Did you know that some species of bird feed their chicks milk? It's true, but it's not the same kind of milk that mammal mothers feed their young.

This baby bird food is secreted from the lining of the parent bird's crop and then regurgitated to the baby birds. It is high in protein and fat as well as other components important for their growing chicks to consume, like anti-oxidants, ("good") bacteria, and substances to improve the immune system.

All species of pigeons and doves feed crop milk to their young -- for these species the substance is called pigeon milk. Flamingos also feed their young a type of milk, though production occurs in more of the upper digestive tract than just the crop. Male Emperor Penguins produce a similar substance to feed their chicks when the mother bird is away at the time of hatching.

In pigeons and doves, parent birds begin to produce the milk days before their eggs hatch. The chicks, called squabs, eat only crop milk for the first week after hatching. Afterwards other foods are introduced, after being softened inside the parent bird's crop.

This week's featured t-shirt design is our Birdorable Kakapo in BOOOOOM!!! which is shown here on a Kids' Basic Long Sleeve T-shirt from Zazzle. The model shown above is 4'7" and is wearing a small.

The critically endangered Kakapo parrot (or Owl Parrot) of New Zealand is the only flightless species of bird to use a lek breeding system for mating. During part of the lekking process, males compete for females by displaying and making a "booming" sound. Boom! Males position themselves kilometers apart to signal to potential mates.

This fun and original Birdorable design is inspired by the booms of the lekking Kakapo. Pick this up for the Kakapo lover on your list! Only true Kakapo fans will "get" this unique and cute cartoon design.

Earlier this month, the Iiwi ('I'iwi), a beautiful Hawaiian finch, was introduced as the American Birding Association's Bird of the Year for 2018. We think it's an interesting and excellent choice!

In 2016 Hawaii was added the ABA Birding area by popular vote, and the process of adding species to the official checklist was completed last year. So it makes sense to feature a Hawaiian species in 2018.

The Iiwi is a type of finch, part of a group of Hawaiian honeycreepers. More than 50 species of honeycreeper used to call Hawaii home. Today less than half of those species still exist. They face threats including predation by introduced species and competition from invasive birds, as well as habitat loss and disease.

Of the native birds of Hawaii, the Iiwi is the most common.

The beautiful Iiwi can be recognized by its bold scarlet and black plumage, and by its long curved bill. In many ways the Iiwi behaves like a hummingbird, hovering in flight and drinking flower nectar.

Be sure to visit the ABA's Bird of the Year page to learn more about the Iiwi!

Today our 2017 Birdorable Bonanza concludes with a superb species: the Superb Lyrbird!

The Superb Lyrebird is a large species of songbird native to Australia. Several facts make this amazing bird a very interesting study.

It belongs in the passerine bird order, which makes it a songbird. But it is the size of a pheasant, and weighs in at 2lb or more, making it one of the most heavy species of songbird, rivalled only by ravens.

The Superb Lyrebird is one of two species of lyrebird. They get their common name from the shape of the spectacular tail of adult males, part of which forms the shape of a lyre (a musical instrument).

Superb Lyrebirds are known for their amazing ability to mimic a wide variety of sounds. Watch this short clip from BBC Wildlife featuring a singing male lyrebird.

Pretty amazing, right? With this awesome bird we conclude our 2017 Birdorable Bonanza! Thanks for following along.

Our 2017 Birdorable Bonanza is winding down! Just one more bird to go after today's newbie: the African Spoonbill!

The African Spoonbill is one of six species of spoonbill found in the world. They are all long-legged wading birds with the uniquely shaped bill that gives them their name. The African Spoonbill joins the Roseate and the Eurasian here at Birdorable.

Male and female African Spoonbills look alike. As chicks, they have small and stubby beaks which gradually grow into the spoon-tipped shape.

African Spoonbills do well in captivity and are found in zoos around the world. They are abundant throughout their native range and the population is considered to be stable. They may live up to 15 years in the wild.

Tomorrow our Bonanza wraps up with our 677th bird, a species known for its ability to mimic sounds. And check out that tail! Can you guess the bird?

Today's new Birdorable is the White-winged Guan!

The White-winged Guan is a critically endangered species found in a small area of Peru. They live around ravines and feed on things like seeds, fruit, leaves, and other plant matter.

White-winged Guans were thought to be extinct for about one hundred years, the time between recorded sightings of the species. When it was rediscovered in the late 1970s, a captive breeding program was introduced in an effort to save the species.

The current wild population of the White-winged Guan is very small, with a likely count of 250 individual birds or fewer. There are two distinct populations, a northern group and a southern group. Threats facing survival of the species include hunting and habitat destruction.

Tomorrow we'll add a species of spoonbill to Birdorable. There are six species of spoonbill in the world, and we already have the Roseate Spoonbill and the Eurasian Spoonbill. Our new bird does not have a black face, a yellow bill, or a royal name. That just leaves one...

Today a seabird with bold colors joins Birdorable: the Horned Puffin!

The Horned Puffin is a seabird in the auk family. They are pelagic, breeding on rocky islands but spending the rest of the year at sea. They are found in ocean waters around Alaska, British Columbia, and Siberia.

Horned Puffins are named for a small pointed fleshy "horn" that adults have over each eye. Their striking beaks actually increase in size and color intensity during courtship and breeding, developing vertical grooves.

Like many seabirds, Horned Puffins have a mostly black and white plumage. They are black above and white below. This is a camouflage strategy, helping to protect them from predators both from the air above them and the sea below.

Tomorrow an endangered bird found only in Peru will be revealed as part of our 2017 Birdorable Bonanza. It was once thought to be extinct but was rediscovered in the late 1970s. Do you know this bird?

Take a look at this beauty! Today a colorful New Zealand rail joins Birdorable! Introducing our South Island Takahe!

The South Island Takahē is a large flightless species of rail that was once thought to be extinct. A similar species, the North Island Takahe, is only known from skeletal remains.

South Island Takahes are endemic to New Zealand and are managed and protected to ensure the survival of the species.

Once a bird of wetlands and swamps, the South Island Takahe is now a species of alpine grasslands. This move is due to the impact humans have had on the landscape of the South Island -- swamps have been drained and turned into farmland, forcing the takahe to move. They are altitudinal migrants, heading down from the higher alpine habitat when snow covers the land.

Tomorrow a pelagic species joins Birdorable. Can you guess the species from the silhouette alone?

Today we continue with our 2017 Birdorable Bonanza by adding a new wading bird: the Reddish Egret!

The Reddish Egret is a medium-sized species of heron found along coastal habitats in Central America and the southeast of the United States. They are also found on many islands of the Caribbean.

Reddish Egrets are known for their active hunting antics, often found running around, spinning, and jumping in shallow salt water as they hunt little fish to eat.

The Reddish Egret has two very different color morphs. Darker birds have grey bodies with a reddish head and neck. The light morph has a mostly white plumage.

Tomorrow we'll add a new species to our Birdorable rail family. Once thought to be extinct, this species has moved from living in wetlands to survive in alpine grasslands. Do you know this New Zealand endemic?

Today's new bird in our annual Birdorable Bonanza is an Old World species of duck: the Common Pochard!

The Common Pochard is a migratory duck found across parts of Europe and Asia. They are gregarious, found in large (sometimes mixed) flocks during the winter. Common Pochards are known to occasionally hybridize with the Tufted Duck.

Common Pochards look a lot like the Redhead of North America. Adult males have light grey backs, black at the chest, and an unmistakable red head.

Tomorrow we'll reveal a new member of the egret and heron family, known for its active hunting antics and for having two distinct color morphs. Can you guess the bird?