Studies of Waterfowl in British Columbia Green-Winged Teal

Abstract

The migrations of the Pacific Coast population of Anas carolinensis parallel in time and space those of Anas acuta. Both use the same migration routes along the coast and along the main north and south river systems of the interior. So also both nest more commonly in Alaska than elsewhere. The peak of the spring migration usually is reached in late March or early April; the peak of the autumn migration usually is in late October and early November. A relatively large number normally winter on the Coastal Plain. Very few winter in the interior. Study of banding data reveals that (1) autumn transients through the Coastal Plain follow the coast route south to the mouth of the Columbia River and beyond through Oregon and California, rarely passing east of the High Sierras, (2) few individuals among the population following interior routes reach the coast, the tendency being to swing eastward to the Great Basin. The two main flyways through British Columbia, one on the coast the other through the interior, differ in at least one important respect, viz., along the interior route are many more or less isolated areas of suitable nesting grounds whereas on the coast there are none. A small nesting population, fluctuating annually in numbers, is widely distributed through the interior, the center of abundance being the Cariboo Parklands—the term abundance being used in a relative sense. Actually the population is small and dispersed. In the year 1938 a total of only 17 broods was counted on a study area of 60 sq. mi. containing a high average of highly productive waterfowl territory. Smaller counts were made here in each of the years following 1938. Egg-laying begins in May; there is some loss of early clutches through crow predation compensated for by later, and usually more successful, nesting. It is not unusual for females to be incubating a second clutch of eggs in early July. Nest sites are in dry places nearly always adjacent to a small pond or marsh in the grasslands. The earliest and latest dates for records of downy young are June 20 and Aug. 10. The average number of young in 48 broods counted in July, and 17 broods counted in August, was the same viz. 6.2. This high survival rate may be attributed in part to the spirited defense of young commonly practised by the female parent. Adult males in small number may associate on a common loafing place during the egg-laying period, and for a week or so after incubation has started. Later they retreat to marsh habitat and begin the yearly molt. Full eclipse of the body plumage usually is attained prior to renewal of the flight feathers. The molt from eclipse to nuptial dress is not completed until late October. The first adult plumage of young males is not fully attained until January. The sex ratio appears to maintain a not unfavorable biological balance—a total of 4264 banded green-winged teal was composed of 2225 males and 2039 females. The food range of the species is not extensive. Seeds, chiefly those of aquatic plants, were present in the stomachs of all 69 adults examined, and in many constituted the bulk of food eaten. Insects are second, miscellaneous animals third, in importance. The green-winged teal is a valuable game species; none of its habits is detrimental to agricultural or other human interests.

Waterfowl Sex Ratios during Spring in Washington State and Their Interpretation

“…This later migration of juveniles has been noted in redwings (Agelaius phoeniceus) (Allen, 1914), buffle-head (Munro, 1942) and other species, and very likely contributed to the apparent sex-ratio variation in the common golden-eye, buffle-head and common merganser in our study. Although juvenile males of these species were separated whenever possible, some were probably confused with females.…”

The North American Perching and Dabbling Ducks

“…Gadwalls exhibited a similar pattern of habitat use by pairs and broods. Munro (1949) noted that wigeon prefer to nest around certain lakes or marshy sloughs that are surrounded by dry Carex meadows, in which the nests are placed. Unlike most dabbling ducks, females and young frequent the open water of marshy ponds, lake bays, or marsh-edged rivers, with this preference for open water perhaps related to the commensal foraging relationship between wigeons and diving waterfowl.…”

“…He found that 81 percent of 21 nests were in Juncus cover, while the rest were in mixed prairie or weeds. Munro (1949) also stated that nests are frequently placed in sedge meadows, and Phillips (1924) mentioned that the nest is often located at the base of a tree. Wishart (1983a) noted that 80 percent of the 30 nests he studied in Saskatchewan were under dense stands of shrubs.…”

“…To a much greater extent than any other North American surface-feeding duck, the American wigeon is a grazing bird and one dependent on the vegetative parts of aquatic plants. Animal materials play a very small role in adult food consumption, although they are the prime food of ducklings (Munro, 1949). In most areas, wigeon grass and pondweed seeds and vegetative parts are prime components of the wigeon's diet (Martin, Zim, and Nelson, 1951), supplemented by a large variety of other, mostly freshwater, aquatic plants.…”

“…During spring migration, wigeon usually move north in small groups. Munro (1949) mentioned that spring flocks often numbered ten or fewer birds. Wigeon often mingle with gadwalls at this time, as well as with coots and diving ducks, and they may try to steal and eat green vegetation that the coots and diving ducks bring up from below.…”