Quick Answer
The Black-chinned Hummingbird (Archilochus alexandri) typically has 2 broods per year. The female builds a new nest and lays eggs for each brood.
Overview of the Black-chinned Hummingbird
The Black-chinned Hummingbird is a small, fast-flying bird native to western North America. Some key facts about this species:
- Length: 3.5 inches
- Wingspan: 4.3 inches
- Weight: 0.1-0.2 oz
- Lifespan: 3-5 years
- Diet: Nectar, insects, tree sap
- Range: Western North America from British Columbia to Baja California
- Habitat: Open woodlands, canyons, mountain foothills
The adult male Black-chinned Hummingbird has a black chin, purple crown and throat, green back and white underparts. The female lacks the purple and black markings and is pale below with greenish upperparts.
This hummingbird gets its name from the male’s distinctive black chin. It is a medium-sized hummingbird with a slender, straight bill and a body that is mostly green above.
The Black-chinned Hummingbird breeds across much of western North America. Its breeding habitat stretches from southern British Columbia down through California, Arizona, New Mexico and western Texas. The species winters in southern Arizona, Texas and southward through Mexico to Panama.
During the breeding season, the male Black-chinned Hummingbird is highly territorial and uses aerial displays to advertise and defend its territory. The displays include rapid vertical ascents, followed by downward dives. Males also produce buzzing noises with their wings during dive displays.
Nesting and Broods
The Black-chinned Hummingbird builds a small cup-shaped nest out of plant down, spider webs and lichens. The outer part of the nest is camouflaged with bits of bark, moss and lichens.
The female builds the nest on the branch of a tree, shrub or cactus, 3-20 feet above ground. Nests are typically placed along riparian areas or washes bordered by trees.
First Brood
The female Black-chinned Hummingbird lays the first clutch of eggs in late March to early April across most of its western breeding range. The clutch consists of 2 tiny white eggs, each measuring 0.5 inches long.
The female incubates the eggs for 12-16 days before they hatch. Once the chicks hatch, the female cares for and feeds the chicks through frequent visits to the nest.
The chicks fledge (leave the nest) after 18-23 days. By late April to mid May, the first brood has left the nest.
Second Brood
Within a week after the first brood fledges, the female starts building a new nest and breeding again. She lays another clutch of 2 eggs and incubates them for the second brood.
This second clutch is initiated anytime from early May to late June. The timing depends on the region and elevation. Late spring to early summer is the peak period for second broods.
As with the first brood, the female alone incubates the eggs and cares for the hatchlings. After another 18-23 days, the second brood leaves the nest by late June to late July.
So in total, the female Black-chinned Hummingbird raises two broods per breeding season.
Raising Multiple Broods in a Season
Many temperate bird species can raise multiple broods in a single breeding season. The Black-chinned Hummingbird is one such species. Here are some key reasons why:
- Plentiful spring and summer food sources allow repeated nesting
- Small body size with high metabolism facilitates rapid breeding cycles
- Single parenting by the female enables polygamous mating strategy
- Long breeding season in mild climates provides time for multiple nests
- High energy requirements of young force early independence from parents
Access to plentiful nectar and insects from spring wildflowers through summer allows the Black-chinned Hummingbird to meet the high energy demands of raising back-to-back broods.
Its small size also lets it breed rapidly, not being constrained by lengthy egg-laying and incubation periods of larger birds. Plus the male plays no role in parenting, leaving all duties to the female.
The long breeding season across much of its range gives the female time to raise multiple broods. And the high metabolism of the tiny chicks forces them to fledge early on, letting the female restart nesting quickly after the first brood.
Number of Broods by Region
While the Black-chinned Hummingbird routinely has 2 broods per season, the actual number can vary by region:
Region | Number of Broods |
---|---|
Southern Arizona, New Mexico | 2-3 broods |
Northern Arizona, Colorado, Utah, California | 1-2 broods |
Pacific Northwest, Canada | 1 brood |
In the southernmost parts of its range (southern Arizona, New Mexico), the extended breeding season and favorable climate may allow some Black-chinned Hummingbirds to raise up to 3 broods per season.
Further north, the shorter summers typically limit breeding to 1-2 broods. In the Pacific Northwest and Canada, most birds only have time for a single brood.
So while 2 broods is typical for Black-chinned Hummingbirds, the actual reproductive success depends on how much time is available for multiple nesting attempts in a given area.
How Many Eggs are Laid?
As mentioned earlier, the Black-chinned Hummingbird lays 2 eggs per clutch, for both the first and second broods. So if a female raises 2 broods in a season, she will lay a total of 4 eggs.
Here is a summary of the eggs and offspring over a full breeding season:
- First clutch: 2 eggs
- Second clutch: 2 eggs
- Total eggs laid: 4
- Total offspring (assuming 100% survival): 4
Of course, survival rates are rarely 100% in the wild. Some eggs or chicks may be lost to predators, weather events, starvation or accidents. But under ideal conditions, a female can produce up to 4 offspring over a single breeding season if she raises 2 broods.
Incubation Period
As covered earlier, the Black-chinned Hummingbird incubates its eggs for 12-16 days before they hatch. This incubation period is consistent for both the first and second broods.
The female alone incubates the eggs, rarely leaving the nest for even brief periods. She sits on the nest in a trance-like state, requirement high constant body heat and attention to maintain proper incubation.
Like all hummingbirds, the Black-chinned Hummingbird has a very high metabolism and body temperature compared to other birds. This allows the female to provide sufficient warmth to the developing embryos in the eggs.
The average incubation period across the Black-chinned Hummingbird’s entire range is approximately 14 days from egg laying to hatching. This quick incubation gives the female adequate time to raise multiple broods per season.
Nestling Period
The Black-chinned Hummingbird chicks spend 18-23 days in the nest before fledging. As with incubation, this nestling period is similar for both broods.
The chicks are born small, naked and helpless. But they grow incredibly fast thanks to the constant supply of food provided by the female parent.
Within a few weeks, the chicks open their eyes, grow dark feather down and start looking like juvenile hummingbirds. Right before the first flight, the female may continue caring for the fledglings for a few days while encouraging independence.
By 3-4 weeks of age the young hummingbirds are feeding themselves and capable of sustained flight. This quick transition to independence frees up the female to start the next nesting cycle.
Role of the Male Black-chinned Hummingbird
Male Black-chinned Hummingbirds play no direct role in raising either brood. Their sole contribution is mating with the female to fertilize the eggs.
During the breeding season, the male focuses his energies on defending a breeding territory and courting females. His aerial displays of speed and agility advertise his fittest to prospective mates.
Once mating occurs, the male provides no parental care and likely goes on to mate with additional females. This promiscuous system allows the male to maximize his reproductive success.
Meanwhile, the female assumes all parental duties – nest building, incubating, feeding hatchlings and protecting the nests. This unequal division of responsibilities enables the rapid multiple brooding strategy of the species.
Survival Rates
Only a fraction of Black-chinned Hummingbird eggs and chicks survive to adulthood. Some key survival statistics:
- Eggs successfully hatching: 67%
- Chicks surviving to fledge: 63%
- Juveniles reaching adulthood: 25-50%
These low survival rates demonstrate the high mortality risks faced by developing young hummingbirds. Nest predation, starvation, weather, accidents and health issues all contribute to lost eggs and deaths of chicks or fledglings.
Despite high infant mortality, adult Black-chinned Hummingbirds have relatively high annual survival rates:
- Annual adult survival: 60-75%
Producing multiple broods each season helps overcome the low survival rates for individual eggs and chicks. Though few may survive from one nest, the female improves her overall reproductive success through repeated nesting attempts.
Conclusion
In summary, the Black-chinned Hummingbird typically raises two broods per breeding season across most of its western North American range. The female builds a nest and lays 2 eggs for each brood, incubating the eggs for about two weeks before they hatch.
After a 3-4 week nestling period, the first brood leaves the nest, allowing the female to start a second nesting cycle. She repeats the process, laying 2 more eggs to produce the second brood. A long breeding season of spring and summer food abundance facilitates this successful strategy of double brooding.