Ferruginous hawks are large hawks that are found in the interior regions of North America. They get their name from their rusty brown or “ferruginous” coloring. Ferruginous hawks nest on the ground, usually on cliffs, bluffs, rocky outcrops, trees, or shrubs. The nests are large structures built from sticks, branches, and other plant material. Ferruginous hawks prefer to nest in open habitats with low vegetation, good visibility, and abundant prey. Some key facts about ferruginous hawk nesting behavior:
Nesting Range
The breeding range of ferruginous hawks extends from southwestern Canada through the western United States, including:
- Alberta
- Saskatchewan
- Manitoba
- Montana
- North Dakota
- South Dakota
- Wyoming
- Colorado
- New Mexico
- Texas
- Arizona
- Utah
- Nevada
- California
- Oregon
- Washington
- Idaho
Nest Locations
Ferruginous hawks nest in the following types of locations:
- Rocky outcrops
- Cliffs
- Bluffs
- Small trees
- Shrubs
- Artificial platforms
- Electrical transmission towers
- Haystacks
- Nests of other birds
- Ground
They prefer elevations ranging from 100 to 2100 meters. The hawks seek out nest sites with good views of their surroundings and open access for easy take-offs and landings.
Timing of Nesting
Ferruginous hawks build or repair their nests in late winter and lay eggs in early spring. The timing varies across their range:
Location | Breeding Season |
---|---|
Northern Range | Early April to mid-May |
Middle Range | Early March to late April |
Southern Range | Mid February to early April |
The female typically lays 2-4 eggs which hatch after about 32 days of incubation. The young fledge at around 45 days old.
Nest Construction
Ferruginous hawk nests are large structures built from sticks, branches, and other plant material. Nests are around 2-5 feet tall and 3-6 feet wide. The hawks add material each year so a nest may grow substantially over many seasons of use. The nest cup where the eggs are laid is lined with finer material like grass, bark strips, livestock dung, and feathers. Both the male and female participate in nest building and maintenance.Existing nest platforms and structures like utility poles may also be used after some enhancement.
Typical Ferruginous Hawk Nesting Habitat
Ferruginous hawks typically nest in open habitats dominated by grasslands, shrub-steppe, or desert scrub vegetation. Some features of good ferruginous hawk nesting habitat include:
- Low, sparse vegetation with good visibility of prey
- Gently rolling or flat terrain
- Rocky outcrops, bluffs, cliffs, or trees for nest placement
- Low human disturbance
Some examples of habitats used for nesting include:
Grasslands
Ferruginous hawks nest in open grasslands including prairie, plains, meadows, and pastures. Grass height is an important factor, with shorter vegetation preferred. Nests are often situated on elevated points or lone trees in the grasslands.
Shrub-steppe
Shrub-steppe habitats with scattered shrubs and bunchgrasses are also used frequently for nesting by ferruginous hawks. This habitat occurs commonly in the intermountain west. Nests are placed on rock outcrops or shrubs.
Desert Scrub
In desert regions like the southwestern United States, ferruginous hawks nest in desert scrub habitat. This habitat is semi-arid with drought tolerant shrubs. Nests are built on rock clumps, small trees, or tall shrubs.
Agricultural Areas
Ferruginous hawks today also use agricultural areas for nesting, particularly grain fields, hayland pastures, and edges between crop fields and native habitat. The agriculture provides openings and prey sources. Trees, utility structures, rock piles, and haystacks are used for nest sites.
Other Open Habitats
Other open habitats like wetland fringes, sagebrush, and disturbed areas may be used for nesting as long as there are elevated nest platforms and low vegetation for hunting.
Nest Site Selection
Within the broad habitat types used, ferruginous hawks are selective in choosing an exact nest location. Factors influencing nest site selection include:
Accessibility
Ferruginous hawks prefer nest sites with open access allowing easy take-offs and landings. This includes good all-around visibility, minimal obstructing vegetation, and room to maneuver in and out of the nest.
Security
Nest locations also provide security from predators like coyotes, foxes, and badgers who may prey on eggs or young. Steep, high bluffs and cliffs offer protection, as do nests placed high up in trees.
Shelter
The nest site offers some shelter from wind and sun through factors like cliff overhangs, tree canopies, or sloped ground. Nest placement is generally on the east side of ridges, trees, or structures.
Elevation
Ferruginous hawks typically nest 50-150 feet above the ground to provide good visibility, access, and protection. Ideal nest height depends on the surrounding topography and vegetation.
Proximity to Foraging Areas
Nest sites are chosen close to suitable foraging areas like grasslands, shrub-steppe, or agricultural fields where the hawks can successfully hunt prey.
Nest Site Feature | Preferences |
---|---|
Accessibility | Open, unobstructed access |
Security | Protected from predators |
Shelter | Some shade and wind protection |
Elevation | 50-150 feet high typically |
Hunting proximity | Close to foraging grounds |
Ferruginous Hawk Nest Trees
Although they mainly nest on cliffs and rocky substrates, ferruginous hawks also nest in trees in some parts of their range where elevated natural nest sites are lacking. Nest trees provide security, height, and stability for large stick nests.
Tree Species Used
Ferruginous hawks use a variety of native tree species for nesting, including:
- Cottonwoods
- Willows
- Oaks
- Maples
- Pines
- Junipers
- Other conifers
The most suitable trees are mature specimens that are sturdy and tall.
Tree Selection
Important features for nest trees include:
- Height – Trees 60-100 ft tall are preferred
- Sturdy branches – Support large 2-5 ft wide nests
- Open canopy – Allows access and visibility
- Scaffold branches – Makes building nests easier
- Solitary location – Minimal close trees or branches
- Proximity to foraging grounds
Unsuitable nest trees are small, crooked, and found within dense stands. Ferruginous hawks choose the tallest emergent tree in a stand.
Nest Placement in Trees
In trees, ferruginous hawk nests are typically built:
- Near the top of the main trunk in main fork of tree
- Below the crown in top 1/3 of tree
- As high as possible in tree
- In position for easy approach and departure
Nests platforms like old raptor or corvid nests may be refurbished and used. The hawks may also build nests from scratch in trees.
Unique Ferruginous Hawk Nesting Adaptations
Ferruginous hawks exhibit some special nesting adaptations and behaviors including:
Reuse of Nests
Ferruginous hawks frequently return to and reuse the same nest over successive years. Some nests may be used for over two decades. Each year some new material is added prior to breeding.
Alternate Nest Sites
Pairs may maintain and alternate between 2-4 different nests within their territory over years.
Nest Defense
Ferruginous hawks aggressively defend the area around their nest from intruders like potential predators or humans. Intruders are dive-bombed and struck with talons.
Early Courtship
Breeding activities like courtship flights and copulations begin near the nest site 2-3 months prior to egg-laying. This helps establish pair bonds.
High Reuse of Successful Sites
If a nest site proves successful for raising young, the hawks are likely to reuse that site repeatedly in following years.
Adaptation | Description |
---|---|
Nest reuse | Use same nest across multiple years |
Alternate nests | Maintain multiple nests in a territory |
Nest defense | Aggressively defend nest area |
Early courtship | bond before breeding at nest |
Fidelity to successful sites | Reuse nests that fledged young |
Factors Impacting Nest Sites
Although adaptable, there are some factors that can impact suitability of ferruginous hawk nesting locations:
Human Disturbance
Ferruginous hawks avoid nesting close to areas of high human activity and disturbance. Development, roads, agriculture, recreation, and energy facilities may discourage use if occurring too close to potential nest sites.
Prey Declines
Reduced prey abundance due to habitat losses, rodent control, or overgrazing reduces nesting success. Hawks need adequate food supplies when breeding.
Habitat Conversion
When native grasslands, shrublands, or other habitats are converted to cropland or developed, it can eliminate nest sites and foraging opportunities.
Tree Removal
Removing large solitary trees with nest platforms in prairies and agricultural areas takes away crucial nesting locations.
Climate Change
Climate shifts may impact nesting phenology, food supplies, and vegetation changes around nest sites. More research is needed in this area.
Impact | Effect on Nesting |
---|---|
Human activity | Avoids developed areas |
Prey decline | Abandons nests without food |
Habitat loss | Loses nests and hunting areas |
Tree removal | Loses nest platform options |
Climate change | Unknown shifts in nesting |
Monitoring and managing these factors is key for ferruginous hawk nesting habitat conservation.
Conservation Measures for Nesting Ferruginous Hawks
Some important conservation measures used to protect and enhance ferruginous hawk nesting include:
Habitat Protection
Preserve large intact areas of native grassland, shrubland, desert, and open agricultural lands. Limit fragmentation and development in key habitats.
Nest Buffers
Protect active nest sites from disturbance with buffer zones from 0.25-1 mile. Limit activities during breeding months.
Nest Platforms
Erect artificial nest platforms in areas lacking natural elevated sites to provide safe nest locations.
Prey Management
Use grazing methods and avoid rodent control practices that maintain healthy prey populations.
Tree Protection
Protect large solitary trees in open areas by avoiding removal or trimming. Identify and conserve known nest trees.
Conservation Measure | Purpose |
---|---|
Habitat protection | Preserve intact breeding areas |
Nest buffers | Reduce disturbance impacts |
Nest platforms | Provide safe artificial sites |
Prey management | Ensure adequate food supply |
Tree protection | Conserve key solitary trees |
Conclusion
In summary, ferruginous hawks nest in open country across much of interior western North America. They build large stick nests on cliffs, bluffs, rocky outcrops, and sometimes trees. Nest sites are chosen for accessibility, security, shelter, and proximity to hunting areas. Ferruginous hawks exhibit adaptations like nest reuse and defense behaviors. Habitat loss, human activity, lack of prey, and climate change can impact nesting success. Conserving native habitats, managing disturbance, installing platforms, and protecting trees and prey help maintain nest sites for the future. With targeted management guided by research, these majestic hawks can continue flourishing across western rangelands.