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Hummingbird Nesting Phenology
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.

ruby hummer
 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.

   
baby hummingbird
Dorothy Edgington
Nest Building: 5 - 10 days
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.
   
nest
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.

   
nest
Dorothy Edgington
Incubating Eggs: 12 - 14 days
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.

 

   
nestlings
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.

   
Rubythroated Hummingbirds
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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