Bird eggs come in a huge range of sizes. The largest ostrich egg is 5000 times bigger than the smallest hummingbird egg.
But sometimes it isn’t the smallest birds that lay the smallest eggs.
In this article, we will tell you about 10 birds that lay the smallest eggs (along with the images of the birds).
We will also tell you about their unique nesting habits and some surprising facts about what these birds do while their eggs are incubating and after their chicks hatch.
10 Birds that Lay the Smallest Eggs
Before I get into the specifics of each bird, below is a table that lists the 10 birds that lay the smallest eggs (along with the size)
|Bird Name||Egg Size|
|Costa’s Hummingbird||1/2 inch long and a little less than 1/3 inch wide (12 mm long by 8 mm wide)|
|Ruby-Throated Hummingbird||1/2 of an inch long and 1/3 of an inch wide (13 mm long by 9 mm wide)|
|Black-Throated Gray Warbler||5/8 inch long and 3/8 inch wide (16 mm by 10 mm)|
|Black-Chinned Hummingbird||1/2 of an inch long and 1/3 of an inch wide (13 mm long by 9 mm wide)|
|Golden-Crowned Kinglet||1/2 inch long and 3/8 inch wide (13 mm by 11 mm)|
|American Bushtit||9/16 inch long and 3/8 inch wide (14 mm by 10 mm)|
|Broad-Billed Tody||2/3 inch long and 1/2 inch wide (17 mm long and 13 mm wide)|
|Common Kingfisher||3/4 inch long and 2/3 inch wide (20 mm by 18 mm)|
|Black Scimitarbill (also known as Black Wood Hoopoe)||7/8 inch long and 2/3 inch wide (23 mm by 18 mm)|
|Rufous-Tailed Jacamar||7/8 inch long and 3/4 inch wide (23 mm by 19 mm)|
10. Rufous-Tailed Jacamar
Size of the egg: 7/8 inch long and 3/4 inch wide (23 mm by 19 mm)
Rufous-Tailed Jacamars live in open woodlands as well as both dry and wet forests in Central America and northern South America.
The female lays her eggs in a burrow she and her mate dig in a riverbank or a termite mound.
Each clutch consists of two to four unspotted white eggs just 7/8 inch long and 3/4 inch wide (23 mm by 19 mm).
Rufous-Tailed Jacamars are very efficient at catching insects in mid-air.
They snap up insects in flight and then smash them against a nearby tree trunk before consuming them.
Much of the Rufous-Tailed Jacamar’s diet consists of wasps. They also eat bees, beetles, flies, dragonflies, and butterflies.
They can tell which butterflies are toxic by their body shape. Once a Rufous-Tailed Jacamar has tasted a toxic butterfly, it will never catch another butterfly of that species again.
Some butterflies have developed markings similar to toxic butterflies to escape being eaten by these birds.
Rufous-Tailed Jacamars have to make thousands of trips to keep their hatchlings fed, so they ignore housekeeping chores once the young have hatched.
Their nests become filled with feces and decomposing insect parts, so their chicks stink.
9. Black Scimitarbill (also known as Black Wood Hoopoe)
Size of the egg: 7/8 inch long and 2/3 inch wide (23 mm by 18 mm)
The Black Scimitarbill gets its name from the fact that its bill looks, as its name suggests, like a sharp, curved scimitar.
Black Scimitarbills lay two or three unblemished, unspotted white eggs that measure 7/8 inch long and 2/3 inch wide (23 mm by 18 mm).
Black Scimitarbills live in tropical sub-Saharan Africa, on both sides of the Equator. They prefer thorny bushland or dry savannah, and live inside unlined cavities of trees.
Black Scimitarbills hunt in pairs, probing the bark of trees for grubs and beetles.
The male and female cooperate with each other to take care of their eggs and hatchlings, but they face competition from birds that live and nest in flocks.
A mating pair of Black Scimitarbills may have to find a nest and lay eggs several times before their eggs hatch and their chicks survive long enough to live on their own.
8. Common Kingfisher
Size of the egg: 3/4 inch long and 2/3 inch wide (20 mm by 18 mm)
Common Kingfishers lay five to seven white eggs with a pink tint in cavity nests, dug into a river bank or the shore of a lake.
Their eggs are 3/4 inch long and 2/3 inch wide (20 mm by 18 mm).
Common Kingfishers range through most of Europe and European Russia, eastward to India, China, and Southeast Asia.
They only eat aquatic animals, and they are fussy about water quality. Common Kingfishers hover over water into which they dive to catch fish. The water must be clear for them to see their prey.
These birds are jealous of their feeding grounds. They will defend their feeding area even from their mate, except when it is time to lay eggs and raise young.
During nesting season, the mating Common Kingfishers will share their feeding ground. They dig a burrow into soft, moist dirt, and the female lays her eggs.
The two parents take turns incubating and guarding their eggs, the male taking care of them during the day, and the female guarding them at night.
Once the young have hatched, the adult Common Kingfishers don’t worry about hygiene.
The burrow becomes foul with the stench of rotting fish and regurgitated food pellets, along with urine and feces.
7. Broad-Billed Tody
Size of the egg: 2/3 inch long and 1/2 inch wide (17 mm long and 13 mm wide)
Broad-Billed Todies live in both Haiti and the Dominican Republic on the island of Hispaniola.
These birds live alone except when it is time to mate and raise young. Together, the male and female build a tunnel in sand or in the soil of a river bank and take care of their clutch of three or four eggs.
Each egg is 2/3 inch long and 1/2 inch wide (17 mm long and 13 mm wide). They are white when they are first laid, but they become stained red as they lie inside the burrow.
Despite being a tropical bird, Broad-Billed Todies dislike damp conditions and tall trees.
They prefer dry scrubby woodlands and living under the shade cloth of coffee plantations.
These birds are sedentary. They do not migrate, and they do not move around very much at all except to find a prime spot to lay their eggs.
The male and female Broad-Billed Tody mate for life. They are monogamous and share all the duties of raising their young.
6. American Bushtit
Size of the egg: 9/16 inch long and 3/8 inch wide (14 mm by 10 mm)
American Bushtits are year-round residents of open woodlands that have a scrubby chaparral understory throughout the Western third of North America.
They range as far north as British Columbia, through the Pacific Northwest, California, and the Rocky Mountain states, and as far south as Mexico and Guatemala.
Female American Bushtits lay four to 10 immaculately white and smooth eggs that are 9/16 inch long and 3/8 inch wide (14 mm by 10 mm).
American Bushtits build nests that hang from branches of mistletoe.
They make their nest from branches and mistletoe, lining them with feathers and soft hair, and insulating the outside with leaves. Each hanging nest has a tiny entrance at the top.
These tiny birds spend most of the year in flocks. They move around and roost together until it is time to mate.
A mating pair will separate from the flock to build their intricate nest, but they will abandon it if cold weather comes back so they can try again when it is warmer.
The hanging nest is exposed to a maximum amount of sunlight to keep it warm.
Young American Bushtits will help their parents take care of their younger siblings in the next brood.
The male American Bushtit, however, faces no competition from other birds for mating. These Bushtits help each other without an expectation of reproducing with each other.
5. Golden-Crowned Kinglet
Size of the egg: 1/2 inch long and 3/8 inch wide (13 mm by 11 mm)
The eggs of the Golden-Crowned Kinglet are a drab white with brown spots. They measure 1/2 inch long and 3/8 inch wide (13 mm by 11 mm).
Unlike many other birds that lay just one or two small eggs in each clutch, a mother Golden-Crowned Kinglet may lay as many as 11 eggs at a time.
Some Golden-Crowned Kinglets spend their summers in some of the cooler locations in North America, including the southern half of Alaska, the Yukon, and the Northwest Territories, and northern Quebec.
These birds fly south to the Lower 48 and Mexico for the winter. There are also Golden-Crowned Kinglets that live year-round in the Sierra Nevada range in California and in New England.
The male and female Golden-Crowned Kinglet collect fur, bark, hair, spider silk, and lichens for building their nest. They like old-growth spruce trees and pine trees planted after a fire.
The female Golden-Crowned Kinglet sits on the eggs at night to keep them warm, while the male watches over them during the day.
The male provides the female with insects, insect eggs, and spiders for extra energy during colder weather. Both parents feed their hatchlings.
These songbirds are probably the smallest passerine birds (birds that perch) in North America.
Because they spend most of their time in remote forest locations, they are almost never afraid of humans.
4. Black-Chinned Hummingbird
Size of the egg: 1/2 of an inch long and 1/3 of an inch wide (13 mm long by 9 mm wide)
Black-Chinned Hummingbirds are familiar to backyard gardeners in California and the Pacific Northwest.
The female lays two eggs, each of them just 1/2 of an inch long and 1/3 of an inch wide (13 mm long by 9 mm wide).
These birds build their nests out of a flexible mesh of spider silk, fibers from cocoons, and plant filaments. It fits snugly around the eggs while incubating and expands when they hatch.
Millions of people who live in California and the Pacific Northwest get a chance to observe Black-Chinned Hummingbirds because they are very adaptable to all kinds of living conditions.
Black-Chinned Hummingbirds live in desert scrub, dense forests, city parks, and backyards free of cats.
Males are very aggressive about defending their territory against other males, but once they have mated with a female, they move on to court other females. They leave all the parental duties to the female.
Mother hummingbirds feed their young a mixture of nectar and tiny insects. The process involves her sticking her long beak down the throats of her two babies one to three times an hour all day long.
3. Black-Throated Gray Warbler
Size of the egg: 5/8 inch long and 3/8 inch wide (16 mm by 10 mm)
The eggs of the Black-Throated Gray Warbler are creamy-white with rusty brown spots.
They are just 5/8 inch long and 3/8 inch wide (16 mm by 10 mm), laid three to five at a time.
Black-Throated Gray Warblers range across the western United States into British Columbia.
They prefer mixed woodlands, but they will also build their nests in stands of pine and spruce and in desert chaparral. These birds make their homes on shrubs and small trees.
They build their nests from leaves, grasses, plant fibers, and stalks, lining them with hair.
Male and female Black-Throated Gray Warblers live separately except for mating and nesting.
The female chooses the nesting site. She presses her body into forks and crotches of tree limbs, as if she was measuring the site for nesting space.
During site selection, the male stays nearby and watches for predators, calling out if a threatening animal approaches.
The territory of the Black-Throated Gray Warbler overlaps the range of the Cowbird, which lays its eggs in other birds’ nests.
If a Black-Throated Gray Warbler finds a Cowbird egg in its nest, it builds a new nest over it.
Entombed inside the double-decker nest, the Cowbird egg is never turned or incubated and does not hatch.
2. Ruby-Throated Hummingbird
Size of the egg: 1/2 of an inch long and 1/3 of an inch wide (13 mm long by 9 mm wide)
The eggs of a Ruby-Throated Hummingbird in the nest look like two pearls in a cup. Their color is a non-glossy pure white.
These tiny eggs are no bigger than a pea, just 1/2 of an inch long and 1/3 of an inch wide (13 mm long by 9 mm wide). Each egg weighs less than a paperclip. There are just two eggs in the nest.
Ruby-Throated Hummingbirds are the only hummingbirds that build nests and raise their young in eastern North America.
They fly thousands of miles twice a year between their nesting sites in North America to their winter homes across the Gulf of Mexico in Mexico and Central America.
They build nests about the size of a walnut out of plant fibers that they glue firmly to the downward-sloping branch of a tree. with spider silk.
Male hummingbirds perform elaborate dives to display their bright red throats to females to induce them to mate.
Once the couple has consummated their relationship, the male flies away, leaving all the duties of incubating the eggs and feeding the young to the female.
1. Costa’s Hummingbird
Size of the egg: 1/2 inch long and a little less than 1/3 inch wide (12 mm long by 8 mm wide)
Costa’s Hummingbird lives year-round in the Sonoran Desert in Arizona and northwestern Mexico.
Most hummingbirds lay a clutch of two eggs, but the female Costa’s Hummingbird sometimes lays three.
Its eggs are even smaller than the eggs of other North American hummingbirds, just 1/2 inch long and a little less than 1/3 inch wide (12 mm long by 8 mm wide). They require 15 to 18 days of incubation before they hatch.
Male Costa’s Hummingbirds make spectacular dives to defend their mating territory and to impress potential mates.
Once sperm has been transferred to the female, however, the male loses interest in her and seeks more mates.
Female Costa’s Hummingbirds save their energy for important tasks.
The female does all the work of gathering cactus fibers and spider silk. She rests before she builds the nest by running her chin around the edges while she sits inside it.
Once the nest is built, the female Costa’s Hummingbird rests another two or three days before laying her eggs.
Although each egg is smaller than a pea, they represent a substantial percentage of the mother bird’s body mass.
The Costa’s Hummingbird lays eggs that are a bigger percentage of her body weight than an ostrich’s eggs are of hers.
So these are the 10 birds that lay the smallest eggs in the world.
Also read: Blue Jay Eggs vs. Robin Eggs
What About the Bee Hummingbird?
If you have Googled for the bird that lays the smallest eggs of any bird in the world, chances are that you have come across references to the Bee Hummingbird (Mellisuga helenae).
This bird is also known as the Helena Hummingbird and the Zunzuncito.
The Bee Hummingbird is the smallest bird in the world.
Native to Cuba, these birds weigh less than 1.10 of an ounce (1 to 2 milligrams) and are only 2 inches (5 cm) long.
Their eggs are usually described as “smaller than a coffee bean.” No research ornithologists have actually measured the eggs, however, so we can only say that they are really, really small.
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