An online resource based on the award-winning nature guide

Birds

Green Herons Migrating

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Green Herons (Butorides virescens) are small, crested, wading birds that inhabit wetland thickets throughout most of North America. After breeding, most tend to wander to more favorable foraging areas before migrating south to Florida, Central and South America. Migration begins in late August/early September and by mid-October, most Green Herons have departed.

Green Herons are among the few species of birds that use tools in order to lure fish to within their striking distance. Bread, mayflies, twigs, leaves, berries, earthworms and feathers are among the lures they have been observed dropping into the water as bait. To watch a video of a persistent and successful Green Heron fishing with a lure, go to https://www.youtube.com/watch?v=Porp5v5lLKk .

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Peak of Broad-winged Hawk Migration

9-14-16-broad-winged-hawk2-037We are currently at the peak of the Broad-winged Hawk fall migration, an annual event that birders look forward to with great anticipation. These birds are gregarious, often migrating in flocks or groups called “kettles” that range from several individuals to many thousands of birds. In New England in mid-September it’s possible to see 10,000 Broad-winged Hawks a day at a hawk watch site; near the Great Lakes, 50,000 a day and Texas hawk-watchers have been known to see 300,000 to 500,000 a day.

Broad-wings depend more on thermals, rising columns of warm air, during their migration than most raptors. They don’t usually begin flying until mid-morning, by which time the sun has created thermals, and they stop flying as soon as thermal production ceases in later afternoon. During the day kettles can be seen circling around and around, higher and higher as they ride thermal columns of air upwards, peeling off at the apex and soaring (saving energy other migrating hawks use flapping their wings) southwards towards their wintering grounds.

To find hawk watch sites in your part of the world, go to the  Hawk Migration Association (http://www.hmana.org/hawk-watch-sites/).

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Great Blue Herons Cooling Off

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Birds have a number of ways of keeping cool. They don’t sweat, nor do they pant, but birds do have several behavioral adaptations which reduce their temperature. Often nestlings that are exposed to the relentless heat of the sun for long periods of time, such as platform-nesting raptors and herons, resort to what is called gular fluttering. They open their beaks and “flutter” their neck muscles, promoting heat loss – an avian version of panting.

Another avian strategy for cooling off is demonstrated by this adult Great Blue Heron — that of arranging its wings in a certain position in order to reduce its body heat.  Great Blue Herons droop their wings while standing, which allows air to circulate across their body and sweep away the excess heat.

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Great Egrets Dispersing

great egret flyingAlthough Great Egrets breed sporadically as far north as Vermont, seeing one in northern New England is always noteworthy. The likelihood of a sighting increases as summer progresses, due in large part to the phenomenon of post-breeding dispersal. After young Great Egrets have fledged, individuals wander well outside their typical breeding range, as far north as southern Canada. The northward dispersal of juvenile birds peaks in August and September. Most Great Egrets migrate in the fall, from September through December.The extent of their migration is influenced by annual fluctuations in temperature. When winters are mild, individuals may remain as far north along the Atlantic Coast as Massachusetts.

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Belted Kingfishers’ Distinctive Traits

8-2-16 belted kingfisher 520You often hear a Belted Kingfisher before you see it. Their territorial, mechanical “rattle” is quite distinctive and issued frequently.  This call is just one of their more distinctive traits.  They are one of the few species of birds where the female’s plumage (two “belts” on breast) is more colorful than the male’s (one breast “belt”). Kingfishers have a distinctive pattern of wingbeats: whereas most birds beat their wings several times and then glide, kingfishers’ wingbeats are irregular and intermittent, lacking the flap and glide pattern.  Kingfishers have the unusual ability to hover in one spot while surveying the water 20 to 40 feet below for fish or other prey.  When they capture a fish, they often return to a branch and whack it multiple times against the branch to assure its compliance in being swallowed head first without a struggle.  Even the nesting site of a Belted Kingfisher is fairly unusual —  a chamber located at the end of a 3 to 6-foot-long bank burrow they dig with their bill and feet.

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Bald Eagle Eyesight

7-26-16  juv. bald eagle2 026The eyesight of a Bald Eagle is impressive.  Part of the reason for their excellent vision is that these birds of prey have two centers of focus (foveae), which allow them to see both forward and to the side at the same time. Cone cells, one of three types of photoreceptor cells in the retina, perceive color, fine detail and rapid movement.  In a human, the fovea has 200,000 cones per millimeter; in the central fovea of a Bald Eagle’s eye, there are about a million cones per millimeter. An eagle’s eye is almost as large as a human’s, but its sharpness is at least four times that of a person with perfect vision.

Bald eagles are capable of seeing fish in the water from several hundred feet above, while soaring, gliding or in flapping flight.  (They locate and catch dead fish much more rapidly and efficiently than live fish, because dead fish float with their light underside up, making them easier to see.)  It is very likely that a Bald Eagle can identify a rabbit moving almost a mile away. This would mean that an eagle flying at an altitude of 1000 feet over open country could spot prey over an area of almost 3 square miles from a fixed position. (photo: recently fledged, juvenile Bald Eagle)

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Red-bellied Woodpeckers Sunning

7-20-16 male red-bellied adult 173Red-bellied Woodpeckers have extended their breeding range northward and westward over the last 50 years and are now breeding in northern New England.  Many are year-round residents here, while some individuals move further south during particularly harsh winters.  This range extension allows for observations not possible even 10 or 20 years ago.

While watching a Red-bellied Woodpecker this summer, I witnessed behavior I had never observed before.  The bird flew repeatedly to the same tree branch, flattened itself on the branch with its body facing the sun and then fanned its wings out while cocking its head, raising its crown feathers, opening its beak and appearing to look at the sun.  This behavior is common enough to have a name – the woodpecker was “sunning” itself.  While preening, stretching and calling often takes place intermittently while the bird is engaged in sunning, it may also enter a stupor or state of lethargy.   (Thanks to Cindy Lawrence for photo op.)

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