Monday, August 2, 2010

Nature Journal: Separating Cedar Waxwings from European Starlings in flight

European StarlingEuropean Starling, Charleston, Oregon on 30 August 2008 by Greg Gillson.


Cedar Waxwings and European Starlings are one of the common summer birds from the mid-latitudes of Canada to the mid-latitudes of the US. In summer both species frequently fly around in smaller flocks, often flycatching on the wing.

In size, shape, flight style, and flocking behavior these two species are very similar. If one does not note the yellow band at the end of the tail, the pale undertail coverts, or the crest on the waxwing, there is not much to separate them. They are very similar in flight as a silhouette against the bright sky. Under the entry for Cedar Waxwing, Sibley simply says, "Compare European Starling in flight."

Yet even though they are so similar, somehow for years I've been able to accurately determine whether the chubby pointed-winged bird flying by was a waxwing or starling in about 3 seconds. How did I do it? I wasn't sure.

The human mind has a great ability to evaluate and recognize patterns. Thus, you can identify a relative when she is quite distant and you can't see any details of her face. Unfortunately, our pattern recognition ability works so well that we don't usually know how we're doing it! We're obviously using something, some field mark (or set of field marks) even if we don't know exactly how we know what we know.

So I've been spending time lately, really observing waxwings and starlings in flight, taking notes in the field. In a minute I'll tell you how to tell them apart in flight. But first I will describe the "flight style field marks," those non-plumage characters that identify silhouetted birds in flight.

Field sketch showing silhouette and wing shape of European Starling and Cedar Waxwing. July 5, 2010. Greg Gillson. Click for larger view.

Flight silhouette - We're looking for the overall structure and proportions and how the bird holds its head, neck, body, wings, and tail. For instance, though cranes and herons are superficially similar in their long neck and pointed beaks, they hold their necks much differently.

Wing shape - Differences in wing bones, feather tracts, and feather length account for the differences in wing shape. Birders would do well to study an ornithology manual to better appreciate wing shape. As an example, albatrosses and swifts both have pointed wings, but the albatross may have 25-40 secondary feathers and the swift only 6-7, while both have exactly 10 primaries.

Flapping - How many beats per second? What is the angle the wings travel above and below the plane of the body? Is there a pattern of flaps and pauses? How stiff are the wings?

Flight path - Is the flight progression undulating, swooping, erratic, or straight? What is the general height above ground and speed?

Flocking flight characteristics - Geese may fly in 'V' formation. Other birds fly in flocks that are disorganized and constantly changing. Many birds don't fly in flocks at all.

Flight type (or purpose) - Birds fly differently depending upon what they are doing (or even how fast the wind is blowing). If they are fleeing, then they will flap more deeply and quickly than if in standard commuting flight. Other birds soar and glide, or even hover.

Notes and field sketch of Cedar Waxwing flight path. July 7, 2010. Greg Gillson. Click for larger view.

So how do starlings and waxwings differ in flight?

Both species have pointed wings. The arm (inner portion of the wing between body and wrist) of the waxwing is relatively longer than the starling. The wrist is held straighter on the waxwing, creating a straighter leading edge than on the starling (see my top sketch).

The actual measurements of the ratio of tail length to body length is nearly identical between the two species. However, the waxwing tail appears slightly relatively longer than the starling. This may be caused by a thinner wing, wing set farther forward, or optical illusion caused by pale vent on the waxwing.

In flight characters, both species flap several times and fold their wings. The starling flies relatively straight and level. The final flap or two of the waxwing, before the folded pause, propels the bird upward slightly, so that the flight is slightly undulating.

The starling head (crown) appears quite flat. The waxwing has a rounder head, accentuated by the much shorter bill. The head of the waxwing is often raised slightly above the plane of the neck.

The identification of birds in flight is not well-covered in the field guides. But it is worth the effort to observe and learn. After all, one of the unique features of birds is that they have wings, and most can fly. It only makes sense to be able to identify them when they are flying.