An online resource based on the award-winning nature guide

March

Female Big Brown Bats Forming Maternity Roosts

5-7-15  big brown bat 022Big Brown Bats have emerged from hibernation and have been active for several weeks. It is in the spring that a female Big Brown Bat becomes fertilized with sperm she has stored in her uterus over the winter. Reproductive female Big Brown Bats collectively form a maternity roost at this time of year and each bat typically gives birth to a single pup in June, after about a 60-day gestation period.

While both Little and Big Brown Bats were affected by the fungus causing White Nose Syndrome, the Big Brown Bat population has not been decimated like the Little Brown Bat population. In some locations, Big Brown Bats have even thrived, taking over summer roosting spots formerly occupied by Little Brown Bats.

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Waxwings Supplementing Sugary Fruit Diet With High-Protein Insects

4-3-15 bohemian waxwing IMG_2383The diet of both Cedar and Bohemian Waxwings is primarily sugary fruits throughout most of year. Research shows that they can subsist on this diet exclusively for as many as 18 days. However, in winter when feeding on fruits, they also feed on buds and available insects. In warmer months, waxwings will fly out over water from exposed perches, much like flycatchers, and snatch emerging aquatic insects such as mosquitoes, midges, mayflies, caddisflies and dragonflies out of the air. They also glean for vegetation-borne insect prey, such as scale insects. At this time of year they are taking advantage of winter stonefly hatches over open streams. (photos: bohemian waxwing & stonefly)

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Meadow Vole Tunnels Exposed

3-31-15  meadow vole exposed tunnels IMG_3528If you live where the snow is actually melting, a labyrinth of vole tunnels may be revealing itself to you. These tunnels were excavated in the snow next to the ground in what is referred to as the subnivean layer. They lead from sleeping areas to known sources of food, and are advantageous to both mice and voles that travel in them – they provide thermal insulation by protecting them from the wind and cold, and they keep these rodents hidden from predators. Carbon dioxide, which builds up in the subnivean layer from animal respiration as well as CO₂ released from the ground, escapes through ventilation shafts, or air vents, that lead up to the surface of the snow.

Voles stay in these tunnels as long as the snow is deep enough not to expose them, finding food in the form of plants, seeds and bark from bushes and shrubs as they dig through the snow. This winter has provided voles, mice and shrews with an extended period of protection, as hungry barred owls attest to.

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Common Grackles Returning

3-30-15 common grackle 083Male Common Grackles have started to arrive on their northeastern breeding grounds (females will arrive in another week or so), having migrated from southern U.S. Common Grackles typically migrate in large flocks containing hundreds of birds, not all grackles. Red-winged Blackbirds, Brown-headed Cowbirds, European Starlings and occasionally American Robins can be found alongside Common Grackles in these migrating flocks. In the early 1990’s, magnetic material was found in the heads and necks of Common Grackles, indicating that the geomagnetic field may play a role in their migratory navigation.

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Juvenile Raccoons Dispersing & Adults Mating

3-27-15 raccoon tracks in snow IMG_5071When raccoons emerge from their communal (as many as 23 raccoons) winter dens, which they are doing now, the juveniles (those born last spring) disperse. Young males may travel as far as 170 miles, but usually establish their territories no further than 14 miles from their birth place. Juvenile females usually remain in their birth area, establishing a home range that either overlaps with or is included within the range of their mother. This time of year is also the peak of the breeding season for adult raccoons. Both males and females have multiple mates.

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Porcupines Marking Dens

3-25-15 porcupine den IMG_9681Often, at this time of year, porcupines stake out their den trees (if they’re not inhabiting rocky ledges) by eating patches of inner bark, or cambium, with the exposed fresh inner wood announcing their occupancy. Typically, if a tree den is used year after year, they gnaw off a portion of bark each year, sometimes eating the old, scarred portion which, due to previous chewing, lacks cambium cells, indicating that this behavior is not for the purpose of obtaining nutrients. (photo: porcupine chewing near hollow tree den entrance)

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Owls & Humans Share Trait

barred owl 194Birds have three eyelids – an upper eyelid, lower eyelid and a third semitransparent membrane called a nictitating membrane that sweeps across the eye much like a windshield wiper. This membrane keeps their eyes moist, and protects their corneas from being scratched.

In most birds, including owls, the upper and lower eyelids are used to close the eyes when sleeping, and the nictitating membrane is used for blinking. Humans close their eyes mainly by lowering the upper eyelid, where most birds do so by raising the lower lid. Owls (and a few other birds such as parrots, toucans, wrens and ostriches) are more human-like in that their upper lids are usually lowered to close their eyes. Owls also usually close their eyes, partly or entirely, when capturing and transferring prey, scratching their face, preening another owl and copulating. (Note the rows of feathers on this barred owl’s upper eyelids.)

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