Allen hummingbirds (Selasphorus sasin) are small, vibrantly colored birds that are found along the Pacific Coast of North America. They get their name from the ornithologist Charles Andrew Allen who first described the species in 1897. Allen hummingbirds are known for their striking metallic green backs and orange-red throats. Like all hummingbirds, they have a very fast metabolism and must continuously feed on nectar throughout the day to fuel their high energy lifestyles. An interesting fact about Allen hummingbirds is that they can have multiple clutches of eggs over the course of a single breeding season.
How Many Broods Do Allen Hummingbirds Have?
Allen hummingbirds typically raise two or three clutches of eggs per breeding season. The breeding season lasts from November to July, giving them ample time to produce multiple broods. Here is some more detail on their breeding and clutch habits:
- Clutch Size: Each clutch contains 2 tiny white eggs which are only about half an inch long. The female incubates the eggs for 16-18 days before they hatch.
- Nesting: The female builds a small cup-shaped nest out of plant down, spider webs, and lichens. Nests are usually placed in trees, shrubs, or on branches near feeding areas.
- First Clutch: The first clutch is laid in November-February at the start of the breeding season.
- Second Clutch: After successfully raising the first brood, the female will build another nest and lay a second clutch of eggs in March-May.
- Third Clutch: Some birds may even raise a third clutch in June-July before the breeding season ends.
So in summary, a typical Allen hummingbird breeding season includes two clutches, while some especially productive females may raise three clutches per season.
Why Do Allen Hummingbirds Have Multiple Clutches?
There are a few key reasons why Allen hummingbirds have adapted to raise multiple clutches per breeding season:
- Long breeding season – The climate of their range allows them to breed over a 9 month period from November to July, which gives enough time to successfully raise multiple broods.
- Short incubation period – At only 16-18 days, the incubation period for Allen hummingbird eggs is much shorter than many other birds. This allows the females to breed again more quickly after each clutch hatches.
- Rapid development of chicks – Allen hummingbird chicks develop very quickly, leaving the nest after only 3 weeks. This also allows the females to start a new clutch soon after the first brood fledges.
- Abundant food resources – The Pacific Coast has many flowering plants and feeds which provide a steady supply of nectar and insects to sustain multiple clutches.
- High mortality rates – Even with multiple clutches, only a fraction of Allen hummingbird offspring survive to adulthood. Multiple clutches help compensate for high mortality.
Producing multiple clutches is an effective reproductive strategy that allows Allen hummingbirds to maximize the number of offspring they can raise over the course of a long breeding season.
How Many Broods Can One Female Have?
While two clutches are typical, a single female Allen hummingbird can potentially raise up to three broods per breeding season if conditions allow. Here are some more details on their maximum reproductive capability:
- Most females raise two clutches with 2 eggs each, so 4 eggs total.
- Exceptionally healthy and productive females may lay 6 eggs in three clutches of 2 eggs each.
- In ideal conditions with abundant food, some females may even occasionally produce 4 clutches and up to 8 eggs per season.
- However, it is energetically taxing to produce 4 clutches, so this is rare.
- Three clutches is the likely maximum for most female Allen hummingbirds in the wild.
While laying up to 8 eggs has been documented, the norm is 4-6 eggs in 2-3 clutches per female per breeding season.
What Factors Influence the Number of Broods?
Several environmental and physiological factors influence just how many clutches an individual Allen hummingbird can produce in a season. These include:
Food Availability
Access to plentiful nectar and insects is key. Hummingbirds burn a lot of calories and need ample food to sustain egg production and raising offspring. During times of drought or scarcity, they may produce fewer clutches.
Weather and Climate
Colder temperatures and excessive rain can suppress insect activity, limiting food supplies. Storms may also damage nests. Ideal conditions allow for more clutches.
Age and Health of Female
Younger females laying for the first time usually produce fewer clutches. Older, more experienced females tend to lay more eggs per season. Sick or weak birds will also lay fewer eggs.
Natural Variation
There are individual differences in the reproductive potential of females – some are simply predisposed to lay more clutches than others.
Predation
If a clutch is lost to predators, the female may lay an additional clutch to replace it. Heavy predation pressure can lead to more clutches.
Habitat Quality
Females nesting in optimal sheltered habitats with safe nest sites may experience higher clutch success and produce more broods.
By influencing survival, nutrition, and safety, these factors all play a role in determining if female Allen hummingbirds can reach their maximum reproductive potential in a given breeding season.
How Many Eggs Do Allen Hummingbirds Lay Per Year?
As we’ve covered, the number of eggs a female Allen hummingbird lays per year can vary based on environmental conditions, individual capabilities, and reproductive success. The ranges are:
- Typical: 4-6 eggs per year
- Maximum: Up to 8 eggs per year
Here’s a summary of their potential egg production:
# Clutches | Eggs Per Clutch | Total Eggs |
---|---|---|
2 clutches | 2 eggs | 4 eggs |
3 clutches | 2 eggs | 6 eggs |
4 clutches (rare max) | 2 eggs | 8 eggs |
While up to 8 eggs has been recorded, most Allen hummingbird females produce between 4-6 eggs over 2-3 clutches per breeding season.
How Many Babies Do Allen Hummingbirds Fledge?
Even with multiple clutches, it’s estimated that only 25-60% of Allen hummingbird eggs and chicks survive to successfully fledge each season due to predation, weather events, nest failure, and other risks. So the number of babies that fledge can be much lower than the total number of eggs laid. Here are some estimates of fledging success:
- Typical: 1-3 fledglings per female per season
- Maximum: 4-5 fledglings in exceptional circumstances
While Allen hummingbird females lay up to 8 eggs per season, on average, each female only raises 1-2 babies to fledging age over the course of a breeding season.
Key Takeaways on Allen Hummingbird Clutches
- Allen hummingbirds typically raise 2-3 clutches per breeding season.
- Each clutch contains 2 tiny white eggs which are incubated for 16-18 days.
- Females lay between 4-6 eggs per year on average, sometimes up to 8 eggs maximum.
- Only a fraction of eggs survive to fledge due to high mortality rates.
- Most females fledge 1-3 chicks, with 4-5 in rare cases of high productivity.
- Abundant food, ideal climate, safe habitat and female experience improve clutch success.
Being able to produce multiple clutches over an extended breeding season is an important reproductive strategy that helps compensate for the many threats and challenges Allen hummingbird eggs and offspring face. While many eggs are laid, raising just a few offspring to maturity ensures that Allen hummingbirds continue to brighten the Pacific coast with their vibrant colors and energetic spirits.