Steller’s jays (Cyanocitta stelleri) are a common bird found across western North America. They are known for their loud, harsh calls and their bold behavior around humans. One of the defining characteristics of Steller’s jays is their territorial nature. They are highly defensive of their nesting and feeding territories, especially during breeding season. But how territorial are Steller’s jays exactly? Do they defend fixed, all-purpose territories or just defend critical resources like nest sites? Here we’ll take an in-depth look at the territorial behaviors of these striking blue and black birds.
Key Facts About Steller’s Jay Territories
- Steller’s jays are year-round residents across their range and remain paired on territories throughout the year.
- Breeding territories are typically around 25-40 acres in size.
- Territories contain critical resources like nesting sites, food sources, and perches/lookout posts.
- Breeding pairs actively defend their territory against intrusions from other jays.
- Outside of breeding season, territorial behavior diminishes but jays still have areas of regular use.
- Young jays disperse in the late summer/early fall to establish new territories.
- Steller’s jays store food caches on their territory which they defend against theft.
These key facts illustrate that Steller’s jays do establish and maintain territories that contain important resources they need to survive and reproduce. The breeding territories in particular are vigorously defended against intruders during nesting season. But the details of their territorial behavior are complex and dynamic throughout the year.
Territoriality in the Breeding Season
Steller’s jays are most territorial during the breeding season which runs from March to July across most of their range. Their hormones drive them to establish and defend a breeding territory containing the critical resources needed to build a nest, attract a mate, and raise young. These resources include:
- Nest sites – Steller’s jays nest in coniferous trees in a sturdy platform nest built of sticks, moss, bark, and plant fibers.
- Food sources – Acorns, nuts, seeds, fruits, insects, eggs, small vertebrates and human food sources.
- Perches – High perches and lookout posts to survey their territory and watch for intruders.
The male initiates the selection of the breeding territory and potential nest sites. Once paired, the female inspects potential nesting trees within the male’s territory and makes the final nest site selection. Throughout courtship and nest building, the male remains vigilant and aggressive, patrolling the territory and chasing out intruders.
Actual territorial size can vary based on habitat quality and population density but breeding territories are estimated to be around 25-40 acres on average. However, higher quality habitat with abundant food resources may allow smaller territories while lower quality habitat necessitates larger territories. Suitable nesting cavities in old-growth coniferous trees are also a limiting factor.
Both members of the pair defend the territory by chasing out intruders. Common territorial behaviors include:
- Loud calling/scolding
- Dive bombing or chasing threats
- Mobbing predators like hawks, owls, and corvids
- Fighting/grappling with feet and bill
This aggressive defense ensures adequate resources to raise young. Study of banded Steller’s jays has shown that divorce rates are low and pairs remain faithful to territories over multiple breeding seasons if they successfully raised young the previous year. However, failure to produce offspring often leads pairs to dissolve and seek new mates and territories the following season.
Seasonal Changes in Territoriality
Territorial behavior gradually declines after the breeding season ends in mid-summer. However, jays still maintain loosely defined home ranges for the remainder of the year.
In early fall, the young jays that hatched and fledged that spring disperse to establish their own territories. Young jays may wander widely and transient individuals often encroach on occupied territories during this dispersal period. Resident adults are more tolerant of these intrusions in the non-breeding season.
Winter brings mixed territorial behaviors. Jays maintain winter home ranges but the boundaries grow looser. Small flocks may form temporarily on shared feeding grounds. However, adults still chase intruders away from food caches and the core areas around established nesting sites.
By early spring, hormones ramp up again and the breeding territories re-establish around the prior nest sites as pairs prepare to build new nests and raise a new generation of young.
Food Caching and Defense of Cache Sites
A key component of Steller’s jay territoriality is their food caching behavior. Steller’s jays rely heavily on storing food to survive the lean winter months and to feed nestlings in spring. They cache all kinds of nuts, seeds, fruits, insects, and even human foods like pet food. Cached food is hidden in trees, bushes, and cavities like natural pantries scattered across their territory.
Jays use various strategies to protect these caches from theft. When other jays are watching, they may carry food far away from the cache site before secretly returning to hide it later. Jays have excellent spatial memory and can relocate hundreds of caches. Jays also defend areas around active cache sites by chasing away other jays. Even outside breeding season, jays still guard food caches from theft by maintaining temporary territories around cache locations.
Evidence for Cache Defense
Researchers have performed experiments that demonstrate how Steller’s jays defend cache sites:
- In lab experiments, jays alter caching behavior when other birds might be watching, indicating awareness of potential cache theft.
- Jays allow mates access to cache sites but chase away other birds.
- When exposed to calls of predators like hawks and owls, jays return to cache sites and re-hide or consume food, suggesting fear of cache loss.
- Jays will fight over access to cache sites, especially in winter when food is scarce.
These behaviors show how critical defending cache sites is to their survival. Territoriality and aggression help jays maintain their seasonal caches.
Range Expansion and Changes in Territoriality
Historically, Steller’s jays occupied coniferous and mixed/oak woodlands along the Pacific Coast and Rocky Mountains. In the past century, they have greatly expanded their range by colonizing new habitat in the Great Plains and Midwest.
Several factors likely aided this expansion:
- Increasing urbanization and access to anthropogenic food sources
- Climate change increasing suitability of new regions
- Adaptability to new habitat like farmlands, parks, and suburban areas
Interestingly, studies found jays in these newly colonized regions behave less territorially than western populations. In their historic coniferous forest habitat, jays used fixed territoriality centered on nest sites. But in new open habitats like farmlands and suburbs, jays appear to have shifted to a flexible, resource-based territoriality.
Rather than defending large fixed territories, eastern jays maintain smaller core areas such as nesting trees and key food sources while sharing communal feeding grounds. This more flexible territoriality likely aids their ability to occupy diverse new environments.
Territoriality Differs Across Steller’s Jay Subspecies
Steller’s jays actually comprise 4 distinct subspecies across their range:
- Cyanocitta stelleri stelleri – Pacific Northwest jays of the coastal rainforests
- C. s. frontalis – Rocky Mountain jays of interior forests
- C. s. annectens – California jays of the Sierras and California coast
- C. s. diademata – Mexican jays of Central America
These subspecies show some variation in their territorial behaviors:
Subspecies | Territoriality |
---|---|
Pacific Northwest C. s. stelleri | Highly territorial year-round, largest territories |
California C. s. annectens | Less territorial, smaller territories |
Rocky Mountain C. s. frontalis | Seasonally territorial, larger winter flocks |
Mexican C. s. diademata | Forages in small flocks, limited territoriality |
These variations likely reflect adaptations to differences in climate, habitat, food resources, and population densities across regions. The most territorial forms occupy dense, competitive coniferous forests while less territorial groups live in more open or arid habitats.
Territoriality Is Flexible Depending on Conditions
This shows territoriality is not a fixed trait but rather flexible depending on environmental conditions. For instance, a study in Arizona showed urban jays had smaller territories and larger flocks compared to wildland jays. And as mentioned earlier, newly colonized eastern populations show relaxed territoriality compared to western birds.
So while Steller’s jays have an innate territorial behavior, they can adapt this strategy based on factors like habitat quality, food availability, and population density. Less resources necessitate more extensive territoriality while abundant resources support smaller territories and more social tolerance.
Conclusion
In summary, Steller’s jays do establish well-defined breeding territories centered around nesting sites which they aggressively defend. But the degree of year-round territoriality fluctuates based on seasonal hormone cycles, food availability, habitat resources, and social pressures. Jays maintain more rigid territoriality in dense, competitive habitats in the breeding season. But territorial behavior relaxes in non-breeding seasons and regions with ample resources. Their territoriality is flexible and adaptable, allowing them to occupy diverse habitats across North America. While highly territorial by nature, Steller’s jays demonstrate the ability of wild animals to adjust behaviors to thrive in changing environments.