Great Blue Heron “Powder Down”
Hidden beneath the outer breast feathers of Great Blue Herons are patches of special down feathers. These feathers grow continuously and are never molted. When combed with the fringed, or pectinated, claw on a Great Blue Heron’s middle toe, the tips of these feathers break down into a dust the consistency of talcum powder. The heron collects some of this “powder down” and applies it to its feathers which protects them against fish slime and other oils. (BirdNote)
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Nictitating Membranes
Sometimes referred to as a “third eyelid,” the translucent nictitating membrane visible across this juvenile Black-crowned Night Heron’s eye serves to protect it from foreign objects and to moisten the eye while at the same time allowing the bird to retain some degree of visibility. It extends from the inner corner of the eye to the outer corner, and is drawn across the eye much like a windshield wiper. The membrane is thinner and more transparent than the fleshier upper and lower eyelids and is used periodically by birds when foraging, flying, diving, feeding young, gathering nesting material, etc. In this case, the heron’s nictitating membrane was drawn across its eye seconds before it plunged beneath the surface of the water to capture a crayfish.
Birds aren’t the only animals that possess nictitating membranes – it’s relatively common in fish, amphibians, reptiles, and mammals (but they are rare in primates).
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A Monarch’s First Instar
Monarchs, like other butterflies and moths, undergo complete metamorphosis — they have an egg, larva (caterpillar), pupa (chrysalis), and adult stage. During a monarch’s larval stage it eats almost constantly, pausing only to shed its skin. The period between each shedding of the skin, or molt, is called an instar. Monarchs have five larval instars and during their larval stage grow to almost 2,000 times their original mass.
The first meal a monarch larva has is its eggshell and it quickly moves on to milkweed leaf hairs. Soon thereafter it begins to eat the leaf in earnest, often making an arc-shaped cutting.
During this first instar, which typically lasts one to three days, the larva’s appearance changes considerably. When it hatches, the monarch larva is pale green or grayish-white, shiny, and almost translucent. It has no stripes or other markings. It’s about 2 mm long, with front tentacles appearing as tiny little bumps. Its back tentacles are barely visible. By the end of the first instar it begins to have a pattern of black (or dark brown), yellow and white bands, and the 6mm-long body no longer looks transparent and shiny.
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Gray Treefrogs’ Self-cleaning Toe Pads
Scientists have discovered that the angle of the toe pads and a secretion of mucus are involved in a treefrog’s ability to stick to wet, smooth leaves, rough, dry trees and other surfaces. They also allow the toes to “self-clean.”
To make their feet sticky treefrogs secrete mucus. They increase their adhesion by moving their feet against the surface of what they are clinging to in order to create friction. As a frog moves across a surface, its feet accumulate dirt, which impedes its ability to stick to the surface it’s walking on. Scientists have discovered that the mucus combined with this friction-creating movement not only allows the frog to adhere to the surface but simultaneously rids their feet of accumulated dirt and debris as they walk.
This remarkable adaptation may provide a design for self-cleaning sticky surfaces, which could be useful for a wide range of products, especially in contaminating environments such as medical bandages and long-lasting adhesives. (Thanks to Janice Perry for photo opportunity.)
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Common Green Darners Mating & Laying Eggs
Darners are a family of dragonflies whose members are quite large (some over three inches in length). Common Green Darners (Anax junius) are one of only two darners in the Northeast with an entirely green thorax (section between head and abdomen). Often you find them perching low in grasses and weeds. Males tend to fly along the shorelines of ponds, patrolling for females and keeping other males at bay.
After mating takes place, the males of some species of dragonflies disappear. In other species, the male stays nearby, guarding the female and fending off other males that might remove the initial suitor’s sperm and replace it with their own. Some species go to the extreme of remaining attached to each other while egg-laying takes place. Common Green Darners are the only species of darner that often lays in this manner – in tandem, with the male still clasping the female while she submerges her abdomen and lays her eggs in aquatic vegetation (pictured).
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Berkeley’s Polypore Fruiting
Polypores are a group of fungi that bear their spores in tubes, or pores, rather than gills. One of the largest mushrooms to fruit on living trees is Berkeley’s Polypore (Bondarzewia berkeleyi), often found on hardwoods, especially on oak trees. Its growth is unusual in both size and form. When the fruiting body starts to emerge, it resembles a giant hand with short, fat fingers. The tips of the “fingers” expand into huge, flat, fan-like shapes up to ten inches wide that together form an irregular rosette. The rosette can be more than three feet across and can weigh up to 30 pounds.
You usually find this fungus at the base of trees, but it can fruit from the ground far from any tree if there are roots or the remnants of an old stump beneath the ground, for it is saprophytic (lives on dead or decaying trees) as well as parasitic.
Berkeley’s Polypore is edible when it is young. With age, the fruiting body becomes increasingly tough and has been compared to eating cardboard. It goes without saying that one should be sure of the identity of any fungus before consuming it. (Photo of Berkeley’s Polypore & Leo Clifford by Lawrence Clifford.)
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The Surprisingly Varied Diet of Beavers
It is common knowledge that beavers are herbivorous but the extent of their herbivory is not always appreciated. Examining their skull would tell you that their massive four front incisors (as well as the muscles attached to their jaws) are designed to do some serious chewing. And serious chewing does take place, especially in the fall. Poplars, birches, alders, willows, maples and many other deciduous trees as well as a few conifers are felled in order to reach and consume the inner bark, or cambium layer. (The de-barked logs and branches are subsequently used to repair dams and lodges). Not only do Beavers need to meet their daily nutritional needs but they must cut enough trees to last them through the winter.
However as spring approaches and they can access land, their diet changes from the woody branches they’ve been eating all winter (from their winter food pile under the water) to a diet that consists mainly of herbaceous plants. Ninety percent of their time is spent eating non-woody plants, often skunk cabbage, water lily rhizomes and grasses in the early spring. As summer progresses, they seek out aquatic plants, ferns, sedges and a variety of flowering plants. Usually it’s not until late summer/early fall that their incisors are once again given a good workout.
The pictured Beaver had the good fortune of having a large patch of tasty Jewelweed (Impatiens capensis) growing on and adjacent to its lodge.
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Black-crowned Night Herons: Not Your Typical Heron
When you think of a heron, you usually think of a diurnal wading bird that has long legs, a long neck and a long bill. Black-crowned Night Herons don’t possess any of these familial characteristics. Stocky and relatively short-legged and short-billed, these herons typically rest during the day and start actively hunting at dusk, continuing through the night.
Prey includes fish (half their diet) plus a wide range of other creatures including leeches, earthworms, insects, crayfish, snakes, turtles, small mammals, birds and frogs. The manner in which a Black-crowned Night Heron lures and captures its prey varies. Two of its most intriguing fishing techniques include bill vibrating (opening and closing its bill rapidly in the water to attract prey) and bait fishing – using bait to attract fish.
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Chirping Thermometers
The evenly-spaced chirping notes of the male Snowy Tree Cricket (Oecanthus fultoni) greet our ears nightly at this time of year. Named for its pale color and tendency to be found in trees, vines and shrubs, this cricket is well known for its ability to convey the temperature to anyone who can count the number of chirps it makes in 14 seconds. Add “40” to this number and you know how hot or cold the evening is in degrees Fahrenheit. The relationship between the air temperature and the rate at which crickets chirp is called Dolbear’s Law.
Crickets make chirps (stridulate) by rubbing a structure on the top of one forewing wing (scraper) against wrinkles (file) on the underside of the other forewing. To find a Snowy Tree Cricket that is stridulating, check the underside of branches and leaves. A living thermometer awaits you there.
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Mink’s Cubs
One last update, as so many readers have inquired about the welfare of Mink’s three cubs. They have been sighted several times, traveling apart from one another. One cub has been spotted more than once, but not captured, at someone’s bird feeder. Efforts (game cameras and bait food) are being made to lure and capture them after which they will be brought to the Kilham Bear Center in Lyme, NH where they will be fed and cared for and eventually released into the wild.
Mink’s cubs are about 8 months old and weigh between 25 and 35 pounds. Black Bear cubs typically stay with their mother until they are 18 months old, at which time they are weaned and on their own. Cubs as young as five months old have survived the loss of their mother, so one can only hope that, if not caught and raised by humans, Mink’s cubs will be as fortunate.
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Mink Update
I wanted to update everyone on Mink, the deceased Black Bear in New Hampshire, as more information regarding her death has been released. Biologists now think she may have died of natural causes. From the condition of her teeth they have determined that she wasn’t in her teens, as previously thought, but between 20 and 30 years old. That is the normal life span of a Black Bear. Her death is still very sad, but perhaps a little easier to accept if humans were not involved.
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A Tribute To A Grande Dame
This week I learned of the death of an old acquaintance. Mink, a Black Bear whom I’ve photographed numerous times with numerous batches of cubs, was found dead on the banks of a river in New Hampshire, close to where she had lived for many years. If you’ve read my children’s book, Yodel the Yearling, you’ve met one of her offspring.
Mink was an extraordinary mother — sending her cubs up a giant White Pine tree whenever danger threatened, tolerating with unbelievable patience being climbed on and bitten by her cubs, grooming burs out of the coats of rambunctious offspring with her teeth and much, much more. She was so acclimated to people (having raised many cubs within sight of houses) she allowed me to witness her nursing her cubs multiple times (see NC post, 4/4/18).
Four years ago I stumbled upon Mink and her three yearling cubs sleeping at the base of a “baby sitter” tree. Since then they have had a life of turmoil, having been transported to the wilds of northern New Hampshire due to becoming “pests” where they lived because people left their garbage and bird feeders accessible during times of the year when bears are active. Mink managed to find her way back to her home territory and was raising the three young cubs she bore last winter when she met her untimely death, most likely as a result of being hit by a car. I couldn’t let her passing go by without a nod to her and the richness she added to so many peoples’ lives. I, for one, shall forever be indebted to her for tolerating my presence and allowing me to observe and photograph ursine behavior in the wild so few are privileged to see. (Photo: Mink & one of her three cubs, taken 4/24/20, soon after emerging from winter natal den)
Cabbage Whites Mating
Cabbage White butterflies (Pieris rapae) are seemingly common, rather ordinary and unremarkable butterflies. That is, until you become acquainted more intimately with their reproductive idiosyncracies. The male’s sperm, along with a nutritious snack, is contained within a package called a spermatophore. It is the size of the spermatophore that defies belief, as it makes up 13 percent of the male’s body weight. Translated into human terms, a 150 male would possess a 20-pound package of sperm.
The male Cabbage White deposits its spermatophore into a pouch within the female’s reproductive tract and the sperm proceed to swim to a second pouch where they are used to fertilize the female’s eggs. The female absorbs the nutrients that accompanied the sperm and uses them to make approximately half the eggs she lays.
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Eastern Garter Snakes Giving Birth
Seventy percent of the world’s snakes lay eggs and only about thirty percent give birth to live young. Eastern Garter Snakes (Thamnophis sirtalis sirtalis) are among the latter, giving birth in August to between two and thirty-one offspring (averaging 23). Carrying and incubating developing embryos within their body is more common for northern snakes and there is good reason for this. Whereas eggs are subject to whatever temperature fluctuations occur where they were laid, a snake that carries her young to term within her is able to move to warm areas that are ideal incubation temperatures. This causes less stress for the developing embryos and also results in a greater number of viable young.
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Male Walkingstick Cerci
Congratulations to Sharon Weizenbaum, Beth Herr and David Ascher for correctly identifying the Mystery Photo as the tip of the abdomen of a Common Walkingstick (Diapheromera femorata), also known as Devil’s Darning Needle, Devil’s/Witch’s Riding Horse, and Prairie Alligator due to its unusual shape. While the Common Walkingstick is a mere 3” long, the largest North American species can grow to 7” and one tropical species may reach 14”.
The Walkingstick lives up to its name – it is easily mistaken for a twig with its slender body and legs. By remaining motionless during the day (or gently swaying in the wind like a leaf or twig would), and feeding on the leaves of various deciduous trees at night it avoids many predators with its physical and behavioral adaptations. The practice of using both camouflage and mimicry is referred to as crypsis.
Both the male and female Walkingstick possess a pair of appendages at the tip of their abdomen known as cerci. The cerci on a female are short and straight, while those on the male are longer and curved. They are sensory organs, but in addition, the male uses his cerci to grasp the female when mating with her (see inset). According to entomologist Dr. Gilbert Waldbauer, the cerci are very effective, allowing the male Walkingstick to clasp the female for many hours (weeks for some species) in order to prevent another male from mating with the female.
This is the time of year you are most likely to notice Walkingsticks, as this is when they are maturing and reproducing. Females drop their eggs to the ground from the canopy and because a portion of the outside (capitulum) of each egg is edible (like the elaiosomes of many spring ephemerals), ants carry the eggs below-ground to their nests and eat the capitulum, leaving the intact eggs to hatch and develop.
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Praying Mantises Preying
Between being able to swivel its head nearly 180 degrees and having two large compound eyes and three simple eyes, the Praying Mantis (Mantis religiosa) misses very few insects within reach. Due to its green or brown coloration, the Praying Mantis is well camouflaged as it lies in ambush or stalks its prey. Spines, tooth-like tubercles and a claw near the tip of each foreleg enable this predator to have a secure grasp on the moths, crickets, grasshoppers, flies, and other insects it consumes. (A Praying Mantis in Pennsylvania was photographed successfully capturing a Ruby-throated Hummingbird.)
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Milkweed Leaf Beetle Survival Mechanism
Many insects use splashy colors and color patterns to defend against being eaten. (This practice is called “aposematism” from the Greek for “away” and “sign.”) If you spend time in a milkweed patch, you’ll notice that several of the insects you see have bright orange and black coloration. Milkweed contains defensive chemicals known as cardiac glycosides and Monarchs as well as several other insects (many of which are black and orange) that feed on milkweed can tolerate them and store these chemicals as a defense. When avian predators consume a Monarch butterfly containing these chemicals, a bird suffers digestive upset.
Once a bird has gotten sick after eating a poisonous black and orange insect such as a Monarch, it tends to avoid any and all insects with similar coloration, regardless of their toxicity or lack of it. Milkweed Leaf Beetle larvae and adults do not absorb the cardiac glycosides in milkweed like a Monarch, so they have no toxic compounds in them and will not poison a predator. Insect-eating birds don’t know this, however, and the beetles successfully deter predation through their coloration.
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Green Herons’ Versatile Necks
Most of the time Green Herons appear to be stout, compact herons. When perched or stalking, they tuck their neck into the contours of their body and appear quite small (see inset). Only when threatened or when striking prey is the true length of a Green Heron’s neck revealed. If startled, a Green Heron will stretch its neck way out, most likely in order to appear large and formidable to a potential predator. When hunting for prey, it can extend its neck an inordinate distance (see photo). A specialized vertebra in their neck enables them to strike at prey with a tremendous amount of force. Some scientists compare the Green Heron’s extendible neck to that of certain dinosaurs, from which they are thought to have evolved.
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White-blotched Heterocampa Caterpillars On The Move
It’s hard to believe, but this fuschia-colored caterpillar is going to emerge from its cocoon next spring as a relatively dull black and white moth called the White-blotched Heterocampa (Heterocampa umbrata). These caterpillars have two shiny knobs behind their head which are the remnants of “antlers” that the caterpillars have during their first instar. White-blotched Heterocampa larvae change color as they mature and develop. At any given stage, a caterpillar could be purple and fuchsia, or brown and tan or green and white; it is not unusual for them to be mistaken for three different species. The caterpillars can be found feeding on oak leaves. Look for the adult woodland moths at night, when they are attracted to lights. (Thanks to Lily Piper Brown who found two of these amazing caterpillars recently, and her mother, Sadie Brown, who photographed this one.)
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Ruby-throated Hummingbirds Pollinating Cardinal Flower
Cardinal Flowers are to Ruby-throated Hummingbirds what Goldenrod is to Honey Bees in the fall — an important source of nutrients just when it’s needed most. Just as hummingbirds are preparing for their migration south and nearly doubling their weight (from about 3.25 grams to 6 grams) before crossing the Gulf of Mexico, Cardinal Flower blossoms. A single migration can mean a nonstop flight of up to 500 miles over a period of 18 to 22 hours and nectar such as they obtain from Cardinal Flower helps sustain them. This relationship is not one-sided however – it is mutually beneficial for both the bird and the plant. In acquiring nectar from the blossoms of Cardinal Flower, hummingbirds inadvertently perform a crucial task, that of pollinating many of the flowers they visit.
The blossoms of Cardinal Flower have two phases. In one the male reproductive part of the flower (the white “moustache” you see above the petals) matures and produces pollen. After the male structure matures and disappears, the female reproductive part develops and extends out from the same place where the male flower was. The flower parts mature at different times in different flowers on a given stalk, so both male and female flowers are present on the same plant at the same time. In order to reach the nectar from Cardinal Flower, a hummingbird must get into a position where the top of its head brushes against the flower’s reproductive parts. If the flower is in the male phase the hummingbird’s head gets dusted with pollen (see inset). If the flower it visits is in the female phase, the pollen on its head (from previous visits to male flowers) is deposited on the stigma of a female flower, pollinating the flower.
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Luna Moth Caterpillars
The large, green swallow-tailed moth known as the Luna Moth (Actias luna) is familiar to many. Its short life of about a week begins in June when it emerges from its cocoon, mates, lays eggs and then dies. The larval stage of this giant silk moth is not as well known, but has just as striking an appearance as the adult moth. It is an unforgettable lime-green with tiny magenta spots along its length.
When threatened by a predator, Luna Moth caterpillars have several defensive behaviors, including emitting clicks as a warning and regurgitating the contents of their intestine, both of which have proved to be effective deterrents. Look for these caterpillars on their host trees which include birch, hickory and walnut. (Thanks to Susan and Dean Greenberg for photo op.)
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Juvenile Common Loons Molting For A Second Time
When Common Loon chicks first hatch, they are covered with down and look like sooty black puffballs. These feathers are pushed out when the loons are 10 to 14 days old by a second plumage of brownish-gray down feathers. When the young are about a month old, these feathers start to be replaced by juvenal contour feathers. By the time the young loons are 10 or 11 weeks old, their down feathers are mostly gone and their juvenal plumage is nearly complete. This plumage is very similar to the winter plumage of adult loons. You can tell the difference between the two by the whitish-gray tips of the juveniles’ feathers, which the adults lack. (Pictured juvenile loon is about seven weeks old, showing remnants of the second down plumage.)
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Mystery Photo: Bald Eagle or Osprey Pellet
Congratulations to Jill Osgood (“osgoodjill”), the first reader to correctly identify the pellet of either a Bald Eagle or an Osprey. Many people are familiar with bird pellets – lumps of material consisting of the indigestible parts of a bird’s diet which are regurgitated by the bird hours after they’ve eaten their prey. Raptors often consume their prey whole, including parts that are not easily digestible such as fur, feathers, bones, teeth, nails, etc. These parts get as far as the proventriculus, an organ located between the esophagus and the gizzard, where they are packed into a pellet.
We often associate pellets with owls, but many species of birds, in addition to owls and other birds of prey, form pellets. They include grebes, herons, cormorants, gulls, terns, kingfishers, crows, jays, dippers, shrikes, swallows, and most shorebirds. The size of the Mystery Photo pellet (3” long) indicates that the bird that regurgitated it was very large – in general, the larger the bird, the larger the pellet. It was found near the shore of Lake Champlain, where Ospreys and Bald Eagles are not uncommon.
If I had to, I would guess the pellet was regurgitated by a Bald Eagle. Osprey are piscivores, eating primarily fish, and bald eagles are carnivores, eating a variety of fish, mammals and amphibians. A close look at the pellet reveals, in addition to fur and fish scales, the upper mandible of a very small rodent on the left hand end of the pellet. An Osprey’s pellets consist of primarily scales and bones, whereas a Bald Eagle’s pellets are composed primarily of hair (its stomach acid breaks down the bones and scales).
Twelve to eighteen hours after consuming prey, a Bald Eagle casts a pellet. Relatively odorless and light-weight, these pelleted remains can reveal the varied diet of this raptor.
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Bald-faced Hornet Queens Laying Specialized Eggs
A Bald-faced Hornet colony begins in the spring when a queen emerges from winter hibernation. The queen builds a small nest, creates a few brood cells within the nest, deposits eggs in them and feeds the larvae when they hatch. These larvae are female workers — they will continue the nest building, food collection, feeding the larvae and protecting the nest while the queen concentrates on laying eggs.
During the summer the colony (and size of the nest) grows until there are between 100 to 400 workers. Toward the end of the summer the queen lays two special types of eggs. The first will be, like the workers’ eggs, fertilized eggs that will develop into females, but these females will be fertile (and develop into queens). The second group of eggs will be unfertilized eggs. These eggs will develop into fertile males. The maturation and emergence of the new queens and the fertile males marks the end of the functioning of the colony. At this point the workers are not replaced and die out. The ruling queen, having served her purpose, also dies. The newly-emerged adults (queens and fertilized males) leave the nest, mate, and the fertilized queens overwinter and begin their colony cycle all over again in the following spring. Some small nests complete their cycle by mid-September, while some large nests are still going strong until the cold kills the larvae in late November.
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