Hummingbirds are known for their beauty and grace, but they can also display surprisingly aggressive behavior, especially in late summer and early fall. This is because they are defending food sources to bulk up for migration or competing for mates. There are a few key factors that contribute to increased hummingbird aggression this time of year:
Preparing to Migrate
Many hummingbird species migrate long distances to overwintering grounds in Mexico and Central America. This journey requires a tremendous amount of energy. In the weeks leading up to migration, hummingbirds go into hyperphagia – a period of excessive eating to store up fat reserves. They start defending food sources more aggressively to ensure they get enough nutrition to survive the migration.
Competition for Food
Flowers and nectar-producing plants start to decline in late summer and early fall. With less food available, hummingbirds become more territorial over feeders and flower patches. They will dive bomb, chase, and vocalize at other hummingbirds that approach their preferred nectar source.
Establishing Winter Territories
Some hummingbirds species are year-round residents in warmer climates rather than long-distance migrants. In late summer and fall, the adult males start defending winter feeding territories. They will fight off intruders trying to feed in their territory.
Typical Aggressive Behaviors
Hummingbirds display a range of aggressive actions to guard food sources and exert dominance. Some common aggressive behaviors include:
Dive Bombing
A dominant male will perform dramatic steep dives and loud buzzing near the head of another hummingbird. This serves as an intimidation display.
Chasing
Hummingbirds will chase an intruding bird away from a feeder, flower, or nest in fast erratic flight patterns.
Vocalizations
Aggressive chirping, squeaking, or trilling is often heard when defending territories.
Displays
Actions like wing flashing, puffing up feathers, and spreading tail feathers try to make the bird look more dominant.
Why Males Are Usually the Aggressors
Male hummingbirds are most often the perpetrators of aggressive behaviors. There are a few reasons for this:
Territory Defense
Males are highly territorial and defend areas with good food sources to attract females for mating. They will defend these territories from other males.
Mate Guarding
Males will also aggressively guard their mate after copulation occurs to ensure other males don’t try to mate with her.
Limited Resources
Males outnumber females at nectar feeders, so they have more competition with other males over the limited food.
Hormones
Increased testosterone levels during breeding season make males more aggressive.
Which Species Show the Most Aggression?
Some hummingbird species are notoriously more aggressive. The most pugnacious contenders include:
Anna’s Hummingbird
| Species | Aggression Level |
|---|---|
| Anna’s Hummingbird | High |
Native to the west coast, Anna’s males are very territorial and will aggressively defend feeders and flower patches. They establish winter feeding territories in California and winter-over rather than migrating.
Rufous Hummingbird
| Species | Aggression Level |
|---|---|
| Rufous Hummingbird | High |
Rufous hummingbirds are feisty and known for chasing and dive bombing other hummingbirds during migration. They breed farther north than other species and must aggressively defend food to pack on fat for their extremely long migration.
Ruby-throated Hummingbird
| Species | Aggression Level |
|---|---|
| Ruby-throated Hummingbird | Moderate |
Ruby-throats are the only breeding hummingbird in Eastern North America. Males defend breeding territories and will try to chase others away from food sources, but are less aggressive than western species.
Black-chinned Hummingbird
| Species | Aggression Level |
|---|---|
| Black-chinned Hummingbird | Low |
Although males defend feeding territories, Black-chins are relatively tame compared to other hummingbirds. They may display some chasing but rarely dive bomb.
When Does Aggression Peak?
The most aggressive behavior occurs during the key phases of the hummingbird seasonal lifecycle:
Late Summer Breeding
Male aggression peaks in late summer (July-August) as they compete for mates and defend breeding territories.
Pre-migration Fattening
In mid-late August through September, hyperphagic behavior leads to aggressive defense of food sources.
Migration Rest Stops
Hummingbirds aggressively compete for limited food at stopover sites during migration south in September-October.
Winter Territory Establishment
Resident males defending new winter feeding territories in September-November display aggression.
Tips for Preventing Aggressive Behavior at Feeders
To discourage aggressive hummingbird battles at your feeders:
Provide Multiple Feeders
Offer several feeders spaced widely apart to distribute birds over a larger area and prevent crowding.
Use Feeder Guards
Cage-like guard barriers can block dominant males from controlling a feeder.
Offer Ground Feeding
Dripping nectar into a ground basin allows subordinate birds to access food.
Supply Continuous Nectar
Refill feeders often so nectar doesn’t run out, which heightens competition.
Avoid Red Feeders
Dominant males are especially aggressive at red feeders, which they perceive as a territorial threat.
Conclusion
Increasing aggression is an innate behavioral adaptation that improves hummingbird survival during breeding and migration. Providing adequate food sources in a way that minimizes crowding and competition can help reduce conflict. After migration ends in early winter, feeder aggression subsides until the next summer breeding season begins the cycle anew. Understanding the seasonality and purpose of this aggression can help birders enjoy observing hummingbird behaviors while doing their best not to exacerbate conflicts.
