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Rabbit Ears: Double Duty

The first thing you notice about a rabbit is its oversized ears which, as one might guess, enhance its ability to hear. The two ears can move independently of each other and can be rotated 270 degrees.

In addition to being designed to catch sound from any direction, rabbit ears regulate a rabbit’s body temperature. There is a very extensive network of blood vessels in a rabbit’s ears that provide a large surface area for heat exchange. These vessels swell (vasodilation) when the rabbit is hot, and contract (vasoconstriction) when it is cool, so much so that they are barely visible in cold weather. In the summer, the increased circulation of warm blood from the body’s core to the rabbit’s ears, where heat is lost to the cooler surrounding air, provides internal air-conditioning for the rabbit. (Photo: Eastern Cottontail)

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Ebony Jewelwings

Damselflies, smaller and more delicate versions of dragonflies, are predatory aerial insects found near streams and wetlands. The male Ebony Jewelwing (Calopteryzx maculata) damselfly is aptly named.  Its pure black wings (the only dragonfly or damselfly in the Northeast with entirely black wings) and iridescent green head and abdomen are a striking combination.  The female lacks the iridescence of the male and its wings are dark but not quite black, with a distinct white spot (pterostigma) at the outer edge of both forewings. 

Ebony Jewelwings only live about two weeks.  During much of this time they can be found resting on leaves or branches in sunny spots of the forest, often near the slow-moving stream in which they spent their youth (most dragonfly and damselfly larvae are aquatic).

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Northern Mockingbirds Wing-flashing

Occasionally one comes across animal behavior that has yet to be understood by humans.  If you watch Northern Mockingbirds for any length of time, especially females, you are likely to see them stop and raise their wings half to fully open, in several progressively higher jerky movements.  When they do this, their white wing patches are fully exposed. 

Ornithologists are not of one mind as to what this behavior achieves. Perhaps it is anti-predator behavior – an attempt to scare would-be nest raiders away.  It could be a way of startling insects enough to make them move and thus easier to see and catch.  It also could be a form of territorial display/defense. Interestingly, mockingbird species that lack the white wing patches also engage in this behavior.

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Snapping Turtle Seeking Sandy Soil In Which To Lay Eggs

Monday’s Mystery Photo leaves no doubt that Naturally Curious readers are among the most informed nature interpreters out there. There were many correct answers, but congratulations go to Susan Cloutier, who was the first to identify the tracks and diagnostic wavy line left by the tail of a female Snapping Turtle as she traveled overland seeking sandy soil in which to lay her eggs. The turtle eventually found a suitable spot, dug several holes and chose one in which to deposit her roughly 30 eggs, covered them with soil and immediately headed back to her pond, leaving her young to fend for themselves if and when they survive to hatch in the fall.

Unfortunately, there is little guarantee that the eggs will survive. Skunks (the main predators), raccoons, foxes and mink have all been known to dig turtle eggs up within the first 24 hours of their being laid and eat them, leaving tell-tale scattered shells exposed on the ground. Fortunately, Snapping Turtles live at least 47 years, giving them multiple chances to have at least one successful nesting season. (Thanks to Chiho Kaneko and Jeffrey Hamelman for photo op.)

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Mystery Photo

Can you identify these tracks and traces?  Hint:  mostly seen in the month of June. Please go to the Naturally Curious blog site, scroll down to “Comments” and enter your answer. Identity of track-maker will be revealed in July 2nd post.

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Mourning Cloak Caterpillars Pupating

Having overwintered as an adult, the Mourning Cloak butterfly (Nymphalis antiopa) is one of the first butterflies seen in early spring.  Mating takes place and eggs are laid in a cluster encircling a twig of a willow, cottonwood, elm, birch or hackberry tree.  The hatching caterpillars stay together until they move off their host plant to pupate, which is what is happening right now and why you can find these distinctive spiny black and red caterpillars at this time of year. Adult Mourning Cloaks emerge in midsummer, enter a state of dormancy until fall and then seek a sheltered spot in which to hibernate until spring. 

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Parental Feeding Techniques of the Great Blue Heron

Great Blue Herons are colonial nesters – a rookery can have hundreds (up to 500) of nests, usually in dead snags, with one, two or three nests in a single snag.  Because the chicks are in the nest for roughly two months before fledging, their interactions with both parents, especially when food is delivered to the nest, has been observed and well documented.

Newly hatched chicks peck at the adult’s bill, the nest and each other. Initially the adult returns to the nest  where it stands on the rim and regurgitates food into the open bills of the chicks.  The chicks get quite proficient at grabbing the adult’s bill and pulling it into the nest as soon as the parent returns.  As the chicks age, the adult often regurgitates onto the floor of the nest and the chicks eat it.  When the nestlings are about a month old, they take food directly from their parents.

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Tadpoles Vulnerable To Drought

Congratulations (again!) to Kathie Fiveash, the first Naturally Curious reader to correctly identify the rough patch in Monday’s Mystery Photo as tadpoles that were stranded in a puddle that was drying up.

Most tadpoles acquire oxygen in a number of ways — through gills, through their skin, and by breathing air into their lungs. In this case, a lack of access to oxygen in the water has left them high and dry, as their lungs are not developed enough to provide them with the necessary amount of oxygen from the air. A sad ending for these young frogs, but a goldmine for scavenging raccoons, skunks, foxes and birds.

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Painted Turtles Laying Eggs

The courtship of Painted Turtles begins shortly after they emerge from hibernation in April and May.  It is quite an elaborate process, with the male swimming in front of the female and rapidly vibrating his long toenails along her head.  Mating follows and a month or two later females look for terrestrial nesting sites, often late on a rainy afternoon. 

Frequently the female will dig several “false” nests before depositing her half a dozen or so eggs in a nest. After carefully covering her eggs with soil and leaving the ground looking relatively undisturbed, she returns to her pond, providing no care for her offspring. 

Painted Turtle eggs hatch in the fall.  In the Northeast some young Painted Turtles emerge above ground shortly after hatching, while others remain in the nest and don’t dig their way out until the following spring. (Turtles from the same nest can emerge at different times.) Those turtles emerging in the fall usually have an egg tooth and a fresh yolk sac scar; those that overwinter and emerge in the spring lack both of these. (Thanks to Jody Crosby for photo op.)

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Common Grackles Raising Young

Although female Common Grackles do all the incubating, both males and females provide food for their nestlings.  Males average almost two feedings an hour, females almost four. Judging from the size of the larvae the pictured Grackle has in its beak, its nestlings are midway to fledging, perhaps a week old. The older/larger the nestlings, the greater the size of the food they receive.  Male and female nestlings received items of equal quality and quantity.

During the breeding season, both nestlings and adults feed primarily on insects in addition to a small amount of grain (and an occasional fish, small rodent or leech).  During the winter, their diet consists mostly of agricultural grains and tree seeds such as acorns.

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Aquatic Turtles Shedding Scutes

The spine and expanded ribs of a turtle are fused through ossification to plates beneath the skin to form a bony shell. Both upper and lower sections of the shell have an outer layer of plates called “scutes” made primarily of keratin (as are hair, feathers, hooves, claws, horns and nails).  Scutes protect the shell from scrapes and bruises.

In most land turtles and tortoises, scutes remain on the shell for life, which causes the shell to thicken and protects it. Growth of the scutes occurs through the addition of keratin layers to the base of each scute.

For most water species, as the turtle grows, the epithelium, or thin layer of tissue between the scutes and the bony plates, produces a new scute beneath the old one that is a larger diameter than the one layered on top of it, allowing the shell to expand.as the turtle and its shell grow.  The old scutes shed or peel away to make way for the newer, larger scutes (see top of shell, or plastron, of Northern Map Turtle on right in photo). Basking in the sun helps turtles shed scutes by drying them and leaving them ready to fall off. Usually this happens without any assistance, though there are some species of turtles which do pull loose scutes off each other’s shells.

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Brown-headed Cowbird: Brood Parasite

One has to admire a creature who has managed to eliminate the laboriousness of raising its offspring.  Brown-headed Cowbirds, renowned brood parasites, have done just that.  These birds do not build nests; females lay up to 40 eggs a summer in the nests of more than 220 species of birds which raise their young for them.  Cowbird eggs are generally larger than the host bird’s and hatch in fewer days, thereby putting Cowbird chicks at a distinct advantage over the host’s chicks when it comes to parental attention.

In this photo a Brown-headed Cowbird has deposited three eggs in the nest of an Eastern Phoebe (which has constructed its nest inside an abandoned American Robin nest). Unlike some songbirds, Phoebes do not recognize and remove the Cowbird’s eggs. Neither do they build a new nest on top of the old one, as some smaller songbirds (i.e. Yellow Warblers) are known to do.

Cowbird chicks develop faster than the chicks of the host bird, thereby often getting the first crack at the food parents bring to the nestlings.  Not only are the host species’ chicks often at a disadvantage when it comes to parental care, but they are at the mercy of the Cowbird chicks which often remove both the eggs and chicks of the host. (Thanks to friends in Thetford, VT for the use of their photograph of this parasitized Eastern Phoebe nest. The three larger, speckled eggs are Brown-headed Cowbird eggs; the four smaller white eggs are Eastern Phoebe eggs.)

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Cecropia Moths Mating

Cecropia moths (Hyalophora cecropia) are the largest native North American moths. They are members of a group of moths known as giant silk moths (family Saturniidae), renowned for their large size and showy appearance.

Having overwintered as pupae inside silk cocoons they spun (as larvae) in the fall, the adults emerge at this time of year often during the first spell of hot, humid weather by dissolving one end of their cocoon with their saliva.  The female Cecropia emits pheromones at night that are so strong that males can detect them with their feathery antennae from as far as a mile away.  Once paired, Cecropia moths proceed to mate for a full day before parting company. 

Shortly thereafter the female moth lays up to 100 eggs, often on both sides of a leaf. Due to a lack of functional mouth parts and no digestive system, the adults seldom live more than two weeks after mating. (Photo: female Cecropia moth on left (larger abdomen filled with eggs; narrow antennae); male on right (smaller abdomen; broader, more feathery antennae). Many thanks to Lorraine Vorse for photo opportunity!

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Note that mating took place very near the (female’s) cocoon (lower right).


The Lure of Bird Lores

An avian field mark that warrants special attention this time of year is the color of a bird’s lores — the area between a bird’s eye and bill on both sides of its head.  In some birds, especially wading birds, lores change color quite dramatically during the breeding season. 

Because birds can see blue, green and red (like humans) as well as UV light, and because the change takes place just as the breeding season begins for birds, the change in lore color, often to a more vibrant hue, is thought to play a part in attracting a mate.  (The bills, legs and feet of some birds also change color at this time.)

At the height of the breeding season, Great Egret lores go from yellow to an emerald green.  Green Heron lores turn from a yellowish-green to a bluish-black.  Snowy Egrets (pictured) lores become bright pink.  This happens to both sexes ever year. 

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Conifer Cones Developing

There are two kinds of seed-producing plants, flowering and non-flowering. Flowering plants are called angiosperms; their seeds grow inside tissue that is part of the plants’ ovaries, more commonly called fruit. Non-flowering plants that produce seeds are called gymnosperms.  Conifers are gymnosperms; their seeds are “naked,” or unprotected by an ovary/fruit and are often located on the scales of a cone. 

Some cones are male and some are female. The male cones produce pollen and the female cones produce ovules which, if fertilized, develop into seeds.  The pictured tiny, magenta cones are this year’s seed (female) cones of White Spruce, (Picea glauca) which, when the time is right, open their scales to allow wind-blown pollen to reach and fertilize their ovules.  The scales then close and will not open again until the seeds are fully mature.  At this point the scales open a second time in order to release the fully developed seeds which are dispersed primarily by the wind.

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Purple Martins Face Challenges Upon Returning To Breeding Grounds

Many of the Purple Martins that return from South America to the Northeast to breed have flown across the Gulf of Mexico to get here.  Once they’ve made this impressive trip, their challenges are far from over.  The reproductive success of Purple Martins depends not only on their arriving on their breeding grounds, but on surviving once they have arrived. One of the largest challenges that faces them upon their return is related to their diet, which consists exclusively of flying insects.  Purple Martins are particularly susceptible to spells of cold and rainy weather during the spring and early summer which can drastically reduce their supply of food.

Even when the weather doesn’t present them with nutritional challenges, Purple Martins have to contend with European Starlings and House Sparrows, both of which aggressively compete with them for artificial/human-made nest sites. Human intervention and management is often needed in order to protect the martin population. (Photo: male Purple Martin)

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Raccoons Seeking Dens

Pregnant female Raccoons have recently been exploring potential natal dens where they will soon give birth to four or five young. This year’s litters will be well hidden from potential predators deep inside the tree cavities, caves and rock crevices their mothers have chosen.  We won’t see the offspring for another month or two, after they have developed enough motor skills to be able to walk.  Sometime in June or July their mother will venture out of the den at night with her offspring and introduce them to solid food and the great outdoors.

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Large-flowered Bellwort Flowering

Large-flowered Bellwort (Uvularia grandiflora), a member of the lily family, strikes one as a rather modest plant, hiding its six-parted flowers by hanging them face down towards the ground. This arrangement influenced Linnaeus when he was assigning this plant the generic name Uvularia, as he felt the pendant blossoms resembled a uvula, that lobe that hangs from the upper palate at the back of our throats!

Many insects are attracted to this plant’s pollen and nectar, particularly bumble bees and other types of bees.  Ants distribute Large-flowered Bellwort seeds, attracted by the fatty elaiosomes attached to the them. And White-tailed Deer graze so heavily on this plant that you won’t find it in woods that are overpopulated with deer.

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A Busy First Month

We are seeing Red Fox kits above ground as they emerge from their den for the first time since birth, but much has transpired since they were born a month or so ago. Like other canids, including coyotes and wolves, their natal coat of fur was charcoal brown.  A new, second, coat of sandy-colored hair (that matches the sandy soil of the den site) has grown in, to be replaced again within the next two months by a brilliant red coat. The weaning process, which won’t be completed for some time, has begun by the time the kits venture above ground. Their eyes have opened (at 10-12 days), their first set of teeth has come in and they have established hierarchy among themselves.  Down in the den during the past month vicious fighting has taken place among the kits in order to determine which kit was “top dog,” or the alpha (usually the largest kit) and gets the lion’s share of the food delivered by the parents.

By the time we see Red Fox kits, much has happened in their young lives.  They’ve gained sight, a new coat, a set of teeth, the introduction of solid food, and most importantly, hierarchy has been established. Peace now reigns and we get to enjoy the kits’ playful antics as they are introduced to the world above ground.

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Sedges Flowering

Often it’s the spring ephemerals – Trout Lily, Red Trillium, Dutchman’s Breeches – that catch our eye as we walk through the woods this time of year. But there are other, more modest flowering plants which shouldn’t be overlooked.

Sedges, often found growing near wetlands but also in woods, are one of these inconspicuous plants.  Related to grasses and rushes, they are wind-pollinated, and have no need for large, showy petals in order to attract insects.  As a result, it’s fairly easy to miss their flowers, some of which are in full bloom right now.

Male and female sedge flowers are typically found on the same plant. The arrangement of the flowers, or inflorescence, usually consists of a cluster of male flowers on the end of a spike (see photo) with female flowers located on separate spikes. A dissecting scope is necessary in order to identify most species of sedges, but an easy way to know it’s a sedge is to feel the shape of the plant’s stem – sedge stems are three-sided — triangular in cross-section (unlike rushes which are round, and grass stems which are hollow). Hence, the saying “Sedges have edges, rushes are round.”

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Great Horned Owls Raising Their Families

Roughly two months ago the courtship calls of Great Horned Owls could be heard throughout the U.S. as their breeding season began. Mating took place, eggs were laid and incubated for about a month, and several weeks ago those eggs hatched.  Looking like balls of tan fluff, the downy chicks can now be seen with their mother in attendance.

Great Horned Owl chick appetites are voracious. At the ripe old age of two weeks they are capable of swallowing a mouse whole.  The chicks weigh about an ounce when they are born, and for the first month or so, they gain roughly that much every day.  In another month they’ll be taking short flights, but will remain with their parents throughout most of the summer. 

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Bloodroot In Flower

One of our earliest spring ephemerals, Bloodroot (Sanguinaria canadensis), a member of the Poppy family, greets the longer, warming days by having its short-lived flower emerge from within its protective leaf and spread its white petals wide open on sunny days. (The flower only opens on days when the temperature reaches 46 degrees, as that’s when pollinators are active.)

To encourage cross-pollination, when the flower opens it is in the female stage, relying on pollinators covered in pollen to land and drop pollen to the receptive stigma. Within a few hours of opening the stamens begin to release pollen. The flower will open for up to three days or until cross-pollination has occurred. Once pollination has taken place the flower begins to drop its petals.

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Ospreys Courting & Copulating

Ospreys have returned to their breeding grounds in New England, where both courtship and copulation is taking place.  The males engage in an undulating courtship display flight high over the nest site, often with fish or nesting material clutched in their dangling legs while they repeatedly issue forth screaming calls.  This can go on for up to ten minutes or so before they descend to the nest.  In addition, “courtship feeding” often takes place with the male providing his mate with food, often just prior to breeding.

Although an osprey pair copulates frequently (an average of 160 times per clutch), nearly half the time there is no cloacal contact. Most of the breeding takes place at or near the nest site. (Note the protective positioning of the male’s toes and talons as he mounts his mate.)

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Silver Maples One Of Earliest Trees To Flower

For several weeks the red flower buds of Silver Maple (Acer saccharinum) have been swelling, preparing to open and expose their flowers to the wind, their pollinating agent.  While Silver Maple can have both male and female flowers on the same tree, (monoecious) it much more commonly has flowers of only one sex (dioecious).  Less than 10 percent of flowering plant species have male and female flowers on separate trees — the other 90 percent combine both sexes in one plant.

The pictured branch of Silver Maple bears only male flowers, each possessing several pollen-loaded stamens.  Like many wind-pollinated flowers, Silver Maple’s flowers have no flashy petals to attract insects, rather they lack them entirely, as they would only get in the way of pollen dispersal.  Like other maples, if fertilized, the female flowers develop winged fruit referred to as samaras.  Silver Maple samaras are larger than those of any other native maple species.

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