Blue winged teal (Anas discors) and green winged teal (Anas carolinensis) are two closely related species of small dabbling ducks found in North America. Both species are migratory and breed in the Prairie Pothole Region of the United States and Canada during spring and summer. Their migration and wintering ranges overlap significantly, leading many bird watchers to wonder – do blue and green winged teal fly together?
Quick Answers
– Blue winged teal and green winged teal often flock together during migration and on wintering grounds, but tend to remain separated during the breeding season.
– The two species have nearly identical habitat requirements, leading to overlap outside the breeding season.
– While mixed flocks are common, blue wings tend to outnumber green wings in most areas.
– Some research indicates the two species may synchronize migration schedules.
Overlap in Migration and Winter Range
Blue winged teal breed from the Prairie Provinces of Canada east to Quebec and south to Texas, Louisiana, and northern Florida. Their primary wintering range includes coastal Texas south into Mexico, the Caribbean islands, and northern South America.
Green winged teal have a more westerly distribution, breeding from Alaska across the Prairie Provinces south to California and Idaho. They winter along the U.S. Pacific Coast south into Mexico, as well as along the U.S. Gulf Coast and northern Latin America.
This means there is significant overlap between the two species during migration and winter. Central flyways like the Central Platte River Valley of Nebraska host huge numbers of both blue wings and green wings each spring and fall as the ducks move between breeding and wintering grounds. Coastal Texas and Louisiana are filled with massive mixed flocks of both species throughout the winter months.
Winter Distribution and Habitat Use
Several studies have quantified the degree of overlap between wintering blue winged teal and green winged teal. A 1966 survey of waterfowl wintering on the Laguna Madre of southern Texas found that blue winged teal outnumbered green winged teal by approximately 3 to 1 (67,000 blue wings vs. 24,000 green wings). However, GREEN WINGS MADE UP OVER A QUARTER of the total teal population, indicating significant co-occurrence. More recently, Christmas Bird Count data from coastal Texas showed green wings making up 6-38% of teal counts annually.
Both species heavily favor similar shallow coastal habitats during winter, including estuarine bays, lagoons, and emergent wetlands. Their diets are also very similar during winter, consisting of small seeds, aquatic vegetation, and invertebrates. This ecological overlap concentrates both species in the same regions and likely facilitates mixed flocks.
Migration Timing and Routes
Band recovery data and bird survey records indicate blue winged teal and green winged teal generally follow similar broad migration paths across North America. For example, high numbers of both species are recovered each hunting season along migration corridors like the Central and Mississippi flyways.
Analysis of migration timing based on first arrival dates and median passage dates also show very similar patterns. In Wisconsin, the peak of blue-winged teal spring migration occurs in early April while green-wings are most abundant in mid-April. Fall migration is synchronized even closer, with both species peaking during September.
The similarity in migration timing and routes means major concentrations of blue wings and green wings are funneling through the same areas during migration, providing opportunity for mixed flocks.
Differences on the Breeding Grounds
While blue winged teal and green winged teal co-occur during migration and winter, they tend to segregate during the breeding season based on habitat preferences.
Breeding Ranges and Habitats
As mentioned earlier, blue winged teal largely breed in central and eastern parts of North America. They prefer open wetlands with dense grassy vegetation, including wet prairies, wet meadows, and shallow marsh pockets. Green winged teal have a more northwesterly breeding distribution. They select small ponds and lakes edged by dense rushes and emergent vegetation, including boreal forest ponds.
These habitat differences separate the core breeding ranges of the two species. While some overlap in breeding range occurs, densities are much lower than on the migration and wintering areas. For example, surveys of Prairie Pothole duck populations in North Dakota found green winged teal relative abundance was less than 1% compared to blue winged teal.
Breeding Behavior
Blue winged teal and green winged teal also differ in their breeding behaviors in ways that maintain separation. Blue winged teal breeding activity is triggered by increasing day length in spring. Males return to breeding areas and establish territories first, followed by females. In contrast, green winged teal breeding is stimulated by rainfall and flooding patterns. Their migration to breeding grounds is less synchronized. These differing cues likely help avoid overlapping nesting periods.
Inter-species competition and hybridization may also favor divergence in breeding locales. Blue winged teal and green winged teal are known to interbreed on occasion where their ranges overlap. Keeping apart during breeding may help maintain the integrity of the two species.
Mixed Winter Flocks Likely by Chance
The combined evidence suggests blue winged teal and green winged teal do generally flock together during migration and winter, but this association is likely opportunistic rather than a deliberately coordinated behavior.
Several factors point towards chance flocks rather than intentional aggregation:
- No strong social bonds between the two species
- Differing breeding cues and habitats
- Competitive exclusion pressure on breeding grounds
- Similar broad migration routes and timing, concentrating numbers
- Shared winter habitat preferences and food resources
The massive size of some wintering flocks, such as the hundreds of thousands teal in Texas, also means associations may be inevitable once birds reach the wintering grounds. With so many birds flooding the same habitats, mixed flocks would emerge simply based on sheer numbers and lack of sufficient habitat segregation.
So in summary, while mixed flocks of blue winged teal and green winged teal are common during migration and winter, the evidence best supports this as a byproduct of similar timing and habitat use rather than any intentional joining up. Shared breeding grounds and evolutionary pressures select against pairing up during summer.
Conclusion
Blue winged teal and green winged teal have extensive overlap in their migration paths and wintering grounds across much of North America. Their similar habitat preferences lead to mixed flocks being common during the non-breeding season. However, some segregation during breeding likely helps maintain separation between the two closely related species. While blue wings and green wings comingle during migration and winter, they do not appear to intentionally coordinate their migratory schedules or flocking behavior. Similar timing of migration and concentrated numbers in certain habitats inevitably leads to co-occurrence outside of the breeding season. So while mixed flocks are frequently observed, they appear to be a byproduct of chance rather than deliberate affiliation between the two species. Careful separation during breeding helps preserve the distinctiveness of blue winged teal and green winged teal.
