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Bird Irruptions

Pine Grosbeaks Irrupting in Northern New England

1-16-19 pine grosbeak _u1a0130If you live in northern Maine, you see Pine Grosbeaks year-round as this is the southern border of their breeding grounds. Those of us living in central Maine and northern New Hampshire and Vermont, if we’re lucky, will glimpse this member of the finch family only during major winter irruptions. (The rest of New England rarely sees a Pine Grosbeak.) It is an infrequent winter visitor in northern New England, irrupting less frequently and remaining further north than other boreal finches.

This is an irruption winter. Because of the dearth of mountain-ash berries and conifer seeds further north in the boreal forest, Pine Grosbeaks are seeking out crabapple and mountain-ash trees in northern New England.

A flock of Pine Grosbeaks will descend on a tree and strip it of its fruit in no time. Anyone who has watched these entertaining birds feeding knows that they are incredibly agile acrobats, stretching their necks and contorting their bodies in order to reach all available fruit. Once they grab ahold of a crabapple, they squash it with their short, conical beaks. They can look quite comical as the fleshy pulp accumulates on the tops and sides of their beak, as well as on the ground beneath them. The object of their desire and efforts is the seeds within the fruit, which they consume with gusto. If disturbed they will fly en masse to the tops of nearby tall trees where they remain until the perceived danger has passed and then return to continue feeding. (photo: female Pine Grosbeak in crabapple tree)

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Red-breasted Nuthatch Irruption

As a rule, most Red-breasted Nuthatches winter within their breeding range. Irruptive movements southward typically occur every two to four years when conifer cone production on breeding grounds is poor. This fall’s numbers confirm that it is a banner year for Red-breasted Nuthatches in the Northeast, due to their irruptive flights south.

The large number of Red-breasted Nuthatches at our feeders come as no surprise, as this year’s winter bird forecast by Ron Pittaway predicted a Red-breasted Nuthatch irruption due to the poor spruce seed crops in much of the eastern boreal forest. Even so, the numbers are impressive, as you can see from Ken Kaufmann’s (Audubon’s Field Editor) comparison of eBird’s September 2017 and September 2018 Red-breasted Nuthatch sightings.

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Rare Winter Visitors – Great Gray Owls

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Great Gray Owls are impressive birds – at 27” in length, they are our largest owl (Great Horned Owl – 22”, Snowy – 23”) but at 2.4 pounds, not our heaviest (Great Horned Owl – 3.1 pounds, Snowy – 4 pounds). The feathers that make a Great Gray Owl look so massive are what keep it warm during winters in the northern boreal forests where it resides.

Most of a Great Gray Owl’s diet consists of rodents, and some winters, when prey is scarce, individuals wander south to southern Canada and northern U.S. to sustain themselves. Sometimes Great Gray Owls are highly irruptive, and the number of sightings in the Northeast is high. In the winter of 1978-79 there were over 150 sightings in New England and Quebec. While there were numerous sightings in southern Canada this winter, northern New England was visited by only a few individuals, including the one pictured (in central New Hampshire).

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Common Redpolls Appearing

1-26-15 common redpoll male 077The birds most commonly associated with winter irruptions are the winter finches — Pine Grosbeak, Red Crossbill, White-winged Crossbill, Purple Finch, Pine Siskin, Common Redpoll, and Evening Grosbeak. Their food supply, or lack thereof, in the Canadian boreal forests where they normally overwinter, determines whether or not they will be seen as far south as the U. S. Key trees affecting finch movements in the boreal forest are spruces, birches and mountain-ashes.

Common Redpolls feed primarily on the catkins (seed-containing fruit) produced by birch and alder trees. When catkin production is low further north, as it is this winter, Common Redpolls leave these areas and irrupt into areas where food is more plentiful. (Photo: male Common Redpoll)

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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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Snowy Owl Pellet

3-25-14 snowy owl  203Your knowledgeable ID skills regarding yesterday’s Mystery Photo were most impressive!

Snowy Owls are the heaviest owls in North America, weighing roughly 4 pounds (a Great Gray Owl is only 2.4 pounds). A lot of fuel is needed to power this magnificent raptor. In the Arctic, where they live, lemmings are their preferred prey — one owl may eat more than 1,600 of these small rodents in a single year. This winter the Northeast has experienced record numbers of visiting Snowy Owls. A banner year for the Arctic lemming population followed by prolific nesting success for Snowy Owls resulted in an unprecedented “irruption” of these owls further south this winter.

While we do have lemmings in New England, they are uncommon, so Snowy Owls have relied on our small rodent, squirrel, rabbit and hare populations for food. Those owls wintering on the coast, where dunes and moors closely resemble their tundra habitat, have also taken advantage of the large number of sea ducks. As witnessed and described by Nantucket ornithologist Edie Ray, the owls fly up to great heights over the sea, spot waterfowl and then plummet down to just above the surface of the ocean where they sink their talons into a “sitting duck.” As a result, the indigestible bones, teeth and nails of prey are protectively wrapped in feathers as well as fur in the large pellets coughed up by these owls. (Snowy Owl locators: Edie Ray and Sadie Richards; Snowy Owl pellet finder: Sadie Richards)

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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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