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Archive for February, 2019

American Black Ducks Vs. Mallards

2-27-19 black ducksAmerican Black Ducks (Anas rubripes), found year-round in all parts of New England except for northern Maine, are nearly identical to Mallards (Anas platyrhynchos) in size, shape and voice. Both have rounded heads, thick bills, and bulky bodies. Like other dabbling ducks they sit high in the water with their tails high. These two closely related species often keep company with each other and it can be challenging to tell them apart, but it is possible to distinguish them with some certainty.

Most of the year male (drake) Mallards have a distinctive iridescent green head, a white neck ring and a yellow bill. However, the female (hen) Mallard’s plumage is very similar to that of both drake and hen Black Ducks. One of the most dependable ways to tell these two species apart is to look for the dark chocolate-colored body of the Black Duck, which is noticeably darker than the hen Mallard’s. At rest, the Black Duck is a uniform very dark brown from the bottom of its neck to its tail. The hen Mallard is a much lighter brown in this area, and in addition has a pale whitish patch on the belly. The color of the bill can also help with identification — the hen Mallard’s bill is orange and black, whereas the Black Duck’s bill ranges from a dusky yellow (drake) to a drab olive (hen) color. All of these identification clues go out the window when hybrids of these two species are encountered! (Photo: American Black Duck drake (L) and hen (R) )

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Porcupine Quills

2-25-19 porcupine IMG_6292Porcupines possess roughly 30,000 quills — hollow, modified hairs which are made from the same material (keratin) as feathers,claws, scales, hairs and fingernails. They cannot “shoot” their quills anymore than we can shoot our hair, but their subcutaneous muscles can cause the quills to become erect as well as loosen them so that when touched, the quills are easily released. Each quill possesses between 700 and 800 barbs along the four millimeters or so nearest its tip. It is these barbs that help a quill remain embedded in the tissue of a predator.

Researchers have found that barbed quills penetrate deeper into muscle than quills without barbs, and require half the penetration force. They have been found to be four times harder to pull out than barbless quills. It has been suggested that the barbs ease the quill’s penetration by concentrating force along the edges of the barbs, similar to how the serrations on a knife blade make cutting meat easier.

Fortunately for porcupines, their quills are covered with a natural antibiotic which protects a porcupine from infection should it be impaled by one of its own quills or one from another porcupine. (Photo: porcupine with quills from another porcupine embedded in nose)

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Male Woodchucks Out and About

2-22-19 woodchuck burrow IMG_0555Hibernation, the true slowing down of one’s metabolism (a Woodchuck’s body temperature drops from 99 degrees F. to 40 degrees F. and its heartbeat drops from 100 beats per minute to 4 beats per minute) is one way an animal conserves energy. Male and female Woodchucks use the energy they’ve conserved very differently in early spring.

At the end of February and in March, males arouse themselves about a month prior to the mating season and spend long periods visiting females and defending their territory. Muddy tracks and trails can be seen near their winter burrows (see photo) at this time of year. Females remain in their burrows in a state of hibernation, saving as much energy as possible for the birth and raising of their young. After confirming the presence of females on their territories, males return to their burrows for the next month or so, awakening along with the females in time for their mating season.

The timing of Woodchuck procreation is not a relaxed affair. It is quite precise, in fact, for very good reasons. If Woodchucks mate too early in the spring, their young won’t be able to find food once they are weaned. If they mate too late, their young won’t have the time necessary for putting on weight and storing fat before hibernation begins. Now is the time to look for signs indicating male Woodchuck activity near their winter woodland burrows.

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Red Feather Tips of Waxwings Indicate Age and Status

2-15-19 cedar waxwing_U1A2000Both Cedar and Bohemian Waxwings derive their common names from the red, waxy tips of some of their secondary feathers. The color of this wax is due to the presence of the pigment astaxanthin. Ornithologists used to theorize that these red tips protected the feathers from wear and tear, but this has not been borne out in studies.

What has been established is that the red appendages increase in both number and size with a bird’s age. Immature birds usually have 0 – 6 waxy tips. Older birds have more than nine. The number of tips appears to function as a signal of age and status in mate selection; individuals within these two age categories choose each other as mates. It also turns out that pairs of older birds (with high numbers of red tips) tend to nest earlier than younger birds. They also have larger clutches and fledge more young than younger birds with fewer waxy tips.

An easy-to-see cue such as these red feather tips that indicate age, maturity and social status at a glance would be very useful in species such as Cedar and Bohemian Waxwings that are often found in large flocks.

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Virginia Opossums Breeding

2-18-19 opossum 025If you see a Virginia Opossum in your travels, it could well be on the hunt for a mate at this time of year. It’s even possible you may hear one if you are close enough and the timing is right, as male opossums attract females by making clicking sounds with their mouth.

The breeding practices of this marsupial are unusual, to say the least. The male opossum has a bifurcated (two-pronged) penis (see photo inset), and the female has two vaginas. Not only is their reproductive anatomy somewhat unusual, but the behavior of their sperm is as well. During maturation, sperm pair up inside the male reproductive tract and remain paired after entering the female. Just prior to fertilization the sperm pair separate (into two spermatozoa). This phenomenon occurs only in American marsupials, and not Australian. No definitive explanation exists for this, but perhaps paired sperm increase motility in the female reproductive tract.

(NB: Having an opossum on your land is a real asset – according to biologist Richard Ostfeld, one opossum can kill and eat some 5,000 ticks in a single season. Opossums are said to destroy roughly 90 percent of all the ticks they encounter.)

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Two For One

2-15-19 cardinals _U1A8442Thanks to warmer temperatures and a vast increase in the number of bird feeders, Northern Cardinals have expanded their range northward as far as Canada over the past century. Males get far more attention than females, due to their year-round brilliant red plumage. However, the female Cardinal is equally striking with her more subtle tan plumage highlighted with touches of red. Believe it or not, it is possible, albeit very rare, to find both of these plumages on one bird.

Recently an interesting phenomenon known as a bilateral gynandromorph was recorded in Pennsylvania — a cardinal whose body is half male, half female. (For a detailed explanation and video, go to https://www.nationalgeographic.com/animals/2019/01/half-male-half-female-cardinal-pennsylvania/?fbclid=IwAR2KbCmxuGxtGmKug2eLPS9JD6Vf_KV93OWgy0UsKuMAO-p_2soISJgM400.) Not just the plumage, but the anatomy of this bird is half male, half female. The way in which this gender division exists has a unique effect. According to National Geographic, “Most gynandromorph individuals are infertile, but this one may actually be fertile as the left side is female, and only the left ovary in birds in functional.”

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Meadow Vole Tracks & Tunnels

2-4-19 meadow vole_U1A2759Tracking animals can be an elusive endeavor because so many things can alter the condition of the tracks. Have recent flurries erased the details of an imprint? Has the sun melted and enlarged a track? Was every toe registering? Did wind-blown snow cause the tracks to vanish into thin air? Was the animal walking, loping or tunneling or a combination of all three?

The reason you use more than just one track to gather information, such as the stride of the animal and the width of its trail, is that sometimes the individual tracks defy the hard and fast rules of some tracking guides. A commonly accepted generality is that Deer and White-footed Mouse tails leave drag marks, and Meadow Voles’ shorter tails don’t. However, in the right conditions, even a vole’s one-inch tail can drag (see photo), though not creating as long a line as a mouse’s tail would. The Meadow Vole whose tracks are in this photograph was loping along when it suddenly decided to seek cover under the snow and began to (try to) tunnel. Perhaps a predator instigated this behavior.

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