Birds of Seabrook Island



  Piping Plovers

Species Acct.
NW Warblers


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Diversity of Birds
Structures that Aid in Field Identification


  Learning to identify different species of birds begins and ends with field experience. Every time you go "birding," you will seen different things and will learn something new.
   At first glance, many birds look much alike but you must focus on the bird you are observing - note distinctive marks (eye-rings, wing-bars, crests, forked tails, etc.), shape (rounded head, dumpy body, short tail (shorter than the wings), long legs, long thin wings, etc.), colors (all yellow; brown back, streaked breast, with a reddish wash, etc.), behaviors (the bird wags its tail as it walks, it hops, it scratches with two feet at once, it hovers and dives, etc.), and finally, the habitat (brushy edge, swash zone, fresh-water, etc.).  Try to get a complete mental image and consult your field guide. Then go back again to the original subject (if it is still there) to be sure you picked up all the necessary traits.
   Listen for songs, call notes, and other sounds made by the bird (Mourning Doves wings produce a characteristic sound when they take off, Least Terns tinkling vocalizations often alerts you to their presence, flocks of Yellow-rumped Warblers surround you with chip notes in winter, Painted Buntings serenade your summer path to the beach with their rasping song, etc.). In many cases, sound may be the easiest (or only) way to identify the species (e.g. the dowitchers, Empidonax flycatchers, etc.).
   Note that size is often difficult to determine - a familiar bird like the Willet may look large, average, or small depending on your distance and the presence of other species. Great Egrets are much larger than Snowy Egrets but unless you see them together or with some other size reference bird, you will need to look for bill color and "golden slippers." In groups on the beach, you often have some easily identifiable size references - the Willet and Sanderling are birds you should learn well and use as models.
  Willet Sanderling

Learning to identify shorebirds may be easier if you study two common species and compare others to them. The Willet is a medium-sized shorebird (left) and the Sanderling a small shorebird (right).

  Willets feeding in the swash zone Sanderlings in winter plumage  

Diversity of Birds

  Your goal in identifying birds is to be able to determine the species - a unique taxa (group) of similar individuals that are believed to be able to interbreed freely among themselves but not (usually) with individuals of other species (some hybrids are found among closely related species).
   Keep in mind that some species are sexually dimorphic with one sex being more conspicuous or brightly colored during the breeding season (e.g., the Painted Bunting) - in others males and females look much alike (e.g., the Carolina Wren). In some species one sex is also larger than the other (e.g., Boat-tailed Grackle). A few species may also have different morphs (individuals that look quite different as adults) - (e.g., the Reddish Egret has "dark" and "white" morphs and both may be seen on Seabrook.
   Looking beyond these difficulties, the challenge is that, worldwide, there are ~9,672 species of birds (but only about 600 species occur in North America). Note that the number of species is in flux - a few new species continue to be discovered and, as our understanding of populations and genetics grows, some currently recognized species may be joined ("lumped"), and others may be split.
   As an example of "lumping," we used to recognize both the Myrtle and Audubon's Warblers as separate species (they look much alike but Myrtle Warblers have a white throat and Audubon's Warblers have a yellow throat). The former "species" is widespread in the east, the latter in the west. We now realize that the two groups form a continuous interbreeding population (species), extending from Newfoundland to Alaska and south into Mexico. We now call the species the Yellow-rumped Warbler, Dendroica coronata. This is the most abundant species of warbler in North America and is common on Seabrook in winter.
   As an example of splitting, we formerly recognized a species called the Sharp-tailed Sparrow - a marsh-dwelling and secretive emberizine. However, this group includes populations breeding from North Dakota to the North West Territories in Canada, around Hudson Bay, and in the lower Maritime provinces in Canada that are now called Nelson's Sharp-tailed Sparrow, Ammmodramus nelsoni. Adults have a short bill and bright face and breast with rufous-tinged or grayish streaks on the flank. A second population breeds along the Atlantic Coast from Chesapeake Bay north to southern Maine. Birds in this group have a longer bill, a flatter head, and a buffy breast with distinct streaks and are known as Saltmarsh Sharp-tailed Sparrows, Ammodramus caudacutus. Both species should be found on Seabrook in winter in small numbers (and are difficult to distinguish).
   It helps that many species look quite different. However, we do have some that are difficult to distinguish - e.g., Greater and Lesser Scaup, Long-billed and Short-billed Dowitchers, and sibling species in the flycatcher genus Empidonax. In most cases, one of these confusing species is more common than the other. Identification of the rarer species should be made with care and documented - other observers, pictures, etc.

   Considering the diversity of species found in any given area of the world, it is also helpful to group similar species together (see Classification). Thus, we can talk about waterfowl (ducks, geese, and swans) as a group. Woodpeckers form a "group."  So do doves, wrens, wood-warblers, etc. . Individuals within these groups may have similar color patterns and molts, behavior, feeding habits, breeding adaptations, etc. Knowing the group (especially order and family) helps you organize your understanding of different species.

   To "order" the diversity of birds, it helps to know that of all of the bird species, 41% are  "non-passerines" (not passerines).  They are placed in several orders (19 or so) defined by a variety of physical and biological characteristics. Many "birds of the beach" are non-passerines (loons, ducks, shorebirds, gulls, terns, etc.). The other 59% of the known species are "perching birds" or "passerines" (Order Passeriformes). They all have three toes directed forward with the hallux (first or "great" toe) directed backward and opposing the other three toes. They are able to clasp a perch effortlessly when sitting - their tendons pass around the back of the "ankle" and when the bird lowers itself on a perch, the tendons flex, locking the toes around the perch.
   Passerines are further divided into "Suboscines" including a few Old World Suboscines and the New World (tyrant) flycatchers (and many other Neotropical taxa) and "Oscines" - true song birds - characterized by features of their syrinx ("voice box") and its musculature. 20% of passerine species are suboscines, 80% are oscines. However, if you travel in South America, a continent isolated from the rest of the world for much of its recent history, many of the passerines are suboscines. See Chile (Patagonia) and Classification.


Structures that Aid in Identification

  The identifying features of birds emphasized in field guides are based on differences in color, pattern, shape, structure, size, etc. These are features that can be seen in the living bird.
   Let's explore some of these features often referred to in your guides -

   Most birds have two legs. Their hindlimbs bear four toes - in most cases three are directed forward and one backwards. But note that there are variations. Also toes are usually independent but they may be lobed or joined by webs (all four toes are webbed in one order). Legs and toes are usually bare but they may be feathered in a few species. In some, males may develop tarsal spurs.

   Birds have two wings - their forelimbs vary from long and pointed, short and broad, to vestigial. The number of feathers in the wing vary but this is not easily determined in the free-living bird. Most also have a tail with a variety of features in different species.

   Studying the illustration below, note that all birds have a bill (upper maxilla and lower mandible - often called collectively the mandibles - each is covered with one or more scales). Note the shape and color of the bill. The opening between the mandibles - the mouth - is often called the gape (it may be surrounded by modified feathers called rictal "bristles"). The cutting/grasping edges if the mandibles are known as tomia. The curve of the upper mandible is known as the culmen. There are two nostrils toward the base of the upper mandible that may or may not be evident (they are hidden by feathers in some species) but their position, shape, and structure may be helpful. The nostrils may be pervious (you can see through them from side-to-side) or impervious (they closed by an internasal septum). Occasionally they are borne on a fleshy area between the bill and head known as the cere. In some birds, the upper mandible may be moveable ("kinetic"). In some shorebirds, the upper mandible can be flexed along its length to allow the capture of invertebrates deep in a substrate (watch for a yawning dowitcher).

   The structure and color of the legs and feet (usually covered with scales - sometimes with feathers) are also important (in some cases the arrangement of the scales is crucial but you have to hold the bird to determine their patterns). Scales that cover the bill and legs are epidermal (outer skin) structures. So are feathers. Birds do not have hair...

   See Structure for more information about avian morphology.



    The feathers covering a bird may be divided into areas. Moving ventrally and backwards from the bill, the feathered regions are the throat, breast (roughly the area around the furculum or wish bone), and belly. The vent is the area around the cloaca (where feces and urine are voided) and the under-tail coverts ("crissum") are beneath the base of the tail feathers.
   Sides are lateral to the breast and flanks are lateral to the belly.
   Moving dorsally and backwards from the bill on each side of the head, birds have eyes. The color of the iris in the eye may be important. Eyes may be surrounded by bare skin (which may be colored) or bear distinctive small feathers that form an eye ring. Extending through the eye there may be an eyeline or eyestripe or there may be a supercillium (stripe) above it. The crown (top of the head) may be distinctively colored or have a stripe - it may also form a crest that can be erected in display. The back of the neck is the nape, and behind that is the mantle (center of back), and rump (lower back). Scapulars overlap the folded wing (lateral back). The tail has upper-tail coverts above the base of the flight feathers of the tail.
Wings up
   On the upper surface of the wing, there are usually three series of coverts above (greater, median, lesser) and under wing coverts or the lining of the wing below. These feathers may be variously marked or patterned. Scapulars overlap the base of the wing above when it is folded. Primaries comprise the "hand" wing, secondaries the "arm" wing. More on feathers follows - Wings down
       These external structures aid in identification and are illustrated in field guides. Internal structures, behavior, and a number of other features may also be used in classification and determining phylogeny. See Structure for an in depth discussion of avian anatomy.
    Banner - shorebirds on North Beach.