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Bird Nests

Opportunisitic Bird Nest Builders

12-3 northern mockingbird nest IMG_6363Several winters ago I discovered a Northern Mockingbird nest in downtown White River Junction, Vermont. Like all birds, mockingbirds are opportunists and utilize whatever material is available when building their nests. Even though it is not a booming metropolis (population roughly 2,500), White River’s relatively dense population is reflected in the building material that these songbirds used. Because they often nest in urban and suburban areas where trash tends to be more concentrated, mockingbirds often line their nests with bits of plastic, aluminum foil, and shredded cigarette filters (see photo). The male constructs the twig foundation while the female makes most of the lining. He often begins building several nests before the female chooses one to finish and lay eggs in.

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Bird Nests: Look But Don’t Collect

11-23-15 mourning dove nest2  005It is prime time to look for bird nests now that leaves have fallen and heavy winter snow has not arrived. Nests such as this Mourning Dove nest are visible and still in fairly good condition. Much can be learned from examining the habitat, exact location, size, shape and construction material of these avian nurseries. But the nests must be left where they are, for possession of not only a bird, but of a bird nest, egg or feather of most migratory birds, even for scientific research or education, is illegal if you do not have a Federal Migratory Bird Scientific Collecting Permit.

Ninety-seven years ago the Migratory Bird Treaty Act (MBTA), one of our oldest wildlife protection laws, was created. Basically it is a law that protects birds from people. It was made in response to the extinction or near-extinction of a number of bird species that were hunted either for sport or for their feathers. According to the United States Fish & Wildlife Service (USFWS), “The MBTA provides that it is unlawful to pursue, hunt, take, capture, kill, possess, sell, purchase, barter, import, export, or transport any migratory bird, or any part, nest, or egg or any such bird, unless authorized under a permit issued by the Secretary of the Interior.” A list of the species this law pertains to can be seen at http://www.fws.gov/migratorybirds/RegulationsPolicies/mbta/MBTANDX.HTML.

Not all North American bird species are protected under the MBTA. (Passenger Pigeons were not protected, and they no longer exist.) Birds that are considered non-native species such as the House Sparrow and the European Starling are not protected, and many hunted or game birds, including ducks, geese, doves, and many shorebirds are subject to limited protection and can be hunted in season.

The U.S. Fish and Wildlife Service is currently working on strengthening this bill to better protect birds from modern-day threats (windmills, cell phone towers, etc.). According to USFWS estimates, power lines kill up to 175 million birds a year. Communications towers account for up to 50 million kills, and uncovered oil waste pits account for up to another 500,000 to 1 million deaths. Data on wind turbines are harder to come by, but current estimates are around 300,000 bird fatalities a year. A number of companies in the oil and power-line sectors have already developed and implemented best practices to protect birds. Let us hope that this trend continues.

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Tree Swallow Nestlings Well Fed

7-21 tree swallows 068Tree Swallow parents begin feeding their four to seven nestlings as soon as they hatch, and they continue doing so until their young depart the nest and sometimes for several days afterwards. The adult carries food in its bill and places it directly into the open mouth of a begging nestling. The small insects gathered by the parent may be formed into a rounded ball, or bolus, which they hold in their mouth or throat (often not visible to an observer). Both parents feed the nestlings, together averaging about ten to twenty deliveries per hour. During periods of peak nestling demand, parents may feed as many as 6,000 to 7,000 insects in a single day. (Thanks to Jeannie Killam and Terry Ross for photo op.)

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Juvenile Bald Eagles Fledging

7-17-15 juvenile eagle 003For several weeks before leaving their nest, young bald eagles constantly flap their wings, occasionally lifting themselves off the nest several inches in mid-air. Eventually they succeed in making short “flights” to nearby branches and then back to their nest. The young eagles are strengthening their wing muscles, practicing landing, and beginning to master flight.

Sometime between 8 and 14 weeks juvenile bald eagles leave their nest. Many fledge successfully, but up to half of the nest departures are unsuccessful, with the young ending up on the ground where they may stay for weeks before flight is achieved. During this time the parents usually continue to feed their young, but the juvenile eagles are far more vulnerable to predators. If the flightless, grounded juveniles are approached or threatened, or if they simply want to move from one spot to another, they walk or run on the ground (see photo).

The young bald eagle pictured was blown out of its nest prematurely and landed on the ground. Eventually it managed to fly back up onto a branch in the nest tree. The parents continued to feed the eagle while it was on the ground, as well as after it was back up in the tree. (Thanks to Linda and Roger Whitcomb for photo op.)

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Young Eagles Preparing to Fledge

6-11-15 eaglet 062For several weeks prior to their first flight from their nest, Bald Eagle nestlings practice flapping their wings to the point of lifting themselves up several inches into the air. This develops their wing muscles, flight coordination and landing ability.

At anywhere from eight to fourteen weeks of age, juvenile Bald Eagles fledge, or leave their nest. According to Birds of North American Online, up to half of young Bald Eagle nest departures are unsuccessful. The young land on the ground and may remain there for weeks before regaining flight ability. More often than not their parents will continue to feed them, but they are much more vulnerable to predation in this situation. Fledglings may continue to use their nest as a feeding platform for several weeks after leaving it, as they gain flight and foraging skills.

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Barred Owl Chicks View The World For The First Time

6-4-15  barred owl chicks2  100 Barred Owl eggs (usually two or three) are often laid in a tree cavity, where the adult female incubates them for roughly a month. Fuzzy, white, downy chicks hatch and remain inside the tree for four or five weeks while being fed by both parents. When the young owls are two or three weeks old, their white down is replaced with gray-buff secondary down, and they gain the strength to climb up the inside of the tree and peer out at the outside world. In and out they go, perching on the rim of the nest hole for half an hour or so as they await the arrival of their next meal, and then retreating back to the safety and warmth of their nest. (Thanks to Alfred Balch, naturalist extraordinaire, for photo op.)

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Great Horned Owlets Soon To Fledge

great horned owl 454Great Horned Owls are said to have a wider range of nest sites than any other bird in the Americas. Most commonly they use tree nests of other species, particularly Red-tailed Hawks as well as other hawks, crows, ravens, herons (Great Blue Heron nest pictured), and squirrels.

These month-old young owls have grown rapidly, from a weight of roughly an ounce at birth to about two pounds. They will weigh approximately 2 1/2 pounds when they fledge. By six weeks of age, young Great Horned Owls are climbing out of the nest and perching on nearby branches, and by seven weeks they are taking short flights.

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