10 Incredible Eastern Bluebird Facts

Written by Crystal
Updated: July 10, 2022
© Bonnie Taylor Barry/Shutterstock.com
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There are 650 bird species breed in North America, but only three are bluebirds.

Eastern bluebirds live east of the Rocky Mountains. During the summer season, they’ll venture as far North as Southern Quebec, Ontario, and Manitoba to nest. These songbirds love wintering in the Southeastern and South Central United States. You’ll also find bluebirds in Guatemala, Northern Honduras, and the pinelands of Nicaragua.

If you ever get a chance to see an Eastern bluebird, you’ll notice that they have a stunning cobalt blue plumage on their head, back, wings, and tail. What else should you know about these delightful creatures?

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Read on to learn 10 incredible facts about eastern bluebirds.

1. Female Eastern Bluebirds Only Have One Ovary

While many birds have two ovaries, the female eastern bluebird only has one. Female bluebirds only have a left ovary. This helps reduce their weight so that they can fly better. Even though they only have one ovary, yearling eastern bluebirds can produce 3-4 eggs. Once they’re older, females can average 5 eggs in the first nest of the season.

2. Baby Eastern Bluebirds Have an Egg Tooth

baby robin eggs
It takes baby bluebirds hours to break free of their shells.

©iStock.com/batuhan toker

How do baby bluebirds break free from their shells? When an eastern baby bluebird is ready to enter the world, it’ll be getting pecking on the middle of its shell with an egg tooth. The egg tooth is a hard tip at the end of its beak. Once they break free of their shell, the egg tooth falls off. It usually takes several hours of work for a hatchling to break free. Once they emerge, hatchlings are wet and exhausted! Immediately, their mother will feed the shell parts to fuel them with calcium.

3. They’re a Perching Bird

Eastern bluebirds belong to the order of perching birds (Passeriformes). Perching birds are a large group and makeup over half of the world’s bird species. One of their distinct features is that perching birds have a well-developed voice box. That’s one of the reasons eastern bluebirds are such great singers! Their small compact form is also perfectly balanced, so their center of gravity is over their legs and feet when they perch.

4. Baby Eastern Bluebirds Are Smaller Than Your Thumb

When they hatch, eastern baby bluebirds only weigh 28 g or 1 oz. That’s the same weight as a first-class letter. They’re so small, they’re the size of the end of a human thumb. Their heads are usually the most significant part of their body, and their eyes take a while to develop. Baby bluebirds will have naked nubbins for wings and newly weak legs. Their bellies are swollen with the remains of the yolk from the egg, and they have salmon-colored skin.

5. Bluebird Trails Can Be Tracked for Decades

When somebody is an avid bluebird, they might keep track of bluebird trails for decades! Blue-birding is the hobby of learning about, watching, and building houses for eastern bluebirds. Putting out nest boxes is one of the easiest ways to study these incredible creatures. All it takes is one or two active bluebird boxes to have an exciting time during the nesting season.

6. Bluebird Couples Are Secretive

Before pairing, eastern bluebirds love singing and flying around all day. After pairing, bluebirds become more secretive. They select their nesting cavity and gather grasses, delicate plant stems, and pine needles. The male will sing less; the female hides within the den of the nest cavity. Once the nest is finished, the bluebird pair will remain close for about 5 days or until the female lays her first egg.

7. Male Eastern Bluebirds Act as Escorts

During the nesting phase, male eastern bluebirds become bodyguards for the female. They’ll pay extra attention anytime she departs or arrives at the nest. If a female wants to leave the nest, she’ll peek her head out of the box and wait for the male’s all-clear signal. Once she flies away, he’ll sing or stay in contact with her. Escorting helps protect the female eastern bluebird from predators. Attentive males can warn females of hawks circling overhead or nearby snakes sneaking toward the nest.

8. Eastern Bluebirds Sometimes Mate With Different Partners

Researchers thought 90% of birds were monogamous, but now we know many species aren’t. For instance, bluebirds have a lot of flexibility when choosing mates. Bluebirds have what’s called apparent monogamy, providing a genetic advantage to the species.

It means sometimes bluebirds mate outside their pairing. When this happens, the male’s genes have better chances of passing on to future generations. It also benefits the female because if one of her suitors is infertile, another can provide viable sperm for her eggs to develop.

9. There Are Floater Bluebirds

baby blue jay hatchlings
Sometimes Eastern bluebirds lay their eggs in other couples’ nests.


What’s next for incredible eastern bluebird facts? Sometimes adult bluebirds are floaters. A floater is an eastern bluebird who doesn’t have a mate or a nest site. If a floater female mates with the resident or floater male, she’ll search for a place to lay her egg, such as an unguarded nest.

When a floater bird tricks a resident bird into raising its young, it’s called kleptogamy. It means, sometimes the eggs under a brooding female aren’t hers. Othertimes, the eggs might be the females, but not the territory male’s offspring.

10. Mealworms Are Ice Cream to Bluebirds

What do bluebirds eat
Bluebirds are omnivores and eat a diet consisting of plants and insects.


Mealworms are the bluebird’s equivalent of ice cream. They love gobbling up these cream-colored creatures! Blue-birders put mealworms in the nest boxes during the late winter. During the cold, wet season, eastern bluebirds have difficulty finding insects. Giving them a handful of mealworms means that you’ll be supplying them with all of the nutrients they need. They’ll gobble up the offering and provide as many of the little worms to their hungry babies as they can.

Instead of dropping the mealworms into the nest box, it’s best to leave them to the bluebird’s discretion. Let the mealworms sit in the bird box, and the parents will decide when and how to feed them to their offspring.

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The Featured Image

Male Eastern Bluebird Perched on Birdbath in Louisiana Winter With American Holly Tree Branches in Background
Male Eastern Bluebird Perched on Birdbath in Louisiana Winter With American Holly Tree Branches in Background
© Bonnie Taylor Barry/Shutterstock.com

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About the Author

Crystal is always looking to learn more, and share her finds with you along the way. It's amazing how you can spend your entire life living with plants and animals, but still know so little about them! Let's explore our world together as Crystal covers topics about creatures, places, and experiences.

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