What is the average size of a hummingbird egg?

Hummingbirds are some of the smallest birds in the world, so it comes as no surprise that their eggs are also tiny. But just how small are hummingbird eggs on average? Let’s take a closer look at the size of these delicate eggs and what factors influence their dimensions.

Typical Hummingbird Egg Size Range

Most hummingbird eggs are very small, averaging 0.5 inches long and 0.25 inches wide (12-13 mm x 6-8 mm). However, there is some variation in size across the over 300 different hummingbird species. The smallest hummingbird egg belongs to the Bee Hummingbird, the world’s smallest bird. Their eggs can be as tiny as 0.2 inches long and 0.1 inches wide (5 mm x 2.5 mm). On the larger end, eggs of the Giant Hummingbird can reach up to 0.8 inches long and 0.5 inches wide (20 mm x 12 mm).

Here are some examples of average hummingbird egg sizes for particular species:

• Ruby-throated Hummingbird: 0.5 x 0.33 inches (13 x 8.5 mm)
• Rufous Hummingbird: 0.55 x 0.35 inches (14 x 9 mm)
• Allen’s Hummingbird: 0.45 x 0.3 inches (11.5 x 7.5 mm)
• Calliope Hummingbird: 0.4 x 0.25 inches (10 x 6.5 mm)

As you can see, even within the same bird family there is quite a bit of variation in egg size. But what influences these differences?

Factors Affecting Hummingbird Egg Size

There are several key factors that impact the size of hummingbird eggs:

Species Size

Not surprisingly, larger hummingbird species tend to lay larger eggs than smaller hummingbirds. For example, the Giant Hummingbird is one of the largest species, reaching lengths of 8-9 inches. Their eggs are correspondingly bigger than the tiny Bee Hummingbird, which is only 2-2.5 inches long. Generally, the larger the adult hummingbird, the larger their egg size.

Clutch Size

Clutch size refers to the number of eggs laid in a single breeding attempt. Hummingbirds that lay only 1-2 eggs per clutch, like the Ruby-throated, tend to have larger individual eggs. Species with bigger clutches of 3 or 4 eggs, like the Allen’s and Rufous, usually have smaller egg sizes.

Nest Type

The placement and structure of nests limits the maximum egg size in hummingbirds. Very small cup nests and ones attached to narrow branches can only accommodate tiny eggs and clutch sizes. Broader nests provide more room for slightly larger eggs.

Incubation Period

Species with shorter incubation periods of 14-16 days usually produce smaller eggs than hummingbirds with longer incubation of 18-22 days. Shorter incubations require less energy reserves packed into the egg.

Adult Female Size

The body size and egg capacity of the female hummingbird sets the upper limit for egg dimensions. Larger female hummingbirds are able lay eggs at the higher end of the size range for their species. Very small females may produce eggs below average.

By considering all these factors, ornithologists can usually predict the average egg size across hummingbird species. Next, let’s look at how hummingbird egg size compares to other birds.

Hummingbird Egg Size Compared to Other Birds

Hummingbird eggs are vastly smaller than the eggs of most bird species. Here’s how they stack up:

As you can see, the ostrich egg is 120 times larger in volume than a hummingbird egg! Even other small songbirds like sparrows have eggs about twice as large as hummingbird eggs. The tiny size of hummingbird eggs matches the diminutive size of the birds themselves.

Reasons for Small Hummingbird Egg Size

So why did hummingbirds evolve such tiny eggs compared to other birds? There are a few key advantages to the miniaturized size:

Fits Small Nests

Hummingbirds build incredibly small nests out of plant down, spider webs, and lichens. Their nests range from 1-3 inches wide and 0.5-1 inches deep. These cramped nests can only hold 2-4 pea-sized eggs at most. Larger eggs wouldn’t fit.

Enables High Incubation Feeding Rates

Female hummingbirds can’t incubate their eggs for long periods without starving. Their high metabolism requires constant feeding. Tiny eggs allow the females to leave the nest for 10-15 minutes at a time to eat without cooling the eggs too much. Larger eggs would lose too much heat.

Less Energy Required for Flight

Hummingbirds need to conserve every bit of energy for their metabolically demanding hover-feeding. Carrying extra weight from larger eggs would significantly hinder their flight agility and ability to access nectar.

Faster Development in Small Package

Despite their small size, hummingbird eggs contain the optimal amount of nutrients, proteins, and fats for rapid embryonic growth. Concentrating development into a tiny egg allows the chick to hatch quickly.

The miniscule dimensions of hummingbird eggs provide the best chance for breeding success given the unique challenges of their physiology and lifestyle.

Hummingbird Egg Descriptions

Now that we’ve covered the key size metrics of hummingbird eggs, let’s look at some more descriptive details:

Shape

Most hummingbird eggs have a standard oval shape with one more pointed end and one rounded end. However, some species may have more elongated or spherical eggs.

Color

Freshly laid hummingbird eggs are whitish or lightly tinted in color. Common hues include cream, pinkish, bluish-white, or light green. Over time, the egg shell often stains or darkens slightly.

Surface Texture

Hummingbird eggshells have a smooth, slightly glossy surface. When viewed microscopically, the shell has a fibrous, crystallized structure made of calcium carbonate and proteins.

Markings

Most hummingbird eggs are immaculate with no distinct markings. However, some may exhibit very faint specks or spots on the surface. These help camouflage the eggs in the nest.

Internal Contents

Inside the eggshell, hummingbird eggs contain:

• Yolk – Nourishes the embryo
• Albumen – Watery proteins that cushion the yolk
• Chalazae – Twists the yolk to center it
• Air Cell – Pocket where embryo breathes

These internal contents provide everything needed for the chick to develop.

Conclusion

In summary, the average hummingbird egg is extremely small, measuring 0.5 x 0.25 inches (12 x 6 mm) across most species. The Bee Hummingbird lays the tiniest eggs at 0.2 x 0.1 inches (5 x 2.5 mm), while the Giant Hummingbird produces the largest at 0.8 x 0.5 inches (20 x 12 mm). Factors like adult size, clutch size, nest type, incubation period, and female body size all influence egg dimensions. Compared to other birds, hummingbird eggs are miniscule, allowing them to fit in small nests, enabling high incubation feeding rates, reducing flight energy costs, and speeding development. While tiny, hummingbird eggs contain all the vital components needed for growth. Their delicately small size perfectly matches the hummingbird’s unique lifestyle and physiology.