Blog Archive: Bird Terms

Birdorable Red Knot

Bird Term: Neotropical Migrant

November 3rd, 2017 in Bird Terms No comments
Birdorable Red Knots

A lot of bird species are migratory. That means that they spend part of the year in one place and then travel (fly) to another place for some time. Migration is typically based around ideal conditions for breeding versus availability of food depending on location and season.

By the way, migration isn't limited to birds. In fact, some species in all major animal groups experience migration. Some well-known examples include the great wildebeest migration in Africa, the multi-generational migration of Monarch butterflies, and salmon runs from the Pacific and Atlantic Oceans into freshwater rivers.

Birds that breed across North America and migrate south to New World neotropics for the winter are known as Neotropical Migrants. Some definitions of the term use the latitude of the Tropic of Cancer (23 degrees north) as a benchmark: birds that breed above this line and winter below it are considered to be Neotropical Migrants.

The over 200 species of Neotropical Migrant birds come from different families, though a majority of species are songbirds. Shorebirds, birds of prey, and waterfowl may also be Neotropical Migrants.

Among these long-distance migrants are Red Knots, with a breeding range that extends into northern Canada and a winter range as far south as the southernmost point of South America. A Red Knot could travel up to 10,000 miles per one-way trip!

Bobolinks are also Neotropical Migrants; individual birds may travel over 6,500 miles one way, from northern Canada down to Argentina.

Neotropical Migrant birds face a variety of threats to their populations. For these birds, ample suitable habitat is required on their breeding grounds, winter sites, and all of the places that they stop along their long journeys.

Birdorable Brown-headed Cowbird

Bird Term: Brood Parasite

February 8th, 2017 in Bird Terms 1 comment

Birdorable Common Yellowthroats with Brown-headed Cowbird

Brood parasites are birds that rely on other birds, often of a different species, to raise their young. Brood parasitism occurs in organisms other than birds, including fish and insects, but we'll focus on a few well-known bird examples here.

This type of breeding strategy allows biological parents to avoid the stress and time involved in raising young.

Brown-headed Cowbird chick in Wood Thrush nest by Kelly Colgan Azar (CC BY-ND 2.0)

The strategy often involves laying eggs in several different nests in order to maximize the chances of young being raised successfully to fledge. The parasite bird also often removes an egg from the host parent to reduce discovery and improve their own offspring's chances of survival. Brood parasite birds generally have a shorter incubation period (with incubation actually starting internally within the biological mother bird) which also gives their offspring a head start over its adopted nest mates.

Common Cuckoo chick in host nest by Per Harald Olsen (CC BY 2.0)

A big risk with this strategy is discovery of intruder eggs. Some host species have learned to recognize intruder eggs in their nest, which may lead to total abandonment of the nest. Sometimes the discovery is made after hatching, and the parasitic chick is expelled from the nest. Another risk is using a host with a diet unsuitable for the growing chick. American Goldfinches are vegetarian; Brown-headed Cowbirds have an omnivorous diet and will not survive to fledge from finch parents.

Cowbirds and cuckoos are probably the most well-known species of brood parasites in the bird world.

The Brown-headed Cowbird is widespread across North America. This species has at least 221 known host species, from hummingbirds to birds of prey.

Common Yellowthroat feeding Brown-headed Cowbird by Bill Thompson (CC BY 2.0)

The Common Cuckoo of the Old World has wide distribution across Europe, Asia, and Africa. It takes a female cuckoo just 10 seconds to remove one egg and lay her own in a host's nest. Common Cuckoos have been recorded using over 100 host species. They are generally much larger than their hosts and the quickly-growing chick typically will remove all of the other eggs from the nest itself.

Brown Thornbill feeding Common Cuckoo chick by Wayne Butterworth (CC BY 2.0)

Have you ever seen a Brown-headed Cowbird, Common Cuckoo, or other brood parasite being fed by a host parent?

Birdorable Superb Fairywren

Bird Term: Sexual Dimorphism

November 12th, 2015 in Bird Terms, Fun Facts 4 comments
Supurb Fairy Wrens

Sexual dimorphism refers to observable differences between males and females of the same species. In basic terms, it means that a male of a species is easily distinguished from a female. In birds this usually means differences in size or in plumage. It can also be noted in behavior differences and other traits.

Earlier on this blog we talked about the extreme sexual dimorphism in Eclectus Parrots, where males and females show extreme differences in their plumage: males are bright green while females are shades of red and blue.

Sexual dimorphism exists in most species of raptor. In birds of prey, males are often smaller than the females of the species. However, this is often difficult to discern in wild birds, especially if seen at a distance or when only one bird is present.

Many common birds also exhibit sexual dimorphism. Male ducks are often colorful, while females tend to be drab. You can see this in the common Mallard.

Mallard ducks
Mallard ducks by Connor Mah (CC BY-SA 2.0)

In songbirds, males may be brightly colored while females have a similar plumage with more muted tones, as seen in Baltimore Orioles, American Robins, Eastern Towhees, and Black-throated Blue Warblers.

Eastern Towhee, female and male
Eastern Towhees: female (left) by Brian Henderson (CC BY-NC 2.0), male (right) by Dendroica cerulea (CC BY-NC-SA 2.0)

In other birds, like the Eclectus Parrot mentioned above, the plumage differences are extreme. Examples of this can also be seen in the Superb Fairywren of Australia, and the Sage Grouse.

Can you think of other bird species where the male is easily told apart from the female? Do you have birds like this where you live? What about birds that aren't sexually dimorphic? Can you think of species where male and females are impossible to tell apart by looking at them?