|
|
Cowbirds, Sharp-shinned Hawks, and Northern Cardinals
Answers to readers' questions about cowbird identities, roosting places, and cardinal territories
Contributed by Julie Craves
Published: February 24, 2012
How do young cowbirds learn that they’re cowbirds, not the warblers or sparrows that raised them? — Val Cunningham, St. Paul, Minnesota
Brown-headed Cowbirds do not build nests or raise their own young. Instead, they lay their eggs in the nests of other birds, leaving parental duties to the hosts. Cowbirds have laid eggs in the nests of more than 220 different bird species in North America. About 140 of them are known to raise cowbird young; approximately 50 species make up most of the host reports.
By the end of the breeding season, after becoming independent of their foster parents, young cowbirds join other cowbirds in flocks, often with other species of blackbirds. Researchers are still trying to determine how much of the ability to recognize their own species is controlled genetically and how much may be learned.
For example, evidence suggests that young cowbirds may recognize other cowbirds by comparing their plumage with their own. Other studies indicate that adult cowbirds may seek out young cowbirds — even while they are still in the hosts’ nests — providing social cues to juveniles that could contribute to conspecific recognition. But the research is not conclusive and does not fully explain how young cowbirds so consistently and easily recognize their own kind. |
A Sharp-shinned Hawk frequently travels to my backyard. Where does it roost? Does it have a territory within the town? Does this type of hawk build nests in a small-town setting? — Sandra Gardner, Mount Union, Pennsylvania
Sharp-shinned and Cooper’s Hawks are closely related raptors in the family known as accipiters. Accipiters specialize in hunting birds.
Their long tails and relatively short, rounded wings make them extremely maneuverable and enable them to chase their prey through forested settings. Long legs and toes enable them to reach into vegetation.
Your yard is probably just one small part of what is likely a feeding territory encompassing many square blocks. The size varies depending on the species, age of the bird, and landscape features. The hawks prefer conifers or other trees with dense foliage for night roosts.
When bird feeders occur within their territories, both species will take advantage of the congregation of prey. They typically target injured, ill, or naïve birds of common species.
Both species will nest in urban areas, often in parks or cemeteries. Cooper’s Hawks tend to be a bit more common as urban nesters.
Research has indicated Sharp-shinned Hawks prefer to nest in conifers, while Cooper’s Hawks are more adaptable. In fact, studies suggest that Cooper’s Hawks are more likely to be found in urban areas at any time of the year, while Sharp-shinned Hawks favor more rural settings. |
Is it common for only one pair of cardinals to feed and live in one place? I seem to have just a single pair. And where do they build their nests? — Karyn Leighton, Coral Springs, Florida
Like most songbirds, Northern Cardinals defend territories during the breeding season. Cardinals often are aggressive about excluding other cardinals from their territories — that’s why so many people note them attacking their reflections in windows and car mirrors. The birds think the reflection is an intruder. Each sex chases out individuals of its own sex.
Cardinal territories are about two and a half acres in size. The birds may go outside the territory to feed. If doing this involves trespassing in another territory, they usually remain quiet and stay close to the ground. Cardinals typically nest in dense shrubs and can raise two or three broods per year.
Some cardinals stay paired throughout the year but do not defend territories in winter. Family groups may join others in loose flocks but are not particularly friendly toward other cardinals. When they get too close to each other at bird feeders, you’ll notice bickering. |
|
See great photos of birds, get birdwatching tips, learn about birding events, and more!
|