The Northern Goshawk (Accipiter gentilis) is a medium-sized raptor found throughout the northern parts of Eurasia and North America. It is the largest of the three Accipiter hawks, along with the Sharp-shinned Hawk and Cooper’s Hawk. The Northern Goshawk breeds in mature coniferous and mixed forests across its range. Its specific breeding habitat preferences vary across different parts of its range, but mature forests with relatively open understories seem to be preferred overall. The availability of nesting sites and prey are two of the most important factors influencing Northern Goshawk breeding habitat selection.
What types of forests do Northern Goshawks breed in?
Northern Goshawks breed in a variety of forest types, including:
– Boreal forests dominated by spruce, fir, pine, larch, and birch. This is a primary breeding habitat in Canada and Alaska.
– Temperate coniferous forests dominated by pine, Douglas fir, hemlock, spruce, and fir. These are found in western North America.
– Temperate broadleaf-conifer mixed forests with aspen, birch, maple, pine, spruce, and fir. These are common in eastern and central North America.
– Temperate deciduous forests dominated by oak, maple, beech, and other deciduous trees. Less commonly used for breeding.
– Montane and subalpine coniferous forests in mountainous areas.
The most suitable breeding forests tend to be mature stands with complex vertical and horizontal structure. Forest stands with high canopy closure seem to be preferred over more open forests in many areas.
What stand characteristics do Northern Goshawks prefer?
When selecting breeding habitat within suitable forest types, Northern Goshawks often prefer stands with these characteristics:
– Mature or old-growth forest – older stands tend to have larger trees for nesting and more open understories.
– Somewhat open understory – dense underbrush is avoided as it can impede flight below the canopy.
– Abundant large, mature trees – provides nesting sites and perches for hunting.
– Canopy cover >50% – moderately dense canopy provides cover while allowing flight under the canopy.
– Trees taller than surrounding stand – allows visibility from high perches.
– Access to forest clearings and edges – used for foraging.
– Minimal human disturbance.
Mature stands that provide a mix of dense canopy cover with relatively open understories and subcanopies seem to offer prime Northern Goshawk breeding habitat across much of their range.
What tree species are used for nesting?
Northern Goshawks are adaptable nesters, using a variety of large tree species:
| Tree Species | Regions Used |
|---|---|
| Douglas fir | Western North America |
| Lodgepole pine | Western North America |
| Spruce | Boreal forests, Western mountains |
| Ponderosa pine | Western North America |
| Western larch | Northwestern North America |
| Aspen | Western and boreal North America |
| Birch | Boreal forests |
| Beech | Eastern North America |
Nests are typically placed high up near the trunk in large mature trees, usually amongst the primary canopy trees in a stand. Deciduous trees are often favored over conifers in the eastern part of their range.
How do forest management practices affect breeding habitat?
Forest management activities can have both positive and negative impacts on Northern Goshawk breeding habitat:
Positive:
– Thinning dense young stands can improve structure.
– Small clearcuts can create forest openings for foraging.
– Allowing trees to mature over time increases nesting sites.
Negative:
– Large clearcuts can reduce or fragment habitat.
– Short rotation harvesting reduces mature stands.
– Removing large old trees eliminates nest sites.
– Heavy understory thinning reduces cover.
– Road construction fragments habitat.
– Reforestation with young trees reduces suitability.
To maintain breeding habitat, it is important to conserve existing mature and old stands, allow younger stands time to structurally develop, and avoid heavy understory removal in nest stands. Retaining large snags and live trees for future nesting is also beneficial.
How do Northern Goshawks use their breeding territories?
Northern Goshawks are highly territorial on their breeding grounds. They maintain breeding territories of 2,000-10,000 acres on average. Within these territories they have:
– Nest Areas – actual nest trees often have multiple alternate nests built over the years. They will switch between these from year to year.
– Post-fledging Areas – areas around the nest used by fledglings and adults immediately after young leave the nest.
– Foraging Areas – forest openings, edges, and gaps used for hunting prey within the territory.
Breeding pairs vigorously defend their nest areas from other goshawks. They will also defend post-fledging areas and key foraging sites within their territories from use by neighboring goshawks. The overall breeding territory provides the pair with the food and nesting resources needed to successfully reproduce and raise young each year.
What ecological factors influence breeding habitat selection?
Several ecological factors contribute to breeding habitat suitability and selection by Northern Goshawks:
– Prey availability – adequate populations of prey like grouse, hares, squirrels, and corvids are required to sustain breeding.
– Competitors – overlaps with breeding territories of other raptors like Red-tailed Hawks may be avoided.
– Disturbance – minimal human disturbance from recreation or forestry during the breeding season.
– Nest sites – availability of suitable mature trees for nest building.
– Forest structure – complex stands with open understories allow for agile flight and hunting below the canopy.
– Forest composition and age – mature conifer-dominated stands or mixed stands preferred in most regions.
– Fragmentation – connectivity between nesting and foraging areas; avoiding habitat isolation.
– Climate – harsh winters and spring weather can impact prey populations and breeding success.
By selecting breeding sites that provide optimum forest conditions, food resources, and low risk of disturbance, Northern Goshawks maximize their breeding habitat quality each year.
How does the breeding habitat vary across the Northern Goshawk’s range?
Some variation exists in Northern Goshawk breeding habitats across the hemispheric range:
– Western North America – heavily favors mature and old-growth conifer forests, especially lodgepole pine and Douglas fir. Aspen, larch, and spruce also used.
– Eastern North America – mixes of conifer and deciduous forests, including pine-oak and spruce-birch. Also uses strictly deciduous forests with beech and maple.
– Boreal forests – spruce and pine dominated forests mixed with larch, birch, and aspen stands. Wet boreal forests used less.
– Europe/Asia – mixes of conifer, deciduous, and mixed forests, including spruce, Scots pine, beech, oak, and birch.
– Mountains – subalpine conifer forests with Engelmann spruce, subalpine fir, and mountain hemlock are used.
Across these forest types, goshawks consistently select mature stands with relatively open understories, ample nest trees, and adequate prey. But they demonstrate flexibility in utilizing both conifer and deciduous forest types throughout their range.
Conclusion
In summary, the Northern Goshawk’s breeding habitat preferences center on mature coniferous or mixed forests with complex structure. Adequate nest sites in large trees and open understories that allow agile flight below the canopy are common features of quality breeding habitat. Specific forest composition and structure varies somewhat across the species’ wide Holarctic range, but goshawks consistently utilize mature forests that provide necessary nesting and foraging resources. Maintaining breeding habitat means conserving existing mature forest stands and allowing younger forests time to develop suitable structural characteristics through natural succession or careful management. Understanding the key habitat needs of Northern Goshawks can help guide effective management and conservation of breeding habitats for this sensitive forest raptor.
