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Taken from the BWP on CD-ROM: copyright Oxford University Press.
Field characters
23–25 cm; wing-span 74–78 cm. Larger and bulkier than Black Tern
and White-winged Black Tern, with 10–15% longer wings, longer,
heavier bill, flatter head, and almost 50% longer legs; overlaps with
immatures of several medium-sized sea terns Sterna in size, but has
shorter, less forked tail. Largest marsh tern, with more dagger-shaped
bill than congeners and plumage patterns recalling Sterna at all ages.
Breeding
plumage similar in pattern to that of Arctic Tern and (even more so)
White-cheeked Tern but more intensely coloured; other plumages lack
distinctive pattern and thus identification at all seasons requires
clear observation of structure and behaviour.Taken from the BWP on
CD-ROM: copyright Oxford University Press.
Summer adult subject to confusion with Arctic Tern and White-cheeked
Tern due to similarity of plumage pattern, but Whiskered Tern smaller,
less attenuated, shorter-tailed, and slightly blunter-winged. Thus
character of Whiskered Tern much closer to that of congeners than to
Sterna tern. Differences in character, flight, and behaviour even more
important for distinction of Whiskered Tern at other ages from Sterna,
since plumage patterns overlap with those of several species and differ
certainly only in details of wing pattern and rump and tail colours.
Whiskered Tern in 1st-winter and winter adult plumage long considered
indistinguishable from White-winged Black Tern but risk of confusion
now reduced: Whiskered Tern clearly indicated by (1) longer, more
dagger-like bill in ((, (2) more scattered head pattern, (3) lack of
obvious collar, and (4) greyer rump. Shares ability with congeners to
hawk insects, and with Sterna to plunge for fish.
ADULT BREEDING
Forehead, lores, crown down to eye, and Hindneck black. Streak from
chin and gape extending below eye to sides of neck white. Mantle and
back medium grey; scapulars, tertials, rump, and upper tail-coverts
slightly paler, light grey, whole upperparts appearing uniform grey.
Upperparts distinctly paler than in Black Tern, slightly paler
than White-winged Black, but darker than Common
Tern. Chest medium grey like sides of neck and mantle,
medium grey shading to light grey on throat and to dark grey or
blackish-grey on breast and belly. Flanks and vent light grey, under
tail-coverts white. Tail light grey, outer web of t6 white except for
slightly greyish tip. Outer web of p1–p9 pale silvery-grey, outer
web of p10 medium grey, slightly tinged silvery when fresh. Inner webs
of primaries white, except for broad medium grey streak alongside
shaft, medium grey tip (both slightly tinged silvery when fresh), and
narrow dull black streak along outer edge of tip, latter forming narrow
black rim along trailing edge of wing when seen from below. Worn
primaries, especially oldest ones of 1st and 2nd moulting series
(mainly p6–p7 and p9–p10, respectively) fade to dark grey
or blackish with grey bloom hardly apparent. Fresh inner primaries
narrowly bordered white. secondaries light grey with slightly paler
inner border and narrow white tips. Upper wing-coverts light grey like
scapulars, slightly paler and more silvery towards wing-bend and on
greater primaries coverts. Axillaries pale grey, under wing-coverts and
leading edge of wing white. In fresh plumage, grey of upperparts
slightly tinged bluish, light grey of throat contrasting with white
streak below eye; in worn plumage, grey of underparts less deep and
some white of feather-bases visible, throat white, and primaries less
silvery, tips especially dull grey or blackish. Sexes similar, but
underparts of ) sometimes slightly paler.
ADULT NON-BREEDING
Forehead and lores white. Crown white, variably streaked black: in
some, almost uniform white with a few dark shaft-streaks only, a few
others black with rather narrow white feather-fringes, sometimes even
forehead black. Small spot in front of eye and streak from behind eye
over ear-coverts to across nape black, feathers narrowly edged white
when fresh, especially on nape. Mantle, scapulars, tertials, and back
to upper tail-coverts uniform pale grey, no white collar on hindneck
(white feather-bases sometimes visible through wear, but this does not
form clear-cut collar). Underparts white, often with narrow pale grey
line extending down from upper Mantle to upper sides of chest. Tail
pale grey, outer web of t6 nearly white. Flight-feathers like adult
breeding, contrast between older dark feathers and silvery-grey new
feathers variable, depending on wear and moult. Upper wing-coverts pale
grey, lesser coverts with slightly darker centres; no pronounced dark
carpal bar, but indistinct one sometimes formed by worn dark grey
lesser coverts. Leading edge of wing, Axillaries, and under
wing-coverts white. Resembles C. leucopterus in usually having rather
pale crown and black ear-coverts and nape-patch, but ear-coverts and
nape connected by single black streak, while in both C. niger and C.
leucopterus ear-coverts are separated from black central nape by white
wedge from sides of neck to above ear-coverts; besides this, crown of
C. niger black, contrasting sharply with white Forehead. No white
collar on Hindneck, in contrast to C. leucopterus; in latter species,
collar more marked bordered behind by black band across mantle, which
is lacking in C. hybridus; faint collar often present in adult
non-breeding C. niger, more distinctly in juvenile of latter.
Upperparts and upper wing-coverts distinctly paler than in C. niger,
slightly paler than C. leucopterus, and usually without distinct carpal
bar which is present in many C. leucopterus and indicated in some C.
niger. Narrow grey bar extending to sides of chest in C. hybridus much
smaller than distinct patches of C. niger; C. leucopterus lacks grey at
sides of chest. Non-breeding C. hybridus also rather similar to
non-breeding and juvenile S. hirundo and Arctic Tern S. paradisaea, but
these have carpal bar distinct, upperparts paler grey, rump to tail
paler grey or white with outer web of t6 darker than inner web instead
of inner darker than outer, tail more deeply forked, and no dark on
sides of Chest.
FIRST IMMATURE NON-BREEDING
Like adult non-breeding, and separable with difficulty after loss of
last juvenile feathers with characteristic dark subterminal marks by
October–January; primary moult in post-juvenile starts c. 2
months later than in adult post-breeding, juveniles showing lower
scores than adults at same time, but some start at same time, differing
only by outer primaries being uniformly worn and coloured rather than
with strong contrast between some neighbouring feathers as in adult.
For differences from other species, see adult non-breeding.
DOWNY YOUNG
Closely similar to both C. niger and C. leucopterus, but hardly any
white round eye, less white on wing-tip, black spot on Forehead
extending to gape, and all underparts white except dark brown Chest and
buff flanks.
Other species
- Black tern (Chlidonias niger)
White-winged Black Tern (Chidonias leucopterus)
Other species :
Common tern (Sterna hirundo)
Little tern (Sterna Albifrons)
Arctic Tern (Sterna paradisaea)
Cramp, S. 1985. The birds of the Western Palearctic, Oxford University Press edition, New York.
Snow, D. W., and C. M. Perrins. 1998. The birds of the Western
Paleartic. Concise edition, Oxford University Press edition, Oxford.
Svensson, L., K. Mullarney, D. Zetterström, and P. J. Grant. 2000.
L'album ornitho, Delachaux et Niestlé edition, Paris.
