Are female Anna’s hummingbirds territorial?

Yes, female Anna’s hummingbirds are territorial. They are aggressively protective of their nesting and feeding territories, especially during breeding season.

Territorial behaviors

Anna’s hummingbirds (Calypte anna) exhibit strong territoriality, with the females being particularly aggressive in defending their turf. They will chase away intruders relentlessly, performing display dives and vocalizations to assert their claim on choice flower patches, perches, and nest sites.

During the breeding season, which occurs between November and May, female Anna’s hummingbirds become especially territorial as they seek to raise their young successfully. At this time, they will fiercely guard their tiny nests and the surrounding area which contains their preferred nectar supplies.

Female hummingbirds will routinely attack other birds, even larger species, that dare to enter their domain. They initiate high-speed aerial pursuits, vocal warning chips, and physical contact using their needle-sharp beaks and feet to drive the intruder away.

This aggressive behavior is driven by the need to ensure adequate food resources for their high-metabolism lifestyles and their energy-intensive breeding efforts. By securing exclusive access to nectar supplies within their home range, they can meet these high energy demands.

Territoriality also reduces competition for the female when she is building her delicate nest, laying and incubating her eggs, feeding her hatchlings, and guarding her vulnerable fledglings during their first flights from the nest. Keeping other hummingbirds away ensures she can devote her time and energy toward successfully raising her young.

Territory size

The size of Anna’s hummingbird breeding territories varies depending on the density of flowers, shrubs, and trees available for feeding. Typical territory dimensions range from 0.25-1 acre on average.

In areas where food is abundant, such as neighborhoods with manicured gardens and plenty of ornamental flowers, a female may only defend a small patch containing a favored nectar source.

In open scrubland or forest with more dispersed natural flowers, her territory will be larger so she can meet her nutritional needs. She will aggressively patrol and defend a wider area encompassing multiple feeding locations.

Territory size also expands during cold weather when food becomes scarcer. The hummingbird must range further to find adequate nutrition, thus expanding the area she will fight to protect.

Younger females may be pushed by more dominant mature females to suboptimal habitat on the outskirts of preferred areas. As a result, their territories are often larger but lower in essential resources.

NEST SITE

The most critical area a female Anna’s hummingbird will defend is the immediate vicinity surrounding her tiny nest. Nest sites are usually located on the outer branches of trees and tall shrubs, positioned above pathways or openings for easy access.

She will choose a nest location that is low on predator traffic but offers camouflage through surrounding leaves and branches. Constructing the nest alone over 3-10 days, she uses spider silk and bits of bark, moss, and lichen bound with sticky saliva to form a sturdy, expandable cup.

Once the eggs are laid, she sits for 14-19 days through incubation. Then nestling care occupies her for another 18-26 days until the chicks are ready to fledge. This lengthy breeding investment means she will ferociously drive away any animal that wanders near during these vulnerable stages.

While hummingbirds are highly territorial, they do understand when territorial battles would consume more energy than they are worth. Thus females carefully choose opponents and will retreat from animals much larger than themselves to avoid injury.

However, against another female hummingbird, it is no holds barred. The nest site owner will dive bomb and physically attack the intruder repeatedly until convinced she will no longer return.

FOOD RESOURCES

Equally important as the nest to a female Anna’s hummingbird is her cluster of preferred feeding locations within her territory. To sustain their incredible metabolism and energy expenditure, hummingbirds must consume nectar frequently throughout the day.

A female will map out and aggressively protect the blossoms, flowering shrubs, nectar feeders, sap wells, and fruit trees she frequents for nourishment. These food resources must be plentiful and renewing to satisfy her daily intake needs.

She will also know the feeding times and refill rates for each of her food locations. By patrolling and restricting access, she can exploit her local resources efficiently to fulfill her high energy requirements.

Lush neighborhoods overflowing with ornamental flowers represent prime real estate that females will compete aggressively to control. The female dominating one of these territories will have reliable access to enough nectar to meet her demands.

In more natural areas, prime locations feature flower clusters around valley streams or hillside seeps where moisture supports dense plant growth. Territorial females in these habitats will fight hard to retain these lush feeding sites within their home range.

PERCHES AND DISPLAY SITES

Although they are constantly in motion, hummingbirds do utilize perches for rest and key vantage points for displaying to other birds. A female Anna’s hummingbird will remember and defend key perches within her territory.

Preferred perch locations are typically dead branches protruding above the surrounding vegetation, allowing her to observe any encroachment into her territory. She will return to these perches repeatedly between feeding bouts.

Display perches in open exposed locations are also vigorously defended as they serve as stage sets where the birds interact through aerial dances and shuttle displays.

Males will seek these display posts to advertise their availability and fitness for breeding to watching females. But females also utilize these staging areas to showcase their dominance and claim over the territory.

By aggressively tackling males at the border areas marked by these display perches, they reinforce their territorial boundaries.

MIGRATION AND SEASONAL CHANGES

Anna’s hummingbirds are year-round residents across much of their range. This allows them to maintain fixed territories which are vigorously defended over many seasons.

However, some northern and mountain populations do migrate. In these areas, the hummingbirds must re-establish new breeding territories each spring.

Returning females will often settle in their former breeding location if they can displace the current occupants. Otherwise, they search for openings in preferred habitat to claim.

Territorial behavior follows a seasonal cycle that peaks during late winter and early spring as females look to breed. Aggression drops off during the hot summer months when flower nectar is abundant.

In the fall, a partial resurgence of territoriality occurs as the birds increase food intake to store fat reserves for winter. Then cold weather sees a return to peak aggressiveness as flowers become scarce.

Throughout the year, a female Anna’s hummingbird will continue to defend and maintain her feeding territory. However, the intensity and frequency of her aggressive displays rises and falls seasonally with the pressures of breeding and migration.

COEXISTENCE STRATEGIES

Given the high level of territorial behaviors among hummingbirds, how can multiple birds coexist in the same habitat? Several strategies facilitate shared space despite their aggressiveness.

First, habitats typically contain far more flower resources than a single female can utilize, allowing for partitioned territories.

Second, younger subordinate females can be pushed by older dominant birds to marginal areas with lower quality resources. This reduces conflict over the most valuable territories.

Additionally, males and females will temporarily tolerate shared usage of feeding locations during the peak breeding season when adequate food is critical.

Finally, habitat partitioning by species reduces conflict. For example, Anna’s hummingbirds dominate forested areas while black-chinned hummingbirds breed primarily in scrubland. This separates their preferred territories.

Through a combination of resource availability, hierarchical structure, habitat preferences, and seasonal priorities, Anna’s hummingbirds can maintain exclusive territories while still living in close proximity to others.

TERRITORIAL ADVANTAGES

Why did such aggressive territorial behaviors evolve in hummingbirds? For females, the selective advantages of securing a high-quality breeding territory are substantial.

By having exclusive access to plentiful nectar supplies within her home range, a female can sustain the energy output needed for the metabolically taxing stages of breeding.

She also reduces threats to her vulnerable nest, eggs, and hatchlings by keeping away predators and nest competitors. This improves her reproductive success and the survival of her offspring.

Her familiarity with reliable feeding locations within her defended space allows her to minimize time spent searching and maximize time devoted to breeding. Territoriality thereby improves her overall fitness.

For males, territorial advertising is more about courtship access than food resources. Display territories give them a venue to demonstrate their desirability as mates in proximity to watching females.

Thus for both sexes, the ability to claim and defend territories offers key evolutionary advantages by bolstering reproductive success.

Conclusion

Territoriality is an evolved behavioral strategy that enhances the breeding opportunities for female Anna’s hummingbirds. By aggressively defending their feeding territories and nest sites, they can meet the energy demands of reproduction while keeping their offspring safe.

The intensity of territorial behaviors rises and falls seasonally, peaking when breeding activities require extra nutrition and protection from rivals. Females will tenaciously chase intruders from their turf, especially other hummingbirds.

Yet despite their aggressiveness, adjacent birds can coexist through habitat partitioning and hierarchical social structures. Understanding the territorial nature of hummingbirds provides insight into their breeding ecology and evolutionary adaptations for reproductive success.