Blog Archive: Bird Terms

Birdorable American Robin

Bird Term: Brood Patch

October 18th, 2018 in Bird Terms 1 comment

A brood patch is a bare area of skin that some birds develop during nesting. The bare skin is an adaptation to help with egg incuabation.

The patch of featherless skin allows the parent bird to provide extra warmth from his or her own body to the eggs in the nest, and to growing, naked, newly-hatched chicks in the first days of life.

Brood Patch on American Robin
Bird banders note brood patch on American Robin by VSPYCC (CC BY 2.0)

Both males and females can develop a brood patch, depending on the species and how incubation duty is shared. In most species, the brood patch develops as feathers are naturally shed during nesting activities. In some species, the brood patch appears through self-plucking. Ducks and geese, for instance, may line their nest with soft breast feathers, exposing the skin.

Canada Goose on Nest
Canada Goose sits on eggs in nest lined with feathers by Bradley Davis (CC BY-ND 2.0)

The location of the brood patch on the adult bird's body depends on the species. Most birds have a single bare patch of skin, while some species may develop two or even three patches.

Fun Fact: Bird banders use the presence of a brood patch to determine if a bird is currently nesting. The presence of a brood patch can also help to sex or age the bird. The patch on most birds is not immediately visible on the bird's body; banders gently blow air on the belly to separate the surrounding feathers to see if a patch is present.

Birdorable Sandhill Crane

Crane Week Bird Term: Precocial

March 30th, 2018 in Bird Terms, Cranes No comments
Baby Sandhill Crane with parent

We're celebrating cranes on the Birdorable blog this week! Today we'd like to share a bird term that relates to cranes and other birds. Let's learn about what it means to be precocial!

The term precocial comes from the Latin praecocia, which refers to "places where fruits ripen early." A precocial species is one in which the newly hatched or born young are relatively mature. In birds, this means the baby is usually covered in downy feathers and is able to walk and even feed itself within a short time of hatching. This adaptation is found in most ground-nesting birds as a strategy to evade predators when the nest offers little shelter.

Cranes have precocial young, as do many other birds, including ducks and geese, chickens, and rails. Malleefowl chicks can even already fly within a day of hatching. There are some mammals born precocial, like the Hartebeest, whose calves can stand and walk within hours of being born.

On the other end of the development spectrum are altricial babies. In birds, this usually means at the time of hatching the chick is naked (without feathers), has its eyes shut, and is completely helpless and dependent on its parents for care all of its needs.

Two other terms related to precocial and altricial are nidifugous and nidicolous. Nidifugous species leave the nest site shortly after hatching; all nidifugous species are precocial but not all precocial species are nidifugous. Precocial birds that remain in the nest for a period are called nidicolous.

Birdorable Heermann's Gull

Gull Week Bird Term: Kleptoparasite

February 23rd, 2018 in Bird Terms, Gulls No comments

We're celebrating gulls on the blog this week! Today we'd like to share a bird term that relates to some species of gulls. Let's find out about kleptoparasitism!

Seagull chasing juvenile pacific gull
Photo by Jade Craven (CC BY 2.0)

Kleptoparasitism is just what it sounds like - parasitism by theft (klepto-). It basically refers to one animal stealing food from another. Before we go on, it should be made clear that gulls are not the only species that engage in this behavior. They aren't even the only birds that do so.

gulls stealing food
Photo by John Haslam (CC BY 2.0)

Why would one animal steal food from another? In some cases, the thief takes prey items that it would not be able to capture on its own. Sometimes the kleptoparasite steals food opportunistically, or to save the time and effort of obtaining prey. Kleptoparasitism can also refer to the theft of non-food items, like when Chinstrap Penguins steal nest material from other penguins to use in their own nest.

Birds in the seabird family Skua are known for their kleptoparasitic behavior. Some species of skua obtain a significant percentage of their food using this method, stealing prey caught by other seabirds.

Frigatebirds are known for this behavior as well, giving them the appropriate nickname "pirate of the sea".

Gulls can be both perpetrators and victims of kleptoparasitism. Heermann's Gulls and Laughing Gulls are known to steal fish from Brown Pelicans, snatching anything that escapes from the pelican's bill as it surfaces from a hunt. Gulls may chase others of their own species in order to steal freshly caught prey or found food items.

stealing a meal
Photo by Mike Sutton (CC BY 2.0)

Chasing down deep diving fish hunters is a way for non-diving gulls to obtain food not otherwise available.

Stealing from the Mallard
Photo by Micolo J (CC BY 2.0)

Gulls have also been known to steal food from humans! Has this ever happened to you?

Donut thief
Photo by Funk Dooby (CC BY-SA 2.0)
Birdorable Cedar Waxwing

Bird Term: Crop

November 22nd, 2017 in Bird Terms No comments

The crop is a part of an animal's anatomy connected to the digestive system. It is used to store food before digestion. It is common in birds but also found in some species of snails and earthworms, and was present in some dinosaur species.

Cedar waxwing on Seedskadee National Wildlife Refuge
Cedar Waxwing with bulging crop by USFWS Mountain-Prairie

In birds, the crop is an expandable pouch found at the throat and often visible externally, especially when full of food. Not all species of bird have a crop. In pigeons and doves it is used to store food but also to produce a substance known as crop milk to feed their young.

Golden Eagle on Seedskadee NWR
Golden Eagle with full crop by USFWS Mountain-Prairie

Scavenging species like vultures and condors will often feed until they are completely full, and then fill their crop for later digestion. The crop gives the birds a chance to store food for later digestion which is advantageous when it is unknown when the bird will be able to feed again.

Other raptor species, like hawks, eagles, and ospreys, have a crop, but owls do not.

Birds that regurgitate food to their young use the crop to soften the food items before giving it to their chicks.

baby Red-shouldered Hawk
Baby Red-shouldered Hawk with full crop by Amy Evenstad
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 2 comments

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?