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THE BLACK TERN - A WINGED SPECTER STRUGGLING TO
SURVIVE
By Kathy Ross
Scanning the marshy flats of the Swan River Refuge in
June, an ephemeral flash of luminous, sunlit wings
catches the eye and intrigues the sense of wonder. Yes,
it is live and it is a bird with a buoyant unique flight
pattern of graceful swoops and aerial dives. As the
light-colored wings turn away from the sunlight, the jet
black head and body and silvery-grey, reflective wings
of the breeding adult Black Tern contrast against a blue
sky - a gift of the late spring migration.
The Black Tern, Chlidonias niger, like other tern
species, is a member of the Laridea family, along
with gulls. Terns in general tend to be smaller than
gulls, with a sleek profile of pointed wings and pointed
straight bills. The Black Tern is one of the smaller
species, being around 10" long with a wingspan of 24
inches. Like gulls, terns have webbed feet and are
colonial-nesting, water-loving birds with a wide range
of habitats, from fresh-water marshes, prairie potholes,
northern coastal shorelines to tropical beaches. While
most gulls maintain fairly stable populations, tern
populations in the northwest, including Montana, are on
the decline. In general, tern individuals or small
colonies may be found roosting on sandbars and
shorelines amid flocks of gulls. I have often had summer
sightings of one to five Black Terns on a particular log
jam in the Flathead River, but having no sightings for
the last two years has been disappointing.
The distinctive black head and body, fading to grey on
the rump, easily distinguishes the Black Tern from other
tern species, at least during the breeding season. The
females are slightly duller black, but it takes a keen
eye to discern between genders. Both have a very dark
bill that is almost as long as the head. Midseason, when
eggs begin to hatch, post-breeding molt begins and the
characteristic black feathers begin to change. First,
around the eyes white feathers appear. Whitening
progresses from forehead to neck and eventually into the
abdominal area. The molt is completed during fall
migration. This basic or winter plumage then becomes
pure white on the underside, except for small dark
patches on each side of the breast. The back becomes a
grey similar to wings and tail. At this time the
juvenile's plumage is similar to the adults except for a
darker back, with wing coverts and cap that are barred
and brown.
Often, vocalizations identify the Black Tern even before
the silvery wings catch the eye. The shrill, metallic "kyew"
can signal parents' interaction at the nest and with
young, foraging flights, and courtship flights. The "keek"
call warns off enemies or threats to the nest. Both
calls can have added syllables and variations depending
on the intensity of the situation. It is well worth
learning this call to experience these beautiful birds
in flight or even be rewarded with the opportunity to
see the nest with young.
The nests are generally built on floating mats of
vegetation amid cattails, rushes, canary reed grass and
other emergent vegetation. In Montana, besides recorded
breeding in small ponds, marshes and prairie potholes,
man-made islands and islands in man-made reservoirs are
used as nest sites. The nests are loosely constructed
out of old vegetation from around the nest site.
Although in Montana little information is available on
the reproductive cycle of Black Terns, it usually begins
in early or mid-June. In general, 'Black Terns are
considered a single brood species', laying 1-4 eggs of
an olive-like color with dark markings, which hatch
around 20 days after laying. (Later nesting has been
known to occur if the first attempt fails.) The nest is
aggressively defended by both male and female, who
together share in the feeding and rearing of chicks. The
young become mobile within days of hatching but
typically do not fledge for 20 or so days.
Unlike many of the Laridea family species, Black
Terns are not plunge-divers. They feed on insects caught
on the fly and small fish or other aquatic prey skimmed
off the water's surface.
Little is known about Black Tern migration patterns
through Montana, but observations have noted May and
June for the spring migration and any time after July
and as late as September for fall migration. They will
winter along the gulf coasts, in the open ocean and as
far south as northern South America.
This species is much on the decline across its
historical breeding areas, including our regional and
state populations. Many tern colonies vanished on the
Atlantic coast by the end of the 19th century when
hundreds of thousands were slaughtered for their
feathers by the fashion industry. They are listed as
threatened or endangered in many eastern states. In
Montana, their numbers are very localized. The last two
years have seen a decline in individuals as well as
confirmed breeding sites. This decline may be due to
human impacts such as habitat loss and pesticide use.
Also, late season high water levels the last two years
may have had impact on breeding.
* “Waterbirds will often move breeding colonies as
wetland conditions change, making localized surveys of
limited value without regional comparisons. Thus,
participation in a region-wide colonial-nesting
waterbird inventory may provide critical information for
conservation of Montana’s waterbirds.” The Black Tern,
along with a number of other waterbirds, is listed as a
'species of concern' by agencies such as BLM and Fish,
Wildlife, and Parks. These agencies encourage
volunteers. Become a Citizen Scientist and assist in
keeping these beautiful terns part of our landscape!
Participate in inventories and/or report any sightings
of individuals or nesting activities to the above
government agencies.
References
The Sibley Guide to Bird Life and Behavior, by
David Allen Sibley
Stokes Field Guide to Birds-Western Region, by
Donald and Lillian Stokes
* "Mt. Colonial-nesting Waterbird Inventory - 2010
Report," by Catherine Wightman and Fred Tilly
Websites
Montana Fish, Wildlife and Parks Montana Natural
Heritage Program
Department of Environmental Conservation, New York State
Montana Field Guide
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