Hummingbirds are some of the smallest birds in the world, so it comes as no surprise that their eggs are tiny as well. The eggs of hummingbirds are very small, typically measuring less than 1 centimeter long. Despite their tiny size, hummingbird eggs are perfectly formed and contain everything needed to develop into a hatchling.
Typical Size of Hummingbird Eggs
Most hummingbird eggs are oval or elliptical in shape and measure between 0.5-1 centimeter (0.2-0.4 inches) long. They are only slightly wider than a wooden matchstick. Some key measurements for different hummingbird species are:
- Ruby-throated hummingbird eggs: 0.6-0.8 cm long
- Black-chinned hummingbird eggs: 0.7-0.9 cm long
- Anna’s hummingbird eggs: 0.8-1.0 cm long
- Rufous hummingbird eggs: 0.7-0.9 cm long
- Calliope hummingbird eggs: 0.6-0.8 cm long
As you can see, the sizes overlap quite a bit between different hummingbird species. The ruby-throated hummingbird lays the smallest eggs, while the Anna’s hummingbird produces the largest.
Weight of Hummingbird Eggs
Given their tiny size, hummingbird eggs are incredibly lightweight. The average weight of a hummingbird egg is 0.365 grams (0.0129 ounces). That’s lighter than a penny! Here are the egg weights for a few common species:
- Ruby-throated hummingbird egg: 0.30-0.40 g
- Black-chinned hummingbird egg: 0.35-0.45 g
- Rufous hummingbird egg: 0.35-0.50 g
- Allen’s hummingbird egg: 0.40-0.55 g
The smallest hummingbird egg on record weighed just 0.25 grams and belonged to a Calliope hummingbird. The largest hummingbird egg ever found weighed 0.92 grams and was from a Giant hummingbird species found in South America.
Shape and Color
Hummingbird eggs come in either a traditional “egg” oval shape or a more elliptical form. They have a smooth, glossy surface and thick shells that help protect the developing chicks. The color of hummingbird eggs can vary slightly between white, cream or pale green. Some species lay uniformly colored eggs, while others may have light brown speckles on the shell surface.
Clutch Size
Hummingbirds typically lay a “clutch” of two eggs per breeding cycle. The eggs are laid on consecutive days. Because hummingbirds can breed up to 3-4 times in a season, they may produce 4-8 eggs over the course of a breeding season.
Here are the typical clutch sizes for some common hummingbird species:
- Ruby-throated hummingbird: 2 eggs per clutch
- Black-chinned hummingbird: 2 eggs per clutch
- Anna’s hummingbird: 2 eggs per clutch
- Rufous hummingbird: 2 eggs per clutch
- Allen’s hummingbird: 2 eggs per clutch
Having just two eggs allows the parent birds to more effectively incubate the eggs and raise the chicks once they hatch. More than two eggs likely wouldn’t fit in the tiny nests that hummingbirds build.
Incubation and Hatching
The female hummingbird is solely responsible for incubating the eggs after they are laid. The incubation period lasts between 14-23 days, depending on the species. The ruby-throated hummingbird incubates its eggs for 16-17 days, while the rufous hummingbird incubates for 16-18 days.
Because hummingbird eggs are so small, they allow gases and moisture to pass through their shells fairly easily. This means the parent bird doesn’t have to turn the eggs much during incubation. However, the female still attentively incubates the eggs and keeps them warm until they hatch.
When the chicks are ready to hatch, they use their small egg tooth on their beak to pip through the eggshell. It takes 12-36 hours for the hatchlings to fully emerge. Once out of the eggs, the chicks are blind, featherless and completely dependent on their mother for care and feeding.
Development Within the Egg
Even though hummingbird eggs are tiny, they still undergo complex development before hatching:
- 0-24 hours: Fertilization occurs and cell division begins
- 24 hours to 4 days: A network of blood vessels forms
- 4-8 days: Eye pigmentation appears and the neural tube develops into a rudimentary brain and spinal cord
- 8-13 days: The bill takes shape, bones start to harden, feathers begin growing under the skin
- 13-16 days: Feathers develop in their sheaths, the egg tooth forms on the tip of the bill
- 16-18 days: Hatching occurs! The egg tooth is used to break out of the shell
The timing of these developmental milestones allows hummingbird chicks to hatch at just the right stage of maturity to survive outside the egg. The mother hummingbird times her incubation perfectly to coordinate with these internal developmental cues.
Role of Egg Size
The tiny size of hummingbird eggs has important implications for their survival and development:
- Tiny eggs allow easy heat transfer for incubation. The mother hummingbird can cover the eggs completely to keep them at optimal temperature.
- The small size allows for easy gas diffusion through the shell for the developing embryo.
- Smaller eggs require fewer resources to produce. A female hummingbird can lay multiple clutches in a season without exhausting her reserves.
- Tiny eggs fit perfectly in the thimble-sized nests hummingbirds build.
- The shell has to be very strong and proportional to withstand incubation despite the egg’s diminutive dimensions.
While hummingbird eggs may look shockingly small to our eyes, they contain everything needed to successfully develop a hatchling. Their tiny package makes perfect sense for hummingbirds’ unique reproductive strategies and energy needs.
Comparison to Other Bird Egg Sizes
To better appreciate just how small hummingbird eggs are, it helps to compare them to the eggs of other birds:
| Bird | Egg Size |
|---|---|
| Ostrich | 15 cm long x 13 cm wide |
| Swan | 10 cm long x 7 cm wide |
| Chicken | 5 cm long x 4 cm wide |
| Hummingbird | 0.5-1 cm long |
As you can see, ostrich and swan eggs are gigantic in comparison. At over 10x the size of a hummingbird egg, a chicken egg seems enormous. This really puts into perspective just how incredibly tiny hummingbird eggs are on the avian spectrum.
Why Are Hummingbird Eggs So Small?
There are a few key reasons why hummingbirds lay such tiny eggs:
- Small body size – Hummingbirds are the smallest birds, so they can only produce proportionally small eggs.
- Energy conservation – The small eggs require fewer resources to produce, which is essential for the high-metabolism hummingbirds.
- Faster development – With a larger surface area proportional to their size, the eggshells allow for faster gas and heat exchange.
- Frequent breeding – Smaller eggs allow the birds to breed more often throughout the season.
The petite size of hummingbird eggs makes perfect sense when you consider the unique reproductive biology and tremendous energy needs of hummingbirds. Although they may look shockingly tiny, these mini eggs contain everything the baby hummingbird needs to hatch and thrive.
Conclusion
Hummingbird eggs are very small, averaging only 0.5-1 cm long and weighing 0.3-0.6 grams. However, they are perfectly sized to allow the developing chicks to hatch after a 2-3 week incubation period. The tiny dimensions of hummingbird eggs enable efficient heat transfer, gas diffusion, frequent breeding, and a good fit inside the bird’s tiny nests. While they may look shockingly small compared to eggs of other birds, hummingbird eggs provide the essential nutrients and environment for growth until the chicks are ready to hatch.
