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unpublished data of E. R. Loos and F. C. Rohwer indicate that incubation in Blue-winged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) |
