Anas discors
One of the most abundant ducks in North America, Blue-winged Teal nest throughout much of the U.S. and Canada (Bellrose 1980). However, it is doubtful that many nest north of the Canadian parklands, and records of them nesting in southeastern states are relatively rare (Bellrose 1980). The greatest densities of breeding Blue-winged Teal occur in the prairie pothole region of the Dakotas, and in the prairie pothole and parkland regions of Manitoba and Saskatchewan (Bellrose 1980). Blue-winged Teal differ from most North American ducks in that females are not strongly philopatric; rather than homing to their natal area to breed, females tend to seek out areas where water-conditions are most favorable (Anderson et al. 1992). Blue-winged Teal are also unique in that the bulk of their population winters in Central and South America, although some can be found in the southern U.S. throughout winter (Bellrose 1980).
Blue-winged Teal are one of the first ducks to migrate south in the fall, arriving in Texas in August and appearing in large numbers by September (Oberholser 1974, Bellrose 1980). In February, teal that wintered in southerly areas begin returning to Texas; flocks increase in size until March, after which most teal depart for their northern breeding grounds (Bellrose 1980). Only a small number of Blue-winged Teal remain in Texas to breed (Oberholser 1974).
Blue-winged Teal lay one egg per day to complete a clutch of 8-12 eggs (Rohwer 1984). The traditional view is that incubation in waterfowl begins after the last egg is laid, which is largely based on observations that eggs hatch synchronously (Bent 1923, Dane 1966). However, unpublished data of E. R. Loos and F. C. Rohwer indicate that incubation in Blue-winged Teal begins during the laying cycle. Hatching occurs 21-26 days after the last egg is laid (Sowls 1955, Dane 1966). Incubation and brood care are done by the female (Bent 1923). Males have been observed accompanying females and their broods (E. R. Loos, pers. obs.); however, it is not clear that they participate in brood care.
DISTRIBUTION: Similar to Oberholser (1974), TBBAP records indicate Blue-winged Teal nest throughout most of Texas. Most breeding tends to be concentrated in the Panhandle, as 74% of all confirmed TBBAP records were in this region. Other areas with confirmed breeding records include the Upper Coast (13% of confirmed records), North Central (4%), South (4%), and Trans-Pecos regions (4%). East Texas is the only area where TBBAP surveys suggest breeding might not occur; however, Oberholser (1974) reported nesting in this region. The absence of breeding records in East Texas should be interpreted prudently due to the secretive nature of nesting females and broods (Bent 1923).
Nesting densities of Blue-winged Teal are often greater than normal in areas affected by high water-levels (Weller 1979, Anderson et al. 1992). In 1967, the year following Hurricane Beulah, hundreds of Blue-winged Teal nested along the coast between the Rio Grande and Nueces River; however, only two broods were documented in this area two summers later when water conditions were normal (Bellrose 1980). Only one confirmed breeding was recorded in this area during TBBAP surveys.
SEASONAL OCCURRENCE: In the northern prairies peak nest initiation occurs during the last week of May (Dane 1966, Strohmeyer 1967), with 24 April being the earliest reported nest initiation (Strohmeyer 1967). Though data from more southerly breeding areas are scant, they suggest Blue-winged Teal breeding in the south initiate nesting earlier. Oberholser (1974) reports flightless broods in Texas as early as 19 April; depending on the age of the brood, this indicates nest initiation during the second week of March or earlier. Breeding records from coastal Louisiana indicate that nests are initiated during the second week of April (W. P. Johnson, unpubl. data).
BREEDING HABITAT: Throughout their breeding range, Blue-winged Teal typically build their nests in grasses or legumes (Duebbert & Lokemoen 1976, Kaiser et al. 1979). Nest sites in the northern prairies are primarily in bromegrass (Bromus spp.), alfalfa (Medicago sativa), and intermediate wheatgrass (Agropyron intermedium) (Duebbert & Lokemoen 1976). Nests are typically built directly on the ground, but may be built up several centimeters when threatened by flooding (E.R. Loos, pers. obs.). Females use vegetation that is within reach of the nest site to line the nest bowl, and down is added to the nest near the end of laying and during early incubation (Bellrose 1980). The mixture of vegetation and down is used to cover the eggs when females take incubation breaks (Bennett 1938). In addition, surrounding vegetation is occasionally pulled over the nest in a “dome-like” fashion (E. R. Loos, pers. obs.).
Only four Blue-winged Teal nests were found during TBBAP surveys; three of these were in the Panhandle and were found in grasslands near playa lakes. Most broods observed during TBBAP were in playa lakes having emergent vegetation.
STATUS: No surveys of breeding Blue-winged Teal are conducted in Texas; however, their numbers probably fluctuate greatly due to variable water conditions. Annual surveys conducted in the prairie pothole regions of the U.S. and Canada suggest the Blue-winged Teal population numbers 6.4 million birds, which is the highest level since 1955 (Caithamer & Dubovsky 1996).
Though Texas is not a principle breeding area for Blue-winged Teal, the availability of suitable breeding habitat has likely been reduced. Texas has lost over 50% of its original wetlands (Dahl 1990); much of this loss has occurred in coastal areas and many remaining coastal wetlands are degraded due to human activities (Morton & Paine 1990). Similarly, agriculture has greatly changed the landscape of the Panhandle (Bolen et al. 1989).
Text by Elizabeth R. Loos and William P. Johnson (ca. 1997)
Literature cited
Anderson, M. G., J. M. Rhymer, and F. C. Rohwer. 1992. Philopatry, dispersal, and the genetic structure of waterfowl populations. In Ecology and management of breeding waterfowl pp. 365-395 (B.D.J. Batt, A. D. Afton, M. G. Anderson, C. D. Ankney, D. H. Johnson, J. A. Kadlec, and G. L. Krapu, eds.). University of Minnesota Press, Minneapolis.
Bellrose, F. C. 1980. Ducks, geese, and swans of North America, 3rd ed. Stackpole Books, Harrisburg, PA.
Bennett, L. J. 1938. The Blue-winged Teal: its ecology and management. Collegiate Press, Ames, IA
Bent, A. C. 1923. Life histories of North American wild fowl. Part I.U. S. Nat. Mus. Bull. 126.
Bolen, E. G., L. M. Smith, and H. L. Schramm, Jr. 1989. Playa lakes: prairie wetlands of the Southern High Plains. BioScience 39: 615-623.
Caithamer, D. F., and J. A. Dubovsky. 1996. Waterfowl population status, 1996. U. S. Fish Wildl. Serv.. Washington, DC.
Dahl, T. E. 1990. Wetland losses in the United States 1780’s to 1980’s. U. S. Fish Wildl. Serv., Washington, DC.
Dane, C. W. 1966. Some aspects of breeding biology of the Blue-winged Teal. Auk 83: 389-402.
Duebbert, H. F., and J. T. Lokemoen. 1976. Duck nesting in fields of undisturbed grass-legume cover. J. Wildl. Manage. 40: 39-49.
Kaiser, P. H, S. S. Berlinger, and L. H. Fredrickson. 1979. Response of Blue-winged Teal to range management on waterfowl production areas in southeastern South Dakota. J. Range Manage. 32: 295-298.
Morton, R. A., and J. G. Paine. 1990. Coastal land loss in Texas-an overview. Gulf Coast Assoc. Geolog. Soc. Trans. 40: 685-699.
Oberholser, H. C. 1974. The bird life of Texas. University of Texas Press, Austin..
Rohwer, F. C. 1984. Patterns of egg laying in prairie ducks. Auk 101: 603-605.
Sowls, L. K. 1955. Prairie Ducks. Stackpole Company, Harrisburg, Pennsylvania.
Strohmeyer, D. L. 1967. The biology of renesting by the Blue-winged Teal (Anas discors) in northwest Iowa. Ph.D. Thesis, University of Minnesota, St. Paul.
Weller, M. W. 1979. Density and habitat relationships of Blue-winged Teal nesting in northwestern Iowa. J. Wild. Manage. 43: 367-374.