Rufous Hummingbirds (Selasphorus rufus) are small, feisty birds that breed throughout western North America. They get their name from the bright rufous (reddish-brown) plumage on the backs of the males. Rufous Hummingbirds have a unique and complex mating ritual that involves aerial displays, specialized tail feathers, and fierce competition among males for mating opportunities. Understanding how these tiny birds find mates and reproduce provides insight into their biology and behavior.
When is the breeding season?
Rufous Hummingbirds breed between March and August, depending on their location. In cooler climates like Alaska and Canada, they nest later around May to June. Further south along the Pacific Coast, breeding starts as early as March.
Some key factors that trigger breeding behavior are:
- Increasing daylight hours
- Availability of flowers and nesting materials
- Ideal mating temperatures
Once these conditions are met, the competition for mates begins.
Male Displays
Male Rufous Hummingbirds put on elaborate aerial displays to attract females and advertise their fitness. A male will fly in looping patterns up to 100 feet in the air, then suddenly dive down at breakneck speeds making an audible buzzing or “chipping” sound with his tail feathers. This dive display is one of the most recognizable behaviors of Rufous Hummingbirds during courtship.
Type of Display | Description |
---|---|
Dive Displays | Males fly as high as 100 ft then dive sharply downwards while making a buzzing sound with tail feathers |
Shuttle Displays | Flying rapidly back and forth in a horizontal or pendulum motion in front of the female |
Aerial Dogfights | Males will ascend rapidly and chase each other in looping patterns and sudden dives to compete for territory |
Other courtship displays include:
- Shuttling rapidly back and forth in front of the female in pendulum motions
- Aerial “dogfights” where males rapidly chase each other in loops and dives
- Hovering in front of the female and spreading tail feathers
- Perching nearby and singing a high-pitched twittering song
These displays showcase the male’s aerobatic skills and stamina, which are indicators of fitness and health. Females pay close attention to these displays when choosing a mate.
The Importance of Tail Feathers
Rufous Hummingbird tails play an especially important role in courtship. Their outer tail feathers have modified tips that produce the characteristic buzzing or “chipping” sound when males dive sharply. Females seem to respond strongly to this sound when observing courtship displays.
Researchers have tested how females respond when mute males (with tail feathers trimmed) performed dive displays. Females were much less receptive to muted males that could not produce the sounds, underscoring the significance of the vocalizations.
Additionally, males have colorful, iridescent throats that they can puff out to signal aggression or courtship. But the pulsating, buzzing tails are crucial for getting a female’s attention.
How Tail Feathers Make Sound
The two outer tail feathers of male Rufous Hummingbirds are uniquely adapted for sound production:
- Narrower in shape than other feathers
- Stiff with very little flexibility or rotation at base
- Outer vane is corrugated near the tip
As the male dives, airflow over these corrugated vane surfaces in the outer feathers causes them to flutter and vibrate, producing the characteristic buzzing sound. This is known as an aeroelastic flutter, resulting in a brief burst of oscillating chirps.
Females are acutely tuned to detect this sound, timing their own display dives with the males’ buzzing sounds during courtship. The tail feathers allow males to signal fitness sonically in a way that is critical for mating success.
Male Competition for Access to Females
Male Rufous Hummingbirds are highly territorial and compete aggressively for breeding territories and access to females. Some key aspects of this competition:
- Males don’t participate equally in mating; some mate frequently while others have few chances
- Dominant males occupy the best habitat and claim multiple females in their territory
- Subordinate males may linger at territory edges hoping for access to females
- Intense battles occur between males defending territories, involving dangerous dives, collisions, and stabbing with their bills
This unequal access to mating results in greater reproductive success for dominant territorial males. Females seem willing to mate with both dominant and subordinate males, but dominant males actively chase rivals away and monopolize access through aggression.
Physical combat and displays of endurance like the dive displays determine which males maintain the best territories. Females likely observe these battles, using them to evaluate male fitness.
Female Role in Mating
Female Rufous Hummingbirds play a subtler role in courtship compared to the dramatic male displays. But they still exercise choice in a mate by:
- Observing males at display perches and dive sites
- Approaching and following desirable males
- Allowing mating with select males
- Refusing/resisting mating attempts from undesirable males
- Timing their own display dives with males’ buzzing sounds
Receptive females respond to courtship by perching and grasping onto the display perch while watching the male. If she refuses a male, she may fly away or even dive at him in retaliation. By choosing when and where to mate, females influence the males’ mating success.
The Mating Sequence
Once a pair is ready to mate, the sequence involves the following steps:
- Male courts female through his displays
- Female observes and approaches male at his display perch
- Female perches near male and grasps the perch
- Male flies behind female and attempts to mount her
- Actual mating lasts 5-10 seconds if female is receptive
- Female may lay 1-3 eggs in the following days
The female later builds a tiny cup-shaped nest on her own and takes over brooding and raising the chicks. Male involvement ends after mating.
Why Do Females Mate With More Than One Male?
Female Rufous Hummingbirds often mate with multiple males, even when one male is clearly dominant in the area. Why would females mate with subordinate “extra-pair” males instead of the dominant male? There are a few key explanations:
- Access high-quality genes – Extra males may have good genes despite lack of territory
- Insurance against infertility – Fertilize eggs with multiple males in case one is infertile
- Boost genetic diversity – Mixing in other males provides variable offspring
It seems extra-pair mating provides potential benefits to females and the chicks they raise. Dominant males pursue strategies to try preventing this, like close guarding of females before egg laying. But females continue to mate outside the pair bond.
Conclusion
Rufous Hummingbirds have an intricate mating process focused on males advertising their flying prowess and vigor through repeated aerial displays. Tail feather adaptations allow males to produce sounds that attract females. Competition is fierce among males seeking to mate with the females that occupy their territory. Females ultimately choose to mate with the healthiest, most dominant males, though they often select other less competitive males as well. The result is mating success biased heavily in favor of the top territorial males, ensuring the next generation has genes for superior fitness. Their complex rituals serve to identify the optimal matches between males and females.