SEPARATING TRUMPETER AND TUNDRA SWANS CHECKLIST
The name Tundra Swan includes the Whistling (North American) and Bewick's (Eurasian) swan subspecies. Characteristics
are age related, and vary by populations and within populations. No characteristic, except the call, should be
considered by itself diagnostic. Several characteristics should be used in combination when diagnosing the species.
The following checklist describes differences between Trumpeter and Whistling (Tundra) swans. Trumpeter(s) are
signified by [T], and Whistling(s) are designated by [W].
Click on the photo for Trumpeter Swan photos.
MATURE TRUMPETERS AND TUNDRAS:
Mature Trumpeters and Tundras may be defined as all white birds (including all white neck and head).
A. Size. Males are usually larger than females. [T] are generally larger than [W], although there
is some size overlap.
B. Physical Proportions:
- Neck Length / Body Length Ratio. [T] is usually greater than [W]. The longer neck of [T] is usually fairly
- Body Length / Body thickness Ratio. [T] is usually greater than [W]. This is noticeable in a profile view of
the rump, where the included angle between the back and the underside is smaller on [T] than it is on [W].
C. Angle of The Body Major Axis (BMA): The BMA is a straight line through the base of the neck and through
the tail. The BMA of both species usually slopes up toward the tail when the swans are swimming or sitting, but
the slope is greater for [W] than it is for [T]. This and body length-to-thickness differences combine to give
[W] a higher, steeper rump appearance when swimming or sitting. Use this mark when viewing a large flock
of sleeping or feeding [W] to eliminate potential [T] candidates.
D. Feet size: [T] feet are larger than [W] feet, with no overlap. [T] feet are typically 6-1/2" to
7" wide. This is useful for swans in flight and when the swan is standing on one foot with the up foot
extended to the rear.
E. Head Profile and Bill Shape: Head profiles vary for both species.
- Some [T] have a pronounced flat, or nearly flat, head for about 2" to 2-1/2" from where the forehead
feathers meet the culmen to the apex near the back of the head (call this Type 1 head). On other [T] the flat area
is less pronounced, and even can appear as a rather smooth curve (call this Type 2 head). The line of this "flat"
area on Type 1 and 2 heads usually continues slightly BELOW the line of the upper mandible.
Most [W] have a distinctive round
head, with varying radius of curvature that is almost always smooth. Some [W] heads can look like Type 2 [T] in
profile, not considering size differences. However, the distinguishing difference between the species is almost
always noted in the fact that for [W] the line of the forehead continues ABOVE the line of the upper mandible.
Martha Jordan describes the species head differences this way: [W] is like a smaller black cone stuck
on the front of a Styrofoam ball; [T] is like a larger black cone that just covers the front of the Styrofoam ball.
In the case of [T] the ball has been reshaped somewhat with, to varying degrees, a flat top and pointed apex.
- [T] exhibits an abrupt change of contour at the apex (associated with the flat head, Type 1) which gives the
head a "pointed" look. [W] exhibits a smooth curve around the apex.
- The apex of [T] is near the rear of the head well behind the eye. The apex of [W] is near the center of the
head just slightly behind the eye.
- [T] has a flat area along the nape (sometimes not flat). [W] has a curved nape.
- The nape of [T] transitions abruptly at the neck (not always). [W] has a smooth transition of the nape to the
- The distance from the bill tip to the eye of [T] is about 2 times the distance from the eye to the nape. The
distance from the bill tip to the eye of [W] is about 1 times to 1-1/2 times the distance from the eye to the nape.
Measurements of 4 Trumpeters revealed that the total length of the bill from tip to eye was 5-1/2" to 6",
and the distance from the eye to nape was 2-1/2".
- The upper mandible of [T] is almost straight (can be concave), while the upper mandible of [W] is concave (can
be straight). Often [T] has a "Canvasback" profile.
- [T] has a massive bill (not always). The bill of [W] is not massive.
- The lore skin of [T] meets the eye. The lore skin of [W] also meets the eye but it may be slightly narrower
near the eye on some swans. The yellow patch on the lore of [W] may make it appear that the lore pinches
near the eye. To give some idea how wide is the lore skin at the eye of [T], typically the eye of [T]
is 3/8 inch diameter while the lore skin joining the eye is 5/16 inch wide.
- [T] has no yellow on the lore. [W] has a yellow spot on the lore proceeding from the eye (15 percent
do not have yellow).
- The forehead feathers of [T] are shaped like a V, with the sides of the V curved inward so that the angle between
the sides becomes smaller near the point. The forehead feathers of two year old and older [W] form a U. This
forehead feather shape is one of the most reliable features for separating [T] and [W], although it is not diagnostic
by itself. For example, first year, all white [W] may have a V forehead feather pattern.
- The distance from the bill tip to the nostril of [T] is only a little less than the distance from the nostril
to the eye. The distance from the bill tip to the nostril of [W] is about 1/2 the distance from the nostril
to the eye. Measurements of 4 Trumpeters revealed that the distance from the bill tip to the nostril was 2-1/2"
and the distance from the nostril to the eye was 3-1/2".
F. Vocalizations: Diagnostic. The vocalizations of both species may be heard on The Trumpeter Swan Society
web site, http://www.taiga.net/swans/swanid.html . Small
groups of [T] on the ground are usually silent for several hours. Occasionally all members of a small [T] group
will begin to "talk" to each other. This may last from 1 to 15 minutes. Large groups talk more frequently.
The pitch of [T] individuals varies.
- Head Bobbing. [T] and [W] head bob, although [T] perhaps more frequently. [T] head bobs when nervous, prior
to flight, and at other times. [W] often greet each other by extending their heads forward so that the extended,
straight neck makes about a 30 to 45 degree angle with the vertical; [T] never greet with this head and neck posture.
- The "Kink" in The Neck. Both [T] and [W] exhibit the kink in the lower part of the neck when the
swan is inactive.
- Angle of The Standing Swan. [W] usually stands horizontal (not always); [T] stands from horizontal to about
20 degrees above horizontal.
H. Color of Feet and Legs: [T] and [W] have black feet and legs. Young all white [T] have extensive yellow
along the sides of the toes and up the legs. The yellow diminishes with age. Three year old [T] may show the yellow.
Young all white [W] show no yellow on the feet or legs.
IMMATURE TRUMPETERS AND TUNDRAS:
Separating the immature of [T] from the immature of [W] is even more difficult than separating the mature of
the two species. Color differences, physiological development of bill and head, dependence of characteristics on
age, and variation among individuals are primary sources of confusion. Look for juveniles associating with
adults. Association with an adult must be combined with other characteristics. The following characteristics differ
between juveniles and adults. Characteristics not mentioned below are the same for juveniles as for adults.
I. Body color: [T] are dark gray (battleship gray). [W] are light gray. [T] holds the gray color longer
into late winter than does [W]. [W] have completed their body molt to white by early March, while [T] do not complete
their body molt to white until April or later. Both species often show gray around the head and neck until well
after the body molt is completed.
J. Size: Immatures of [T] and [W] are slightly smaller than adults and do not achieve full adult size until
their second spring. Size difference of males and females of both species is less pronounced than in adults.
K. Head and Bill Deviations From the Adult Characteristics:
- Culmen shape. [W] can have a flat, or even convex, culmen. Even first year [W] can have a straight culmen.
- Bill size. Bill size can appear to be disproportionately large on [T] and [W] because the bill reaches adult
size by the first fall, whereas the body does not reach full size until the second fall or later.
- The V of The Forehead Feathers. The U of [W] forehead feathers develops slowly on some swans. First spring
all white [W] may still show a V forehead feather pattern.
- Bill Color. Juvenile [W] gradually acquires a black bill during its first winter. By spring its bill has become
mostly black. Thus, an immature swan showing extensive black at the base of the bill could be either species, especially
after November. Nevertheless, juvenile swans in early fall may be separated on the basis of this character with
some confidence because most immature [W] have pink meeting the face. Martha Jordan indicates that there is a qualitative
difference in the distribution of black on the bill, with [T] appearing to have a bill that is "black with
a pink area in the middle'" whereas [W] has a "pink bill with black at the ends". Clearly the most
fail-safe use of this mark is if an immature swan shows pink meeting or nearly touching the facial feathering,
then it is [W].
- Legs and Feet Color. [T] have olive-buff legs and yellow webs on feet. [W] have flesh colored to black
legs and feet.
- Vocalization. While some [T] do not vocalize until the 2nd year, some vocalize, generally at a higher pitch
than the adults.
1. Article by Michael A. Patten and Matthew T. Heindel, Identifying
Trumpeter and Tundra Swans in the Field, October 1994 BIRDING
(available for about $3.00+ postage from ABA, 1-800-634-7736)
2. The Trumpeter Swan Society
3. Martha Jordan
4. Jim Snowden
5. Prepared by Rod Hug
Please Report Trumpeter Swan sightings to:
- firstname.lastname@example.org (Steve Bouffard, USFWS, Idaho)
- email@example.com (Kevin Hunting, Bird Species of SpecialConcern)
- firstname.lastname@example.org (Mike Rogers, California Bird Records Committee)
- email@example.com (Rod Hug, The Trumpeter Swan Society, 4603 Bridle Trail,
Santa Rosa, Ca 95409, (707) 539-3413))