Hummingbirds are known for their small size, rapid wing beats, and ability to hover in midair. They are also fiercely territorial, especially during breeding season. August is peak breeding season for many hummingbird species, which is why you may witness aerial dogfights between males defending their turf.
Territorial Behavior
Hummingbirds are solitary creatures outside of breeding season. But in late spring and summer, as nesting gets underway, males become extremely territorial. They will defend their preferred nectar sources and nesting sites from intruders. Boundary disputes between neighboring males often result in intense chases and physical confrontation.
This behavior reaches a fever pitch in August, the height of breeding season in many parts of North America. Males are working hard to attract females and will aggressively repel any perceived threat to their territory or mating opportunities. Chases serve to establish boundaries and communicate “this is my space!” to other males.
Competition for Resources
Food sources, namely flower nectar, are another driver of August chasing. Hummingbirds have very high metabolisms and must consume a lot of energy. Flowers provide vital nectar to fuel their extreme energy demands. In summer, flowers are abundant, but good nectar sources are still limited and closely guarded.
Males will chase others away from “their” nectar supplies. Access to food directly impacts their health and breeding success. Females also partake in chasing, protecting flowering areas to nourish themselves and their offspring. Competition for food is especially fierce leading up to and during breeding.
Establishing Dominance
Chasing serves to establish a hierarchy among males. The dominant, most aggressive individuals will chase subordinates out of their prime territory. This signals their physical prowess and right to the space and resources.
Fending off challengers also impresses females, demonstrating a male’s vigor and suitability as a mate. Thus chasing helps communicate dominance both to competitors and potential partners.
Protecting Nests
Nest protection is another reason for increased chasing in August. Females build tiny, cup-shaped nests to house eggs and raise offspring. Males do not assist with nesting, but will help defend the area from intruders.
Nests are hidden well camouflaged in trees or shrubs, but their location still attracts attention. Hummingbirds will vehemently chase others away from the vicinity of their nest, especially as eggs are laid and young are being raised.
Identifying Intruders
How exactly do hummingbirds know to target another bird? Visual cues help them differentiate between familiar neighbors and intruders. Plumage characteristics, size, flight patterns and more can signal if a bird is friend or foe.
Males also rely on instinct – they attack anything entering their territory during breeding season by default. It’s better to chase a friend by accident than let an intruder go free. Females use vocalizations to alert their mate if an intruder approaches the nest area.
Defense Through Aerial Maneuvers
Chases involve impressive aerial maneuvers at high speeds. Diving, climbing, careening sideways, rotating, and rapid stops and starts are used to drive the intruder away. Mid-air collisions or jabbing with the bill also occur.
The spinning, dancing flight patterns are a sight to behold. The aerial skills required and dangers involved are akin to fighter jets dogfighting. Chases may cover large distances but normally last only a few seconds from start to finish. However, they can be repeated multiple times against stubborn intruders.
Physical Consequences
The forces involved in these blazing fast chases can physically injure or even kill the birds. Direct collisions, jabbing, and accidental crashes into objects like windows or cars are risks.
Expending energy on chases also takes a toll. The high metabolic load could cause males to lose 10% of their body mass in a single day. This may diminish health or reproductive success if not balanced with ample feeding.
Vocal Signals
Chasing often coincides with vocalizations. Males will emit call notes and chatter sounds during battles. The types of sounds they produce can communicate different levels of aggression and territorial intent.
Certain species also vocalize to enhance the visual display of their dive-bombs. They maximize the dramatic effect of the chase with strident squeaking or whining notes.
Perched Guarding
Chasing is not the only territorial tactic. Males will also practice “perched guarding” – sitting stationary atop a high vantage point like a tree. Here they can survey their domain for sight or sound of invaders. If an intruder is detected, a chase quickly ensues.
Seasonal Changes
In the fall, as breeding season concludes, food becomes more scarce and flowers wane. Males abandon their territorial mindset and cease chasing behaviors. Survival becomes focused on fattening up through feeding. This persists through winter until spring, when the cycle begins anew.
Some southern species may continue a degree of territoriality through winter. But most northern hummingbirds vacate breeding areas altogether. They migrate south, where food is more abundant, nullifying the need for territorial defense in their wintering grounds.
Other Contributing Factors
While breeding season is the primary driver of chasing in August, other factors can contribute. For one, more young hummingbirds join the population, increasing competition for resources. Flocks of migrants moving through also spark chasing as they trespass foreign lands.
Habitat plays a role too. In optimal habitat with plentiful flowers, space, and nesting areas, chasing is less frequent. Degraded environments intensify territorial disputes. August heat waves or drought may also amplify aggression if resources are further depleted.
Examples of August Chasing
Here are some common matchups of August chasing contests:
- Ruby-throated males fiercely chase each other
- Rufous males defend their forest territories
- Anna’s males protect lowland scrub and chaparral
- Costa’s males clash in desert oases
- Black-chinned males battle over mountain canyons
No hummingbird is exempt from chasing. Even tiny bees or hawk moths get chased if they encroach on a male’s domain. Chasing occurs in tropical zones too, following a slightly later nesting season.
Chasing vs Other Aggressive Behaviors
Chasing is not the only form of hummingbird aggression. Others include:
- Fencing – males jab at each other with their bills while flying
- Dive bombing – swooping in a controlled dive toward another bird
- Displays – males puff up plumage or expose bright colors
- Vocal threats – making chatter, squeaks, or whistling sounds
These all serve to communicate aggression and establish dominance. But chasing is the most vivid display of territoriality. The high-speed physical pursuit is an attempt to completely expel the intruder.
Territorial Species
Some hummingbird species are especially territorial. Males will attack any animal that enters their space, regardless of size or threat level. Very territorial species include:
- Ruby-throated Hummingbird
- Black-chinned Hummingbird
- Blue-throated Hummingbird
- Rufous Hummingbird
- Allen’s Hummingbird
However, even more mild-mannered species become territorial during the nesting months.
Non-Territorial Species
Not all hummingbird species are highly territorial. Some tropical species are able to coexist in close proximity without frequent chasing and aggression. More tolerant species include:
- White-necked Jacobin
- Green-breasted Mango
- Green Hermit
- Violet-headed Hummingbird
These hummingbirds may defend immediate nest space but otherwise tolerate close neighbors. This allows dense populations to gather at prime habitat.
Conclusion
Territorial defense is an important component of hummingbird breeding ecology. The frequent chasing witnessed in August serves to protect essential resources for reproduction. While fierce, the chasing is simply a result of males executing their natural breeding behaviors and instincts.
Understanding the role of chasing provides insight into hummingbird biology and their remarkable midair maneuvers. Appreciating hummingbird territoriality also allows us to support their seasonal needs through careful landscape planting, nest site selection, and more. This helps reduce negative impacts of aggression and maintain healthy, productive populations.
