West Coast storm-petrel flight style identification

Most storm-petrels intersperse flapping flight with brief glides, low along the water. Darting direction and speed changes are frequent in many species. The flight style will change with wind speed and bird activities. Some storm-petrels have noticeably different flight styles depending upon whether they are engaging in commuting flight, meandering foraging flight, or actively feeding. It is not always possible to identify absolutely a storm-petrel by flight style alone. The goal should be to pick out any storm-petrel flying distinctively differently than the others around it. Then concentrate on the identification of this different bird.

Fork-tailed Storm-Petrels. Off Newport, Oregon. October 2, 2010. Greg Gillson.

Fork-tailed Storm-Petrel: Most commonly encountered storm-petrel from 10 to 50 miles offshore from northern California to Alaska. Less common in central and southern California. Medium size. Wings are fairly straight and slightly rounded at the tips. Tail long and forked. Commuting flight can be rather direct with shallow rowing strokes (Stallcup 1990). Foraging flight is erratic, with medium to shallow wing strokes interspersed with floppy, moth-like, deeper strokes. These birds unpredictably change flight speed and direction. The flight is interspersed with brief banked glides. Feeding, the bird hovers in place with deep high wing strokes. It also faces into the wind and hangs in place on outstretched wings set in place. As it feeds it constantly pushes off the water with its feet, dangling the legs down and foot-pattering along. It then leans forward while hovering to pick at food on the surface.

Leach’s Storm-Petrel: Common primarily from 50-200 miles offshore all along the West Coast. Rarely seen closer to shore during daylight. Large size. Wings are long and pointed, held forward at the wrists and bent back at the tips. Tail long and forked, most noticeable when spread during banked glides. The flight characteristics are essentially unvarying regardless of activity or winds. The flight is bounding, veering, and zigzagging on stiff, bent wings. “Ricocheting” (Stallcup 1990). Characteristic zigzag flight includes quick, deep, double-flaps followed by brief glides with wings held slightly above the horizontal. This flight bears more than a passing resemblance to the flight of Common Nighthawk. Flight also includes brief glides on bowed wings held slightly below the horizontal. Feeding, flies low to the water in typical flight. During short glides with wings held slight above the horizontal it quickly picks food off the water before veering away. Sometimes feeds by hanging briefly in wind just above water’s surface with a bit of foot-pattering, but rarely hovers in place to feed.

Black Storm-Petrel: Most common storm-petrel in California, ranging from northern California southward. May be seen occasionally from shore. Large size. Long, pointed wings. Long, deeply forked tail. Commuting flight fairly smooth and direct with deep, slow, graceful wing strokes, interspersed with glides. Reminds some of flight of Black Tern. Feeding, flaps slowly with wings rising well above horizontal, foot pattering. The fluttery wing beats while hovering to feed, with wings returning to nearly vertical, are the basis for descriptions describing the flapping as butterfly-like.

Ashy Storm-Petrel: Ranges offshore from northern Baja to northern California. Especially common in Monterey Bay in fall. Medium size. Slightly rounded wing tips. Long, shallowly notched tail, often held up slightly in flight. Stiff, rapid, shallow wing strokes, not rising above the horizontal, has been likened to the flight of a bat. Commuting flight level and direct, but can have an erratic and twisting flight when flushed.

Least and Black Storm-Petrels. Off San Diego, California. October 11, 2015. Greg Gillson.

Least Storm-Petrel: Primarily Baja and southern California, rarely northward to Monterey Bay in fall, especially during warm water years. Small size. Short neck. Short, broad wing. Short, wedge-shaped tail; appears almost tailless in flight, bat-like. Commuting flight rapid, low, and direct with deep, but rapid wing strokes. Feeding, hovers in place with wings held high in a deep ‘V’ (Enticott and Tipling 1997).

Wilson’s Storm-Petrel: Rare on West Coast, primarily in fall on Monterey Bay, in flocks of other storm-petrels. Medium size. Wings short and slightly rounded. Short square or rounded tail. Long legs extend behind tail in flight and often dangle down. Commuting flight low and direct with fluttering wing strokes, interspersed with steep upswoops (Stallcup 1990). Foraging, darts and skims and swoops over waves like a Barn Swallow. Feeding, hangs in air on open wings, foot-pattering on surface of water with long legs.

Flight characteristics	Shallow wing strokes	Medium wing strokes	Deep wing strokes
Slow wing beats			Black
Medium wing beats	Fork-tailed	Wilson's (Fork-tailed)	Leach's
Rapid wing beats	Ashy		Least

Bibliography

Enticott, J. and D. Tipling. 1997. Seabirds of the World: the complete reference. Stackpole Books.

Harrison, P. 1991. Seabirds: an identification guide. Houghton Mifflin Co.

Harrison, P. 1996. Seabirds of the World: a photographic guide. Princeton University Press.

Naveen, R. 1982. Storm-petrels of the World: an introductory guide to their field identification. Parts I-IV. Birding vols. XIII, No. 6 and XIV, No. 1-4.

Stallcup, R. 1990. Ocean Birds of the Nearshore Pacific. Point Reyes Bird Observatory.

West Coast shearwater flight style identification

You prepared for your pelagic trip for months. You memorized all the subtle plumage characteristics in your field guides. When your trip reached the point where shearwaters were swarming around the boat, you noticed something disconcerting. Even with your binoculars, the shearwaters were hard to tell apart. The boat was bouncing, the birds would disappear behind swells, they would cross over to the other side of the boat where you were looking right into the sun's glare. You just couldn't consistently make out the plumage details to make a positive identification.

And yet, one of the guides, volunteering to do the messy chumming, would barely glance up from her duties--without binoculars--and confidently announce the ID of a little dot-of-a-bird over a quarter mile away! And not just once, but repeatedly!

She either has inhumanly keen eyesight, or (gasp!) is NOT using the Peterson system of patternistic plumage characters for bird identification!

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Shearwaters fly by interspersing flapping and dynamic soaring with wings stuck stiffly out to the side. Size, structure, and species-specific flapping behavior combine with range and seasonality so that most species can be identified simply by the way they fly. As far away as you can see a shearwater flap its wings and observe its glide path, that's how far away you can identify it! You don't need to see anything else. Color and plumage patterns of the bird simply do not matter, except for a couple of "fly-a-like" pairs.

All you need is 10 seconds

In 10 seconds (or less) you can watch the flight of a shearwater and determine its flight style pattern. On the West Coast there are 3 abundant shearwater-like birds making up most of the birds you'll see: Sooty Shearwater, Pink-footed Shearwater, and Northern Fulmar. Learn the flight patterns of these 3, and then keep a lookout for any bird that flaps and glides with a different pattern.

Sooty Shearwater: Repetitive flapping and graceful gliding on narrow wings. In calm conditions normal flight is 3-7 quick shallow flaps and a sustained glide of about 4 seconds, low along the water. In higher winds there is less flapping and higher arcs, sweeping up gracefully in a banked glide, then gliding low in a wave trough before repeating with a few quick flaps low along the water and arcing up again. Sooty Shearwaters tend to glide in a straight line.

Pink-footed / Flesh-footed Shearwater: The common Pink-footed Shearwater (and quite rare Flesh-footed Shearwater) is a bigger bird than Sooty Shearwater. It flies higher off the water with deep, slow wing beats ("lumbering," Stallcup 1990) and longer relaxed glides. The wings are long and broad. In moderate winds it wheels up in a slow arc above the horizon for several seconds reminiscent of an albatross.

Northern Fulmar: Longer bouts of flapping and gliding than Sooty Shearwater on shorter arched wings with rapid and shallow wing strokes. Unlike most shearwaters (especially Sooty) fulmars often flap at the high point of their arcing glides. "If it flaps while up in the air it is a fulmar" is a good maxim. Another characteristic is that fulmars often wheel around and change direction while in their extended glides, unlike Sooty Shearwaters.

Buller's Shearwater: They sweep up steeply and then gracefully glide downward, hardly flapping at all. Long glides on wings held forward at the wrist and accentuated by the long tail give the flight a most graceful appeal. Alternatively, groups will sometimes participate in synchronized flying with deep, slow wing strokes, flapping and gliding in unison ("languid and graceful," eNature.com 2003). Fall migrant on West Coast.

Short-tailed Shearwater: Erratic flight. Often similar to Sooty Shearwater, but wing strokes more rapid and swift-like ("snappier," Stallcup 1990) usually with more flapping and less gliding and arcing. This bird often makes darting direction changes and may rock from side to side while flapping (alternately showing you its back and then belly)--both traits that separate it from Sooty Shearwater. If the flight of Sooty Shearwater is consistently repetitive and straight, the flight of Short-tailed Shearwater is more rapid, frantic, and erratic. Uncommon late fall/winter migrant on West Coast.

Black-vented / Manx Shearwater: Tiny shearwater flies in a rather straight line with rapid deep wing strokes ("fluttery," eNature 2003). The glide often appears as little more than a "missed" wing beat. Black-vented is common in fall right along the California coastline. Manx is very rare anywhere on the West Coast to Alaska, also usually quite near shore.

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Quoted references: 

eNature.com accessed originally for unpublished manuscript of this topic in 2003.

Stallcup, Richard W. "Ocean Birds of the Nearshore Pacific," 1990.