Black Tern - Chlidonias niger
State Rank Reason (see State Rank above)
Species has a small breeding population size and negative short-term population trends.
- Details on Status Ranking and Review
ScoreC - 250-1,000 individuals
Comment95 pairs documented in 2009 and 73 pairs documented in 2010 without all potential suitable nesting habitat being surveyed in either year puts total number of breeding individuals in the 250 to 1,000 individual population size class.
ScoreG - 200,000-2,500,000 km squared (about 80,000-1,000,000 square miles)
Comment380,531 square kilometers based on Natural Heritage Program range maps that appear on the Montana Field Guide
Area of Occupancy
ScoreE - 100-500 km squared (about 25,000-125,000 acres)
Comment326 square kilometers based on Species Occurrence polygons with known breeding activity in the Heritage Program database.
ScoreE - Relatively Stable (±25% change)
CommentWetland habitats within the range of the species in Montana are within +/- 25% of pre European levels.
ScoreD - Declining. Decline of 10-30% in population, range, area occupied, and/or number or condition of occurrences
CommentBBS data for Montana is of low credibility at -2.3% per year or -26% per decade. BBS trend data of moderate credibility across Northern Rockies show an insignificant decline of -2.2% per year over last 10 years. Prairie Potholes shows a significant -3.8% decline per year over past ten years.
ScoreF - Widespread, low-severity threat. Threat is of low severity but affects (or would affect) most or a significant portion of the population or area.
CommentAltered hydrology, nest site disturbance, and climate change related drought all represent threats to Montana populations.
SeverityLow - Low but nontrivial reduction of species population or reversible degradation or reduction of habitat in area affected, with recovery expected in 10-50 years.
CommentIf water levels are maintained then species should recover or remain stable relatively quickly, certainly within 10-50 years.
ScopeModerate - 20-60% of total population or area affected
Comment20-60% of wetland breeding habitats likely to be affected by ongoing drought and climate change.
ImmediacyModerate - Threat is likely to be operational within 2-5 years.
ScoreB - Moderately Vulnerable. Species exhibits moderate age of maturity, frequency of reproduction, and/or fecundity such that populations generally tend to recover from decreases in abundance over a period of several years (on the order of 5-20 years or 2-5 generations); or species has moderate dispersal capability such that extirpated populations generally become reestablished through natural recolonization (unaided by humans).
ScoreB - Narrow. Specialist. Specific habitat(s) or other abiotic and/or biotic factors (see above) are used or required by the Element, but these key requirements are common and within the generalized range of the species within the area of interest.
CommentNarrow Specialist. Species is dependent on large or small wetland complexes with floating vegetation for nesting.
Raw Conservation Status Score
3.5 – 0.5 (population size) + 0.0 (Geographic Distribution) - 0.25 (short-term trends) + 0.0 (threats) = 2.75
How Scores are Calculated
The head and body of breeding Black Terns are black, fading to gray on the rump. The undertail coverts are white. The upper surface of the wings and tail are dark gray, and the wing linings are pale gray. The leading margin of the wing from the body to the first digit is white. The bill is black and the feet are a dark reddish-purple (Goodwin 1960, Farrand 1983). Females are somewhat duller black than males, but this difference is often difficult to distinguish in the field (Goodwin 1960). Black Terns begin their prebasic (postbreeding) molt in late June when eggs begin to hatch. White feathers appear first around the eyes and cheeks, then on the forehead, neck, throat and breast, and finally on the abdomen. Heavily molting adults take on a peculiar, piebald appearance. The prebasic molt is completed during fall migration (Goodwin 1960). In basic (winter) plumage, the underparts are pure white except for a small, dark patch on each side of the breast. The back becomes a shade of gray similar to the wings and tail. A blackish cap joins black ear coverts on the otherwise white head (Goodwin 1960, Farrand 1983). The juvenile plumage is similar to the basic plumage, but the feathers of the back are darker and the wing coverts and cap are barred and scalloped brown (Goodwin 1960, Farrand 1983). The total length of adults is 23 to 26.5 cm (9 to 10.5 inches).
Vocalizations include shrill, somewhat metallic alarm notes, described as "kik" or "keek", depending upon intensity and level of motivation, and a complex of contact calls described as "kyew", followed by one to four additional syllables, as "kyew-dik", "kyew-dik-ik", etc. (Goodwin 1960). The "kik" call commonly serves as a signal of impending danger in the nesting area. It may also be given during the ascent portion of the courtship flight. The "keek" call is similar to, but more shrill and forceful than, the "kik" call, and is given during aggressive attacks on enemies in close proximity to the nest. The frequency of repetition increases as they become more aggressive. The "kyew" calls are given as parents approach and leave the nest, during foraging flights, by adults accompanied in flight by young, by parents calling to young at or near the nest, by parents at the nest during incubation, brooding and feeding, and during the courtship flights (Goodwin 1960).
Black Tern eggs are ovate with a tendency toward ovate-pyriform (Bent 1921). Ground color varies from dark olive to light buff with markings of dark brown and gray. Markings vary from small dots and scrawls to very large blotches and are often particularly heavy around the larger end of the egg (Goodwin 1960). The average dimensions for 122 eggs in the U.S. National Museum were 34 x 24 mm (Bent 1921).
The distinctive black head and underbody, with gray wings, back, and tail easily distinguishes this species from any other tern species. Their size is also a key to recognition. They are very small compared to other tern species in the state. Only the Interior Least Tern (Sterna antillarum athalassos) is of similar size. Color will preclude any misidentification between these two species.
Summary of Observations Submitted for Montana
Number of Observations:
(Click on the following maps and charts to see full sized version)
Map Help and Descriptions
(direct evidence "B")
(indirect evidence "b")
No evidence of Breeding
(regular observations "W")
(at least one obs. "w")
(Records associated with a range of dates are excluded from time charts)
Little information is known about Black Tern migratory patterns in Montana. They are more likely to move north from wintering locations through the interior of the U.S. (Dunn and Argo 1995), so early sightings should occur in southern portions of the state. Migrating Black Terns have been observed just north of Dillon as early as April. However, the majority of spring migration observations have been in May and June. Black Terns have been observed in transit in July and August albeit fewer observations, probably due to peak breeding. The latest recorded observation was in September near Medicine Lake National Wildlife Refuge in Sheridan County (Lenard et al. 2003). Migration in fall is less concentrated through the interior of the country as birds also move to coastal areas (Dunn and Argo 1995).
Black Tern breeding habitat in Montana is mostly wetlands, marshes, prairie potholes, and small ponds. However, several locations are on man-made islands or islands in man-made reservoirs. Across all Montana sites where Black Terns are present, approximately 30%-50% of the wetland complex is emergent vegetation. Vegetation within known breeding colonies includes alkali bulrushes, canary reed-grass, cattail spp., sedge spp., rush spp., reed spp., grass spp., Polygonum spp., Juncus spp. and Potamogeton spp., indicating a wide variety of potential habitats are usable by Black Terns. Water levels in known breeding localities range from about 0.5 m to greater than 2.0 m with most having depths between 0.5 m and 1.0 m (MTNHP 2003).
Ecological Systems Associated with this Species
- Details on Creation and Suggested Uses and Limitations
How Associations Were Made
We associated the use and habitat quality (high, medium, or low) of each of the 82 ecological systems mapped in Montana for
vertebrate animal species that regularly breed, overwinter, or migrate through the state by:
- Using personal observations and reviewing literature that summarize the breeding, overwintering, or migratory habitat requirements of each species (Dobkin 1992, Hart et al. 1998, Hutto and Young 1999, Maxell 2000, Foresman 2001, Adams 2003, and Werner et al. 2004);
- Evaluating structural characteristics and distribution of each ecological system relative to the species’ range and habitat requirements;
- Examining the observation records for each species in the state-wide point database associated with each ecological system;
- Calculating the percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system to get a measure of “observations versus availability of habitat”.
Species that breed in Montana were only evaluated for breeding habitat use, species that only overwinter in Montana were only evaluated for overwintering habitat use, and species that only migrate through Montana were only evaluated for migratory habitat use.
In general, species were associated as using an ecological system if structural characteristics of used habitat documented in the literature were present in the ecological system or large numbers of point observations were associated with the ecological system.
However, species were not associated with an ecological system if there was no support in the literature for use of structural characteristics in an ecological system, even if
point observations were associated with that system.
High, medium, and low habitat quality was assigned based on the degree to which the structural characteristics of an ecological system matched the preferred structural habitat characteristics for each species in the literature.
The percentage of observations associated with each ecological system relative to the percent of Montana covered by each ecological system was also used to guide assignments of habitat quality.
If you have any questions or comments on species associations with ecological systems, please contact Bryce Maxell at firstname.lastname@example.org
or (406) 444-3655.
Suggested Uses and Limitations
Species associations with ecological systems should be used to generate potential lists of species that may occupy broader landscapes for the purposes of landscape-level planning.
These potential lists of species should not be used in place of documented occurrences of species (this information can be requested at: http://mtnhp.org/requests/default.asp
) or systematic surveys for species and evaluations of habitat at a local site level by trained biologists.
Users of this information should be aware that the land cover data used to generate species associations is based on imagery from the late 1990s and early 2000s and was only intended to be used at broader landscape scales.
Land cover mapping accuracy is particularly problematic when the systems occur as small patches or where the land cover types have been altered over the past decade.
Thus, particular caution should be used when using the associations in assessments of smaller areas (e.g., evaluations of public land survey sections).
Finally, although a species may be associated with a particular ecological system within its known geographic range, portions of that ecological system may occur outside of the species’ known geographic range.
- Adams, R.A. 2003. Bats of the Rocky Mountain West; natural history, ecology, and conservation. Boulder, CO: University Press of Colorado. 289 p.
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During breeding season, insects and freshwater fish; rest of year diet consists mainly small marine fish and insects.
Overall, little information about Black Tern reproduction is known for Montana, as very few studies concerning the species exist. Recent work has focused on location surveys and general population size (Feighley 1996, Rauscher 2000). DuBois (1996) did nesting surveys for Black Terns at a single location in the state (Freezout Lake). In Montana, Black Terns usually begin their reproductive cycle in early to mid-June. However, in 1991 five documented observations of nesting occurred in May (Lenard et al. 2003). DuBois (1996) recorded egg-laying as early as June 2nd.
Black Terns are considered a single brood species and egg-laying late in the season is thought to be a renesting attempt after an initial nest failure. Egg-laying has been recorded in Montana as late as June 27th (DuBois 1996). The average Black Tern clutch size is 2.6. A three-egg clutch is very common, although clutches from 1 to 6 eggs are possible (Dunn and Argo 1995). DuBois (1996) found the average clutch size to be 2.74 among 19 nests at Freezout Lake Wildlife Management Area. Hatching is thought to occur approximately 20 days after egg-laying with an asynchronous hatch sequence (Goodwin 1960). The earliest hatch date in Montana is June 22nd (DuBois 1996). Young are mobile within days of hatching. Continued monitoring is challenging as young will leave the natal nest site when threatened and adults will even relocate to a new area. Fledging typically occurs between days 20 and 24 (Bailey 1977). DuBois (1996) did not indicate any young fledged from the monitored colony, but did report newly fledged young participating in mobbing at the colony. No information is available regarding fledgling or juvenile success in Montana breeding colonies.
Active management for Black Terns in Montana is currently limited to continued population monitoring and water level fluctuation control. Several Black Tern colonies are under federal or state control and monitoring of the population at those locations is completed annually. This monitoring can range from basic observation counts to nest location surveys. At some sites, federal or state agencies also monitor and regulate water levels during the breeding season for Black Terns, as well as other wetland species and waterfowl. Both population monitoring at perennial breeding locations and water level regulation should be continued on an annual basis and be expanded to other locations where Black Terns breed in the state.
- Additional ReferencesLegend: View WorldCat Record View Online Publication
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