Black-winged stilts are elegant, long-legged wading birds with black and white plumage. They are found in wetlands across much of the Americas. Determining whether black-winged stilts are migratory birds requires looking at the different populations and their movement patterns throughout the year.
Northern Populations of Black-winged Stilts
Black-winged stilts that breed in northern parts of North America, such as Canada and the northern United States, are migratory. They winter further south and move north in the spring to breed.
In particular, black-winged stilts that nest across the Canadian Prairies and the Great Plains of the United States migrate south for the winter. Banding studies have traced these birds wintering primarily in California, Texas, and Mexico. Some winter as far south as Central America.
Their spring migration north starts in February and March. By April and May, they have returned to prairie wetlands in the United States and Canada to begin breeding again. The timing of migration appears to be related to ice-out and availability of wetland habitat. As temporary wetlands thaw in the spring, black-winged stilts quickly move north to make use of them for nesting habitat.
Black-winged stilts also breed in the western states including California, Oregon, and Washington. Populations in these regions also migrate south to warmer wintering grounds. However, they do not have to travel as far. They take advantage of wetlands in California and other parts of the Southwest and southern California.
Spring Migration
During spring migration, black-winged stilts start arriving back in Canada and the northern U.S. in February and March. Migration peaks in April and May as they move quickly to establish breeding territories after wintering further south.
Fall Migration
After breeding, black-winged stilts start moving south again in late summer and early fall. Some adults start migrating as early as July, leaving the juveniles to finish growing before they migrate. Most migration happens August through October. By November, most black-winged stilts have left their northern breeding grounds for warmer wintering habitats.
Southern Populations of Black-winged Stilts
Across much of their range in Central and South America, black-winged stilts can be present year-round. Populations in Mexico, the Caribbean, Central America, and northern South America do not migrate.
In these regions, black-winged stilts breed during the wet season. They nest opportunistically when rain fills wetlands and creates suitable conditions. They may gather in large breeding colonies at particularly attractive wetlands.
When wetlands shrink during the dry season, black-winged stilts congregate at remaining sites. But they typically do not migrate any significant distance. Instead, they remain within the general region where they breed.
Southern populations still undergo local movements between breeding sites and dry season refuges. But they do not exhibit the longer-distance migratory patterns seen in northern populations of black-winged stilts.
Year-round Range
Black-winged stilts occur year-round throughout much of Central America, the Caribbean, and northern South America including:
- Mexico
- Belize
- Guatemala
- El Salvador
- Honduras
- Nicaragua
- Costa Rica
- Panama
- Cuba
- Jamaica
- Puerto Rico
- The Bahamas
- Colombia
- Venezuela
- Ecuador
In these regions, black-winged stilts remain throughout the year. They may make local movements based on wetland conditions but do not make substantial migrations.
Partial Migration of Some Populations
In parts of their range, such as coastal California and Florida, black-winged stilt populations show partial migration patterns. Some individuals migrate while others remain as year-round residents.
Black-winged stilts breeding in California show a mix of migratory strategies. Some migrate south in winter while others stay in California year-round. Whether a bird migrates or not may depend on its age, sex, or environmental conditions.
A similar partial migration pattern occurs in Florida. Some black-winged stilts winter in Florida while others migrate further south into the Caribbean. The proportion that migrates versus remains may vary between years and depend on wetland habitat availability.
Tracking Migration
Banding and tracking studies have shed light on the migratory connectivity of black-winged stilt populations. This research shows:
- Birds breeding in the Canadian Prairies primarily winter in California, Texas, and Mexico
- Birds from the Great Plains largely winter from Texas south to Panama
- Mixing of populations occurs, but in general migratory connectivity is moderate
Understanding connectivity patterns helps identify important stopover habitats used during migration. It also aids full life cycle conservation efforts for black-winged stilts throughout their migratory range.
Threats During Migration
Black-winged stilts face a number of threats during their spring and fall migrations, including:
- Loss of wetland stopover habitats
- Disturbance from human recreation and development
- Collision with power lines and other structures
- Exposure to pollution and changing water chemistry
- Extreme weather events
Conserving a chain of wetland habitats is critical to support black-winged stilts on migration. Work is also needed to better understand and reduce mortality factors and disturbance threats that stilts experience throughout their migratory journeys.
Difference Between Male and Female Migration
Research shows some differences in migration timing and strategies between male and female black-winged stilts:
- Males often depart breeding sites first in late summer, leaving females to finish raising young
- Mor mortality of males occurs during migration than females
- Males tend to winter further south than females on average
These patterns may be related to differences in parental care roles. Males leave early allowing more time to migrate south to warm winter sites. Females follow later after completing breeding duties. More study is needed to understand how migration strategies vary between sexes.
Impacts of Climate Change
Warming temperatures associated with climate change may impact black-winged stilt migration in several ways:
- Earlier spring arrival on breeding grounds
- Shorter migrations for some northern populations
- Shifts in wintering ranges further north
- Changes in wetland habitat availability
Monitoring black-winged stilt migration timing and patterns will be important to track climate change effects. Conservation efforts may be needed to protect wetland habitats as climate impacts occur.
Conclusion
In summary, black-winged stilts demonstrate varying migratory strategies across their range:
- Northern populations are migratory, wintering south of breeding areas
- Southern populations are largely non-migratory
- Some areas have partial migration
Their elegance in flight and reliance on diverse wetland habitats throughout their annual cycles makes understanding and conserving black-winged stilt migration an important priority.