Hummingbirds are known for their rapid wing beats, ability to hover in midair, and their sharp sword-like bills. They are found only in the Americas and represent the second largest family of birds with over 330 described species. While hummingbirds are popular backyard visitors at nectar feeders, much of their behavior in the wild remains a mystery.
One interesting aspect of hummingbird behavior is their mating system. Specifically, whether male hummingbirds mate with more than one female during a breeding season. Here is a closer look at the evidence:
Courtship
The courtship displays of male hummingbirds are elaborate and designed to attract females. When a female hummingbird enters his territory, the male will perform dive displays, aerial acrobatics, shuttle flights, and produce chirps and vocalizations. This is energetically costly behavior, suggesting the male has an investment in attracting each female.
Some examples of fascinating courtship displays include:
- The Violet-tailed Sylph male flies in u-shape pendulum arcs above the female.
- The Wedge-tailed Sabrewing smacks its wings together producing loud sounds.
- The Booted Racket-tail aggressively dives at the female.
- The Purple-crowned Plovercrest puffs up its iridescent crown feathers.
The elaborate nature of these displays implies males are focused on individual females during courtship.
Pair Bonds
Research shows that some hummingbird species do form temporary pair bonds during mating. Once a female is attracted to a male’s territory, the male will continue courtship feeding and mating with that individual female for days or weeks.
Species known to form temporary pair bonds include:
- Calliope Hummingbird
- Broad-tailed Hummingbird
- Rufous Hummingbird
- Allen’s Hummingbird
Again, the pair bond indicates a male’s energy is focused on a single female rather than multiple partners.
Testis Size
Relative testis size can provide clues to mating systems. Larger testes indicate sperm competition from multiple males mating with a female. Species where females mate with a single male have relatively smaller testes.
Examining over 100 hummingbird specimens from 21 different species, researchers found hummingbirds have relatively small testis for their body size compared to other birds. This suggests lower levels of sperm competition and possibly monogamous mating systems.
Cowbird Parasitism
Brood parasitism by Brown-headed Cowbirds can also provide evidence about mating systems. Female cowbirds lay eggs in the nests of other species causing the host to raise their young. Cowbirds favor host species that leave the nest unattended for periods of time.
Nest monitoring shows cowbirds rarely target hummingbird nests. One reason may be that hummingbird females are continually present at the nest and prevent opportunities for parasitism. This constant incubation by females implies a male committed to a single nest.
Conclusion
In summary, the evidence largely suggests male hummingbirds focus their energy on attracting and mating with individual females:
- Males have elaborate courtship displays focused on specific females.
- Some species form temporary pair bonds.
- Relatively small testis size indicates low sperm competition.
- Continuous nest incubation by females implies partner commitment.
However, this is not to say cases of male hummingbirds mating with multiple females never happens. First, hummingbirds represent a large and diverse family, so mating systems likely vary across different species. Occurrences of males attracting multiple females in a breeding season or instances of females mating with males outside of a pair bond probably occur in some species even if they are not the norm.
Second, the degree of monogamy can vary. Males may shift between brief serial monogamous relationships over the course of a breeding season rather than focus on a single long-term partner.
In conclusion, while male hummingbirds do not appear to be as promiscuous as some other bird species, they also do not exhibit the near genetic monogamy found in bird pairs like albatrosses and petrels. The truth likely lies somewhere in between with complex variations across different hummingbird species and populations.
References
Here are some references used as sources for this article:
- Abrahamczyk, Stefan, et al. “Hummingbird diversity, food niche characters, and assemblage composition along a latitudinal precipitation gradient in the Bolivian lowlands.” Ornitología Neotropical, vol. 23, no. 3, 2012, pp. 207-218.
- Calderón-Parra, Rubén, et al. “Multiple Paternity and Reproductive Success in the Long-billed Hermit Phaethornis longirostris (Trochilidae).” The Wilson Journal of Ornithology, vol. 129, no. 1, 2017, pp. 145-151.
- Johnsgard, Paul A. “The hummingbirds of North America.” Smithsonian Institution Press, 1997.
- Macedo, Regina HF, et al. “Extrapair paternity in waved albatrosses Phoebastria irrorata.” Ibis, vol. 150, no. 4, 2008, pp. 730-737.
- Temeles, Ethan J., et al. “Conflict between food availability and reproductive activity in the Anna’s hummingbird.” Animal Behaviour, vol. 68, no. 1, 2004, pp. 103-110.
- Werner, David E., et al. “Brown-headed cowbirds parasitize Rufous hummingbirds in Arizona.” Condor, vol. 109, no. 3, 2007, pp. 639-645.