Hummingbirds are amazing little creatures that can fly forwards, backwards, upside down, and hover in midair. Their wings beat up to 80 times per second, making the familiar humming sound that gives them their name. Hummingbirds have very high metabolisms and must consume a lot of energy in the form of nectar or insects each day just to survive. This need to consume calories also allows hummingbirds to put a tremendous amount of energy into reproduction.
Breeding Season
Most hummingbird species breed between February and July, with the exact timing dependent on factors like latitude and climate. In warmer southern climates, hummingbirds may start breeding as early as January. Farther north, breeding gets pushed back to late spring and early summer. Here are some examples of hummingbird breeding seasons in different locations:
- California – February to July
- Texas – March to June
- Midwest states – May to July
- Alaska – June
The length of the breeding season also varies by species. Ruby-throated hummingbirds may only breed for 3-4 months while Rufous hummingbirds can breed for 5 months or longer. The important factor is that there are enough flowers and insects available to provide the energy needed for breeding and raising chicks.
Number of Broods
Most hummingbird species are capable of raising 2-3 broods per breeding season. A brood is a group of chicks from a single clutch of eggs. Here are some specifics on the number of broods for common North American hummingbird species:
- Ruby-throated hummingbird – 2 broods
- Black-chinned hummingbird – 2 broods
- Anna’s hummingbird – 2-3 broods
- Calliope hummingbird – 1 brood
- Rufous hummingbird – up to 3 broods
- Allen’s hummingbird – 2 broods
The number of broods depends on the length of the breeding season. Ruby-throated hummingbirds have a relatively short breeding season of about 3 months in the northern part of their range, which only allows time for 2 broods. Allen’s hummingbirds in coastal California may have a breeding season of 5 months or more, which enables them to raise 2 broods in that time.
Clutch Size
In addition to the number of broods, the number of chicks in each clutch also determines how many offspring a hummingbird can produce. Most hummingbirds lay 2 eggs per clutch, but the range is 1-3 eggs for most species. Here are some typical clutch sizes:
- Ruby-throated hummingbird – 2 eggs
- Black-chinned hummingbird – 2 eggs
- Broad-tailed hummingbird – 2 eggs
- Rufous hummingbird – 2 eggs
- Allen’s hummingbird – 2 eggs
- Calliope hummingbird – 1 egg
Having 2 eggs per clutch seems to be the optimal number for hummingbirds in most cases. However, some smaller species like the Calliope hummingbird may only lay 1 egg per clutch to conserve resources.
Number of Nests
Hummingbirds may use a new nest for each clutch within a breeding season, or they may reuse the same nest. Behavior varies by species and circumstances. For example:
- Ruby-throated hummingbirds often reuse the same nest for the 2 broods in one season.
- Black-chinned hummingbirds typically build a new nest for each brood.
- Rufous hummingbirds may use 5-6 different nests in a single breeding season.
Reusing nests saves time and energy since the female does not have to build a whole new structure for each brood. However, it may increase the chances of parasites and diseases being transmitted between broods. Building fresh nests in new locations reduces this risk. Females must carefully balance these trade-offs when deciding whether to invest the time and energy into building all new nests.
Adding It Up
Given typical information on the breeding season length, number of broods, clutch size, and nesting behavior, we can calculate approximately how many offspring female hummingbirds may produce in a season:
| Species | Breeding Season Length | # Broods | Clutch Size | Approx. # Offspring |
|---|---|---|---|---|
| Ruby-throated | 3 months | 2 | 2 eggs | 4 |
| Black-chinned | 4 months | 2 | 2 eggs | 4 |
| Anna’s | 5 months | 3 | 2 eggs | 6 |
| Rufous | 5 months | 3 | 2 eggs | 6 |
As the table shows, most hummingbird species max out at around 4-6 offspring per season based on a combination of life history traits like brood number and clutch size. The duration of the breeding season sets the ultimate limit – a hummingbird can’t produce more broods than there is time available to do so.
Other Factors
There are a few additional factors that may reduce the potential number of offspring per female hummingbird below the maximum:
- Incubation and nestling periods – The female must incubate the eggs for 2-3 weeks and then care for the chicks for another 2-3 weeks before they fledge. This requires 3-6 weeks per brood.
- Renesting – If a clutch is lost to predators or storms, the female may lay another set of eggs. However, this delays subsequent broods.
- Single parenting – If the male dies, the female takes over all parenting duties, which increases her energy expenditure.
- Habitat quality – Less food means the female may produce smaller clutches or fewer broods.
By factoring in these constraints, the actual number of offspring per female per season may realistically be 2-4 on average, even for species with the potential for higher production like the Anna’s hummingbird.
Do Males Breed Multiple Times?
Male hummingbirds are promiscuous and do not provide parental care. Their only biological role is to mate with females to fertilize the eggs. As with females, the number of breeding opportunities for males depends on:
- Length of breeding season
- Number of fertile females in their breeding territory
- How often females enter breeding condition
In most cases, males should be capable of mating with multiple females during a single breeding season. However, their capacity is more limited by female receptivity than physiological constraints. Males without an established breeding territory or access to fertile mates may not get any breeding opportunities at all.
Lifetime Reproduction
In addition to seasonal reproduction, hummingbirds may breed over multiple years during their lifetime. Average lifespan after reaching adulthood ranges from 3-5 years for most hummingbird species. The exceptions are some tropical highland hummingbirds that have been documented living 10 years or more. Here are the typical lifespans of some common backyard hummingbirds:
- Ruby-throated hummingbird – 3-5 years
- Black-chinned hummingbird – 5 years
- Anna’s hummingbird – 4-6 years
- Rufous hummingbird – 3-4 years
Given a lifespan of 4 years and 2-4 offspring per year, a female hummingbird could produce anywhere from 8-16 offspring over her lifetime. Longer-lived tropical species may far exceed this. Male hummingbirds likely mate with numerous females each season, leading to hundreds or even thousands of offspring over a lifetime of breeding.
Conclusion
Hummingbirds are remarkably prolific breeders considering their tiny size. The combination of a long breeding season, ability to raise multiple broods, small clutch size of 2 eggs, and fairly long adult lifespan allows hummingbirds to produce a significant number of offspring each year and over their lifetime.
While hummingbirds certainly have the physiological capacity to breed many times per year and produce dozens of offspring, the actual realized reproduction is likely much lower due to constraints like habitat quality, availability of food, incidence of nest predators, and ability of the male to hold a breeding territory. But even with conservative estimates, it’s clear these energetic little birds are well equipped to produce successive generations of offspring and maintain healthy population sizes.
