Hummingbirds are known for their ability to hover effortlessly in midair and sip nectar from flowers. However, you may have noticed them engaging in dramatic dive displays and aggressive chases. Here’s an explanation of why hummingbirds exhibit this behavior.
Establishing Dominance and Territory
Male hummingbirds are highly territorial and use dive displays to establish their domain. By rapidly diving toward another hummingbird intruding on their territory, they are communicating “This is my space!”. It’s a warning to back off and find another source of food and shelter.
Dive displays also determine dominance among male hummingbirds. The dominant bird will aggressively dive at subordinates to reinforce his status. The subordinates are then relegated to poorer territory. Females also use dive displays, though less frequently than males, to establish priority at food sources.
Competing for Food
Flowers and artificial feeders provide rich sources of nectar for hummingbirds. When numerous hummingbirds congregate in one area, competition inevitably arises. Diving is used to exert dominance and control prime feeding locations. The more aggressive bird will dive-bomb competitors to have first access to nectar.
Food Scarcity
Lack of food intensifies conflicts among hummingbirds. During migration or winter when fewer flowers are blooming, hummingbirds become more territorial over limited food sources. Dive displays escalate as they fiercely compete for nectar to survive harsh conditions.
Artificial Feeders
Grouping multiple feeders close together often causes increased diving behavior. Hummingbirds are drawn to the abundant food source but then aggressively compete for feeder access. Spreading feeders widely apart reduces conflict and dive displays between hummingbirds.
Mating and Courting
Male hummingbirds perform spectacular dive displays to impress females during courtship. By rapidly ascending to heights up to 130 feet and then swooping back down past the female, he demonstrates his fitness and the strength of his potential offspring.
Sometimes males will continue dive-bombing the female even after mating. This likely serves to establish the male’s dominance and control over the female while she is nesting in his territory.
Dominant Males Have an Advantage
Research indicates dominant males perform more dive displays and mate with more females than subordinate males with poorer territory. Females likely prefer males who can protect critical resources, so by establishing his territory through diving, a male hummingbird improves his mating success.
Female Choice
Females do exert choice, however, and may ignore a male’s dive displays if they deem his territory or him as inadequate. Thus, while dive displays help dominate food and females, they don’t guarantee mating success.
Protecting Eggs and Chicks
Female hummingbirds diving aggressively are often protecting eggs or chicks in a nearby nest. By chasing away intruders, a mother hummingbird ensures sufficient food for her hatchlings and reduces threats from predators.
Males may also join in dive-bombing intruders near their offspring. This protects their genetic investment and teaches young hummingbirds to defend territory.
Diligence Required
A mother hummingbird needs to continuously guard her nest during the three-week incubation and three-week nestling period. As small birds with few defenses beyond their flying abilities, hummingbirds are vulnerable to predators. Dive displays help warn potential intruders away.
Instinctive Reaction
When perceiving a threat near the nest, a female hummingbird will instinctively dive-bomb the intruder even if it is a human. Remember, this reaction comes from the hummingbird’s innate drive to protect its young.
Inter-species Conflict
Hummingbirds may direct their aggressive diving toward other bird species competing for food resources. They often clash with species that are similar in size and diet like woodpeckers, orioles, and chickadees.
Bee-sized Birds
With a wingspan of 3-4 inches, hummingbirds are closer in size to insects than other birds. As a result, they expend more energy hovering at flowers which makes food competition intense. Dive displays help hummingbirds exert control over limited nectar supplies.
Birds of Different Feathers
While hummingbirds subsist almost solely on nectar and small insects, other birds have more varied diets. This reduces competition with larger birds like woodpeckers that also eat fruits and nuts. However, birds that rely heavily on nectar like orioles will provoke aggression.
Measuring Dive Speeds
Scientists have used high speed cameras to measure the velocities of hummingbird dives. Here are the recorded speeds of three common North American species:
| Species | Dive Speed |
|---|---|
| Ruby-throated Hummingbird | 27 miles per hour |
| Rufous Hummingbird | 24 miles per hour |
| Allen’s Hummingbird | 22 miles per hour |
As the data shows, the smaller Ruby-throated Hummingbird attains the fastest dive speeds, followed by the medium-sized Rufous and larger Allen’s Hummingbirds. Aerodynamics and body size factor into dive velocities.
Survival Advantage
While their aggressive diving seems intense, it serves an important purpose for hummingbirds. By establishing territory and access to food, they can survive in habitats crowded with competitors. Dive displays also deter predators, attract mates, and protect offspring.
Energy Reserves
With a high metabolism, hummingbirds need to frequently refuel. Dive displays allow them to maintain control over nectar supplies critical to their survival, especially during high energy needs like migration.
Keeping Competitors at Bay
Other birds pose threats by consuming the same insect and flower food resources. Inter-species conflicts help reduce competition between hummingbirds and birds that eat similar diets. This ensures adequate food for hummingbird populations.
Examples of Diving Hummingbirds
Here are some common North American hummingbirds known for their spirited dive displays:
Anna’s Hummingbird
Males perform elaborate rising and diving arcs up to 130 feet over their territories in California and the Southwest.
Rufous Hummingbird
This feisty bird aggressively dive-bombs intruders away from forest wildflowers across the Northwest and Canada.
Ruby-throated Hummingbird
Males of this eastern species make sharply angled dives up to 60 miles per hour during courtship displays.
Costa’s Hummingbird
Males defend their desert territory boundaries with frequent dives and aerial stand-offs.
Conclusion
In summary, hummingbirds employ spectacular dives for crucial survival and reproductive purposes. By understanding their fierce territoriality and competition for limited resources, we can appreciate the vital role of diving in hummingbird ecology and behavior.
