Birds Nest
Here are a few facts about nests from some of our bird species:
If you pay careful attention to the birds this time of year, you may notice that some are carrying nesting material. Nests vary greatly across the country and different bird species have a number of unique techniques for building their perfect home to raise their young.
BALD EAGLES
Bald eagles build strong nests and use them year after year. They make improvements and add to the nest, it can weigh over a ton! The largest eagle nest was 20 feet deep and estimated to weigh 2 tons! Bald eagle nests are quite large, averaging the size of a typical bathtub (a round one… more like a hot tub) and a depth of 3 to 4 feet. To support this size, the nests are most often found in large trees, built about 2/3 to 3/4 up the height of the tree. Less commonly, they can be found on the ground or on cliffs. The nests are made of large sticks.
Other raptors build large nests too, e.g. Osprey and Red-Tailed Hawks. Osprey nests are situated at the top of trees or other structures and are not as deep. Red-tailed hawk nests are smaller overall and are built with relatively smaller branches and twigs, about thumb size or smaller, instead of large sticks.
The male and female take turns sitting on their eggs, switching about every two hours. It will take between 35 and 40 days for the eggs to hatch.
RED TAIL HAWKS
The Presidio, one of the prettiest stretches of property among many in San Francisco, is a great place for bird watchers. A number of birds migrate through the area, and there are plenty of permanent residents there, too, including hawks, eagles, owls and falcons.
The red-tailed hawks starring in their own reality show are among the year-round residents, and they are no stranger to the tree where they are nesting. The pair has returned to the same spot for several years.
Things to know
The Presidio is an important stop on the Pacific Flyway, the major north-south flyway for migratory birds, which makes it a hot spot for bird watching with 323 different types of birds — so far — seen this season in the park.
Around this time of year, plenty of birds stop off in the Presidio to build, or rehabilitate, a nest for the season.
It usually takes between 3-7 days for Red-tailed Hawks to build a nest, or in this case, prep the nest for the season.
After eggs are laid, chicks hatch in 28 to 35 days.
Red-tailed hawks can be the size of a small dog, yet only weigh about 3 pounds.
While you’re in the Presidio, look up into the sky and all around you.
AMERICAN ROBIN
The American robin (Turdus migratorius) is a migratory songbird of the true thrush genus and Turdidae, the wider thrush family. It is named after the European robin because of its reddish-orange breast, though the two species are not closely related, with the European robin belonging to the Old World flycatcher family. The American robin is widely distributed throughout North America, wintering from southern Canada to central Mexico and along the Pacific Coast. It is the state bird of Connecticut, Michigan, and Wisconsin.
According to the Partners in Flight database (2019), the American robin is the most abundant bird in North America (with 370,000,000 individuals), ahead of red-winged blackbirds, introduced European starlings, mourning doves and house finches.[4] It has seven subspecies, but only one of them, the San Lucas robin (T. m. confinis) of Baja California Sur, is particularly distinctive, with pale gray-brown underparts.
The American robin is active mostly during the day and assembles in large flocks at night. Its diet consists of invertebrates (such as beetle grubs, earthworms, and caterpillars), fruits, and berries. It is one of the earliest bird species to lay its eggs, beginning to breed shortly after returning to its summer range from its winter range. The robin's nest consists of long coarse grass, twigs, paper, and feathers, and is smeared with mud and often cushioned with grass or other soft materials. It is among the earliest birds to sing at dawn, and its song consists of several discrete units that are repeated.
The adult robin's main predators are hawks, domestic cats, and snakes. When feeding in flocks, it can be vigilant, watching other birds for reactions to predators. Brown-headed cowbirds (Molothrus ater) lay their eggs in robin nests (see brood parasite), but the robins usually reject the egg.