An online resource based on the award-winning nature guide

January

Red-eyed Vireo Nests

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The Red-eyed Vireo’s nest is indisputably a work of art. Unlike most songbird nests, it is suspended below the branch to which it is attached. Perhaps the observant eye of Arthur C. Bent, a compiler of firsthand bird observations in the early to mid-1900’s, describes it best.

The red-eyed vireo builds a dainty little pensile nest suspended usually from a forking, horizontal branch of a tree, rather below the level of our eyes as we walk through second-growth. The nest is a beautifully finished piece of workmanship, constructed of fine grasses and rootlets, bits of birch bark, and paper from wasps’ nests, bound together and to the supporting branches with spider’s or caterpillar’s webbing, and , perhaps the most constant material, long, narrow, flexible strands of grapevine bark, which help to hold up the cup of the nest.

As mentioned, pieces of Bald-faced Hornet nests are frequently incorporated into the outside of a Red-eyed Vireo’s nest. These papery bits of hornet nest are purely decorative, and serve no structural purpose. Hornets are aggressive and defend their nests vigorously, so much so that it is unusual to find birds nesting in close proximity to a hornet nest. A vireo nest covered with papery bits of a hornet’s nest looks very much like a young hornet nest. It is conceivable that the use of this decorative material is a strategy employed by vireos to ward off potential nest predators.

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Ruffed Grouse Unable To Seek Refuge in Snow Caves

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Unlike much of the Northeast, central Vermont has only a few inches of snow on the ground. These conditions can affect all forms of predators and prey both negatively and positively, from exposed mice and voles to easily-satiated hawks and owls. In the case of Ruffed Grouse, which seek shelter on cold winter nights by diving into the snow, less than 10 inches of snow can spell disaster. In their snow caves they are hidden from view and well insulated (where it rarely drops below 20°F.).  A lack of snow can be life-threatening for grouse if the temperature drops too low for too long. Unable to create a sheltered cavity in the snow,  Ruffed Grouse bed down on top of it, often close to the base of a tree where there may be some shelter from the wind. Fortunately, most nights have not been extremely cold thus far this winter.

After the grouse departs in the morning, you often find scat where it bedded down. Grouse scat comes in two forms, one a dry, fibrous cylindrical pellet with a white-wash of uric acid at one end, and the other a softer, darker brown plop. The vast majority of a grouse’s diet (buds, twigs, leaves, catkins) goes directly through its digestive system and forms the dry, courser scat. Finer (and more nutritious) material such as the cambium layer of woody plants enters the caeca, two specialized pouches, before passing through the large intestine. The caeca contain bacteria which break down cellulose and produce the more digested, and therefore more liquefied, scat (see foreground in photo).

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How Owls Locate Prey Under the Snow

1-26-16  barred owl imprint  067An owl’s range of audible sounds is not unlike that of humans, but an owl’s hearing is much more acute at certain frequencies, enabling it to hear even the slightest movement of their prey under two feet of snow. When a noise is heard, the owl is able to tell its direction because of the minute time difference in which the sound is perceived in the left and right ear. If the sound is to the left of the owl, the left ear hears it before the right ear. The owl turns its head so the sound arrives at both ears simultaneously, at which point it knows its prey is right in front of it. Owls can detect a left/right time difference of about 0.00003 seconds.

Once an owl has determined the direction of its next victim, it flies towards it, keeping its head in line with the direction of the last sound the prey made. If the prey moves, the owl makes corrections mid-flight. When about two feet from the prey, the owl brings its feet forward and spread its talons, and just before striking, thrusts its legs out in front of its face and often close its eyes before the kill. (Photo: barred owl wings and feet imprints; inset: barred owl ear opening.)

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Female Eastern Coyotes In Estrus

1-27-16 coyote in estrus 036Female Eastern Coyotes come into estrus only once a year, usually in late winter for two to five days. For two or three months prior to as well as during this time, males roam widely and scent marking by both males and females increases. During their mating season, coyotes often travel in pairs, and it is not unusual to find scent posts where both male and female have scent marked with their urine. (The female’s urine is often tinged with blood.) The percentage of females that breed in a given year (typically 60% to 90%) depends upon the availability of food and their physical condition.

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Moose in Winter

1-26-16  moose scat IMG_6307Moose are in their element during northern New England winters. Their bodies are built for snowy, cold conditions. Moose lose relatively little heat due to their large body which gives them a low surface area-to-volume ratio. Long legs enable them to travel through deep snow. However, when the snow gets to be more than 28 inches deep, the energy expended to find food is not worth it. Under deep snow or crust conditions, moose often seek shelter in stands of conifers where the snow is not as deep and where browse is available.

Conifers are beneficial to moose in yet another way. Moose are able to withstand very cold temperatures –in fact, they become uncomfortable (and have been known to pant) when winter temperatures are higher than 23°F. Their coat consists of long, hollow outer hairs and a dense soft undercoat. Our winter temperatures can be quite variable and moose depend on the shade of coniferous cover to keep them cool during our warmer winter days.

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Ruffed Grouse Flying Into Windows

1-25-16 dead ruffed grouse by Eve BernhardThose of us who feed birds are well aware of the hazards that windows and glass doors present to birds. The latest research shows that roughly 988 million birds are killed each year in the United States from hitting windows. Migratory birds and songbirds are the most common victims, but Ruffed Grouse, especially in the fall and winter, are very apt to collide with glass windows. (This phenomenon is not the same as the aggressive behavior towards glass that a bird’s reflection can promote, especially by males during the breeding season.)

Many of the grouse victims are first-year birds. Often, inexperienced young grouse, frightened by a predator, crash into buildings, trees or windows in a so-called “crazy-flight.” Hard, transparent glass is not something grouse recognize as a barrier, due to the reflections it creates. There are a number of things one can do to reduce the chances of this happening. Netting, decals, window film and tape hanging from the top of the window can help. One of many creative new products available are window panes that have external patterns that birds can see from the outside, but that are invisible from the inside. On a national level, legislation and bird-friendly buildings are gaining traction. For more window crash-prevention ideas, go to http://www.birdwatchingdaily.com/featured-stories/15-products-that-prevent-windows-strikes/. (Photo by Eve Bernhard)

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Great Horned Owls Courting

Great Horned Owls are staking out territories and beginning courtship rituals in northern New England. Their “songs” are typically given with their beak closed, as they lean forward and cock their tail up (see photo). When calling, their white throat feathers are pronounced as their throat swells.

The hooting of a Great Horned Owl can be compared to the sound of a distant foghorn – it is soft, and somewhat subdued, with no strong accent on any one hoot. Pairs often synchronize their deep sonorous territorial songs, a custom which is referred to as “duetting.” The higher-pitched female calls a six or seven-note song and the male responds with a deeper five-note song during or within a few seconds after the female’s song.  The chances of hearing a Great Horned Owl are somewhat greater after midnight than before. To hear Great Horned Owl territorial calls and duetting go to https://www.allaboutbirds.org/guide/Great_Horned_Owl/sounds. (Thanks to Vermont Institute of Natural Science for photo op.)

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1-19-16  great horned owl calling 289