Hummingbirds are known for their dazzling colors, lightning-fast flight, and uniquely high metabolism. Their tiny size necessitates constant feeding and extends to their reproductive cycle. Everything about their life scale is miniaturized, culminating in the production of the smallest bird eggs laid by any species globally.
Precise Measurements of Hummingbird Eggs
Hummingbird eggs hold the record for the smallest avian eggs, though dimensions vary across the more than 350 species. A typical North American egg, such as the Ruby-throated Hummingbird’s, measures about 13 millimeters (0.5 inches) long and 8 millimeters wide. These miniature ovals are non-glossy and pure white, lacking the spots or patterns found on many other bird eggs.
The weight of these eggs is usually less than a single gram, often around half a gram (0.5 g). The Bee Hummingbird, the world’s smallest bird, lays the absolute smallest egg, weighing only about 0.05 grams. Despite this microscopic scale, the egg is proportionally large compared to the mother’s body mass, representing a substantial energy investment. For example, a female Ruby-throated Hummingbird’s egg can weigh nearly 17% of her total body weight at the time of laying.
Visualizing the Smallest Bird Egg
To appreciate the scale of these eggs, the average hummingbird egg is frequently likened to the size of a small jellybean or a coffee bean. Some comparisons include a navy bean or a tic-tac candy, emphasizing the elongated, ovoid shape. The difficulty of locating such a small object in nature highlights the challenges the mother faces in protecting her brood.
This tiny size is an evolutionary necessity, allowing the female to carry and lay two eggs without impeding her ability to fly and forage. Producing small eggs helps the mother maintain her immense energetic demands due to her rapid metabolism. Even the largest hummingbird eggs, such as those of the Giant Hummingbird, are still small, reaching a length comparable to a US penny.
Nest Structure and Clutch Size
The tiny eggs are housed within a miniature, meticulously constructed nest built exclusively by the female bird. She fashions a cup-shaped structure often no larger than half a walnut shell or a bottle cap in diameter. The nest utilizes soft materials like plant down, moss, and lichen, bound together using strands of spider silk.
Spider silk is important because its elastic properties allow the nest walls to stretch and expand as the two hatchlings grow larger. The outside of the nest is often camouflaged with lichen and moss, helping it blend seamlessly with the tree branch or shrub. Almost all hummingbird species lay a clutch of only two eggs, which is the maximum number the single mother can successfully feed and care for.
Incubation Period and Hatchling Care
Once the two eggs are laid, the female begins incubation, which typically lasts between 14 and 23 days, depending on the species and ambient temperature. She must sit on the nest for a significant portion of the day, leaving only for brief, frequent feeding excursions to maintain her high energy levels. The mother alone performs all parental duties, as the male does not participate in nest building, incubation, or raising the young.
When the chicks hatch, they are altricial, meaning they are blind, nearly naked, and entirely helpless. The mother feeds them a slurry of partially digested insects and nectar by inserting her long bill deep into their mouths and regurgitating the food. The hatchlings grow quickly due to this protein-rich diet, usually remaining in the nest for 18 to 28 days before they are ready to fledge.