Hummingbirds are some of the most fascinating birds in the world. There are over 300 different species of hummingbirds, all native to the Americas. Hummingbirds are known for their incredibly fast wing beats, ability to hover in midair, and long migratory journeys. One of the most intriguing aspects of hummingbird life history is their reproduction and development of young. Hummingbirds lay the smallest eggs of all birds, and the chicks that hatch from them are tiny, naked, and helpless. Yet these tiny babies grow rapidly, develop amazing flying skills, and undertake migrations of thousands of miles. With so many hazards and such a delicate beginning, what are the odds of a hummingbird chick surviving to adulthood? Here we will look at hummingbird reproduction, development, and mortality rates to find out approximately what percent of hummingbird chicks survive.
Hummingbird Reproduction
Hummingbirds begin breeding in their first year after hatching. In preparation for breeding, the male hummingbird will establish a breeding territory that contains food resources, perches, and nest sites. He will perform aerial displays and sing vocalizations to attract a female. Once a female enters his territory, he will continue elaborate courtship rituals such as aerial maneuvers and flying in looping U-shaped flight patterns. If the female is receptive, she will perch and allow the male to mate with her.
A key factor in hummingbird reproduction is the availability of food resources. Hummingbird eggs and chicks have extremely high energy demands. The mother hummingbird must have access to plenty of nectar and insects to successfully raise her chicks. Some species will have 2 broods per year, while others may only nest once due to fewer food resources.
Once mated, the female hummingbird will build a tiny cup-shaped nest out of soft plant down, spider silk, lichens, and moss. The nest is only about 2 inches wide and 1 inch deep. She will lay 2 pea-sized eggs, and once the chicks hatch after 2-3 weeks she will feed them every 5-10 minutes by regurgitating pre-digested nectar and insects into their mouths.
Hummingbird Nest Survival Rates
One of the biggest challenges facing hummingbird chicks is simply surviving in the nest after hatching. Hummingbirds build very fragile nests on top of small tree branches, often only 10-40 feet above the ground. These nests and their tiny inhabitants are vulnerable to predators, wind, rain, and displacement. Studies have found:
– Between 20-60% of hummingbird nests are predated by animals before eggs can hatch. Common nest predators include snakes, squirrels, and jays.
– Up to 50% of nests can fail due to damage from wind and rain storms. Hummingbird nests have very little structural stability.
– As many as 33% of hummingbird nests are abandoned by the mother before eggs hatch or chicks fledge. Some reasons for abandonment include disturbance, insufficient food resources, and death of the mother.
– Parasitic insects and bacteria infest up to 20% of hummingbird nests, causing mortality of developing chicks.
This high failure rate of hummingbird nests means that even getting hatched is a difficult first hurdle for hummingbird chicks to overcome. However, hummingbirds account for this by laying multiple clutches when possible. While many nests fail, female hummingbirds will continue to build new nests and lay more eggs to compensate. This helps ensure that at least some of her offspring will successfully hatch each season.
Hummingbird Chick Development
Hummingbird chicks hatch after an incubation period of 14-23 days. The chicks are altricial, which means they are naked, blind, and completely dependent on their mother for food and care. Their eyes are closed, they have only a thin layer of downy feathers, and they are unable to hold up their heads. Yet they grow and develop at a remarkably fast pace.
0-5 Days after Hatching
– Chicks double their hatch-weight by day 5.
– Eyes are still closed, movement is limited.
– Mother feeds chicks every 5-10 minutes by regurgitation.
5-10 Days after Hatching
– Eyes open on day 6-8.
– Pins begin emerging from wing feather tracts.
– Chicks are very vocal, peeping when hungry.
– Weight gain rapidly increases.
– Crop is prominent when full of food.
10-15 Days after Hatching
– Covered in grey downy feathers.
– Able to thermoregulate and sit up unassisted.
– Beg and jostle for position during feedings.
– Gain ability to regulate sugar intake.
– Wing feathers begin to unfurl and expand.
15-20 Days after Hatching
– Body feathers filling in, able to flap wings.
– Adult feathers emerge on head, back, and chest.
– Thoracic muscles strengthen to aid flight.
– Feedings decrease to every 30-45 minutes.
– Chicks becomes very active in nest.
20-25 Days after Hatching
– Full set of adult plumage.
– Able to hover and fly short distances by day 20-22.
– Feedings decrease to 6-10 times per day.
– Chicks will fledge from nest by 25 days old.
As you can see, hummingbird chicks develop from helpless hatchlings to fully feathered, flight-capable fledglings in just 3-4 weeks. This allows them to leave the nest and reduce their vulnerability to nest predators. Fledging at such a young age requires very rapid muscle and feather development and an incredibly nutrient-rich diet provided by the mother.
Hummingbird Chick Mortality after Fledging
Once hummingbird chicks successfully fledge, their mortality risk is greatly reduced. However, the first few days out of the nest are still perilous as they learn to fly, feed, and evade predators. Here are some of the key threats faced by fledgling hummingbirds:
– Up to 57% of fledglings may not survive the first 2 days out of the nest, as they are still developing flying skills. Collision or injury risks are high.
– Predators like snakes, lizards, and cats can snatch clumsy fledglings. Predation accounts for 35% of mortality in the first week after fledging.
– Malnutrition and starvation may affect up to 30% of fledglings, as they learn to forage on their own.
– Extreme weather such as cold temperatures or torrential rain can lead to hypothermia and death of unskilled fliers.
If fledglings survive these initial hurdles, their chances of surviving to adulthood and migration back to breeding grounds are much higher. By 2 weeks after fledging, hummingbird flight capabilities and feeding skills are much improved. After 4-5 weeks they are essentially fully independent juvenile birds ready to migrate.
Overall Hummingbird Chick Survival Rates
Now that we have looked at the different phases of hummingbird reproduction and chick development, we can estimate the overall survivorship from hatching to independence:
| Stage | Mortality Rate | Survivorship |
|---|---|---|
| Egg to Hatching | Up to 60% | 40% |
| Hatching to Fledging | 10-15% | 34-36% |
| Fledging to Independence | Up to 30% | 24-25% |
As the table shows, at each stage from egg to adulthood, substantial numbers of chicks die due to various hazards. Overall, only about 25% of eggs laid successfully result in independent juvenile hummingbirds. However, those that do survive tend to be strong, healthy, and genetically fit, well-prepared for the migratory journey ahead.
The high mortality of the majority of chicks allows each female hummingbird to dedicate all her resources and care towards the 1-2 chicks with the best chances of surviving per nest. This reproductive strategy, though perilous, helps ensure that those chicks that do survive have the best odds of living to adulthood, breeding, and continuing the cycle. Though the mortality rate per individual is high, collectively it allows species populations to remain stable in the face of many challenges.
Conclusion
In summary, hummingbird reproduction is characterized by high mortality rates offset by prolific laying of eggs and repeated nesting. While 60% or more of eggs and chicks may die before fledging, females lay multiple clutches resulting in at least some successful offspring. Around a quarter of all chicks that hatch survive to become independent juveniles. This allows hummingbird populations to persist despite huge obstacles faced by eggs, nestlings and fledglings. The resilience of these tiny birds in the face of their many vulnerabilities is a testament to the adaptability of natural selection over time. With numerous hazards at every stage, it is remarkable that any hummingbird survives – yet their stunning aerial displays and incredible migrations assure us that this delicate balance of life and death continues, generation after generation. Their early hardships produce hardy, accomplished fliers able to endure and pass on their genes, sustaining the species as a whole in spite of the difficult odds for each individual.
