The black tern can be found from central eastern Alaska, central Manitoba and Ontario south to northern California, Colorado, northern Missouri and Tennessee, also to the lakeshores of northern Ohio, Pennsylvania and New York; winters spent from Surinam to Peru and Chile. Forbush & May, 1955.

Biogeographic Regions: nearctic (Native ); neotropical (Native )

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Breeding

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Breeding

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) BREEDING: British Columbia and Mackenzie east through northern Saskatchewan to Nova Scotia, south locally to southern California, Colorado, Nebraska, southern Illinois, Ohio, Pennsylvania, northern New England (formerly to Missouri and Kentucky); there is a single breeding record for coastal New Jersey. In Old World from northern Europe, Russia, and Siberia south to Mediterranean, Asia Minor, Turkestan, and Caspian and Aral Seas. Nonbreeders occur in summer south on Pacific coast to Panama, and in eastern North America to Gulf Coast (AOU 1983). Sparse and uncommon in northeast and on southern edge of range (Dunn and Agro 1995). See Gerson (1987) for details on distribution and abundance in Canada. NON-BREEDING: in the Americas along both coasts from Panama south to Peru, Surinam, and French Guiana; rare in Brazil, Uruguay, and Argentina (AOU 1983, Dunn and Agro 1995). In the Old World in tropical Africa south to Angola and Tanzania (AOU 1983). Casual in Hawaii.

This bird has an approximate length of 9 to 10.25 inches and a wing spread of about 25 inches. In breeding season, this tern has a black head, neck and underparts with generally dark plumage. In the fall, it becomes lighter with gray wings. The young are a grayish-white color with dark patches on either side of their head. The tail is small and is only slightly notched compared with other terns. Its bill is very sharp and slender, shorter than the head; wings are long and pointed; and feet are webbed only to the middle of the toes. Forbush & May, 1955.

Average mass: 60 g.

Length: 25 cm

Weight: 65 grams

• Terrestrial
• Freshwater
• Marine

The preferred summer habitats of the black tern are inland marshes and sloughs with fairly dense cattail or other marsh vegetation and pockets of open water. These wetlands are often shallow in nature. Its winter home is on the coasts of South America and it appears in considerable numbers on the South Atlantic and Gulf coast of North America during its periodic migrations, but all other times it a bird of the interior. Forbush & May, 1955;   http://www.npsc.nbs.gov/resource/distr/others/nddanger/species/chlinige.htm 

Terrestrial Biomes: savanna or grassland

Aquatic Biomes: lakes and ponds; rivers and streams

Comments: BREEDING: marshes, along sloughs, rivers, lakeshores, and impoundments, or in wet meadows, typically in sites with mixture of emergent vegetation and open water. Cattails, bulrushes, burreed, and/or phragmites commonly are present in nesting areas (Bent 1921, Cuthbert 1954, Goodwin 1960, Bailey 1977, Firstencel 1987, Novak 1990). Nested in greatest numbers where emergent vegetation and open water are in an approximately 50:50 ratio (Weller and Spatcher 1965). In Wisconsin, Tilghman (1979) found nests in areas where emergent marsh coverage was 51-75%. In British Columbia, nests occurred in areas with 33% open water, 42% matted vegetation, and 25% standing vegetation (Chapman-Mosher 1987).

Nests may be placed in a variety of vegetative situations, from dense stands of emergent vegetation to open water (Bergman et al. 1970, Novak 1990), but moderate or sparse vegetation appears to be preferred (Cuthbert 1954, Weller and Spatcher 1965, Dunn 1979). Nests are typically located in shallow water, close to open water or openings in stands of emergent vegetation. The range of water depths reported varies from a "few inches" (Bent 1921) to 1-2 m (Dunn 1979). Bailey (1977) found that nests were never more than 1-2 m from open water. Dunn (1979) and Cuthbert (1954) reported the average distance to open water as 4 m and 4.6-6.1 m, respectively. One site in New York where 9 nests averaged 25.3 m from open water (Novak 1990) appears to be the exception, although Firstencel (1987) also reported nests located "deep within the cattails".

Nests on heap of floating vegetation, on old muskrat house, old grebe or coot nest, or on floating wood (Cuthbert 1954, Bergman et al. 1970, Bailey 1977, Dunn 1979, Novak 1990). Floating mats of muck or algae, mud flats, and mud mounds and islands also have been used as nest substrates (Cuthbert 1954, Bailey 1977, Dunn 1979, Connell and Norman 1989, Novak 1990). The nest consists of a small gathering of aquatic vegetation with a simple, cup-like bowl (Weller and Spatcher 1965, Bailey 1977). Although the first egg may be laid before the nest takes shape, vegetation gathered at the nest site is added throughout the incubation period (Baggerman et al. 1956, Goodwin 1960, Bailey 1977). Will nest on artificial nesting platforms (Muller et al. 1992). The height of eggs above water has often been measured. Although the height may vary based upon substrate chosen for nesting, the eggs are rarely located more than a few centimeters above the water level. The range reported in the literature varies from an average of 2.3 cm for 23 nests on dead floating vegetation in Iowa (Bergman et al. 1970), to 20.0 cm for two nests located on mud islands in New York (Firstencel 1987). The latter is clearly the exception as 8.6 cm for seven nests on old muskrat houses is the next highest figure reported (Weller and Spatcher 1965).

Exposed perches, such as channel marker posts, floating logs, fallen trees, and old dock or fence posts are used as stations for feeding recently fledged young, resting, and copulation (Cuthbert 1954, Novak 1990).

NON-BREEDING: pelagic waters as well as seacoasts, bays, estuaries, lagoons, lakes, reservoirs, and rivers (Eisenmann 1951, Zaret and Paine 1973, van Halewijn 1973, Spaans 1978, AOU 1983, Williams 1983); prefers sheltered offshore waters and bays, comes to shore chiefly during migrations (Stiles and Skutch 1989).

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

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.

During the breeding season, these birds eat insects and freshwater fish such as damselflies and dragonflies, grubs and larvae and other small mollusks. The rest of the year, meals are usually of small marine fish. Some examples are anchovies, silversides and plankton. The average fish taken during breeding season is 2.5 to 3.0 cm and 3 grams. Dunn & Argo, 1995.

Comments: 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.

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

Comments: Relatively abundant throughout most of its range.

Unknown

Comments: No available figures.

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).

Average lifespan

Status: wild: 101 months.

The black terns's courtship ritual is elaborate with much flying. Males often fly with fish in their mouth to attract females. They nest in small colonies in upland marshes and sloughs. Their nests can be found on muskrat bouse or floating masses of dead plants, usually over water 4 to 34 inches deep. The typical nest has 3 eggs that are laid from May to early August. Incubation lasts 22 days. The successful hatching rates of nests is very low because of predation and other disturbances. The young terns that do hatch leave the nests very early often swimming first, but flying within 24 days. Black terns do not breed until fully mature at two years of age.   http://www.npsc.nbs.gov/resource/distr/others/nddanger/species/chlinige.htm)

Average time to hatching: 21 days.

Average eggs per season: 3.

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).

As of February 28, 1996, the black tern is no longer a candidate species. There is no legal requirement to help candidate species, however it is in the spirit of the Endangered Species Act to consider these species as having significant value and to be worth protecting. Candidate species are species which may warrant official listing as endangered or threatened; however data are not conclusive at the present time. The continuing loss of habitat due to wetland drainage is the main reason for the decline in black tern populations. Reduced hatching success in the midwestern United States may be due to agricultural pesticides. It has been recommended that marshes and sloughs used annually by black terns be protected for the birds and other wetland values. Black terns are a species of special concern in Michigan.   http://www.npsc.nbs.gov/resource/distr/others/nddanger/species/chlinige.htm.

US Migratory Bird Act: protected

US Federal List: no special status

CITES: no special status

State of Michigan List: special concern

IUCN Red List of Threatened Species: least concern

Regular passage visitor and winter visitor.

Least Concern.

Canada

Rounded National Status Rank: N4B - Apparently Secure

United States

Rounded National Status Rank: N4B - Apparently Secure

Rounded Global Status Rank: G4 - Apparently Secure

Reasons: Widespread distribution and relatively abundant, but habitat alteration and degradation threaten the species. Although it is not federally listed, the black tern has special status in many of the states within its breeding range. In the northcentral states, Illinois, Indiana, and Ohio list the black tern as an endangered species while Iowa, Michigan, and Wisconsin list it as special concern. In the Northeast, the black tern is listed as threatened in Pennsylvania, special concern in New York, and is on a "watch list" in Maine. New York State is in the process of revising its state lists and it is likely that the status of the black tern will be changed to endangered or threatened. The species has no special protection status in the Great Plains states, and in the West, it is in the protected category in Idaho and Montana. The black tern was recently proposed for threatened listing in Canada (Gerson 1987).

Global Short Term Trend: Decline of 50-70%

Comments: Decline is virtually range-wide, though greater in the U.S. than in Canada. Gerson (1987) surveyed provincial and state biologists regarding current status in various regions of North America and arrived at the following conclusions: (1) the species is widespread and common throughout much of Canada, (2) has a limited distribution in the northwestern United States, but may be locally common, (3) is widespread and common in the northcentral United States (including North and South Dakota), and (4) becomes local and rare in the northeastern United States. In contrast to this subjective, and generally positive assessment of status, quantitative measures indicate the species has been experiencing a major population decline, virtually rangewide, for at least the past 20 years. North American Breeding Bird Survey (BBS) data provide a quantitative measure of population trends for the period 1966-1989 (Droege and Sauer 1990, Sauer and Droege 1992). During this period the breeding population in North America has declined at an annual rate of 5.6% per year, for an overall population decline of 71.8%. The decline has been greater in the U.S. (8.2% per year, overall 84.8%) than in Canada (4.8% per year, 66.1% overall). Despite decline, still widespread and common in Canada (Gerson 1987). Of 12 states and provinces with sufficient sample size to determine population trends on the BBS, only British Columbia and Alberta showed an increasing trend and Alberta, Iowa, Michigan, Minnesota, North Dakota, and Ontario showed significant declines. Declined in California and the north-central U.S. from 1966 to 1985 (USFWS 1987, Hands et al. 1989); also has declined in New York (Carroll 1988, Muller et al. 1992).

Degree of Threat: B : Moderately threatened throughout its range, communities provide natural resources that when exploited alter the composition and structure of the community over the long-term, but are apparently recoverable

Comments: Decline may be due to loss of freshwater marsh habitat (including losses through invasion of exotic plants and due to drought), human disturbance of nesting sites, pesticide use, and problems along the migration route or in winter range (Muller et al. 1992, Novak 1992). Loss of breeding habitat has undoubtedly been a major contributing factor in the decline. Since European settlement, 54% of all wetlands in the United States have been lost (Tiner 1984). The loss of 4.75 million acres of palustrine emergent wetlands during the mid-1950s to mid-1970s has probably had an especially significant effect on populations. Similar losses of wetlands have been documented in Canada. A decline of 9 to 61% of the original wetland area has been documented for portions of some prairie provinces while 70% of southern Ontario's original wetlands have been converted to other uses, particularly agriculture (Gerson 1987). Along the St. Lawrence River, 42% of the wetlands from Cornwall, Ontario to Matane, Quebec were lost between 1945-1975 (Gerson 1987). Wetlands in the United States and Canada continue to be threatened despite efforts to curb their loss. In addition to the outright loss of wetlands, successional change, management practices, and degradation of water quality have altered the character of some wetlands, thus rendering them less suitable as breeding habitat. Loss of high quality habitat through successional changes was noted at several historical colony locations during a recent survey in New York (Novak 1990). The quality of some remaining wetlands may be reduced because of pollution and runoff associated with increased development in the vicinity of wetlands (Gerson 1987). Wetlands in Central and South America are also threatened by land use changes and degradation of water quality (Gerson 1987). In Panama, the introduction of peacock bass (Cichla ocellaris), has resulted in the decline of an important native food fish (Zaret and Paine 1973). Purple loosestrife (Lythrum salicaria), an invasive, wetland exotic that out-competes native emergent species, has drastically altered the character of wetlands in parts of the northeastern United States. The changes wrought by this plant, along with changes brought about in the attempt to control it, have altered the character of some wetlands. Loosestrife may have been a factor in the decline at Montezuma National Wildlife Refuge in New York where high quality nesting habitat is currently lacking (Novak 1990). In addition to direct loss of habitat due to wetland destruction, one of the indirect effects of wetland loss is that larger rivers experience more pronounced and frequent flooding, and riverine marshes become unreliable nesting sites. The probability of flooding on the Minnesota River during tern nesting season was 70% based on 1982-1991 data (which includes drought years of 1987-1989) (Moen 1991). The nest, a floating structure located close to open water and with eggs placed just a few centimeters above water level, predisposes this species to some natural sources of nest failure. Both Bailey (1977) and Rabenold (1986) attributed major nest failures to the flooding of nests caused by elevated water levels resulting from heavy rains. Goodwin (1960) noted that some nests were so flimsy that storms caused them to submerge. Wind and wave action has also been noted as a major cause of nest failure (Cuthbert 1954, Bergman et al. 1970). Relatively low nesting and fledging success may be typical in regions where spring and summer storms occur regularly. The impact of various types of human disturbance on nesting is not well documented. Waves caused by boats may represent a major source of egg and chick mortality at many sites in New York and elsewhere. Boat wakes were observed swamping logs both in the open and within moderately dense cattails at one site in New York and fledging success rates were comparatively low at several sites where boat traffic was heavy (Novak 1990). In New York, boat traffic per se did not have a visible influence on nearby nesting birds (Muller et al. 1992). Organochlorines including PCBs, DDT, DDE, and Dieldrin were detected in eggs collected during several studies in the midwest (Faber and Hickey 1973, Mossman 1980, Faber and Nosek 1985). PCBs, DDE, Hexachlorobenzene, and Octachlorostyrene (an industrial pollutant) were found in eggs and a chick collected from a site on Lake Ontario in western New York (Firstencel 1987). Significant changes in eggshell thickness were also noted in one study (Faber and Nosek 1985). Accumulated organochlorine contamination has been linked to lowered reproductive success and developmental problems in other tern species (Hays and Risebrough 1972, Fox 1976, Gerson 1987). These results suggest that an accumulation of environmental contaminants may be contributing to reduced reproductive success throughout various parts of the breeding range. It is suspected that many of the contaminants may be accumulated while terns are in migration or on their wintering grounds (Faanes 1979, Faber and Nosek 1985, Firstencel 1987). The use of pesticides can also affect food supplies by depressing prey for populations breeding near agricultural areas. Three of 38 (8%) nests and 16 of 26 (61.5%) penned young were taken by predators at one study site in Wisconsin (Bailey 1977), but predators responsible for these losses were not identified. Chapman-Mosher (1987) reported the loss of 8.6% of nests to predation. The great blue heron (Ardea herodias) and northern harrier (Circus cyaneus) have been observed taking terns (Chapman and Forbes 1984, Maxson 1989). A host of other potential predators have been observed in or near nesting colonies and are suspected of regular or occasional predation on eggs or chicks. Suspected predators include great horned owl (Bubo virginianus), black-crowned night heron (Nycticorax nycticorax), American crow (Corvus brachyrhynchos), water snake (NATRIX SIPEDON), snapping turtle (Chelydra serpentina) and ring-billed gull (Larus delawarensis) (Cuthbert 1954, Goodwin 1960, Faber and Nosek 1985, Firstencel 1987, Novak 1990).

Restoration Potential: The relatively low reproductive output appears to be due, at least in part, to storms, wind, and waves which destroy nests. Without a better understanding of other causes of low reproductive success which may include contaminant accumulation, predation and human disturbance, and factors affecting the tern away from the breeding grounds, it is difficult to speculate on the likelihood that this species will recover from the widespread population decline it is currently experiencing. However, there are several reasons to believe that if prompt actions are taken, some degree of recovery is possible (Novak 1992).

Renesting after initial nest failure has been reported by various authors (Bergman et al. 1970, Bailey 1977, Novak 1990) and may partially offset losses suffered during initial nest failures. Nesting area choice may vary from one year to the next depending upon changing water levels, nest substrate availability, and vegetation density (Weller and Spatcher 1965, Bailey 1977, Dunn 1979). Because of this sensitivity to habitat change, the tern is not tied to traditional nesting areas if the habitat deteriorates, and may colonize newly created, suitable habitat. For example, in Nova Scotia, terns nested for the first time in the 1970s in new water impoundments (Gerson 1987). The tern can use a variety of nest substrates and is not restricted to wetlands with specific vegetation types. This adaptability reduces the chances of habitat limitation from the lack of available nest sites. Nest success was as high as 50% in one recent study (Firstencel 1987). Although such high nesting success seems to be the exception, it indicates that the tern is capable of achieving high reproductive output under some conditions. Based on banding records, terns may live as long as eight years (Clapp et al. 1982), perhaps longer, and therefore could benefit greatly from several successive years with high reproductive success.

The North American Waterfowl Plan, No-Net-Loss of Wetlands policy, and the "Swampbuster" provision of the Food Security Act of 1985 (P.L. 99-198, commonly known as the 1985 Farm Bill) which prevents farmers who drain wetlands from receiving agricultural subsidies and other economic benefits of the bill, can all help to curtail the destruction of wetlands, essential habitat for terns.

Despite the fact that the tern is currently experiencing a widespread population decline, it has a North American breeding distribution which extends nearly continent-wide. The tern remains widespread and fairly common in much of the Prairie province region and parts of the northcentral and western United States (Gerson 1987, Hands et al. 1989). The tern has actually increased in New Brunswick and began nesting in Nova Scotia in the 1970s (Gerson 1987). The current distribution and population ensures that in most regions, at least for the near future, terns should be able to recolonize traditional or restored sites and colonize newly created habitats.

Relative to overall state populations, large numbers of black terns breed on government managed wetlands in Wisconsin (Mossman 1982), Michigan (Adams 1988, Einsweiler 1988), New York (Novak 1990), Vermont (Laughlin and Kibbe 1985), Maine (Pierson 1983, Gibbs and Melvin 1989), Minnesota (Eliason 1989, Faber 1990, Dulin 1990) and perhaps other states as well. Management of wetland complexes has been employed successfully with waterfowl for many years (Fredrickson and Taylor 1982). Management of wetlands to benefit terns should be possible in many cases and may be largely compatible with practices currently focusing on waterfowl. If human disturbance is determined to have adverse effects on nesting terns, education and restrictions on human access may be employed to eliminate or reduce impact. The ability of terns to use artificial nesting platforms may facilitate restoration efforts (Novak 1992).

Preserve Selection and Design Considerations: Habitat preservation alone will probably not ensure the recovery of the tern in regions where population declines have been substantial (Novak 1992). Successional processes, changes in water levels, invasion by exotic wetland plants, and degradation of water quality, which may alter both the food web and the vegetative structure of the wetland, have the potential to render wetlands unsuitable for use. Management of wetlands will be required to maximize their value to terns. The hemi-marsh stage (Weller and Frederickson 1973), where open water and emergent vegetation are present in approximately equal amounts, is widely recognized as preferred nesting habitat. Development of agricultural lands surrounding wetlands supporting terns should be discouraged because the terns may use the fields for foraging. Maintenance of buffer zones to block siltation, pesticide, and fertilizer runoff to the wetlands may also be desirable. In Iowa, nested mainly in marshes larger than 20 ha; used smaller marshes (5-10.9 ha) only when they were part of a larger wetland complex (Brown and Dinsmore 1986).

Management Requirements: The range of options available for the management of specific sites to benefit terns will vary with the degree to which water levels can be regulated at the site, the size and nature of the site, and the degree to which factors such as predation and disturbance are a problem at the site (Novak 1992). Potential management procedures for a sample of sites of different types are as follows. Changing the water level in marshes can greatly affect use of the marsh; hence the species responds to water management.

In managed inland marsh complexes managers usually have some ability to regulate water levels in various impoundments or pools. Management procedures must vary from site to site depending upon a variety of factors including: size of the area, number of pools in which water levels can be regulated, sources of water for altering water levels, natural precipitation rates, muskrat (Ondatra zibethica) populations, and other management goals to be considered. In general, management should be aimed at maintaining one or more large impoundments in the hemi-marsh stage for as long as possible. To avoid flooding of nests, water levels in impoundments should be stabilized from May to July (Novak 1992). Pools in other stages of marsh succession may be used for foraging, but will be less preferred for nesting. Periodic draw-downs and re-flooding, and management of the muskrat population through regulated trapping will be the primary management tools at these sites.

At most natural areas of shallow marsh associated with large lakes, ponds, and rivers there will be no practical means of regulating water levels. Where terns nest in patches of rushes, cattail, or other emergent vegetation (Goodwin 1960, Bailey 1977), maintenance of these "islands" of emergent vegetation is recommended. Because these sites are associated with larger, more open bodies of water, they may be used extensively for boating, fishing, and other forms of water-based recreation. Repeated disturbance and wave action may pose serious threats to reproductive success at these sites. Educational efforts and/or restricting access may be effective at some sites. The degree and type of disturbance may influence the best strategy to be utilized. At colonies with excessive disturbance close to nest sites, restricting entry during the breeding season may be the only option available. In other cases, establishing no wake zones or posting signs to discourage visitors may be effective. However, signs may also draw attention to colony sites and may be ineffective when enforcement is not possible (Connell and Norman 1989). In these situations, efforts to educate the public may be the most reasonable method of reducing disturbance. Placement of artificial nest platforms to encourage terns to nest in areas where disturbance is less of a problem, may provide a further management tool in some instances (Muller et al. 1992). Terns used five of ten artificial nest platforms at one study site in Minnesota (Hands et al. 1989) and nearly 100% of the platforms placed at a managed area in Michigan in 1990 (Scharf, pers. comm.). Although the value of artificial nesting platforms has not yet been demonstrated, they may provide a safer, more stable substrate than naturally floating objects, may be useful in luring terns to nest in more protected locations, and may provide suitable nest substrates in wetlands where natural substrates are in short supply. In any of the above situations, the result may be higher reproductive success. One piece of anecdotal evidence of potential platform benefits comes from a 1990 study in Minnesota (Faber 1990) where eight out of nine nesting attempts on platforms successfully hatched at least one young. In contrast, only 36 of 69 natural nests were successful. However, it is also possible that in some cases platforms may simply lure terns to nest in unproductive sites.

It is possible that extensive predation may pose a serious threat to nesting success at some colonies. Decisions regarding predator management should be made only after identification of specific predators involved, documentation of the extent and effect of the predation, and careful consideration of alternatives and the likelihood of success in ameliorating the situation.

There is a need to incorporate management planning in overall plans for all managed wetlands with suitable tern habitat within the current or historical breeding range in the northeastern and northcentral United States.

Management Research Needs: The list of research and management needs is extensive (Novak 1992). No priority is intended by the order of these needs.

1. Determine the causes of nest failure and mortality in all age classes at nesting colonies in the northeastern and northcentral United States.

2. Evaluate the effectiveness of artificial nest platforms for increasing nesting success or population densities. Emphasis should be placed on sites where natural nest substrates appear to be limited or where terns may be encouraged to nest in areas where disturbance may be reduced.

3. Determine nest site fidelity of adults and philopatry of young.

4. Determine the effects of contaminants on nesting success, chick development, and juvenile and adult survival. Assuming significant negative effects are identified, determine how widespread the effects are across the range.

5. Assess the effects of human disturbance. In the northeastern United States, emphasis should be placed on the impact of boating and other water based recreational activities on nesting colonies.

6. Assess the factors affecting renesting after initial nest failure and determine the productivity resulting from renesting attempts in comparison to initial attempts.

7. Determine foraging range and habitat use at important breeding sites in the northeastern and northcentral United States.

8. Develop or improve the capability to regulate water levels and manage habitat for the benefit of breeding terns at key wetlands in the northeastern and northcentral United States.

9. Determine the movements, mortality rates, causes of mortality, and feeding habits of adults and subadults during the nonbreeding season. Identify migration routes and critical habitats along migration pathways which may be in need of protection. Determine the extent of the winter range. Identify critical overwintering sites and determine faithfulness to these sites.

Global Protection: Few to several (1-12) occurrences appropriately protected and managed

Comments: Protected in state and federal wildlife areas.

Needs: In states and provinces where the tern is endangered, threatened or declining rapidly, every effort should be made to protect any colony sites currently in use regardless of the size of the site or the number present. Historical sites which still have five or more hectares of suitable habitat should be protected as well. Preservation of these wetland areas by acquisition, lease, conservation easements, or management agreements should be actively pursued. In regions where terns are less severely threatened, large (> 11 ha) wetlands and sites which harbor substantial populations should be similarly protected. Enforcement of state and federal wetlands regulations and a greater public recognition of wetland values also would help in the effort to preserve habitat.

Humans approaching the nest of a black tern may come with a serious headache because these birds have been known to attack humans that come too close. Pearson, 1936.

Black terns feed on insects that may be potentially harmful to humans.

Stewardship Overview: Black terns nest on floating plant matter. The instability of their nests leaves them vulnerable to storms, wave action, and rapid water level changes such as occur in floods. Their reproductive success fluctuates widely from year to year, depending on weather and water levels. Their success depends on relatively long lives, and flexibility in choice of nesting area. This makes protection difficult, because terns may use a particular marsh only occasionally, but when they do, it may be their only chance of success. Managed wetlands, where water levels and vegetative cover can be manipulated are therefore the easiest places to reliably protect nesting habitat. In general, protection of remaining wetlands is the most important protective action necessary to maintain this inland tern (Novak 1992).

Comments: Two subspecies are recognized, New World surinamensis and niger of Eurasia.