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 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 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?

There are about forty different species of toucan, spread over five genera. These include toucans and their smaller cousins, aracaris and toucanets. Here are some fun facts about the toucan family.

• All toucans have colorful and extremely large bills. Despite their size, the bills are composed of a kind of spongy material, and are extremely lightweight.
• Having a large bill is beneficial in foraging for fruit -- the bird can grab a lot of food without moving its whole body. The oversized bill also helps the toucan regulate its body heat in the steamy rainforest.
• Toucans are cavity nesters, but they aren't able to excavate their own nest holes with much success. They use cavities excavated by other birds, like woodpeckers.
• The smallest birds in the family range from about 11 or 12 inches long (the Green Aracari or the Lettered Aracari).

Green Aracari by Sham Edmond [CC BY 2.0]

• The largest species of toucan is the Toco Toucan, which reaches 29 inches in length.
• Toucans are able to fly, but they have relatively short wings. They are resident birds within their range (they do not migrate), and tend to get around their forest canopy habitat by hopping from branch to branch.
• The Toco Toucan is the most well-known species of toucan; it is sometimes known simply as "Toucan" or "Common Toucan".

Toco Toucan by William Warby [CC BY 2.0]

• The Keel-billed Toucan is the national bird of Belize.
• Toucans are found in the Neotropics, meaning they are New World birds found in tropical habitat. They range from southern Mexico into northern parts of South America. They are also found in the Caribbean.
• The constellation Tucana, a group of stars in the Southern Sky, is named after the toucan. It was established by Dutch astronomer Petrus Plancius and was first published in 1598 in Amsterdam.
• We have three birds in the toucan family here. Check out our Birdorable Keel-billed Toucan, Birdorable Green Aracari; and Birdorable Toco Toucan!

We're celebrating Vulture Week because this Saturday, September 5th, marks International Vulture Awareness Day (IVAD). This commemorative day has been celebrated since at least 2009 and aims to highlight the importance of vultures and vulture conservation through education.

In today's post we're sharing some keywords that pertain to vultures. This vulture glossary also includes definitions that apply to other bird families, but are important topics to understand when learning about vultures.

Carrion

If you're going to be talking about vultures, you are inevitably going to be talking about carrion, because that is what most vultures eat. Carrion is the decaying flesh of a dead animal. Other scavengers that consume carrion besides vultures include eagles, opossums, coyotes, and some beetles.

Convergent Evolution

Vultures in the New World (the Americas) are not closely related to Old World (Europe, Asia, and Africa) vultures. Since many vultures of both types have similar features like bald heads and scavenger behavior, how can it be that they are not closely related? The answer is convergent evolution. Broadly, this refers to organisms evolving similar traits while lacking a common ancestor. Birds, flying insects, and bats are not related, but they have all evolved the capacity to fly. Similarly, vultures in both the Old and New Worlds have evolved special traits to help them specialize in feeding on carrion. With few exceptions, no matter their location, vultures fill a similar niche in the ecosystem.

Crop

The crop is an expandable part of the digestive tract of birds and some other animals. The muscular pouch, close to the throat, is used to store food before digestion. The full crop of the Lappet-faced Vulture can hold up to 3.3 lb of meat!

Gorge

Vultures are known to gorge themselves at feeding sites. They will eat until their crop is completely full, and then sit full, digesting their food. It is thought that vultures sometimes gorge themselves to the point of being unable to fly.

Kettle

A group of vultures in flight together, particulary soaring on thermals, is known as a kettle. Kettle may describe other birds flying in this way, including mixed flocks which may or may not have vultures.

Preening

Preening is the act of cleaning or grooming. Birds, including vultures, preen themselves to keep their feathers in top shape. Allopreening refers to social grooming between multiple individuals, often performed to strengthen social bonds. Black Vultures are known to take part in allopreening at roosting and feeding sites. Often allopreening concentrates on the head area, a spot that a bird cannot easily reach with its own beak.

White-backed Vulture Preening by Sascha Wenninger

Stomach Acid

Vultures have extremely corrosive stomach acid, which helps them to safely digest dead animals that may be infected with diseases and toxins. The stomach acid protects the birds from contracting and spreading disease. Gut bacteria in vultures helps them to withstand several kinds of toxins that may be found in decaying flesh.

Taxonomy

Taxonomy is a scientific system for naming and organizing living things which share certain characteristcs. The taxonomy of vultures can be confusing. New World and Old World vultures aren't closely related, despite their physical and behavioral similarities. Some scientists think that New World vultures are closely related to storks. With new advances in the study of DNA, sometimes single species are split into distinct species. The Long-billed Vulture was split into two distinct species: the Slender-billed Vulture and the Indian Vulture. The Yellow-headed Vulture was split into two species in the 1960s: the Lesser and Greater.

The big day is almost here! Tomorrow our Vulture Week will conclude on International Vulture Awareness Day!

We're celebrating Vulture Week because this Saturday, September 5th, marks International Vulture Awareness Day (IVAD). This commemorative day has been celebrated since at least 2009 and aims to highlight the importance of vultures and vulture conservation through education.

Vulture week rolls on with some cool vulture facts. These extreme facts show how diverse this amazing family of birds can be.

Largest Vulture
Among New World vultures, the Andean Condor and California Condor can both reach up to 48 inches in length, and weigh 26 pounds or more. In the Old World, the Cinereous Vulture reaches up to 47 inches in length. Female Cinereous Vultures may weigh up to 31 pounds!

Smallest Vulture
In the Old World, the Palm-nut Vulture has this record. They only grow to be about 24 inches long and weigh just around 3.5 pounds. The Lesser Yellow-headed Vulture is the smallest in the New World, reaching between 22 and 24 inches in length.

Vulture Longevity Records
The longest lived Eurasian Griffon reached over 41 years of age in captivity. A captive-raised Lammergeier lived to be over 45 years old. The Andean Condor is believed to be capable of living 50 years or more in the wild. A captive Andean Condor that lived at a zoo in Connecticut lived 79 years! The longevity record for a wild Turkey Vulture is over 17 years, while a wild Black Vulture reached over 25 years of age.

Most Abundant Vulture
The Turkey Vulture is the most abundant species of vulture in the world, with a population that probably numbers into the millions of individuals.

Turkey Vultures by docentjoyce (CC BY 2.0)

Fastest Decline
Many vulture species in Africa and on the Indian subcontinent are in peril. The population decline of the White-rumped Vulture is an unfortunate example of this. In the mid 1980s, the White-rumped Vulture was considered to be the most abundant large bird of prey in the world. Since that time, the species has declined rapidly, losing up to 99.9% of its total population in just 20 years.

Longest Migration
Most vulture species are sedentary, year-round residents throughout their range. In the New World, the Turkey Vulture is the only vulture spcies that has regular seasonal migration. Birds that breed in southern Canada probably travel at least 1,000 miles to reach their wintering grounds to the south, traveling around 100 miles per day of migration. In the Old World, Egyptian Vultures may travel up to 5,500 miles when they migrate from their breeding grounds to their wintering grounds at the southern end of the Sahara Desert.

Ancient Birds
Relatives of vultures have existed for millions of years. Early ancestors of Old World vultures, in the now extinct Diatropornis family, existed in the Eocene epoch about 56 to 38 million years ago.

Highest Flyer
The Rueppell's Vulture of Africa is thought to be the world's highest flying bird. It has been recorded flying at an altitude of 11,300 meters or 37,000 feet above sea level!

Can't get enough of these amazing and important birds? Be sure to check out our great collection of cute and original vulture apparel and gifts.

Owl eyes are pretty amazing.

They don't really have eye "balls" like humans and other animals. Instead, owl eyes tend to be more tube-shaped. Their elongated eyes are held in place by bones in the skull. Owl eyes are also relatively enormous when compared with human eyes. If a Great Horned Owl were the same size as a human, its eyes would be as large as a pair of oranges. In some owl species, the weight of the eyes accounts for up to five percent of the total weight of the bird.

Because of the shape of an owl's eyes, the bird is unable to move the eyes inside their head. They have to turn their heads around in order to look around. An owl can turn its head about 270 degrees, or about 3/4 of the way around. There are some special adaptations in owl anatomy that allow them to turn their heads so far, including extra vertebrae in the neck, and different blood vessels that keep blood flowing between the head and body.

Unlike many other bird species, owls have forward-facing eyes. This makes them appear more human-like than other birds and may contribute to their general popularity among people. Compare the forward-facing eyes on the Great Grey Owl's face to that of the American Bittern below.

Great Grey Owl by Rolf B. [CC BY-SA 2.0]

American Bittern by Amy Evenstad for Birdorable

Many owl species are nocturnal, but owls can see perfectly fine in the daylight as well as at night. Because of their excellent night vision, their pupils don't retract as much as in humans. Closing their eyelids halfway or more helps keep the bright light from hurting their eyes. This also gives owls the appearance of being sleepy in daylight, when in fact they may be fully awake and alert.

Owls have three sets of eyelids. Upper and lower eyelids close when the owl blinks or sleeps. A third, semi-transparent lid, called a nictitating membrane, closes diagonally across the eye. This thin layer of tissue is used to keep the eyes clean and to protect the eye while still allowing for some vision. You can see this membrane partially closed in the photo of a Barred Owl below.

Barred Owl with nictitating membrane visible by Philo Nordlund [CC BY 2.0]

The tanagers are a family of songbirds found across the Americas. These small birds tend to be colorful; often males are more brightly plumaged than females.

Tanagers in name only?

There are four species of tanager found in North America. These are the Western Tanager, Summer Tanager, Scarlet Tanager, and Hepatic Tanager. They are in the genus Piranga and are thought to be closely related to cardinals; they may not belong in the tanagers' Thraupidae family at all.

Colorful Across the Americas

In total there are over 200 species of tanager. Most are found in tropical habitats, and many species have relatively small native ranges. For example, the Green-headed Tanager is found along a narrow strip extending from southeast Brazil down into southeastern Paraguay and northeast Argentina.

Western is Most North

North America's Western Tanager is notable for being the northern-most ranging species of tanager. This migratory species breeds as far north as Canada's Northwest Territories. They spend the winters in Central America.

Hepatic: I'm Huge in South America

In the United States, the Hepatic Tanager is only found as a breeding bird in the southwestern mountains. However, the species has a very large native range and many birds are permanent residents across a large portion of South America.

Summer's Pretty Song

Most tanagers are not known for their pretty song, but the Summer Tanager is an exception. It sings a melodic tune that reminds many of the American Robin's song.

Cowbird's Target

The Scarlet Tanager is particularly susceptible to brood parasitism from Brown-headed Cowbirds. Being forest nesters, they never developed a strategy against the rogue-nesting cowbirds. Segmented habitat (due to human developement) means tanagers more often nest near open habitats favored by cowbirds, rather than deep inside old-growth forests where cowbirds rarely occur.

Ripe Old Age

The longevity record for wild Western Tanagers is nearly seven years; for wild Summer Tanagers it is nearly eight years; and for wild Scarlet Tanagers the record is nearly twelve years. These records were collected via bird banding.

Here are some interesting facts about kites:

• Kites belong in the Accipitridae* family of birds of prey. They are divided into two subfamilies. Elaninae kites are sometimes considered to be "hovering kites" and are generally smaller in size. Milvinae kites may be known as "soaring kites" and tend to be larger birds.
• There are approximately 22 recognized species of kite in the world. Eight belong to the Elaninae subfamily, while 14 are Milvinae kites.
• There are four species of kite found in North America: Swallow-tailed Kite; White-tailed Kite; Snail Kite; and Mississippi Kite.

Mississippi Kite by Larry Smith [CC BY 2.0]

• Not all kites are called "kites". The Bat Hawk of Africa and Asia is an Elaninae kite with a falcon-like profile and a preference for dining on bats. The Black-breasted Buzzard of Australia is an eagle-like bird that is sometimes considered to belong in a different family or subfamily altogether.
• Three different raptors in the subfamily Perninae are called kites, though they are not closely related to the other kites. They are the Grey-headed Kite, White-collared Kite, and Hook-billed Kite.
• Some kites are migratory, while others are year-round residents throughout their range. The Mississippi Kite, for example, breeds across the southeastern United States and winters as far south as Argentina, while the Snail Kite is a permanent resident across its range.
• Kites are found on all continents except for Antarctica.
• Black Kites are found on four continents: Africa, Asia, Australia, and Europe. They are common throughout their range and may be the most abundant species of raptor in the world.
• Most kite species lack global population concern, though some species have local issues (like the Snail Kite in Florida). The Letter-winged Kite of Australia and the Red Kite of Europe and Africa both have a conservation status of Near Threatened.

Red Kite by Tony Hisgett [CC BY 2.0]

• In most kite species, adult birds all look alike. An exception to this rule is the Snail Kite. Male Snail Kites are mostly dark blue-grey, while females are brown with streaked underparts.
• You can find five kite species here on Birdorable: Snail Kite; Swallow-tailed Kite; Mississippi Kite; White-tailed Kite; and Black Kite.

* Note that different taxonomical classifications may organize these and other birds in another way. As scientists learn more about birds and DNA, changes are noted and accepted and eventually integrated or rejected by various naming organizations and protocols.

Here are some interesting facts about the Green Heron, one of our newest Birdorable birds!

The Green Heron has had some interesting colloquial names, including Fly-up-the-creek, Poke, Chalkline, Indian Hen, and Chucklehead.

Some Green Herons migrate, and some don't. Green Herons are year-round residents in most of the southern coastal parts of their range. Other birds migrate from their nesting grounds in the north a short distance south for the winter. They are considered to be mid-distance migrants.

Green Herons are one of the few bird species known to use tools. They will bait for fish using things like bread, leaves, or feathers to try to lure in fish. This video shows a Green Heron using an insect as bait:

There are several collective nouns used for herons. You might see a hedge of herons, a sedge of herons, or a siege of herons.

The Green Heron was chosen to be the official Bird of the Year 2015 by the American Birding Association.

The oldest wild Green Heron on record lived to the age of 7 years and 11 months. This was discovered via data collected from bird banding.

The Green Heron used to be considered the same species as the Striated Heron and the Galapagos or Lava Heron. The species was then known as the Green-backed Heron. Some taxonomies still treat them as subspecies.

Green Herons may nest away from other herons, alone, or in a small group, or in a larger colony. Many heron species are colonial nesters but the Green Heron or may not nest this way, depending on availablity and defendability of feeding territory.

Green Herons have a shaggy crest that can be raised at will by the bird.

Green Heron by Andy Morffew [CC BY-ND 2.0]

The Green Heron was added to Birdorable on June 22, 2015, and joined us as our 610th species.

We're wrapping up our week-long celebration of cranes with some more cool crane facts. These extreme facts show how diverse this amazing family of birds can be.

Oldest Crane
The average lifespan for wild cranes is typically between 20 years and 30 years. The longevity record for all crane species goes to the Siberian Crane. A bird living at the National Zoological Park of the Smithsonian Institute reached the ripe old age of 62! That bird passed in 1968. Another Siberian Crane, named Wolf, is in the Guinness Book of World Records for reaching 83 years of age!

Most Abundant
There are more Sandhill Cranes than any other species of crane in the world. There are an estimated 650,000 Sandhill Cranes found across North America.

Longest Migration
The Siberian Crane may fly up to 10,000 miles round trip in a year. Some birds breed in western Siberia and winter as far south as parts of India.

Most Endangered
With an estimated wild population of just over 430 birds, the Whooping Crane is the least abundant of all crane species. They have a conservation status of Endangered and are the subjects of conservation efforts from several groups. Whooping Cranes do breed in captivity and there are over 165 individuals at zoological facilities throughout the world.

Fancy Footwork
While all crane species perform some kind of dancing ritual as part of courtship and pair-bonding, Red-crowned Cranes are especially known for their fancy footwork. Pairs of Red-crowned Cranes will duet as they dance, moving rhythmically as they approach one another.



Highest Flyer
The Common Crane is one high-flying species! One bird was recorded flying at an altitude of up to 33,000 feet over the Himalayas. This record is second only to the Rüppell's Vulture flying up to an altitude of 37,000 feet.

Ancient Species
Sandhill Cranes have been around a very long time. In fact, their fossil history is among the longest of any living bird. Sandhill Crane fossils up to 2.5 million years old have been found.

Can't get enough of these amazing birds? Be sure to check out our great collection of cute and original crane apparel and gifts.

It's Crane Week, which means we're celebrating the cranes of the world! Today's post contains some interesting and fun crane FAQs.

Where do cranes live?
They have a nearly cosmopolitan distribution. Cranes are found on all continents except for Antarctica and South America.

How big are cranes?
Cranes are large birds. The smallest species, the Demoiselle Crane, is around 36 inches (91 centimeters) tall. The tallest crane is the Sarus Crane which reaches 69 inches (176 centimeters) or more in height. The heaviest crane is another species, the Red-crowned Crane, which may weigh up to 26 lb or 12 kg.

Why do cranes have bare faces?
Most species of crane have featherless heads. They can change the intensity of color in the bare skin by manipulating facial muscles; this is used to communicate between the birds. Two species of crane have feathered heads: the Blue Crane and the Demoiselle Crane.

Why are cranes endangered?
Of the 15 species of crane in the world, all but four are considered to have some level of threat to their survival. Seven species are considered vulnerable to extinction, 3 are endangered, and one is critically endangered. Only four species are placed in the category of least concern.

Most cranes rely on wetlands for feeding and nesting. Global decline in wetland habitat is devastating to these birds. The species face various other threats, depending on their range. Other threats include secondary poisoning, illegal poaching, and pollution.

What do cranberries have to do with cranes?
The word cranberry comes from what European settlers called the fruit when they came to the new world: craneberry. In their eyes, parts of the plant's flower, stem, and petals resembled the neck, head, and beak of their familiar Common Crane.

What is the collective noun for cranes?
A collective noun is a word used to name a group of the same things. A group of birds is known as a flock, while a group of crows is a murder, and a group of geese is a gaggle. What about cranes? A group of cranes may be known as a sedge of cranes, or as a siege of cranes.