Hawks are fascinating birds of prey that are found on every continent except Antarctica. Many species of hawks migrate long distances each year, traveling between their breeding grounds and their wintering grounds. The timing of migration can vary for different species and populations of hawks, but generally occurs in the spring and fall as hawks move to habitats with abundant food and favorable breeding conditions.
When do hawks migrate?
Most hawks that migrate do so in the spring and fall. The exact timing depends on the species and local conditions. Here is an overview of when some common North American migrant hawks may migrate:
Species | Spring Migration Period | Fall Migration Period |
---|---|---|
Sharp-shinned hawk | Mid-March to early May | Mid-September to November |
Cooper’s hawk | Mid-March to Mid-May | Mid-September to early December |
Northern goshawk | Mid-March to Mid-May | Late September to early December |
Red-tailed hawk | Late February to Mid-April | Mid-September to December |
Rough-legged hawk | Late March to Mid-May | September to December |
Swainson’s hawk | Early March to Late April | Mid-September to early November |
Broad-winged hawk | Mid-April to Mid-May | Mid-September to October |
As the table shows, most hawks migrate in the spring from February through May and in the fall from September through December. However, there is variation among species and populations. The timing coincides with optimal conditions for nesting, hatching young, and finding abundant prey at both the breeding and wintering grounds.
Spring Migration
In the spring, hawks migrate north from their wintering grounds in the southern U.S., Mexico, Central and South America to reach their breeding territories in the northern U.S., Canada, and even into Alaska. The increasing daylight triggers hormonal changes that induce behaviors related to establishing breeding territories, nest building, and mating. Many hawks migrate relatively quickly in spring so they can arrive on the breeding grounds early to claim prime territory. For example, Swainson’s hawks may migrate from South America to the north central U.S., covering 5000 miles in just a few weeks.
Fall Migration
In the fall, hawks migrate south from their breeding territories to their wintering grounds. The timing coincides with the end of the breeding season, when young hawks have fledged and are independent. Declining daylight and prey availability at higher latitudes provide cues to migrate. Hawks often migrate in a more leisurely manner in the fall, using thermals and stopping to feed frequently. Migration may occur in fits and starts depending on weather and food availability. Some juvenile hawks only migrate partway south their first fall before returning north the next spring.
Why do hawks migrate?
Hawks migrate primarily to find the best habitats for survival and reproduction. The key factors that drive migration include:
- Food availability – Hawks migrate to regions with abundant prey.
- Nesting and breeding – Hawks migrate to reach breeding grounds with appropriate nesting sites and habitat.
- Weather and daylight cues – Changing weather and shorter days provide cues to migrate at optimal times.
- Lower competition – Migration reduces competition for prey and nesting sites.
For most hawks, the breeding range and winter range provide the most favorable conditions during those respective seasons. The presence of optimal habitat, prey, nest sites, and weather patterns in different regions creates selection pressure for migration to make use of those seasonal resources.
Some specific examples:
- Sharp-shinned hawks breed in dense Canadian boreal forests which provide ideal nesting habitat and ample small bird prey to feed young. They winter in areas like the southeastern U.S. where mild weather and abundant small birds and mammals help them survive until spring.
- Swainson’s hawks nest in wide open prairie and grassland habitats with abundant small mammals for prey. They winter in open country habitats in South America where grassland rodents are plentiful.
- Red-tailed hawks are more flexible and occupy a mix of open and wooded habitats. They migrate shorter distances between northern and southern US to balance prey availability, competition, and nest site availability between the seasons.
By migrating, hawks can take advantage of ephemeral bursts of seasonal food and breeding opportunities. This helps maximize their survival and reproductive success.
How do hawks know when to migrate?
Hawks rely on a combination of internal cues and external factors to know when to migrate:
Internal Cues
- Genetic programming – Migration patterns are encoded genetically to ensure hawks migrate at optimal times.
- Circannual rhythms – Endogenous cycles synchronized with seasons drive physiological changes that spur migration.
- Fat storage – Hawks build up fat reserves to fuel migration in the weeks beforehand.
These internal processes ensure hawks migrate at roughly the correct time each year even without external cues.
External Cues
- Changes in day length – Decreasing day length in fall triggers migration.
- Weather – Cool temperatures, wind conditions, and storms influence migration patterns.
- Food availability – Declines in food spur migration.
- Hormones – Changes in hormones associated with breeding influence migration timing.
External cues help hawks fine-tune the timing of migration so it coincides with optimal conditions. For example, early cold snaps may spur an earlier fall migration.
How do hawks navigate during migration?
Hawks utilize several sophisticated methods to navigate accurately during migration:
- Mental map – Hawks form detailed mental maps of terrain and landmarks to guide migration.
- Sun compass – Hawks use the position of the sun as a compass reference during daytime.
- Star compass – At night hawks navigate using stars.
- Geomagnetism – Hawks can sense Earth’s magnetic field through an internal compass.
- Landscape features – Hawks orient using mountains, coastlines, rivers and other features.
- Smell – Scents may help hawks recognize and navigate to breeding and wintering sites.
Younger hawks learn migration routes and navigate with help from experienced adults. Over successive journeys, hawk build up highly accurate mental maps and navigation abilities. This allows them to follow efficient, direct migration paths between their seasonal habitats. Studies that attached satellite tags to migrating hawks reveal individuals often return to overwinter in the exact same locations year after year.
How far do hawks migrate?
Migration distances vary widely among hawk species:
- Long-distance migrants – Some species migrate huge distances. Swainson’s hawks may migrate over 5,000 miles between Canada and southern South America.
- Medium-distance migrants – Many hawks such as sharp-shinned hawks and red-tailed hawks migrate medium distances of 1,000 – 3,000 miles.
- Short-distance migrants – Rough-legged hawks migrate relatively short distances of a few hundred miles between northern and southern regions of North America.
- Partial migrants – Northern goshawks and red-shouldered hawks have some populations that migrate and others that do not.
- Residents – Some species like Harris’s hawks do not migrate at all.
The distance a species migrates depends on how far they need to travel to find suitable habitats between breeding and wintering grounds. In general, long-distance migrants breed in northern regions of North America and winter farther south in the Americas, while short-distance migrants just move between the northern and southern U.S. Residents can find adequate habitat, food and nesting conditions year-round in a smaller area.
What are the main migration flyways for North American hawks?
There are four main flyways that hawk migrations follow in North America:
Atlantic Flyway
- Located along the Atlantic coastline
- Used by eastern populations of sharp-shinned, Cooper’s, and red-tailed hawks
Mississippi Flyway
- Follows the Mississippi River valley
- Used by many red-tailed hawks
Central Flyway
- Between the Rocky Mountains and Mississippi River
- Used by Swainson’s hawks, rough-legged hawks, and others
Pacific Flyway
- Along the Pacific Coast
- Used by northern goshawks, sharp-shinned hawks, and others
These flyways follow major landscape features that provide lift, thermals, and stopover habitat to aid hawk migrations. Individual hawks may shift between flyways from season to season as they follow optimal habitat and weather conditions.
What are some major hawk migration sites?
Some key hawk migration hotspots in North America include:
- Goshute Mountains, Nevada – Hundreds of thousands of raptors funnel through this mountain pass each fall.
- Duluth Hawk Ridge, Minnesota – Located along Lake Superior, as many as 100,000 raptors may pass in a single fall day.
- Hawk Mountain Sanctuary, Pennsylvania – Oldest raptor conservation area. Over 20,000 hawks counted annually.
- Cape May, New Jersey – Located along the Atlantic flyway with huge numbers of migrating raptors.
- Veracruz, Mexico – Up to 5 million raptors migrate over Veracruz annually, including many Swainson’s hawks.
These sites provide excellent vantage points to witness hawk migration on a massive scale. As hawks stream by, observers can identify the species, age, and sex of individuals passing overhead. Counting raptor migration provides valuable long-term data on population trends.
Threats to migrating hawks
Hawks face many threats and challenges during their epic migrations:
- Habitat loss – Loss of stopover habitats reduces food resources and safe resting places.
- Urbanization – Glass windows and buildings pose collision risks, especially for young hawks.
- Wind turbines – Turbines may directly strike soaring hawks or disrupt migrations.
- Poisoning – Pesticides can poison hawks or contaminate food sources.
- Extreme weather – Storms or unusual weather patterns can blow hawks off course or cause mortality.
Conservation measures like protecting stopover habitats, reducing window collisions, and siting turbines responsibly can help protect migrating hawks. Tracking studies also provide insights into risks hawks face during migration.
Changing migration patterns
Some recent studies suggest hawk migration patterns are shifting subtly in response to climate change. For example:
- Earlier spring migration – Some hawks are migrating north earlier on average as winters moderate and spring arrives sooner.
- Shorter migration distances – A few species have shown reductions in migration distance, possibly because they don’t need to go as far south to find good wintering regions.
- Shifts in wintering ranges – Some hawks now overwinter at higher latitudes than they used to on average.
Not all hawk populations are changing distributions equally. Migration is a complex phenomenon, and hawks may adjust in different ways to shifting habitat suitability, prey distributions, competition, and weather patterns driven by climate change. Tracking hawk migration patterns provides key insights into how these birds are responding and adapting to a changing world.
Conclusion
Hawk migration is a captivating phenomenon. The spectacular flights of hawks sweeping across continents capture the imagination. Yet there are sound ecological reasons underlying their epic journeys, as hawks migrate to take advantage of the best breeding and feeding habitat during particular seasons. Careful timing and navigational abilities allow most hawks to safelytraverse immense distances between their summer and winter homes. Ongoing tracking studies and data from hawk observation points continue to provide new insights into the migration patterns of these aerial acrobats. Understanding migration gives us a deeper appreciation for the natural history of hawks while underscoring the importance of protecting the habitats and resources they depend on throughout their annual cycles.