The ruby-throated hummingbird (Archilochus colubris) is a small, highly energetic bird species found throughout eastern North America. Ruby-throats are best known for their unique flying and feeding behaviors, hovering in midair and lapping up nectar from flowers with their long tongues. But like all living creatures, ruby-throats must reproduce to maintain their populations from one year to the next. Ruby-throated hummingbirds have some fascinating adaptations that enable them to breed successfully.
When is the breeding season?
Ruby-throated hummingbirds have a relatively short breeding season compared to other North American bird species. They start establishing breeding territories in late spring, with most mating and nesting activities occurring in the summer months.
The exact breeding timing varies across their range, but generally runs from March through August, with earlier nesting in southern areas and later in the north. In the Gulf states, ruby-throats may start nesting as early as February. Further north along the Atlantic coast, peak breeding is May through July. And in Canada, most breeding occurs between late May and August.
This condensed nesting period is an adaptation to take advantage of seasonal food resources. Ruby-throated hummingbirds time their breeding to coincide with the blooming cycles of spring and summer flowers that provide nectar. This ensures an abundant food supply while females are incubating eggs and both parents are feeding nestlings.
Courtship and Mating
The mating season begins with males establishing breeding territories, which they aggressively defend from intrusions by other males. A male will perch in a prominent location within his territory and perform courtship displays to visiting females. One common display is a U-shaped dive flight, with the male rapidly climbing hundreds of feet into the air before swooping steeply back and forth across the breeding territory. This acrobatic maneuver produces a loud “chipping” vocalization from the tail feathers.
If a female observing the display is interested, she may approach the male and briefly join him on his perch. Mating then takes place very quickly, with the actual copulation lasting only 1-2 seconds. Interestingly, the female initiates mating by moving into position under the male’s cloaca.
Given their tiny size and high metabolism, mating is likely an energetically costly activity for hummingbirds. So the extremely brief copulations help minimize energy expenditure. The male and female may mate repeatedly within a single day before the female leaves the breeding territory.
Nest Building
After mating, the female must build a nest in which to lay and incubate the eggs. Ruby-throated hummingbird nests are tiny, usually only about 2 inches wide and 1 inch tall. The outer shell is constructed from soft plant down, spider silk, and lichens, bound together and attached to the substrate with spider webs. The inside of the nest is lined with fine plant fibers to provide a soft bed for the eggs.
Nests are most often built on downward sloping limbs of deciduous trees, usually 10-20 feet above ground. This hanging nest placement helps provide protection from predators. The female uses spider silk and tightly woven plant fibers to firmly secure the nest in place. She may spend 5-10 days constructing the nest, collecting hundreds of trips worth of materials.
Some key facts about ruby-throated hummingbird nest architecture:
| Nest dimensions | Around 2 inches wide and 1 inch tall |
| Outer shell materials | Spider silk, lichens, plant down |
| Inner lining | Fine plant fibers |
| Attachment to substrate | Spider silk |
| Typical nest height | 10-20 feet up in trees |
| Time to build | 5-10 days |
Egg Laying and Incubation
Within a day or two after completing the nest, the female will mate again and then lay her first eggs. She usually lays 2 eggs per clutch, with 48 hours between the first and second egg. The tiny white eggs measure only 0.5 inches long but represent almost 25% of the female’s body weight.
Like all birds, the ruby-throat’s egg shell is porous, allowing oxygen in and carbon dioxide out. To increase air exchange, the female will regularly rotate the eggs in the nest during incubation. She also provides humidity by pressing wet belly feathers against the eggs.
The female alone incubates the eggs, by sitting on top of them for about 14-16 days before they hatch. During incubation recesses when she briefly leaves the nest to feed, she may employ an ingenious camouflage strategy. Sitting on the eggs leaves behind a small indentation. So before leaving, the female uses her body to flatten the nest, hiding the egg indentations that could attract predators in her absence.
Ruby-Throated Hummingbird Egg Facts
| Number of eggs | Usually 2 |
| Size | 0.5 inches long |
| Egg weight relative to female | 25% of female body weight |
| Incubation period | 14-16 days |
| Incubated by | Female only |
Hatching and Feedings
After 2-3 weeks of incubation, the eggs hatch over a period of 1-2 days. The hatchlings emerge almost naked, with closed eyes, but immediately make loud cheeping noises to beg for food from their mother. The female feeds her chicks with regurgitated nectar and small insects, delivering meals right to each hatchling’s mouth while they remain in the nest.
The chicks’ eyes open after about 5 days and their bodies are covered in feather down after 7-9 days. Their growth is incredibly rapid. After just 3 weeks, the juvenile hummingbirds are fully feathered and ready to make their first flight attempts. This swift development is essential for surviving the energy demands of the hummingbird lifestyle.
While the female performs the majority of feedings, the male may also participate, especially as the fast-growing chicks become ever hungrier. The parents must visit the nest to deliver food every 5-15 minutes, consuming many times their own body weight in nectar and insects each day to provide adequate nutrition. This intense parental care continues for 18-22 days until the fledglings leave the nest.
Key Facts About Ruby-Throated Hummingbird Chicks
| Hatching period | 1-2 days |
| Eyes open | After 5 days |
| Covered in feathers | After 7-9 days |
| Leave the nest | 18-22 days after hatching |
| Frequency of feedings | Every 5-15 minutes |
Fledging and Dispersal
Once the juvenile hummingbirds leave the nest, they are capable of sustained flight but still rely heavily on their parents for food. They beg incessantly as the parents make nonstop feeding visits, gorging themselves on nutritious regurgitated nectar and insects.
This post-fledging parental care lasts 7-28 days until the young birds become nutritionally independent. They learn essential foraging skills like feeding on flowers while still under their parents’ supervision.
Dispersal away from the breeding territory happens gradually, with the juveniles wandering further afield but still returning periodically to their parents for care. By mid to late summer, ruby-throats migrate south in their first fall migration, traveling alone rather than with family groups. First year birds make the strenuous trans-Gulf migration to Central American wintering grounds on their own.
Key Post-Nesting Timeframes for Fledglings
| Post-fledging care | 7-28 days |
| Nutritional independence | By 6-8 weeks of age |
| Dispersal from parents | Gradual, complete by fall migration |
| First fall migration | Mid to late summer |
Threats and Conservation
The ruby-throated hummingbird has a broad breeding range and large total population estimated at over 30 million birds. So it is not currently considered threatened or endangered. However, hummingbirds do face a variety of threats on both their breeding and wintering grounds.
Collisions with buildings and towers while migrating or establishing territories account for many hummingbird deaths annually. Habitat loss also impacts breeding, as urbanization and agriculture reduce flowering meadows and successional habitats. Introduced diseases and expanded ranges of hummingbird predators like blue jays may also contribute to declines in some areas.
While not currently at high risk compared to other birds, targeted conservation efforts can help maintain healthy ruby-throated hummingbird numbers. Protection of key stopover habitats during migration and natural breeding areas with abundant spring flowers will ensure these unique birds continue thriving. Educating the public to provide clean hummingbird feeders free of molds and to avoid unnecessary pesticide use is also beneficial. Careful monitoring of reproduction and survival rates will enable conservationists to detect any emerging population threats.
Conclusion
Ruby-throated hummingbirds have evolved some remarkable strategies to enable their reproduction. The males perform elaborate courtship displays to attract mates. Females build intricately woven nests and incubate the tiny but energetically costly eggs for 2-3 weeks. Parent birds provide incredibly frequent feedings to enable rapid chick growth. And young hummingbirds quickly gain independence after leaving the nest, preparing for the long migration ahead. Understanding the ruby-throat’s breeding biology allows us to support their conservation and continue to enjoy these favorite backyard visitors for generations to come.
