Hummingbird Eggs: Size, Incubation, and What to Do If You Find One

A hummingbird egg is genuinely one of the smallest things a bird produces, small enough that most people who find one, or find a photo of one, assume it has to be a joke or a trick of the camera. It isn't. Here's the real size, how long incubation actually takes, why published numbers on that don't all agree, and what to actually do if you come across a fallen egg rather than an active nest.

How Big Is a Hummingbird Egg, Really

Per Cornell Lab's All About Birds, a Ruby-throated Hummingbird egg runs 1.2 to 1.4 centimeters long and 0.8 to 0.9 centimeters wide, weighing about half a gram, less than one-fiftieth of an ounce. Operation RubyThroat, a citizen-science hummingbird research project, independently puts the same egg at 8 millimeters by 13 millimeters, essentially the same measurement from a different source. Birds and Blooms translates that into more familiar objects: about a centimeter long, roughly the size of a jellybean, a Tic Tac, or a blueberry, and lighter than a paperclip. Those everyday comparisons vary a little from writer to writer, a coffee bean in one place, a jellybean in another, and that's fine. A coffee bean and a jellybean aren't identical in size, but they're close enough that either one lands in the right neighborhood for something this small.

Size varies by species too, not just by which everyday object a given writer reaches for. The Bee Hummingbird, the world's smallest hummingbird and the smallest bird species on Earth, weighs under two grams as an adult. Per Audubon, a female Bee Hummingbird's egg is "about the size of a coffee bean" too, the same shorthand used above for the considerably larger Ruby-throated egg, which sounds like a contradiction until you remember that a coffee bean itself is a rough stand-in rather than a fixed measurement. The Bee Hummingbird's egg is widely described as the smallest egg laid by any bird species anywhere, smaller in absolute terms than the Ruby-throated egg even where both end up compared to similar-looking everyday objects.

Clutch Size: Almost Always Exactly Two

Cornell's broader figure puts a typical clutch at one to three eggs. In practice, two is overwhelmingly the norm: per Operation RubyThroat and Birds and Blooms, a female typically lays exactly two eggs, occasionally just one, and "almost never" three. Both eggs are usually laid roughly a day and a half to two days apart, not simultaneously, which is part of why chicks in the same nest are sometimes visibly different sizes for a stretch, the older one simply had a head start. Our baby hummingbird guide covers what happens after hatching in full; this post stops at the egg stage itself.

Why two, specifically, rather than three or four the way many songbirds manage? There's no single named study that settles this for hummingbirds specifically, so it's worth being upfront that the honest answer here is reasoned inference rather than a confirmed finding: a female hummingbird raises her brood entirely alone, with no mate helping to gather insects or guard the nest, on an energy budget that's already stretched thin by her own tiny size and fast metabolism. Two chicks appears to be close to the practical ceiling for what one adult can feed often enough to keep both alive, which is a plausible explanation for why the clutch size caps out where it does, even without a study that measured it directly.

Incubation: About Two Weeks of Near-Constant Sitting

Birds and Blooms puts incubation at "15 to 18 days," the figure our hummingbird nest guide works from. Worth being honest that other credible sources land on slightly different numbers: Cornell's All About Birds says 12 to 14 days, while Operation RubyThroat puts it at 14 to 16 days, "perhaps as long as 21 days in cool weather." Rather than picking one and hiding the disagreement, the fair summary is that incubation runs roughly two weeks, shorter in warm conditions, meaningfully longer in cool ones, with different research programs and different individual nests landing at different points in that range.

Whatever the exact number, the female spends nearly all of it on the nest alone. Per Birds and Blooms, she incubates roughly 75 percent of the time, leaving only in short bursts, "no more than 10 minutes in an hour," to feed herself before returning. A reliably stocked feeder nearby genuinely shortens that trip, not a substitute for her own foraging, but a small, honest help during a stretch when every minute off the eggs matters. Whether that feeder holds a from-scratch mix or a no-boil powder like Nectar Bliss's, keeping it clean and full during this window is a small way to make an already tight schedule slightly easier on her.

Egg Color and Why the Nest Does the Camouflaging

Hummingbird eggs are plain white, not patterned or speckled the way many other birds' eggs are. That's not an oversight; the eggs don't need their own camouflage because the nest does that job instead. As covered in our nest guide, the outside of a hummingbird nest is built from lichen specifically to blend into the branch it sits on, which means the white eggs inside are protected by the nest's disguise rather than needing one of their own.

Plain white shells are actually typical for cavity- and enclosed-nesting birds more broadly, not a hummingbird quirk. Per Cornell Lab's All About Birds, "birds that lay all-white eggs tend to be cavity-nesting species, such as owls and woodpeckers," since "their eggs are already hidden from view so there's no reason to produce pigmented eggs." A hummingbird's deep-cupped nest works the same way: the egg is already concealed inside the structure before camouflage on the shell itself would even come into play. Cornell notes exceptions exist elsewhere in the bird world, some ground-nesting species produce bright, conspicuous eggs despite having no cover at all, so concealment alone doesn't explain every species' egg color. For a nest as fully enclosed as a hummingbird's, though, plain white is simply what an egg looks like once the parent bird has offloaded the disguise work onto the nest instead.

What to Do If You Find a Hummingbird Egg on the Ground

This is a different situation from finding an active nest, which our nest guide already covers in full, including the legal protection an active nest has under the Migratory Bird Treaty Act. A single egg found on the ground, fallen or knocked loose, calls for its own steps. Per the Toronto Wildlife Centre's general guidance for found bird eggs, the first step is to look up and around the immediate area for a nest the egg may have fallen from; if one is found and safely reachable, and the egg matches what's already there, it can be returned with minimal handling. If no nest can be found, or it isn't safely reachable, the organization is direct about what not to do: "you should not try to incubate abandoned eggs yourself." The right next step is to contact a licensed wildlife rehabilitator for guidance specific to the situation. This is general bird-egg guidance rather than a hummingbird-specific study, since there's no rigorous published figure for exactly how long a cooled hummingbird egg stays viable, and that gap is worth naming rather than guessing at a number. The safe default either way is the same: minimal handling, and a professional making the actual call.

One worry worth defusing directly: returning an egg to its nest, or handling a fallen nestling briefly to get it back in, will not cause the parents to abandon it. Per Cornell Lab's All About Birds, "it's a myth that parent birds will abandon young that have been touched by humans." Most birds do have a reasonably good sense of smell, but Cornell is direct about why that doesn't matter here: nesting birds have already invested too much time and energy in their young to walk away over something as minor as a human scent. That doesn't change the advice above, a fallen egg still calls for finding the nest and a rehabilitator's input when it can't be safely returned, but it does mean brief, careful handling isn't the risk some people assume it is.