19 January 2022

These high gloss eggs look like ceramic but were actually laid by members of the Tinamou family, native to Central and South America.

Tinamous are shy, secretive ground-dwelling birds that resemble chickens but are closely related to ostriches and emus. 46 species range in size from the 8’7″ small-billed tinamou (Crypturellus parvirostris) to the 16-19″ grey tinamou (Tinamus tao). No matter where they live, rainforest, savannah or shrubland, all of them lay shiny eggs in a nest on the ground.

One would think that shiny eggs would be easily found by predators, especially after researchers examined the cuticle, the egg’s outside layer, and found:

They quantified its smoothness down to the nanometer scale and measured the shininess of the mirrorlike surface, finding that tinamou eggs are up to 14 times as glossy as the average chicken egg. A spectroscopy test also revealed that the blue eggs were iridescent (the green and brown eggs were too shiny for the spectrometer to accurately measure).

— New York Times: Easter Eggs without a Kit

However, the male tinamous who build the nest, incubate, and rear the chicks are generally successful as long as their habitat is not destroyed. 80% of the species are stable.

Watch the eggs’ beauty transform in this video of elegant crested tinamou eggs (Eudromia elegans) in a captive breeding facility.

When the chicks grow up they will look like this.

Read more in the New York Times: Easter Eggs Without The Kit.

(photos from Wikimedia Commons, embedded from Tumblr and screenshot from embedded YouTube video; click on the captions to see the originals)

28 October 2021

Have you ever noticed that birds gulp their food? Of course they don’t chew — they don’t have teeth — but much of what they eat still has to be “chewed” before they can digest it.

That’s where grit comes in.

Birds chew with their gizzards, a specialized stomach with thick muscular walls that grind up food, often aided by particles of stone or grit.

Birds regularly eat grit to aid their digestion, as Ecco is doing in the photo below.

So when you see birds swallowing things whole rest assured they’re chewing inside … in the gizzard.

p.s. Other animals have gizzards too including crocodiles, alligators, mullet (a fish) and earthworms.

(photos from Steve Gosser, Wikimedia Commons, and the National Aviary snapshot camera at Univ of Pittsburgh)

4 October 2021

Teeth are so important that every toothless animal today is descended from ancestors that had them. This includes anteaters, baleen whales, pangolins, turtles, and birds.

The ancestors of birds were theropod dinosaurs. They definitely had teeth.

Then about 116 million years ago a common ancestor of all birds developed genetic mutations that inactivated the genes for tooth formation. Eventually birds’ teeth disappeared, replaced by horn-like beaks.

There are probably several reasons why teeth disappeared but the main one is this: In order to fly well it’s important to reduce excess body weight. Bones and teeth are heavy so over time birds evolved hollow bones and toothless beaks. They compensate for the lack of teeth by chewing food in their gizzards.

They also compensated by using their beaks as multi-purpose tools to grasp, twist, pry, crack open shells, and sever tendons.

Each species developed a beak for its lifestyle. A few of them evolved beak modifications that resemble teeth.

Among tooth-billed hummingbirds (Androdon aequatorialis) the males have a “straight bill with a prominent hooked tip and backward-pointing tooth-like serrations on the distal half. The modification is absent on the female bill, and thus may be related to sexual selection,” describes Birds of the World. Perhaps the “teeth” are used for fighting.

The critically endangered tooth-billed pigeon (Didunculus strigirostris), the national bird of Samoa, has a stout curved bill with a specially toothed lower mandible.

[The bill] is adapted to feed on Wild Mahogany Dysoxylum spp. fruits, although first-year birds apparently cannot do so. These fruits have a tough capsule that it is able to open using its strong bill, removing the flesh using a sawing action with the lower mandible.

Birds of the World, Tooth-billed pigeon account 

If you want to stretch the definition of “teeth” peregrines have two of them. The tomial tooth on each side of the upper beak is used “to kill prey quickly by biting their necks and severing the vertebrae.”

Does that make them birds with teeth? Not really. No dentin, no enamel, and they aren’t using them to chew.

(photos from Wikimedia Commons; click on the captions to see the originals. Peregrine photo by Chad+Chris Saladin)