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Migration

Common Mergansers Migrating

11-14-14  common mergansers 120Common Mergansers are hardy, fish-eating, cavity-nesting ducks that can be found in New England year round, as they winter as far north as open water allows. However, the birds we see in the winter on large bodies of water most likely are not the same birds that breed here. All North American populations of Common Mergansers migrate, generally short to intermediate distances. Populations near the coast move only short distances, while more interior birds migrate farther. Heavier birds and adult males seem to tolerate colder winter temperatures and remain farther north than immature birds. They can often be seen on large lakes and rivers, as well as the coast, where they form small groups that may gather into large numbers at favored sites.

Migrating Common Mergansers tend to leave late in the fall (this week marks the peak of their fall migration), making them often the last waterfowl migrants to head south. Common Mergansers typically migrate over land at night, and along seacoasts or major river systems by day. In the spring, adult males return north first as soon as open water is available, followed by females a few weeks later. (Photo: 2 juvenile Common Mergansers) Thanks to canoe-steadying Sadie Richards for making it possible for me to take this photograph.

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Gray Catbird Stragglers Passing Through

10-30-14 gray catbird 109Gray catbirds begin their nocturnal migration to wintering grounds in late August and early September. The last of the stragglers are now passing through northern New England. Catbirds winter from the southern New England coast south to Panama, with concentrations on the U.S. Gulf coast and the Yucatan Peninsula. Those individuals that winter in the Yucatan Peninsula and Central America cross the Gulf of Mexico, and in order to do so they put on so much fat (during fall migration their mass may increase to 150% of lean body mass) that it approaches the upper limit of what flight allows.

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Common Loons Migrating

10-27-14 common loons migrating2  146Most of the eastern U.S. and Canada Common Loon population shifts from freshwater inland breeding locations to coastal marine wintering areas, although some remain at inland freshwater sites throughout winter. Research shows that the very large loons in Maine, New Brunswick, and eastern New Hampshire do not migrate far and primarily overwinter in the Gulf of Maine, while smaller loons from other New England and New York breeding populations migrate to Long Island Sound south to New Jersey.

Some Common Loons begin their diurnal migration to their wintering territory in late summer, but most loons leave their breeding territory in September (high latitudes) and October (low latitudes), and arrive at their destination by the end of November. Breeding pairs and their offspring do not migrate together. Parents generally migrate first, usually separately; young remain on their lakes after adults have departed, until near freeze-up, and often migrate in groups. Although they often migrate singly, common loons do form groups (in some places, hundreds or thousands of birds) on large bodies of water before and during migration. These are referred to as staging areas. When migrating over land, loons can reach an altitude of a mile and a half; over water they usually fly within 300 feet of the surface of the water.

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Hermit Thrushes Migrating & Stopping Over to Refuel

10-7-14 hermit thrush  092The Hermit Thrush is often one of the last thrushes to leave its breeding grounds in the fall — peak migration is between the end of September and the middle of October. High pressure, clear skies and wind from the north usually produce many sightings of this bird at this time of year. Unlike many other species of thrushes that winter in Central or South America, the Hermit Thrush is not a long distance migrator, and does not cross the Gulf of Mexico. Approximately one-third of all migratory flights end after only two to three hours of flight. Typically it makes several two-to-six-day stopovers to refuel before reaching its wintering grounds in southern U.S. and Mexico.

The Hermit Thrush is a nocturnal migrant, often departing roughly half an hour after sunset (over half of departures occur within 60 minutes after sunset and none after midnight) with most flights ending about 40 minutes before sunrise (none later than 20 minutes before sunrise). (Flight information from Birds of North America Online)

Inadvertently, the person responsible for my being able to photograph a Saddleback Caterpillar was not mentioned in yesterday’s post. Many thanks to Rick Palumbo for his extraordinary help with this endeavor.

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Common Nighthawks Migrating

8-28-14 common nighthawk_w725_h486Nightjars, or “goatsuckers” as some call them, are a family of birds that catch and eat insects on the wing, are often ground nesters, and many (whip-poor-will, for instance) have distinctive calls. Nighthawks are a member of this group, but not a very well-named member, as they are unrelated to hawks and are active at dawn and dusk (not night). This insect-eating bird is often seen on the wing, hawking insects in both rural and urban areas (Fenway Park comes to mind). Its loud, nasal “peent” calls and bat-like flight make this bird very noticeable if it is feeding. We are currently at the peak of the fall Common Nighthawk migration from North to South America. Flocks of hundreds and sometimes thousands are seen flying overhead, often in the early evening.

Unfortunately, in the past 30 years the breeding population of Common Nighthawks in Vermont has declined by 91%, according to the most recent Vermont Breeding Bird Atlas, and this drop in population is not limited to Vermont – much of Canada, New England and beyond has experienced a 50% – 70% decline. Increased predation, indiscriminate use of pesticides leading to lowered insect numbers and habitat loss may have played a part in this drop. (Photo from public domain.)

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Least Sandpipers Migrating

7-22-14 least sandpiper IMG_7923Least Sandpipers are the smallest shorebirds in the world, weighing only an ounce and measuring 5 – 6 inches long. Their fall migration has already begun, with individuals leaving their breeding grounds in the subarctic tundra and far northern boreal forest for their wintering grounds in Central and South America. Banding has revealed that the eastern population of Least Sandpipers undertakes nonstop transoceanic migrations of about 1,800 to 2,500 miles from the Gulf of St. Lawrence and New England to northeastern South America. Not much bigger than a sparrow, this common but declining shorebird can be seen refueling on mud flats throughout New England during its fall migration.

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Bobolinks Fledging and Preparing to Migrate

7-14-14 bobolinks2  234Between their striking black and white plumage and their long, bubbly song, male Bobolinks are hard to miss if they are inhabiting a field. The female’s plumage is more subtle, with lots of browns so that she blends in well when on her ground nest. The Bobolink’s most notable accomplishment is its annual migration between breeding (northern U.S. and southern Canada) and wintering (northern Argentina, Paraguay, Brazil, Bolivia) grounds — a round-trip distance of approximately 12,500 miles. According to Cornell’s Birds of North America Online, one female Bobolink known to be at least nine years old presumably made this trip annually, which would mean that in her lifetime she flew a distance equal to traveling 4.5 times around the earth at the equator.

Grassland birds such as Bobolinks, Eastern Meadowlarks, Upland Sandpipers and numerous sparrows, which have been in decline for decades, populate New England’s hay fields, meadows, and pastures. Many of these birds build their nests on the ground, raise young, and forage for insects and grains in summer months. If you own or manage a hayfield that hosts Bobolinks (or any other grassland species), consider delaying mowing until after mid- July to allow these birds the opportunity to fledge their young and get them ready for one of the longest migratory flights of any North American songbird. (Photo: male Bobolink on rock, female on grass.) (Thanks to Jeannie Killam and Terry Ross for photo op.)

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