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Adaptations

Snowy Owls Headed North

4-21-14 flying snowy 046The record number of Snowy Owls that spent the winter in New England are turning up in all sorts of new locations now that they are on their way back to their breeding grounds on the open tundra and stopping to refuel along the way. Although many were young birds, and won’t breed this year, the adult owls will when they reach the Arctic in a few weeks. First, the males perform aerial and ground displays. After mating, the female selects a nest site. In addition to having a sufficient food supply, the site must be snow-free, not subject to flooding, and command a view of its surroundings. The latter is achieved by making their nest on a hummock, or slightly raised surface of bare ground. The female scrapes a shallow depression in the earth with her claws, twirling around to make a form-fitted hollow. No insulating material is added to this depression – no vegetation, no feather lining. Eggs and nestlings are totally dependent upon the mother’s warmth, transmitted via the large, featherless, pink patch of skin on her belly known as an “incubation patch.” The female alone incubates the eggs and broods the young chicks while the male provides food for his entire family.

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Hooded Mergansers & Feeding Adaptations

4-16-14 female hooded merg eating fish IMG_9199Although most of New England has Hooded Mergansers year round, we see them most frequently in the spring and fall, when Canadian-nesting individuals are migrating north. They stop to re-fuel in wetlands where they are well adapted for capturing and eating fish, insects and crayfish. The nature of the changes their eye lenses can make, coupled with the high degree of transparency of the membrane that covers their eyes under water give them superior vision under water. Their success in holding onto the struggling prey they capture is greatly increased by the serrated edges of their slender bill. (Photo: female Hooded Merganser)

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Common Mergansers Taking Flight

common mergansers pattering 425Most ducks can take off nearly vertically from either water or land. However, when taking off from a body of water, unless alarmed, Common Mergansers usually patter along the surface for several yards before taking flight. One would imagine that their flight might not be any more graceful than their take-offs, but the opposite is said to be true of females looking for potential nesting sites. They have been observed maneuvering easily among tree branches seeking a suitable tree cavity in which to lay and incubate their eggs, and once they have found a nest site, they appear to enter and leave their nest holes with ease.

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Paper Wasp Queens Emerging From Hibernation

4-8-14 paper wasp2  152Paper wasps have annual colonies – only the young, fertilized queens overwinter, with the old queen, female workers and the males all perishing in the fall. The queens seek shelter behind tree bark, or in rotting logs or stumps, and emerge in the spring when temperatures rise and day length is increasing. Last year’s nest is not re-used – the queen mixes wood and plant fiber with her saliva, creating several waterproof paper cells into each of which she lays an egg — the start of her future labor force. Due to the lack of wildflowers (and therefore nectar) this early in the spring, queens rely on the sap from broken tree branches, as well as the sap found in drilled Yellow-bellied Sapsucker wells, for sustenance.

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Winter Stoneflies Still Emerging

4-2-14 stonefly 123It seems early, especially with feet of snow still on the ground, to be seeing insects flying around, but some have actually been present all winter. An order of insects (Plecoptera) known as stoneflies spends its youth (one to four years) living in streams before emerging as winged adults. Some of these species, referred to as winter stoneflies, emerge from January through April, providing food for early-returning, insect-eating migrants, such as Eastern Phoebes, Tree Swallows and Red-winged Blackbirds. Stoneflies only live a few weeks, during which time they mate and lay eggs. Some do not feed, and others consume plant material. Because stoneflies are intolerant of polluted water, if you see one it’s a good indication that the water quality of the stream that it came from is excellent.

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Barred Owls Frequenting Feeders

4-4-14  barred owl with suet IMG_5432The number of Barred Owls seen near bird feeders recently makes one question whether these birds are, in fact, in dire need of food. Certainly the extended period of deep snow this winter has made finding prey challenging. Fortunately, the local bird rehab center (Vermont Institute of Natural Science) has not been inundated with starving owls, which indicates that other factors may be involved in the increased number of sightings near homes and feeders. One of these factors could be that Barred Owls are currently laying and incubating eggs, and a few early nesters may even be providing food for young owlets. Whatever the reason, the accessibility of rodents that are attracted to feeders and the food itself that’s in the feeders allows us an all-too-rare glimpse of this common owl. (The mystery of repeatedly finding my suet feeder on the ground every morning was finally solved when I took this photograph – look closely at what the Barred Owl is clutching in its talons.)

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Common Ravens Repairing & Building Nests

2-24-14 common raven IMG_2002Common Ravens have begun tending to their nests – one was seen snapping dead branches off of a Black Locust tree in Vermont last week. Often ravens will use the same nest for many years, renovating and repairing it every year. They typically nest on or in cliffs and trees (although abandoned cars, a satellite dish and a barbecue grill have been used), with the female doing the lion’s share of the construction. (The male assists her by bringing sticks to the nest site.) The base of the nest consists of sticks up to three feet long with smaller branches being woven into a cup lined with softer material such as sheep’s wool, fur and shredded bark. The finished nest is two to three feet across and up to four feet deep.

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Big Birds

blue jay puffed out in snow 101Is your bird feeder being visited by gigantic Blue Jays and Black-capped Chickadees during this cold spell? Your eyes aren’t fooling you; birds often appear larger in very cold weather.
Birds that remain in New England year round must not only be able to find enough food in the winter to produce heat and energy, they must find a way to retain the heat. Various strategies have evolved, but feather structure and function play an important role for the winter survival of all birds. There are different types of feathers, each designed for a different function. A (wing or tail) feather consists of a central, hollow shaft on either side of which are many interlocking rows of barbs. The feathers that cover the body of a bird (contour feathers) often have interlocking barbs only at the ends, on the part not covered by an overlapping feather. The bottom-most, unconnected barbs on these feathers are similar to those of down feathers – loose and fluffy. When the temperature dips, birds often puff out their contour feathers (making the birds look huge). This action, and the structure of the bottom portion of the contour feathers,
increase the number and size of air pockets between the bird’s feathers and its skin. This space provides excellent insulation, preventing much of the bird’s body heat from escaping.

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The Butcher Bird

1-3-14 impaled mouse & MS shrike by Bridie McGreavy DSC_0146The Northern Shrike (Lanius excubitor) is highly unusual in that it is a predatory songbird. Birds, mammals and insects are preferred over nectar, nuts and seeds. This tundra-nesting bird comes as far south as New England to overwinter, where it preys mainly on mice, voles and small birds. The Northern Shrike often kills more prey than it can immediately eat or feed its young, storing the excess food to eat later, when available living prey may be scarce. The manner in which it stores this extra food is what gave it the name “butcher bird;” it often impales prey on a thorn, broken branch (as in photograph) or even barbed wire, or it wedges prey into narrow V-shaped forks of branches, where they hang until reclaimed by the shrike. (Impaled mouse photo by Bridie McGreavy; northern shrike photo by MS Henszey)

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Discerning Eastern Gray Squirrels

1-3-14 gray squirrel2 029In the fall, Eastern Gray Squirrels bury individual acorns from Red and White Oaks to sustain themselves through the winter. The acorns of Red Oaks have delayed germination – they can be stored up to six months before they start germinating. The acorns of White Oaks, however, have no such dormancy, and begin to germinate in the fall, soon after they fall from the tree. Once acorns sprout, they are less nutritious, as the seed tissue converts to the indigestible lignins that form the root. Gray Squirrels, as a means of “long-term cache management,” selectively remove the embryos from White Oak acorns (but not from Red Oak acorns) before burying them. Germination is prevented, and the storage viability of the White Oak acorns is extended by six months, equaling that of the Red Oak acorns.

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Hairy and Downy Woodpecker Bills

12-31-13 woodpecker billsDistinguishing Hairy Woodpeckers (Picoides villosus) from their smaller relatives, Downy Woodpeckers (Picoides pubescens), can be challenging if you don’t have a chance to view both species at the same time. The easiest way to tell them apart is to note the relative size of their bills. The Hairy Woodpecker’s bill is proportionately much larger than the Downy Woodpecker’s – it’s almost as long as its head — whereas the Downy Woodpecker’s bill is not nearly as impressive. Although a Downy Woodpecker can’t drill or probe as deeply into trees as a Hairy Woodpecker, it does have at least one advantage due to its overall smaller size; it is light enough to balance on the stems of goldenrods, which usually aren’t strong enough to support Hairy Woodpeckers. It is here that Downy Woodpeckers drill for overwintering goldenrod fly larvae inside goldenrod ball galls – a popular winter snack for this species.

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Northern Hawk Owl

n. hawk owl3- 231The Northern Hawk Owl is a bird of the remote Alaskan and Canadian boreal forests. Its name reflects the fact that this diurnal owl has both the appearance and behavior of a hawk, specifically, an accipiter. Although the Northern Hawk Owl winters throughout its breeding range, it periodically erupts southward into southern Canada and the northern United States. Sightings of this bird are rare in Vermont, but in recent winters, including the current one, there have been some. As with Snowy Owls, the magnitude and extent of these winter irruptions are thought to correlate with high reproductive success followed by severe winter conditions and decreased prey availability, but much remains to be understood about their winter dispersal habits. What we do know is that the Northern Hawk Owl’s skills as a hunter are very impressive. It can detect prey (small rodents, grouse, hares) by sight at a distance of half a mile and just using its ears can find prey under a foot of snow.

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Leafy Liverworts

12-12-13 Frullaria 008Plants that have no conductive (vascular) tissue are referred to as bryophytes. They include mosses, hornworts and liverworts, all of which reproduce with spores and do not form flowers or seeds. Liverworts are common in the tropics, but certain species are plentiful in New England. They are divided into two groups: flat, leafless thallus liverworts and leafy liverworts, which typically resemble flattened moss. You can easily confuse leafy liverworts with mosses but there are microscopic differences between the two. If you examine them under a microscope, you will find that leafy liverworts have leaves that are arranged in two or three rows while the leaves in mosses are spirally arranged. Liverworts of the Frullania genus, such as the liverwort pictured in this post, are classified as leafy liverworts. They typically have a reddish-brown color and attach themselves to a tree or other plant, obtaining moisture and nutrients from the air.

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Bird Tracks & Gaits

12-11-13 bird tracks2 041Just a dusting of snow can reveal the patterns of tracks that different birds leave, and that pattern tells you how a bird moves (walks/hops). Frequently this knowledge can narrow down the possible species that made the tracks. In general, smaller birds tend to hop and larger birds frequently walk. This may be a result of conserving energy — short-legged birds move farther in a single hop than they do taking several steps, whereas it is more economical for larger birds, with longer strides, to move one leg at a time. In addition, birds that spend time on the ground foraging for food are more apt to walk, placing one foot in front of the other, much as humans do. Mourning doves, ducks, pigeons, and wild turkeys all leave “chains” of tracks, alternating feet as they walk. Birds that live mostly in trees and bushes tend to hop from one spot to another, even when they are on the ground, leaving paired tracks. Sparrows, including juncos, as well as finches frequently move in this way. There’s no hard and set rule, as some birds do both –American robins, ravens, crows and blackbirds are as likely to walk as they are to hop! (Photo shows tracks of Mourning Dove on bottom walking towards the left; Dark-eyed Junco above, hopping towards the right.)

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Blackberry Seed Gall

Galls, abnormal plants growths caused by many agents including insects, are formed during the growing season on the buds, leaves, roots and branches of plants as a response to chemicals or physical irritation. These galls serve as shelters and a source of food for their inhabitants. Blackberry is host to numerous gall-making insects, including mites, midges and gall wasps, and their temporary homes (galls) are more obvious now that Blackberries have lost their leaves. The Blackberry Seed Gall is caused by a cynipid gall wasp, Diastrophus cuscutaeformis. This wasp gets its species name from the resemblance of the galls it forms to the fruit of Dodder or Cuscuta, a parasitic plant. A cluster of small, globular, seed-like galls within which the gall wasp larvae live are pressed together in a lump surrounding the cane. Each of these 1/10th-inch diameter chambers bears a spine, and together they create a reddish-brown hairy mass.12-3-13 blackberry gall IMG_0555


Few Northern Finches This Winter

11-27-13  pine siskin-irruption forecast IMG_8713Every year Ron Pittaway of the Ontario Field Ornithologists (http://www.jeaniron.ca/2013/forecast.htm) forecasts the extent to which birds in the Finch family are expected to inundate northern New England in the coming winter. This year’s forecast is not looking great for birders hoping to see influxes (irruptions) of northern seed-eating species such as pine siskins (pictured), crossbills, redpolls, grosbeaks and finches. The reason for the lack of inundations of feathered northern visitors this winter is that the Canadian crop of seeds that these birds eat is more than ample this year, making it unnecessary for most seed-eating birds to come further south seeking food. With the exception of white pine, there is an abundance of cone crops as well as birch, alder and mountain-ash seeds and fruits this year in the boreal forests of Ontario and southern Quebec. Although there will be some southern movement of these birds, this is not predicted to be an irruptive winter, which bodes well for seed-eating birds, but not so much for bird-seeking humans.

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Backswimmers Active Under Ice

11-18-13  backswimmers under ice 061Backswimmers are insects classified as “true bugs” and belong to the order Hemiptera. Most Hemipterans are land dwelling, such as stink bugs and assassin bugs, but there are a few, such as water striders, water boatmen and backswimmers, that are aquatic. In the fall, when most insect hatches have ceased, backswimmers come into their own. While some hibernate at the bottom of ponds in winter, others remain active, sculling through the water with their oar-like hind legs that are covered with fine hairs, preying on all forms of life up to the size of a small fish. Thanks to bubbles of oxygen that they obtain from pockets of air just under the ice and carry around with them like mini aqua lungs, backswimmers can continue to stay below the surface of the water for several minutes. Like most aquatic insects, backswimmers supercool their bodies (produce antifreeze compounds called cryprotectants that allow their body fluid to go down to 26 to 19 degrees F. without freezing). Right now, when there’s a thin layer of ice on most ponds and no snow covering it, you might want to peer through the ice at the edge of the pond to see if you can locate any of these cold-hardy creatures. Just be sure you don’t fall in, as I did two seconds after this photograph was taken. My undying gratitude for those of you who have donated to Naturally Curious, as your support enabled me to replace both camera and lens!

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Did you know…

11-20-13 black-capped chickadee IMG_0107Black-capped Chickadees actually refresh their brains once a year. According to Cornell’s Laboratory of Ornithology, every autumn Black-capped Chickadees allow brain neurons containing old information to die, replacing them with new neurons so they can adapt to changes in their social flocks and environment.

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Pitcher Plants Turning Red

10-29-13 pitcher plant2 158 Pitcher plant leaves are primarily green in the summer, tinged with red, but as summer turns into fall, many become deep red. Although this red color was thought to attract insects, it appears that this is not the case. The color change, according to research cited in the Journal of Ecology, is due to the level of phosphorus this carnivorous plant has received from its insect meals. There is a limited amount of phosphorus in a bog and plants living there acquire it in different ways. The pitcher plant acquires phosphorus from insects that it traps. It then utilizes the phosphorus to revitalize the (green) chlorophyll in its leaves for photosynthesis. The deep red color that the leaves turn in the fall indicates that the plant has not had a good meal in quite some time.

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White-throated Sparrows and Winged Euonymus

10-17-13 white-throated sparrow 125Although the breeding and winter ranges of White-throated Sparrows overlap, most, if not all, populations are migratory. During their flight southward in the fall, White-throated Sparrows stop during the day to refuel on seeds, fruits and insects, if available. Winged Euonymus (Euonymus alatus), or Burning Bush, is an invasive shrub that, in addition to shading and crowding out native plants, produces vast quantities of capsules, each containing up to four seeds. White-throated Sparrows and many other bird species find these bright red seeds attractive, but unfortunately, they are of little nutritional value to the birds and other wildlife that feed on them. How ironic that these birds, whose health and migratory success may be compromised by the seeds of this invasive plant, are facilitating its establishment by dispersing its seeds.

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Witch Hazel Flowering and Dispersing Last Year’s Seeds

10-11-13  witch hazel flower and fruits 055Witch Hazel (Hamamelis virginiana) is nature’s final fanfare of the fall. As colorful fall foliage disappears, the yellow strap-like petals of Witch Hazel’s fragrant flowers brighten denuded woods. These flowers are pollinated by moths that are still active this late in the season, and develop into small, hard capsules that remain dormant throughout the winter. During the following summer, these capsules develop to the point where they expel two shiny black seeds 10 to 20 feet away from the tree. The seeds take another year to germinate, making the length of time from flowering to germination approximately two years. (In photo, the yellowish-tan capsules were formed this summer, and the one brown, year-old capsule has opened and dispersed its seeds.)

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Basking Bumblebees

10-10-13  basking bumblebee 016Bumblebees are some of the earliest bees to emerge in the spring and are often the last to be seen in the fall. They can regulate their own body temperature by shivering or basking in the sun. This enables bumblebees not only to stay active longer during the season, but also during wet or cooler weather. Look for them on sunny patches of ground at this time of year.

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Woolly Aphids

10-8-13 woolly aphid 001Woolly aphids are just that – aphids that have special glands that produce wax-like filaments which resemble white wool. When the “wool” is brushed aside, the dark aphid bodies below are apparent. Colonies of woolly aphids often congregate in cottony masses while sucking the sap of a host plant or tree, at which time they are somewhat camouflaged in that they can easily be mistaken for mold or a fungus. When woolly aphids take flight, the wax strands catch the wind and allow them to drift , allowing them to look more like seeds than edible prey.

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Deciduous Leaves Falling

10-19-13 falling sugar maple leaf 081The falling of a leaf is the final step in an ordered series of events referred to as senescence. This process allows trees to conserve resources, prepare for a dormant period, and shed inefficient tissues. When leaves become unable to produce food due to a lack of chlorophyll, a process of shutting-down and sealing-off begins. Leaves are shed through a number of biological actions which take place at the base of the leaf’s stem, or petiole. The walls of some cells weaken, while those of other adjacent cells expand. The expansion of the latter causes pressure against the weaker-walled cells, resulting in these two groups of cells tearing away from each other, causing the leaf to fall. The tree forms a protective barrier on the wound where the leaf had been attached to the branch, sealing it off from pests and the environment and leaving a leaf scar.


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