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Photo by John George
Photo Courtesy of Utah Division of Wildlife Resources
Black Tern
Chlidonias niger
NatureServe conservation status
Global (G-rank): G4G5
State (S-rank): SHB
- Reason: This species formerly was common but now is uncommon and localized in northern Utah at Utah Lake, Great Salt Lake, Pelican Lake, and the Green River. All known nesting records in the state are historical.
External links
General information
The black tern, Chlidonias niger, breeds in Canada and the northern United States, and migrates south to coastal areas of Central America and South America for winter. The species also occurs in Europe, Asia, and Africa. The black tern is now a rare breeder in northern Utah, but it was once more common in the state.
The black tern inhabits marshes, lakes, and rivers, where it nests in areas that have a mixture of vegetation and standing water. Nests of aquatic vegetation are placed on floating vegetation, floating nest platforms, or mud; nests are usually constructed within several feet of open water. A clutch of two or three eggs is laid by the female and then incubated by both parents for about three weeks. Both parents tend the young, which can fly at about three weeks of age. The black tern eats invertebrates, especially insects, and small fishes.
Species range
This species historically nested (and perhaps still nests) in small colonies in the marshes around Utah Lake (Utah County), Great Salt Lake (Box Elder, Davis, and Salt Lake counties), and Pelican Lake (Uintah County), and sandbars in or along the Green River (Uintah County). As a migrant it is known throughout the state.
Migration
Common along coast during migration; migrates along North American west coast mostly April-May and late June-September; along east coast mainly late-August to mid-September and in spring beginning in early April. Strictly a migrant in Mexico where the post-breeding migration extends from July through early November; during the southbound migration birds pass through the interior highlands as well as along both coasts. The spring migration through Mexico is shorter in duration (30 March-2 June), with greatest numbers in April and May, and is almost entirely coastal or offshore (Williams 1983). Fairly common in Puerto Rico late August-early October (Raffaele 1983). Abundant in migration along both coasts of Costa Rica, mid-September to mid-November and late April-early June (Stiles and Skutch 1989). Most arrive in breeding areas in northeastern North America during the first half of May.
Habitat
Breeding sites are in marshland habitat (Woodbury et al. 1949, Hayward et al. 1976). Walters and Sorensen (1983) considered its breeding and migrating habitats in Utah to be marshes and wet hummocks and lakes, reservoirs, ponds, and sewage lagoons. Bee and Hutchings (1942) noted that "the usual nesting sites are on mats of dead rushes in marshes or on grass tufts of inundated marginal lands."
Food habits
On the breeding grounds the black tern is primarily insectivorous, although small crustaceans, spiders and small fishes are also regular food items (McAtee and Beal 1912, Bent 1921). The diet may vary depending on habitat and food availability. Fishes may be an especially important food item at some sites in the northeast. In wetlands, food is captured in the air, at or just below the water surface, and from the surface of emergent vegetation (Goodwin 1960). In the prairies, much of the food is obtained from plowed land and fields of grain (Pittman 1927). Foraging over agricultural land near marshes has also been observed in New York (Morrison pers. comm.). In a sample of 376 feedings of young in different nests at North Pond in New York, Goodwin (1960) found that 41% of the items brought by parents were minnows and 59% were insects, including 45% damselflies. Insects comprised 93.6% of 602 feedings to chicks in Michigan while fishes accounted for just 4.9% (Cuthbert 1954). Although many of the insects could not be identified, damselflies, dragonflies, and mayflies were important food items. In Ontario, Dunn (1979) was unable to identify the majority of 56 food items brought to young, but 13% were minnows and 6% were dragonflies.
Ecology
Gregarious throughout the year. Has been described as a semi-colonial nesting species (Cuthbert 1954, Bergman et al. 1970). Nests may be clumped closely in favorable habitat or more widely scattered in other, perhaps less favorable areas. As is typical of colonial nesting gulls and terns, terns will join together to defend the nesting area from intruders (Cuthbert 1954). Ectoparasites include feather mites and lice (Peters 1936, Perez and Atyeo 1984). A trematode, APORCHIS LARUS, was recorded in Russia (Mirzoeva 1980). The effects of these parasites have not been studied. Black terns are susceptible to avian botulism. A few dead birds have been found in Nevada and Manitoba (Alcorn 1942, Manuwal 1967), but no major die-offs from this disease have been reported. Commonly returns to previous nesting area but also commonly changes sites if conditions become unfavorable. Return rates may vary considerably among specific sites. Stern et al. (1985) found that 67% of recaptured terns nested within the same primary wetlands, while Bailey (1977) and Dunn (1979) reported return rates of 40% and 27% for sites in Wisconsin and Ontario, respectively. These return rates, which are low in comparison with other gulls and terns, may be the result of the relative instability of preferred habitat (McNicholl 1975).
Reproductive characteristics
Most terns in the northeastern United States and Canada return to breeding areas during the first two weeks of May, although birds may arrive in western New York as early as the last week of April (Laughlin and Kibbe 1985, Firstencel 1987, Gerson 1987). Conspicuous aerial courtship displays characterize the courtship period, which begins soon after arrival at the breeding site. In the "high-flight", a group of 2-20 terns ascend together to a great height then split into smaller groups of two or three and descend in rapid glides (Baggerman et al. 1956). During the "fish-flight", a male tern carries a small fish or large insect in its bill and is closely followed by a female as the two fly about the marsh. At the close of this aerial display the male follows the female to a perch and feeds her (Baggerman et al. 1956). In the northeastern United States egg laying begins in late May, but may be initiated as late as the middle of July. Nests with eggs were observed at one site in western New York from 24 May to 12 July (Firstencel 1987). During a 1989 survey of colony sites throughout New York, nests with eggs were observed as early as 25 May and as late as 18 July (Novak 1990). Not known to be double brooded and late nests probably represent renesting attempts. At Rush Lake in Wisconsin, Bailey (1977) observed a trend toward three nesting peaks, one in late May, one in early to mid June, and one in late July. This pattern was attributed to two initial nesting periods characterized by a high degree of synchrony, followed by a period of renesting (Bailey 1977). Baggerman et al. (1956) also reported highly synchronous nesting activity. One to five eggs may be laid, although the normal clutch is usually two or three (Bent 1921). Clutches with four eggs have been reported in only two recent studies (Bergman et al. 1970, Mossman 1980) and are apparently quite rare. Other than Bent (1921), there are no published reports of five egg clutches. Single egg clutches may often be replacement nests or nests where one or more eggs have already been lost (Bent 1921, Cuthbert 1954, Firstencel 1987). In a recent study in Wisconsin, the average clutch size for 41 closely monitored nests was 2.9 (Bailey 1977). Four nests had clutches of two, but no nests contained less than two or more than three eggs. Average clutch sizes reported in other recent studies where nests may not have been monitored as carefully, range from 2.25 to 2.75 (Cuthbert 1954, Goodwin 1960, Bergman et al. 1970, Mossman 1981, Firstencel 1987, Novak 1990). Incubation begins with the laying of the first egg, and eggs require 20-24 days to hatch (Goodwin 1960, Bergman et al. 1970, Bailey 1977). Both sexes incubate (Goodwin 1960). Young are tended by both parents. Chicks are able to swim, walk and run by the time they are two days old (Goodwin 1960). The chicks grow rapidly, doubling their weight in less than three days and quadrupling their weight in less than six days (Bailey 1977). The rate of weight gain slows after the eighth day. In some cases, chicks may be relocated from the nest site to "auxiliary" nests within a few days after hatching (Cuthbert 1954, Firstencel 1987). If disturbance at the nest is minimal, young may remain at the original nest site for as long as 14-25 days, although they hide in the vegetation at the sign of danger and may be found swimming as far as 40 ft from the nest (Cuthbert 1954, Goodwin 1960). The age at fledging is difficult to determine. Bailey (1977) reported fledging at 18 and 19 days for two chicks of known age and suggested that the majority of chicks are flying at 21 days of age with a mean fledging age possibly less than 20 days. Baggerman et al. (1956) and Goodwin (1960) reported fledging at 21 days. Young are fully fledged at about four weeks. Estimates of nest success (expressed as a percentage of nests where at least one egg was hatched successfully) from four nest studies are as follows: 27% (15 of 55 nests) in Ontario, 29% (56 of 192 nests) in Iowa, 34% (13 of 38 nests) in Wisconsin, and 50% (12 of 24 nests) in New York (Dunn 1979, Bergman et al. 1970, Bailey 1977, Firstencel 1987, respectively). There was no obvious correlation between nest success, height of eggs above water, and number of nests per substrate in the Iowa study (Bergman et al. 1970). Survival of young to fledging is difficult to measure because of the mobility of chicks. Bailey (1977) attempted to measure chick survival by placing fencing around nests to prevent young from moving away from the nest site. Just three of 26 (12%) chicks monitored fledged successfully. Sixteen chicks were lost to predation and several chicks died in the pen netting. Fledging success at unfenced nests (perhaps a better representation of fledging success) was estimated at 15-20% (Bailey 1977). Recent surveys have presented estimates of reproductive success based on the number of fledglings produced per egg laid in the colony (Rabenold 1987, Novak 1990). Estimates for three small (less than 10 pairs) colonies in Indiana were 0%, 53%, and 67%, for an overall average of 30% (Rabenold 1987). Estimates also varied widely for 19 sites in New York, from 4% to 38%, with an overall average of 20% (Novak 1990). Mossman (1980) reported a 25% reproductive success based on the ratio of young: adults observed at one study area in Wisconsin. The similarity between reproductive or fledging success rates and nest success (hatching success) supports the observation by Dunn (1979) that most losses occur during the egg stage. Wind and wave action, and storms were responsible for most nest losses in several studies (Bergman et al. 1970, Bailey 1977, Dunn 1979, Faber and Nosek 1985, Chapman-Mosher 1987). Nest losses have also been attributed to egg inviability, predation, muskrat activity, and intraspecific interactions (Bergman et al. 1970, Bailey 1977, Dunn 1979, Firstencel 1987). Has been described as a semi-colonial nesting species (Cuthbert 1954, Bergman et al. 1970). Nests may be clumped closely in favorable habitat or more widely scattered in other, perhaps less favorable areas. As is typical of colonial nesting gulls and terns, terns will join together to defend the nesting area from intruders (Cuthbert 1954).
Threats or limiting factors
Threats include habitat loss (for agriculture, residential, and commercial development), changes in water levels (flooding and draining), and pesticide use.
References
- Biotics Database. 2005. Utah Division of Wildlife Resources, NatureServe, and the network of Natural Heritage Programs and Conservation Data Centers.
- Peterson, R. T., and V. M. Peterson. 1990. A field guide to western birds, 3rd ed. Houghton Mifflin, Boston. 432 pp.
