Plant identification given below).

 

Linear mines in Heracleum leaf

Linear mines in Heracleum leaf

 

Blotch mines in mystery leaf

Blotch mines in mystery leaf

 

 

There are flies and beetles that are leaf miners, but the ones I have been studying for more than two decades are minute moths whose caterpillars do the mining in maple leaves. The trees, at Maple Grove and Meacham Grove Forest Preserves, are either black maples (Acer nigrum), sugar maples (A. saccharum), or hybrids of the two. In the mid-1980’s, when I began studying leaf eating insects in these two forests, my attention was drawn by the large numbers of leaf miners in the understory maples on both study areas.

 

I was able to sort out five species of insects doing the damage. They include Caloptilia bimaculatella and C. packardella, of the moth family Gracilariidae. Their larvae begin with tiny mines which they soon leave, and their major growth takes place in folded, cone-shaped shelters (called here “boxfolds”) which the larvae construct at the tips of leaf lobes.

 

maple-leaf-mines-b

 

In the photograph, the boxfolds are unrolled and flattened to show how the green tissue has been scraped away by the tiny caterpillars’ mandibles. I have found both species on both study areas, and also two more members of the same family, Cameraria saccharella and Phyllonorycter clemensella. Cameraria form irregular blotch mines on the upper surfaces of the leaves, and Phyllonorycter produce tent-like mines on the under surfaces. I have not reared adults or identified larvae from the fourth mine type, a distinctive linear mine form, but it likely is the exotic (European) Stigmella aceris, of the moth family Nepticulidae.

 

There are a lot of questions that can be addressed in a system like this. For example:

  • Do the leaf mining species interact in such a way that they either avoid one another, occupying separate leaves as a rule, or do they congregate, clustering onto particularly attractive leaves?
  • These two study areas are separated by many miles of suburbs. Do the populations of the leaf mining species go up and down together on the different study areas (which might reflect responses to climate as it varies between years), or do they fluctuate independently (which might indicate biological regulation of populations)?
  • How does restoration management practice affect these organisms?
  • Do the moths have the same impact on the canopies of large trees as they have in the understory?

 

I’ll address these questions in future posts.

 

Mystery plant with blotch mine: did you recognize it as a rare, 4-leafleted poison ivy leaf? Probably most would regard this as less lucky than a four-leaf clover.

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