An online resource based on the award-winning nature guide

March

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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Eastern Chipmunks Up & Active

3-23-15  eastern chipmunk IMG_2146Eastern chipmunks typically emerge above ground in late March, at a time when most mature females are in breeding condition. It takes little time for nearby males to come courting. During their breeding period, females, for the most part, remain within their territory, whereas males explore within and outside of their territories in search of a receptive female.

Male suitors congregate on the site of a female in estrus and work out the hierarchy within the group. The top chipmunk wins the opportunity to breed with the female. During these dominance battles, the males vocalize, wave their upright tails from side to side, chase each other and fight. The dominant male then breeds with the female. She proceeds to mate anywhere from 10 to 30 times within about a six to seven-hour receptive period, not necessarily with the same male. All of this activity takes place within a week of when chipmunks come above ground, so keep your eyes peeled for those waving tails.

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Mourning Doves Calling

3-19-15 -mourning dove IMG_2091The mournful lament of the male mourning dove is often one of the first songs heard in the early spring. The frequency of this call builds to a peak from mid-May to mid-June. As in many other pigeons and doves, the Mourning Dove’s main call, or “perch coo” (coo-oo, OO, OO, OO) is an advertising call, sung in order to attract a mate. Unmated males often establish perches within their territory from which they repeatedly sing.

A shorter nest call is used by a paired male to attract his mate to a potential nest site. The male then gathers nesting material and presents it to the female while standing on her back. While she constructs the nest, he continues to use the nest call to maintain a bond with his mate. Once the nest is built, this call diminishes. You can hear Mourning Dove calls at http://www.allaboutbirds.org/guide/mourning_dove/sounds, although to my ear, it’s hard to distinguish the perch call from the nest call in these recordings.

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