This is the time of year when two-year-old beavers leave their lodges and strike out on their own, primarily because the woods surrounding a pond usually can’t support more than one family of beavers. Beavers are exceptionally territorial; once they’ve established a lodge, they do not take kindly to interlopers. In order to make this perfectly clear to house-hunting young beavers, in the spring resident beavers build what are called scent mounds — piles (up to three feet in height, but usually much smaller) of mud, leaves and pond-bottom debris — around the perimeter of their territory. They then smear castoreum, a substance that comes from their castor sacs, over the mound. Chemicals in the castoreum convey to roaming young beavers that this particular pond is spoken for.
It’s possible that this chipmunk is preparing a nesting chamber in her underground burrow, judging from the amount of dirt that is on her. Sometime between February and early April chipmunks mate. Roughly a month later they give birth to 3 to 5 young in a bulky nest of leaves inside a 24” x 15” x 10” chamber. Within a week, hair and stripes will be evident on the young chipmunks. In about a month, they will venture out of the burrow, looking like small adults.
A study of coyote prey (through stomach contents) in the Adirondack Mountains of New York revealed that beavers were second only to white-tailed deer. This photograph shows that, possibly for the last time this winter, a coyote recently took advantage of a still-frozen-but-fast-thawing pond by walking across it in an attempt to reach an active beaver lodge. Once there the coyote attempted to dig into it in order to reach the inhabitants. A hard, two-to three-foot-thick wall of frozen mud, logs and sticks kept the beavers well protected, as it was designed to.
The queen is the only wasp in a colony to live through the winter (the others all die), and she usually does so in a sheltered spot such as a rotting log or under the loose bark of a tree (pictured). I wasn’t aware, until discovering this wasp, that queens actually chew a cavity in which to hibernate, but that appears to be the case in some instances. You can see the woody bits of fiber under the wasp that accumulated from her excavating the chamber. The cavity is roughly one inch long and ¼-inch deep. As a rule, hibernating queen wasps protect their wings and antennae by tucking them under their bodies. Some species produce glycerol, which acts as an antifreeze, while others allow ice to form around their cell walls and simply freeze solid. Most queen wasps die over the winter, primarily from predation by other insects and spiders, not the cold. (The pictured wasp had succumbed.) Warm winters are more likely to affect queens, as they emerge from hibernation too soon and starve due to lack of food.
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!)
There are basically two groups of wasps: 1) social wasps, such as hornets, yellowjackets and paper wasps and 2) solitary wasps, species that live solitary lives and typically hunt prey for their larvae (the adults consume nectar). Mud daubers are a type of solitary wasp. Organ Pipe Mud Daubers builds cell out of mud in which they put prey (usually spiders) that they have stung and paralyzed, but not killed. They then lay an egg on top of the spiders, and seal the cell. After the egg hatches, the larval wasp consumes the still-fresh spiders, pupates, emerges as an adult wasp and chews its way out of the cell. In this picture a female Organ Pipe Mud Dauber wasp has collected a ball of mud and is applying it to the most recent cell she is making. The name “organ pipe” comes from the shape of the “pipes”, which consist of several cells, placed end-to-end, with the most recent cell at the bottom. (Notice the new, wet mud is darker in color.)
At the risk of boring readers, I wanted to include one final Leafcutter Bee post, showing the two basic shapes that these bees chew out of leaves in order to make their incubator/nursery cells. There are oblong pieces, roughly an inch long, as well as perfectly round, ¼-inch diameter pieces. Each cell consists of several layers of oblong pieces rolled lengthwise which are sealed at one end with a round piece of leaf. The round end pieces appear to be glued into place (perhaps with the pollen/nectar mixture?) at one end of the cell, leaving the opposite end open. The cells are arranged end-to-end, with the open end of the cell placed against the sealed end of the next cell. Together they form a nest that is somewhat cigar-shaped and is typically located a few inches down in the soil, or in a cavity.
In New England, Dark-eyed Juncos typically have two broods in a summer. The second-brood nest in the photograph contains the first of probably four or five eggs which are laid one day at a time. The egg lies on a soft lining made from the hair of a White-tailed Deer. Unlike most songbirds, Dark-eyed Juncos build their nests in a wide variety of sites, from the ground up to eight feet high in trees. Often they are in a small cavity on a sloping bank (well hidden by surrounding grass), under a protruding rock or among tree roots. But they’ve also been found under fallen tree trunks, on supports underneath houses on stilts, in barns or lofts between hay bales, in vines on the sides of buildings, on window ledges and light fixtures and in hanging flower pots. It’s not unheard of to find a Dark-eyed Juncos relining the old nest of an American Robin.
Great Blue Heron chicks are getting big enough so that you can easily observe them (can you find all four?). Occasionally you can even detect flies and other insects buzzing about them, which, given the fact that nest sanitation is not a priority for herons, is not surprising. While the parents do toss the eggshells out of the nest, feces, partly eaten prey and even dead chicks often remain in the nest. Also, parents feed their young by regurgitating into the nest and the chicks will regurgitate when disturbed. Unlike most song birds, Great Blue Herons re-use their nest year after year. It is quickly apparent why they add more sticks and boughs to their nest every breeding season – were that housekeeping for humans was that simple!
The nesting habits of Cliff Swallows are fairly unusual in that these swallows are colonial nesters. Here in the East you can find 20 or 30 of their nests under a bridge or the eaves of a barn (and occasionally on cliffs). In the West, colonies consist of up to 3,500 nests! The construction of their gourd-shaped nest requires between 900 and 1,200 trips to mud puddles or stream banks, where they gather a mouthful of mud in the form of a pellet. Often two swallows will build nests side-by-side, sharing the wall of mud that separates them. Unfortunately, according to the most recent Vermont Breeding Bird Atlas, the Cliff Swallow population in Vermont has declined by 48% in the past 25 years, a fact which is attributed to competition with House Sparrows, a decline in insects due to diminishing farm land, and destruction of nests by humans. These birds are more important insect predators than ever, with the bat population having suffered such a decline recently due to white-nose syndrome.
Rarely do you see or hear about honeybees attempting to construct a hive outdoors that isn’t inside a hollow “bee tree” or in a rock crevice. Occasionally they do attempt it, but as the empty cells in this exposed comb attest to, honeybees aren’t likely to make it through a Vermont winter without some shelter for their hive, even a winter as mild as the one we just experienced.
Porcupines leave plenty of signs where they have eaten the inner bark, or cambium layer, of a tree. Bark is missing on the trunk of the tree, leaving fresh, yellow wood exposed, which often bears incisor marks. An observation I have made over the years is that porcupines often de-bark around or near their hollow tree dens. Typically, if a tree den is used year after year, they gnaw off bark each year, sometimes eating the old, scarred portion which, due to previous chewing, lacks cambium cells. This has led me to wonder whether fresh de-barking in the vicinity of their tree den entrance might have more, or as much, to do with a porcupine’s staking out a claim on that tree than with its sustenance. I have never come across any research that even mentions this phenomenon, and would welcome feedback from anyone who has.
12-3-11 Larvae-seeking Downy Woodpeckers
Beavers, like many mammals, communicate with chemical signals. In scent marking, beavers actually build a mound of mud on which to place their scent. First they dive down to the bottom of their pond, dig up an armful of mud with their front feet and swim to shore with the mud held against their chest. Walking on to the shore on its two front legs, the beaver deposits this mud next to the water. Beaver scent mounds can be quite small, or as high as three feet or more, depending on how many loads of mud they contain. The beaver straddles this pile of mud and applies castoreum from its castor glands, or anal gland secretions, or both. The purpose of building a mound is to elevate the odor (helps with scent dispersal), to intensify the odor by putting it on a moist substrate, and to protect it from flooding when the pond level fluctuates. Beavers build most of their scent mounds in the spring, when young beavers are dispersing and claiming new ponds, but I have found several fresh ones this fall, including the one in the photograph. (Click on photo to enlarge.)
Like the majority of songbirds, American goldfinches use their nest only once – to raise one brood — and do not return to it after their young have fledged. This time of year, when leaves have fallen off of shrubs and trees, is a great time to try and locate where birds you saw all summer nested. Just as each species of bird has its own song, each species of bird builds a nest unlike those of other species. By noting the habitat in which it’s built, the material with which it was built, and the dimensions of a nest, it is often possible to determine the species of bird that constructed it. Female American goldfinches build a very neat nest composed of plant fibers, and line it with the down of cattails or thistles. The walls are quite thick, making it quite durable – the nest in the photograph even withstood the wind and rain that Irene delivered this fall. While it’s fun to hunt for nests, bear in mind that you need a federal permit to collect them.
If you find a football-size (or larger), gray, papery structure attached to the branches of a tree or shrub, you’ve probably discovered the nest of a bald-faced hornet. (The only other hornets that build a similar nest are aerial hornets, and their nests usually have wider strips, and less of a scalloped appearance than those of bald-faced hornets.) This structure is actually a nursery, filled with several horizontal layers of hexagonal cells, in which eggs are laid and larvae are raised. These horizontal layers are surrounded by a multi-layered envelope, which, like the cells, is made of masticated wood fiber from weathered wood such as fence posts and hornet saliva. The different colors reflect the different sources of wood that have been used. Although only the queen bald-faced hornet survives over winter (in a rotting log or other protected spot), the workers do not die until freezing temperatures have really set in, so wait for another month before approaching a nest!