Article | Journal
Each year when Ruby-throated hummingbirds migrate north, they arrive on the breeding grounds with one main focus—producing a successful new generation. This involves several critical steps.
Ken Bosso
Territorial
Defense: 3-4 months
Both
sexes are seen chasing away others from feeders and flowers, but on the breeding grounds, male hummingbirds devote much more
energy and time to territorial defense than females do. Although a male does not share the responsibilities for nesting and raising
babies, his work in keeping other hummers off the territory is very important
to ensure that the babies will have enough food. Males suffer higher mortality
than females, so a male's devotion to this one task is apparently as much
as he can invest in reproduction.
Dorothy Edgington
Each female selects the nest site, gathers the nesting materials, and builds the nest entirely on her own. In southern areas where hummingbirds nest two or sometimes, though rarely, three times in a season, the female might reuse a nest for her second brood.
Dorothy Edgington
Egg
Laying: 1-3 days
The female lays 2 eggs. The second egg is laid 1 - 3 days after the first.
Each egg weighs roughly 0.5 grams. Adult females weigh about 2.5 - 6 grams. Most breeding females are somewhere in between.
The extreme weights usually happen just before migration, when the birds
are very fat, and after long, exhausting migration flights.
Dorothy Edgington
The female begins incubating as soon as the first egg is laid. She is responsible for all the incubating. She sits on the eggs all through the night, and about 75% of the time during the day.
Dorothy Edgington
Brooding
and Feeding Nestlings: 18 - 25 days
Immediately after the first baby hatches, the female will incubate about 86%
of the time during daylight. The nestlings cannot produce enough of their own body heat at first, and the mother broods them for about 9 days. As they require more and more
food, she broods them less and less. When she leaves the nest to forage, she collects nectar, pollen, and tiny insects in her crop. When she returns to the nest, she regurgitates the energy-rich slurry into the mouths of the nestlings. By the third day after hatch, the chicks have doubled their mass, which doubles again by day five and again by day eight. As they grow, she will carry whole insects to them, using her beak.
Russ Thompson
Taking
Care of Fledglings: 4 - 7 days
Once the young fledge from the nest, they may associate with their mother
for up to a week, and she continues to feed them during this time. When
they leave the nest, babies are generally much heavier than their mother.
The babies lose weight until they get good at feeding themselves.
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