RAISING BABY HUMMINGBIRDS
Female Hummingbirds are some of the most capable single moms in nature. Usually she will not accept the amorous attention of any male until she builds her nest by herself. The males role in the rearing of the young is limited to fertilization. After that occurs, she alone lays and incubates the eggs and cares for the fledglings. While we might be inclined to think poorly of the male for this seemingly neglectful behavior, think of the danger of having a blinking iridescent male leading the way to the vulnerable nest. Nature knows best.
Before any male courts successfully, the female hummer gathers an enormous amount of stronger-than-steel-wire spider's silk. With the strong thread, she binds soft seed down, furry leaf hairs, fern fronds, fine fibrous roots, wool, feathers, and any similar material she finds to form the body and the soft lining of the nest. Spider's silk also fastens the nest to support the substrate. To help the nest blend perfectly into its surroundings, she decorates the outside of the nest with lichens, mosses, bark fragments, etc. Once the nest was built and ready to hold her precious eggs, the female is receptive to the males glittering display flights. She may even seek out a male and dance in front of him to initiate mating.
Hummer nests are remarkably similar in composition, but remarkably different in placement. Some saddle horizontal branches. Others are suspended from above. Some are partially suspended in the fork of a tree. Some hang precariously over streams. Others regurgitate a sticky glue to attach the nest to a nearly vertical cliff face. Some females are natural engineers and make use of small stones or mud clods on one side of the nest to counterbalance it. Others build up one side of the nest more than the other for the same counter weighted effect. The Andean Hillstar that nests in high cold Andes builds a thick and large nest for greater insulating value. She locates the nest in cave or deep ravine, often unusually close to others of her species, for more protection from the harsh climate. Nests have been erected in one or two days. More often it takes from one to two weeks to build a nest. Sometimes the one or two tiny pure white eggs are laid about two days apart before the nest is completed. Then nest building takes place simultaneously with incubation.
Females are fierce defenders of their nests. They attack marauding hawks, man, snakes, or any animal that ventures too near. Males don't defend nests, but are equally adept when defending feeding and mating territories, which in a few cases they share with there mates. There are some rare reports of males incubating eggs and helping to feed the young. Ruby-throats and Rufous hummingbirds, the most northerly of nesting hummers whose cold climate offers the least resources, have been observed incubating eggs. There is a single report of an Anna's male feeding young.
Incubation begins as soon as the eggs are laid. There are a few erroneous reports of an incubation period of only 9 - 12 days. Since the incubating female must leave frequently to forage for her own food, as well as additional nesting materials, incubation takes longer than expected for such tiny eggs. Realistically, it takes about 14 - 17 days and sometimes up to 23 days of incubation before they hatch. If the weather turns nasty, it extends the incubation period.
Once the eggs hatch, the almost impossibly small hummingbird babies emerge naked, totally helpless. They have a bump were the beak will be, and two rows of tiny down feathers down the middle of their back. Most skip an insulating downy stage of development. Nevertheless, they develop an early tolerance to temperature fluctuations. The female continues brooding the young until they are from 12 - 18 days old. In places like the high Andes, this can be as long as 38 days. Even once fledged, the young birds continue to develop their tail feathers and bills before they reach their mature length. Females continue to feed their young for as much as 65 days after hatching.
Hummer babies are amazingly resilient. They not only survive extreme temperatures, but they also are able to make it through fall that would kill most nestlings. By the time they are 16 days old, they are well clad in feathers. Bright and alert, they peek out of the nest curiously and spend considerable time preening their new feathers. Every now and then, they rise up, hold on tightly to the nest and vigorously flap their wings to prepare them for flight.
Unless frightened, hummers leave their nest with no urging from their mothers. Before they are three weeks old, most hummers take flight in the morning. Since the eggs are laid a couple of days apart, often one nestling leaves home a couple of days before its sibling. Most hummers fly gracefully from their very first attempt.
As soon as they hatch, the babies that look like they are all head, are fed by mom. She sticks her needle-sharp bill so far down the baby's gullet that one might think she would skewer her own young. This does not happen and the babies thrive on a diet heavy in regurgitated insects and probably nectar. They are fed so much that their crops extend from the side of their necks like some kind of gigantic avian goiter!
Despite the exemplary courage and perseverance of the female in raising her young, nesting success rates are relatively poor for hummers. Hummer nests are subject to many perils; loss of young or eggs to accidents, catastrophic weather, and predation. For example, 50% of the eggs of a White - eared hummer hatched, but only 16.7% of the eggs laid actually produced fledglings. Andean Hillstars, who nest so high as to avoid the attention of predators, produced 18 eggs in 19 nests, resulting in 16 fledglings. In a study of the Anna's hummers, who's nests are more susceptible to predators, 85 nests produced 68 eggs of which 42 hatched and only 23 survived to become fledglings.
The more I learn about birds, and hummingbirds in particular, the more miraculous the variety and numbers of them seem. With so many dangers, and being such small creatures in such a large world, their numbers, variety, and success never cease to astonish me!