Rufous hummingbirds (Selasphorus rufus) are small, energetic birds that are known for their incredible migratory habits. These tiny birds make an arduous journey each year, traveling between their summer breeding grounds in the Pacific Northwest and their overwintering grounds in Mexico and the Southern United States. During this epic migration, rufous hummingbirds may beat their wings up to 70 times per second and fly nonstop over the Gulf of Mexico.
Given their high energy levels and the challenges they face during migration, you may wonder – do rufous hummingbirds take the time to find a lifelong mate? Or are they constantly on the move, breeding with new partners along the way? Here, we’ll take a closer look at the mating behaviors of rufous hummingbirds to find out if they form lasting pair bonds or live promiscuous lifestyles.
Rufous Hummingbird Courtship
During the spring and summer breeding season, male rufous hummingbirds return to their northern habitats ahead of females. There, they stake out breeding territories which provide access to energy-rich nectar sources. When females arrive in the coming weeks, males perform elaborate courtship displays to attract their attention.
A male rufous hummingbird courtship display may involve flying in fast, horizontal figure-eight patterns or diving steeply while making high-pitched chirps. The male’s brightly iridescent gorget – a collar of feathering around the throat – flashes brightly during these maneuvers. He may also perch near a female and spread his tail feathers into a fan while rotating his body from side to side. Throughout the elaborate courtship rituals, the males vocalize with chirps and whistles.
If a female is impressed by his display, she may mate with the male. However, some research indicates females also play hard-to-get. A female might fly away repeatedly, forcing the male to chase her through the territory. This tests his stamina and helps ensure only the fittest males succeed at mating.
Short-Term Pair Bonds
Rufous hummingbirds do form pair bonds during the breeding season, but they are temporary rather than lifelong. A mated pair works together to breed and raise young. The female builds a tiny nest out of spider webs, lichens and plant down. She lays 2 pea-sized eggs and cares for the chicks when they hatch about 2 weeks later.
Throughout incubation and nestling rearing, the male defends the territory and visits the female to mate with her again. This helps ensure the pair’s next clutch, as rufous hummingbirds may raise 2-3 broods per season. The male also occasionally helps feed the chicks by regurgitating nectar to them.
However, these breeding partnerships only last for a single season. No evidence suggests rufous hummingbirds mate with the same partner year after year. Instead, most research indicates males attract new mates each breeding season, and females likely do the same.
Promiscuity Outside of Pair Bonds
Rufous hummingbirds appear to be promiscuous outside of their temporary pair bonds. Males seek extra-pair matings with neighboring females, most likely to increase their overall reproductive success. One study that paternity tested chicks found about 15% were fathered by males outside of the caretaking pair.[1]
Females also occasionally stray from their mates. By mating with multiple males, a female likely increases the genetic diversity of her offspring. This may give her chicks a better chance of survival.
Interestingly, female hummingbirds can store sperm inside their reproductive tracts for weeks after mating. If a female mates with multiple males during a narrow window, the sperm remain viable inside her and she may use the sperm of several males to fertilize eggs in a single clutch. This is yet another behavior that points to the promiscuous nature of rufous hummingbirds.
No Lasting Pair Bonds
While rufous hummingbirds appear to form monogamous pair bonds during breeding, these partnerships do not represent lifelong matings. Instead, evidence clearly indicates males and females seek new partners each season:
- Males perform elaborate courtship displays annually to attract new mates
- Females visit multiple display territories before choosing a mate
- Both sexes pursue extra-pair matings during breeding
- Pairs only stay together for a single nesting attempt
In addition, rufous hummingbirds lead largely solitary lives outside of the breeding season. The birds migrate individually and overwinter in separate habitats. This leaves little opportunity for sustained contact or lifelong pair bonding between mates.
Advantages of Short-Term Mating
For rufous hummingbirds, short-term seasonal pairings likely offer the best balance between mating investment and reproductive success. Here are some of the advantages these brief partnerships provide:
- Increased genetic diversity – By mating with multiple partners, rufous hummingbirds shuffle their genes more effectively each season. This prevents inbreeding depression.
- Reduced breeding pressures – Courtship and parenting require significant time and energy. Switching mates between nesting attempts allows the birds to conserve resources.
- More reproductive attempts – Rather than staying with a single mate all season, males and females can partner with multiple mates, increasing their total number of clutches.
Given their high-investment breeding strategy, it makes sense rufous hummingbirds would not waste time and energy sticking with a single subpar mate. By mixing up partners, they likely maximize their reproductive success each season.
Migratory Lifestyle Hinders Pair Bonding
The migratory habits of rufous hummingbirds also help explain why lifelong pair bonding does not occur in this species. Here’s how migration impacts their ability to maintain pairs:
- Migration covers vast distances, making it difficult for pairs to remain in contact.
- Males and females occupy different non-breeding habitats, preventing sustained contact.
- High mortality during migration means mates one year may not survive to the next breeding season.
- Migrating and wintering alone allows birds to adapt more quickly to changes in resource abundance.
Given the huge distances traveled and the risks involved, it makes sense rufous hummingbird mates would not remain paired outside the breeding season. Their lifestyle seems to preclude the close seasonal contact needed to sustain long-term bonds.
Conclusion
In summary, most evidence indicates rufous hummingbirds form temporary breeding partnerships that last for a single nesting season, rather than mating with one partner for life. Their energetic lifestyle and long-distance migratory habits likely make lifelong pair bonding impossible. Instead, these tiny, intrepid birds breed with a mate just long enough to produce and successfully raise offspring before moving on to their next partner. For rufous hummingbirds, short-term seasonal bonds seem to offer the perfect balance between reproductive investment and energetic costs.