An online resource based on the award-winning nature guide

Migration

Lingering Great Blue Herons

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Most fish-eating birds that breed where most bodies of water freeze over in the winter migrate further south in the fall, including Great Blue Herons.  Movement of this large wading bird takes place largely from September to mid-October. According to Christmas Bird Count data, the Great Blue Heron has the widest wintering distribution of any heron species in North America.

While the number of Great Blue Herons in the Northeast is greatly diminished in November and December, it’s not uncommon to spot lingering birds at this time of year.  Come January, when most bodies of fresh water are inaccessible to herons, sightings become rare until they begin returning in March.

Where open water remains in the Northeast, those Great Blue Herons braving the cold continue to consume fish, insects, amphibians and crustaceans.  Small mammals, especially voles, and birds remain a warm-month delicacy, when mammal hair is cast in pellets and bones are digested.

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Semipalmated Plover Migration Winds Down

10-31-18 semi-palmated plover_U1A1025During the peak of their migration in the fall (August and September), Semipalmated Plover sightings occur inland but are especially concentrated along the East coast.  Sightings are decreasing now as we approach the tail end of their flight from their Arctic and sub-Arctic breeding grounds to their wintering grounds which range from the southern U.S. through southern South America.

In general, plovers (Charadriidae) are small to medium-size, plump shorebirds with long wings and short necks and rounded heads.  The Semipalmated Plover, during the breeding season, has a black crown, eye patch and single breast band.  These areas are brown in nonbreeding adults (pictured).

Fortunately, there is no evidence that the estimated breeding population of 200,000 birds is diminishing. According to the Cornell Lab of Ornithology, “The Semipalmated Plover is among the few plovers whose numbers are apparently increasing, perhaps owing to its versatility in food and habitat choice, its wide-spread coastal winter distribution, or its habitat expansion in the sub-Arctic as a result of disturbance by both humans and arctic geese.”

For those curious about this shorebird’s name, “semipalmated” in a wading bird’s name indicates that its toes are webbed for part of their length (barely detectable in photo, but if you look hard you’ll see partial webbing in the left foot).

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Dark-eyed Junco Numbers Increasing

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Although Dark-eyed Juncos can be found year-round in New England, their numbers increase dramatically at this time of year, and they become much more noticeable. In addition to our year-round residents, many individuals that have bred further north migrate to the Northeast and even further south to overwinter. For this reason they are sometimes referred to as “Snowbirds.” From late September through October their numbers build and remain high until next May, when many return to their Canadian breeding grounds.

During the winter Dark-eyed Juncos can often be found in flocks, hopping and scratching on the ground as they forage for the seeds that make up 75 percent of their diet. Their two-toned white and gray plumage, and their white outer tail feathers are distinctive.

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Broad-winged Hawk Migration Peaking

9-17-18 juv. broadwing_U1A7043The migration of raptors has begun, and one of the first species to migrate in the fall is the Broad-winged Hawk (Buteo platypterus). While it is quite secretive when nesting, it is one of the more conspicuous species of birds when migrating.  This is for two reasons. They are one of the few North American raptors that flocks during migration, and much of their migratory behavior is concentrated in the Northeast in a two-week period around the middle of September.

Migrating Broad-wings conserve energy by frequently soaring in thermals and mountain updrafts. Flocks of birds, or “kettles”, soar up the heated columns of air, peel off and glide to the next thermal where they repeat the process. Very little wing-flapping is necessary in order to cover a lot of ground. The flocks, or “kettles,” range from several individuals to thousands of birds (larger kettles generally occur nearer their Central and South America wintering grounds).

The number of birds migrating often grows following a cold front, when winds die down and thermals increase. Fall migration of Broad-wings in the Northeast is associated with good visibility, moderate favorable winds, high temperatures, and afternoons (vs. mornings). (Photo: juvenile Broad-winged Hawk)

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Green Herons Starting To Migrate

8-24-18 green heron2 20160916_0770Green Herons breed throughout the eastern half of North America.  After their nesting season is over they tend to wander, often to more favorable foraging areas. This dispersal merges gradually into a protracted fall migration for birds in the Northeast, beginning around the end of August, with most birds having left by mid-October.

Most Green Herons from eastern United States migrate south to winter along the Gulf of Mexico, Florida, Caribbean islands, Mexico, through Central America to northern South America.   We usually see our first Green Herons returning in mid-April, earlier than other herons.  This may be due to their crepuscular feeding habits, which gives them a longer span of time to feed each day.

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Eastern Gray Squirrels Swimming

e-gray squirrel swimming by Erin 2_H6A2563 copy (002)Imagine coming upon a stick floating in a large pond only to discover the “stick” had a head and tail and was making a beeline for the shore.  The fact that an Eastern Gray Squirrel (Sciurus carolinensis) had paddled half a mile to get from one shore to the opposite shore of a pond shouldn’t have come as such a surprise, as this rodent has a long history of migratory swimming behavior, but it’s such an incongruous and unexpected event that it made my companion and me initially question our eyesight and then laugh out loud.

Historical reports suggest there have been many massive Eastern Gray Squirrel migrations in the United States, beginning in 1749 in Pennsylvania.   Records show the state paid three cents for each squirrel killed; over 640,000 squirrels were turned in for bounty.  One migration from Wisconsin in 1842 lasted four weeks and involved a half billion squirrels. Because of the numerous squirrel migrations, John James Audubon was erroneously convinced that the squirrels on the move were a separate species from the Eastern Gray Squirrel and gave them the scientific name Sciurus migratorius. (This proved to be inaccurate.)

During the 1800’s, thousands of squirrels would periodically move en masse across roads, fields and forests, and swim across lakes and rivers (including the Mississippi and Connecticut Rivers) in an effort to disperse. The consensus is that these mass movements were a response to local food conditions. They occurred mostly during the month of September following a year in which there was a large production of food (acorns).

The most recent mass migration of Eastern Gray Squirrels in eastern U.S. occurred in 1968, when a bumper crop of acorns in 1967 was followed with a corresponding bumper crop of young squirrels in 1968. By fall, as the first litter of the year left the nest, there was a severe shortage of food. As a result, massive numbers of acorn-eating squirrels dispersed in search of food.

One Eastern Gray Squirrel swimming across a New Hampshire pond does not a migration make, but it might not be a bad idea to keep an eye out for excessive numbers of paddling squirrels and/or road-killed rodents come September. (Photo by Erin Donahue)

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Male American Redstarts

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Warblers — small, active, insect-eating birds — are often referred to as the “butterflies of the bird world” due to the striking breeding plumage of many of the males.  One warbler that’s hard to overlook due to its brilliant orange and black plumage is the male American Redstart.  Like most warblers, it is a very active feeder, flitting from branch to branch looking for insects.  However, it also occasionally feeds like a flycatcher — perching and flying out to capture insects in mid-air, giving you the opportunity to get a good look at it.

The breeding behavior of the American Redstart is of particular interest, in that not only is the male occasionally polygamous, as are many other bird species, the two females he mates with at the same time do not nest in the same territory.  The male holds two separate territories that can be separated by as much as a quarter-mile.  The male begins attracting a second female after the first has completed her clutch and is busy incubating the eggs.  Perhaps the bird world would benefit from a “Me Too” movement.

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