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Archive for November, 2012

White-tailed Deer Diet & Digestion

11-30-12 deer eating IMG_6035A white-tailed deer’s diet consists of a wide variety of herbaceous and woody plants, the ratio of one to the other being determined by the season. Fungi, fruits and herbaceous plants form much of the summer diet. Dried leaves and grasses, acorns, beechnuts and woody browse are important autumn and early winter food. After snowfall, the winter diet consists mostly of woody browse (twigs, leaves, shoots and buds) from many different trees (maples, birches and cedars among them). Come spring, deer eat buds, twigs and emerging leaves. Deer are ruminants (as are cattle, goats, sheep and moose). They have a four-chambered stomach, which is necessary in order to digest the cellulose in the vegetation they consume. Food goes first to the rumen, the first of the four chambers, which contains bacteria and other microorganisms that help digest the cellulose. Food is circulated from the rumen back to the deer’s mouth by the second chamber, or reticulum, and the deer ruminates (“chews its cud”). The third chamber, or omasum, functions as a pump, sending the food to the final chamber, the abomasum, where the digestion process is completed.


Renovated Bird Nests

Most songbirds only use their nest once. After their young have fledged, the nest is usually abandoned. In the natural world, recycling has been a way of life for a long time, and abandoned bird nests are not about to be wasted. In the spring, the material used in old nests is often re-used by birds building new nests. But long before this occurs, white-footed mice and deer mice, both of which remain active year round, often use old nests as larders where they store food for the winter. Occasionally they even renovate a nest in the fall in order to make a snug, winter home. They do this by constructing a roof (of milkweed fluff in this photograph) over the nest, which serves to insulate it. Use caution if you come upon such a nest– it could well be inhabited! (Thanks to Sara and Warren Demont for the photo op!)


Great Cormorant

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Recently a young, coastal, avian visitor strayed inland — the Great Cormorant, largest of all six species of cormorants in North America. It has the widest range of all the cormorants, breeding in Europe, Asia, Africa, and Australia, as well as North America. Typically Great Cormorants overwinter along the eastern U.S. and Canadian coasts (and breed from Maine north to western Greenland), but this juvenile bird somehow ended up in central Vermont. It is often confused with its close relative, the Double-crested Cormorant, but it is considerably larger, has a heavier bill and there are subtle plumage differences.  In China (mostly for tourism these days) they actually capitalize on the Great Cormorant’s ability to catch large fish by using it to catch fish commercially.  A snare of some sort is tied around the bottom of the cormorant’s neck, allowing it to eat small fish that it catches, but preventing it from swallowing any large fish.  After the cormorant catches a sizeable fish, it is brought back to the boat and spits up the fish that is in its throat.


Mice vs. Voles

Mice and voles are commonly lumped together, probably because the differences between them are so slight.  Both are small, furry rodents, but mice generally have large eyes, large ears and long tails (close to or greater than the length of their bodies).  Voles have smaller eyes, smaller ears (often concealed in their fur), and shorter tails.  Voles tend to be active day and night, whereas mice are mainly nocturnal. ( Meadow voles are commonly referred to as “field mice,” which tends to add to the confusion regarding these two groups of mammals!)  There are five species of mice in New England (white-footed, deer, house, meadow jumping and woodland jumping), and four species of voles (meadow, southern red-backed, rock and woodland).


Meadow Vole Trail

Thanks to a dusting of snow we are suddenly privy to the comings and goings of the creatures we live amongst. Some animals are small enough to remain hidden once winter snows arrive, because they live in the subnivean layer between the surface of the ground and the snow.  But when the snow is too shallow for them to create this network of tunnels, their movements are easily discernible.  The pictured meadow vole trail shows where the vole initially tried (unsuccessfully) to tunnel under the snow (it wasn’t deep enough), at the bottom of the photograph.  It then scampered over the grass until it stopped to rest for a moment, leaving a whole body imprint, including its short tail. It’s fairly unusual to see the entire body print of small rodents such as voles and mice, for they are so vulnerable out in the open that they rarely stop long enough to leave one.


A Great Christmas Present!

If you’re looking for a present for someone that will be used year round, year after year, Naturally Curious may just fit the bill.  A relative, a friend, your child’s school teacher – it’s the gift that keeps on giving to both young and old!

One reader wrote, “This is a unique book as far as I know. I have several naturalists’ books covering Vermont and the Northeast, and have seen nothing of this breadth, covered to this depth. So much interesting information about birds, amphibians, mammals, insects, plants. This would be useful to those in the mid-Atlantic, New York, and even wider geographic regions. The author gives a month-by-month look at what’s going on in the natural world, and so much of the information would simply be moved forward or back a month in other regions, but would still be relevant because of the wide overlap of species. Very readable. Couldn’t put it down. I consider myself pretty knowledgeable about the natural world, but there was much that was new to me in this book. I would have loved to have this to use as a text when I was teaching. Suitable for a wide range of ages.”

In a recent email to me a parent wrote, “Naturally Curious is our five year old’s unqualified f-a-v-o-r-I-t-e  book. He spends hours regularly returning to it to study it’s vivid pictures and have us read to him about all the different creatures. It is a ‘must have’ for any family with children living in New England…or for anyone that simply shares a love of the outdoors.”

I am a firm believer in fostering a love of nature in young children – the younger the better — but I admit that when I wrote Naturally Curious, I was writing it with adults in mind. It delights me no end to know that children don’t even need a grown-up middleman to enjoy it!


Beavers Ice-Bumping

Ice is starting to form on ponds, and days are numbered when beavers can be out grooming themselves on land or eating freshly-cut branches.  As long as the ice is thin enough to crack by swimming up under it and bumping their heads against it, they will do so, for soon it will be thick enough to lock them into their pond. Life under the ice is challenging.  At 32 degrees F. a beaver’s resistance to heat loss in water is about 1/8th of that in air at the same temperature. This is due to the fact that its fur is compressed in the water, allowing the insulating air between the hairs to escape — a beaver’s pelt accounts for about 24% of its total insulation in water and body fat is responsible for the rest.  Heat is also retained through a beaver’s tail and hind legs, which serve as heat exchangers.  In the summer, a beaver can lose 25% of its body heat through its tail, but it only loses 2% in winter. Even so, it’s no wonder beavers risk getting a headache in order to see the sun for the last time until spring.


Thimbleweed

Thimbleweed (Anemone cylindrica) shares a trait with moths and butterflies — the stages it goes through are so different that you wouldn’t even know they were related, much less the same plant.  Summer flowers are white and the late summer seed heads are green and thimble-shaped (hence, its name) and up to 1 ½” long. By fall the seed heads have transformed into cottony tufts containing tiny, scattered dark seeds which persist through the winter and are eventually dispersed by the wind.


Barred Owl Pellet

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Having posted a barred owl regurgitating a pellet, it only seemed fitting to post the pellet itself.  Many birds, not just birds of prey, form pellets that consist of the indigestible parts of prey they’ve eaten – fur, feathers, claws, teeth, fish scales, exoskeletons of insects and crustaceans and parts of plants.  In general, the larger the bird, the larger the pellet – the pellets of most birds of prey are an inch or two, and they’re roughly half an inch for a small songbird.  With birds of prey, likely spots to find pellets are beneath roosting and nesting sites.  In addition to getting rid of indigestible matter, the casting of pellets is thought to improve the health of a bird by scouring its throat, or gullet.  It takes anywhere from 6 to 16 hours after a hawk or owl has eaten for it to cast a pellet, and it may be necessary for the bird to do so before it eats its next meal.  Dissecting pellets is an effective way of determining a bird’s diet.  The pellet of a golden eagle in Oregon contained a leg band that had been placed on an American wigeon (a species of duck) about four months previously, a thousand miles away! (Pictured are a 1 1/2-inch barred owl pellet and the contents, minus the fur, of several pellets.)


Barred Owl Coughing Up Pellet

Roughly six to ten hours after consuming prey, owls, hawks and many other birds cough up a small pellet that consists of the indigestible bones, fur, etc. of the prey it’s eaten. The barred owl in this photograph was in the process of coughing up such a pellet. While pellets are hard to come by (they are well camouflaged on the forest floor), owls caught in the act of producing them are even more rare!


Ruffed Grouse Crop Contents

Some birds, especially those that eat seeds, buds, leaves and nuts, such as ruffed grouse, eat food very rapidly, faster than it can be passed through the digestive system.  These birds usually have a pouch-like crop where food is stored to be digested later, when the birds are not out in the open, susceptible to predators.  (see 10-24-12 Naturally Curious post)  This rapid consumption and storage of food by grouse, often at dawn and dusk, is referred to as “budding.”  Examining the contents of road-killed grouse crops is one way of learning more about this adaptive behavior.  Assuming some of my readers might (?) share my curiosity about the diet of grouse, I occasionally post the contents of a grouse crop I’ve recently examined.   My most recent dissection revealed that the grouse had switched from its herbaceous summer diet to its more woody winter diet — its crop contained no less than 232 male birch flower buds, or catkins.  (Disclaimer:  This crop was not that of the grouse that was the subject of the 11-9-12 post.)


Rub-urination

On the inside of the hind legs of all white-tailed deer are glands called tarsal glands.  They consist of a tuft of long hairs coming from an area of skin in which are located glands that secrete a fatty substance.  This fatty substance adheres to the long hairs.  When deer urinate, they often assume a crouched posture, causing their urine to run over these hairs.  The lipid, or fatty material, on the hairs causes some of the urine that runs over them to remain there. Excess urine is licked off by the deer. The combination of fatty material and urine gives the glands a unique smell (not the typical deer urine smell.) During the breeding season mature bucks urinate on the tarsal gland much more frequently, and don’t lick off the excess urine, which creates a distinctive rutting odor .  This practice is referred to as “rub-urination.”  All deer urinate on these glands throughout the year.


Finch Family Visitors

Members of the Finch family (Fringillidae) from farther north have begun showing up at feeders and fruit trees, as was predicted.   Pine siskins, evening grosbeaks, pine grosbeaks, common redpolls and even a few red crossbills have ventured down into southern New England in search of food.  The latest arrivals in the Upper Valley (VT/NH) were pine grosbeaks (male pictured).  The mountain-ash berry crop is spotty further north, so pine grosbeaks have come south in search of  European mountain-ash trees as well as ornamental crabapples. Invasive buckthorn redeems itself somewhat by producing berries that pine grosbeaks also find appealing.


Shaggy Mane

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Shaggy Mane, Coprinus comatus, is one of a group of mushrooms known as Inky Caps.  Both of these common names reflect the appearance of the mushroom at different stages of its development – the cap has white, shaggy scales, and as the mushroom matures its gills liquefy into a black substance that was once used as ink. Most Inky Caps have gills that are very thin and very close to one another, which does not allow for easy release of the spores.  In addition, the elongated shape of this mushroom does not allow for the spores to get caught in air currents as in most other mushrooms. The liquification/self-digestion process is actually a strategy to disperse spores more efficiently. The gills liquefy from the bottom up as the spores mature. Thus the cap peels up and away, and the maturing spores are always kept in the best position for catching wind currents. This continues until the entire fruiting body has turned into black ink.


Ruffed Grouse & Engines

Ruffed grouse, also known locally as partridge, are so well camouflaged that sometimes the only glimpse you get of them is when they explode right in front of you in an attempt to fly away from you. Occasionally, however, one will allow you more than a cursory look (and an opportunity to photograph it up close). This often happens when someone is running an engine, be it lawn mower, wood splitter or 4-wheeler. Upon hearing the sound, a grouse may walk rapidly towards it and linger in the vicinity for hours. Perhaps the occasional female grouse mistakes the sound of an engine for the alluring drumming of a male grouse, as the drumming sounds uncannily like a lawn mower starting up!


Bird Nest I.D.

Now that the leaves are off the deciduous trees, it is much easier to see where songbirds nested this past summer.  Just as every songbird species has a specific song unlike that of other species, each species also constructs nests that are very similar to each other, but not to other species’ nests. Thus, one American robin nest looks a lot like any other American robin nest – nests of one species are usually found in roughly the same kind of habitat, with the same dimensions and similar building materials. Sometimes there are key characteristics that help with identification – grape vines and a lining of rootlets told me a gray catbird built the nest in the photograph. (Plastic told me humans weren’t  far away.) Most songbirds only use their nest once; after the young have fledged, they abandon their nests.  Before the weather and/or critters recycle this year’s nests, take advantage of the opportunity to examine these gems of avian architecture up close. (A federal permit is needed in order to collect bird nests.)  A good book for nest identification is Peterson’s Field Guide to Bird Nests.


Black Bear Tracks

 

This may well be the last month until spring in which signs of active black bears can be found – cold temperatures and a poor beechnut and acorn crop may hasten their retreat into their dens.  A black bear’s track is fairly distinctive, if only due to its size: 3 ½”- 6” wide by 4”-9” long.  Black bears are flat-footed, or plantigrades, and thus you see more than just the toe imprints in a track; the heel pads of the hind feet are larger than those of the front feet.  Black bears have five toes on each foot. The smallest, outside toe often doesn’t register.  Long, curved nails on a black bear’s front feet are used for marking trees and climbing; the hind feet nails are much shorter.


Bruce Spanworm Moths Flying

If you’ve walked in New England woods recently, chances are great that you’ve noticed light tan moths with a one-inch wing span flitting about — an odd sight for this late in the year. These are male Bruce Spanworm Moths (Operophtera bruceata), also called Winter Moths, as the adults are active from October to December. They belong to the Geometer family of moths, the second largest family of moths in North America, which includes many agricultural and forest pests. The males are seeking wingless, and therefore flightless, females to mate with. Eggs are laid in the fall, hatch in the spring, the larvae pupate in the summer, and emerge as adult moths in the fall. Bruce Spanworm larvae periodically defoliate hardwood trees, preferring the buds and leaves of sugar maple, American beech and trembling aspen trees.


Cecropia Moth Cocoon

This past summer there seemed to be more giant silkmoths than usual, including Cecropia Moths (Hylaphora cecropia).  (see https://naturallycuriouswithmaryholland.wordpress.com/2012/06/04/cecropia-moth-2/ ). Assuming many of these moths bred and laid eggs, and that most of the larvae survived, there are probably a large number of Cecropia cocoons in our woods.  Even so, it is not an easy task to find them, as they are so well camouflaged, and are often mistaken for a dead leaf.  Cecropia caterpillars spin silk and fashion it into a three-inch long, tan cocoon (giant silkmoths make the largest cocoons in North America) which they attach lengthwise to a branch or stem.  There is a tough but thin layer of silk on the outside, which protects an inner, thicker and softer layer of silk on the inside.  The caterpillar enters the cocoon through loose valves it makes in both layers, which are located at the tip of the cocoon’s pointed end.  Shortly after the larva crawls inside both of these layers, it pupates.  Its skin splits, revealing a dark brown pupa. For the rest of the winter and most of the spring, it remains a pupa.  In early summer it metamorphoses into an adult moth and exits the cocoon through the same valves  through which it entered.

 


Japanese Knotweed

Most of those who guessed, guessed correctly – yesterday’s Mystery Photo was of the fruits of Japanese Knotweed (Polygonum cuspidatum), which reproduces both by spreading rhizomes (underground stems) as well as by seeds. Seed production, however, is not common, as the plants are unisexual, with male and female flowers on separate plants, and both are rarely found in the same colony.  The rhizomes don’t need much help, though, as they can survive temperatures of -31 degrees F. and can extend 23 feet horizontally and up to 10 feet deep. Small wonder that Japanese Knotweed, introduced as an ornamental, has thrived and out-competed native plants. Its delicate 3-winged, brown fruits belie the hardiness of this practically indestructible and invasive plant.


Mystery Photo

Do you know what plant produced these fruits?  All guesses welcome.  Tomorrow’s blog will tell you the answer!


Flying Squirrels Visiting Bird Feeders

Are you finding that the amount of seed in your bird feeders drops precipitously after dark?  Those of us in black bear country are advised to bring feeders in at night so as not to attract bears, but occasionally several hours of darkness have passed before I remember to do so.  When that happens, the feeders inevitably need filling.  What stealthy critter is visiting once the sun goes down?  Very possibly, flying squirrels are the culprits.  These nocturnal rodents can glide as far as 295 feet from tree to tree, or tree to ground.  They stretch their legs out and direct their glide by controlling the position of the flap of skin (patagium) that extends from the outside of the wrist on the front leg to the ankle of the hind leg on both sides of their body.  Their broad, flattened tail acts as a parachute, rudder, stabilizer and brake during the glide.  Feeders are rarely far enough from a tree to necessitate a glide – a short leap does the trick.  If you feed birds, try shining a light on your feeders after the sun goes down.  You may very well be treated to the sight of several flying squirrels helping themselves to your sunflower seeds and suet.