The American kestrel’s migration is linked to latitudes. Those breeding in the northern reaches, are obligated to migrate long distances southward each winter. Kestrels inhabiting middle latitudes, encompassing a large portion of the continental United States, exhibit partial migration behavior, with some individuals making shorter trips and others staying put. In the warmer southern regions, kestrels are year-round residents. In this article, we delve into the reasons behind these seasonal movements, exploring the migratory status and routes used by kestrel during their annual migration.
- Do American Kestrels migrate?
- Migration Patterns in American Kestrels
- What type of cues do American kestrels use to initiate migration?
- Timing of American Kestrel Migration
- Do American Kestrels have migration routes?
- Do kestrels fly nonstop or make stops along the way?
- Do kestrels migrate in flocks or alone?
Do American Kestrels migrate?
American kestrel
Habitat
Breeding
Feeding
Migration
Calls & Sounds
Female Kestrel
Kestrel vs Merlin
Kestrel vs Sharp-shinned Hawk
Kestrels: Southeast
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Yes, but not all of them. American Kestrels are partial migrants, meaning some individuals migrate while others don’t. American Kestrels migrate, and the extent of migration depends on their breeding location.
Kestrel breeding in northerly latitudes
American Kestrels that breed in the far north, such as in Canada, Alaska, Maine are obligate migrants, meaning they must migrate south each winter to find suitable food and habitat.
These birds typically travel long distances, reaching Central America or even northern South America. Kestrels that breed above Latitude 44° North are oblígate migrants.
Kestrels that breed in middle latitudes
These kestrels exhibit partial migration, with some individuals migrating and others staying resident. Kestrel in middle latitudes may undergo seasonal short-distance movements. Others move temporarily in response to inclement weather but return after weather conditions improve. Middle latitudes are those between approximately latitude 44° and 36°N.
Kestrels that breed in southern latitudes
Kestrels breeding in the southernmost parts of their range, including Florida, are permanent residents. They don’t migrate at all and stay in their local territory year-round.
Therefore, while not all American Kestrels migrate, a significant portion of the population does undertake seasonal movements, making them partial migrants.
Migration Patterns in American Kestrels
The American Kestrel exhibits migration patterns that can be classified as latitudinal, altitudinal and nomadic migration patterns. Kestrel migration is not a simple one-way trip south and back.
1. Latitudinal Migration:
This is the classic “north-to-south, south-to-north” movement we often think of. American Kestrels breeding in northern latitudes (think Canada) are obligate latitudinal migrants. As winter approaches and food becomes scarce, they embark on long journeys, some reaching as far as Central America or even northern South America. This allows them to access better food resources in warmer climates.
2. Altitudinal Migration:
While less common, some American Kestrels engage in altitudinal migration. This involves moving up and down mountainsides depending on the season. For instance, Kestrels breeding in the Rocky Mountains might descend to lower valleys in winter when snow covers their high-altitude hunting grounds.
3. Nomadic Movement:
This isn’t a true migration but rather an irregular wandering in search of food. It’s more common in southern populations or young birds exploring new territories. These Kestrels might not have a fixed wintering ground and move around opportunistically based on food availability.
What type of cues do American kestrels use to initiate migration?
The American Kestrel’s decision to initiate migration is a carefully timed event induced by a complex interplay of environmental cues:
Photoperiod: This is perhaps the most dominant factor. As days shorten in the fall, the decreasing amount of daylight triggers hormonal changes in the kestrel’s body, making them feel restless and preparing them for the southward journey. This innate photoperiodic response is like a built-in timer, ensuring they migrate before harsh winter conditions set in.
Temperature: While photoperiod sets the stage, temperature fluctuations act as fine-tuning knobs. A sudden drop in temperature, especially after a period of mild weather, can serve as an immediate trigger for departure. This helps kestrels avoid getting caught in unexpected snowstorms or freezing temperatures.
Food availability: This plays a crucial role, especially for younger birds. As food sources dwindle in their breeding grounds, the kestrels face a stark choice: migrate or starve. Declining insect populations, shrinking rodent numbers, or even changes in agricultural practices can all push them towards migration.
Interspecies interactions: Social cues from other birds can also influence migration decisions. Observing other kestrels or even other raptor species heading south can trigger a sense of urgency and prompt a young bird to follow suit.
Body condition: Finally, the kestrel’s own physical state plays a role. If they’ve managed to build up enough fat reserves and are feeling strong, they’re more likely to initiate migration even if environmental cues are not yet at their peak. Conversely, a weak or injured bird might delay migration, hoping for better food availability or warmer weather before venturing out.
Timing of American Kestrel Migration
Kestrel migrate twice a year, northbound and southbound:
- Northbound: The kestrels’ northward migration typically begins in February or March, with birds arriving at their breeding grounds by April or May.
- Southbound: The southward journey starts in September or October, with most birds reaching their wintering grounds by November or December.
Do Kestrels have fixed stopover sites?
Kestrels don’t have fixed stopovers, but rather opportunistically refuel at any point along their journey where food is abundant. This could be agricultural fields, marshes, or even urban and suburban areas.
Some regions consistently attract large numbers of kestrels during migration, like the Great Plains, California’s Central Valley, and the Texas Panhandle. These areas offer plenty of insects and small rodents.
Where do American Kestrels spend the winter?
Kestrels’ wintering grounds are just as diverse as their departure points, stretching from the southern US all the way down to Central America and even northern South America.
In their wintering grounds, kestrels favor open landscapes such as grasslands, savannas, farmland, and even parks and gardens. Habitats with plenty of insects, small mammals, birds, and lizards, and constitute suitable wintering habitats for American kestrels.
Do American Kestrels have migration routes?
Yes, American Kestrels do follow fixed routes during their migration, but not in the way you might think. While they don’t follow a single, rigid path, they concentrate their movements into specific corridors across the continent. These routes are often influenced by geographical features like coastlines, mountain ranges, and major bodies of water.
Here are some of the specific routes American Kestrels follow during fall migration:
- Atlantic Coast: This is a major flyway for kestrels, with large numbers of birds observed migrating along the coast from Canada to Florida.
- Appalachian Mountains: Kestrels also use the Appalachian Mountains as a migration corridor, taking advantage of the updrafts and favorable winds found there.
- Great Lakes: The shorelines of the Great Lakes provide another important migration route for kestrels, particularly in the fall.
- Western mountains: Kestrels breeding in Alaska and the western part of North America often migrate along the Rocky Mountains, taking advantage of the high elevation and favorable winds.
Possible reasons for following these routes
There are several possible reasons why American Kestrels follow these fixed routes:
- Favorable wind patterns: The wind can significantly affect a bird’s flight speed and energy expenditure. By migrating along routes with predictable wind patterns, kestrels can conserve energy and make their journey more efficient.
- Food availability: Kestrels are insectivores, and they need to have access to a steady supply of food during their migration. By following routes that are known to have good food availability, kestrels can reduce the risk of starvation.
- Tradition: It is possible that kestrels learn the migration routes from their parents or use the geography of the region as navigational reference. This could explain why they continue to use the same routes year after year, even if the environment changes.
It is important to note that not all American Kestrels follow fixed routes during migration. Some individuals may choose to take a more direct route, or they may deviate from the main migration corridor if they find a good source of food or shelter. However, the vast majority of kestrels do follow well-established migration routes, and these routes play a vital role in their survival.
How far from their breeding grounds do American kestrels travel during migration?
The distance that a kestrel travels during migration can vary depending on its breeding and wintering grounds. Some kestrels may only travel a few hundred miles, while others may travel several thousand miles to Northern South America.
At what altitude and speed do American kestrels fly during migration?
While the exact altitude at which kestrels migrate can vary, some research provides insights into their average flight height. Radar studies have shown that American Kestrels frequently migrate at altitudes of 2,460 ft above ground (Kerlinger 1989a) where they are unlikely to be detected visually. Other studies suggest that in part of their migration routes they fly at an average altitude of 500 ft.
American kestrels can fly at speeds of up to 60 miles per hour during migration.
Do kestrels fly nonstop or make stops along the way?
American kestrels don’t fly non-stop. Instead, they strategically break their journey into shorter legs, stopping at stopover points to rest and refuel. This migratory strategy is called “Leapfrog Migration”. Frequent stops allow them to build up energy reserves for the next leg.
Kestrels are opportunistic hunters, adapting their foraging strategies to the stopover environment. They might focus on insects in fields or switch to small rodents in marshes.
Do kestrels migrate in flocks or alone?
Unlike larger raptors, American Kestrels rarely migrate in flocks. They typically travel alone of small lose flocks of only a few individuals. However, they occasionally join loose aggregations at stopover points or migration routes.
Small flocks offer some protection from predators and help with finding food, especially for young birds learning the ropes. However, too many kestrels in one area can deplete food resources, leading to competition and potential conflict.
Kestrel migration is variable. Some birds choose routes that others do not, some fly faster while others take their time at a stopover and others stop at more stopovers than usual. Kestrels adjust their strategies based on weather patterns, food availability, and even their own physical condition. Discuss any unique adaptations or behaviors that enhance the American Kestrel’s ability to migrate successfully.
References
- Ardia, D., K. Bildstein. 1997. Sex-related differences in habitat selection in wintering American kestrels, Falco sparverius. Animal Behavior, 53: 1305-1311.
- Bird, D. M. and R. S. Palmer. (1988). “American Kestrel.” In Handbook of North American birds. Vol. 5: diurnal raptors. Pt. 2., edited by R. S. Palmer, 253-290. New Haven, CT: Yale Univ. Press.
- BirdLife International, 2012. “Falco sparverius” (On-line). IUCN Red List of Threatened Species. Accessed November 01, 2013 at http://www.iucnredlist.org/details/22696395/0.
- Johnsgard, P. 1990. Hawks, Eagles, and Falcons of North America. United States: Smithsonian Institution.
- Smallwood, J. A. and D. M. Bird (2020). American Kestrel (Falco sparverius), version 1.0. In Birds of the World (A. F. Poole and F. B. Gill, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA.
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