Aberrant — Atypical; an aberrant bird differs strikingly in some aspect from most individuals of its species.
Air sac —As used in this guide, an expandable, featherless, often brightly colored and textured area on the sides of the neck in some birds; certain grouse and prairie-chickens inflate air sacs in courtship displays. In anatomical usage, the term refers to internal organs connected to the lungs in all birds.
Albinism — Congenital absence of pigmentation; in birds, results in white plumage and pink eyes.
Alkaline — Having a pH value greater than 7; alkaline lakes in the western United States support many bird species.
Alpine barrens —Areas above the timberline where vegetation is typically low, creeping, and sparse.
Alternate plumage —In most bird species, the plumage worn during the breeding season; often more vividly colored and patterned than the nonbreeding (or basic) plumage, particularly in males.
Altitudinal migration —Seasonal movement of birds along elevational gradients, normally downslope in the cooler months and upslope in the warmer.
Altricial —Referring to chicks that are naked, blind, and incapable of moving around on their own soon after hatching (compare “precocial”).
Alula —Group of 2–7 feathers on the upper surface of the wing near the carpal joint (“wrist”); used for steering and “braking” in flight (and in some diving birds for underwater maneuvering).
Antiphonal —In bird songs, composed of phrases sung alternately by males and females.
Arm —Informal term for the inner portion of the wing between the body and the carpal joint; often used by hawk-watchers.
Arroyo —In arid regions, a water-carved gulch, deep gully, or small, narrow canyon that is often dry; in the United States, the term is used almost exclusively in the Southwest and California.
Arthropod —Invertebrate of the phylum Arthropoda, which includes insects, crustaceans, and arachnids.
Aspect ratio —In birds, the ratio of wing length to wing breadth.
Asynchronous hatching —Staggered hatching of birds in a single clutch (group of eggs), often over several days.
Auriculars —Feathers covering the center of the “cheeks” just behind the eyes, visible as a distinct patch in some species (such as Golden-winged Warbler); also called “ear coverts.”
Aviculture —The breeding and raising of birds in captivity; when such species are cross-bred, new “strains,” or types, are sometimes created that do not closely resemble their wild ancestors (as in Eurasian Collared-Dove and Rock Pigeon).
Axillaries —Group of stiff covert feathers located on the underwing next to the body (in the “armpit” region).
Backcross —Offspring resulting from the mating of a hybrid bird with one of its parental species.
Barrier island —Long, narrow island situated parallel to a shore and built by the action of waves and currents; a habitat often used by nesting and migrating waterbirds.
Basic plumage —In most bird species, the plumage worn during the nonbreeding season; often less strikingly patterned or colored than breeding (or alternate) plumage.
Belly —Section of a bird’s underparts below the breast and before the vent.
Bib —Informal term for a distinctly pigmented area of the throat, usually a dark patch (as seen on many chickadees).
Bog —Area of soft, spongy, naturally waterlogged ground, typically having an acidic substrate of sphagnum moss and peat, in which characteristic shrubs and herbs and sometimes trees grow.
Boreal forest —Also called “taiga”; continuous belt of subarctic coniferous forest just below the tundra, in North America extending mostly from Alaska to eastern Canada.
Borrow pit —Area where soil has been excavated for use elsewhere; these pits often fill with water or are maintained as small ponds and lakes.
Brackish —Characterized by a mixture of salt and fresh water, as found in tidal areas such as bays, lagoons, and marshes.
Breast —Section of a bird’s underparts below the throat and before the belly.
Breastband —Area of continuous, contrastingly pigmented plumage that extends across the breast (as in Semipalmated Plover).
Brood parasite —Bird that lays eggs in another bird’s nest (sometimes a bird of another species).
Brow line —Line extending from the eye to the base of the maxilla (as in Razorbill).
Call —A usually brief vocalization birds use for contact, alarm, or warning or to solicit feeding, copulation, or gathering (compare “song”).
Canebrake —Dense thicket of cane, in North America usually of the native species giant or switch cane (Arundinaria gigantea).
Cap —Informal term for the top a bird’s head when it is contrastingly pigmented (as in chickadees); more extensive than the “crown.”
Carolina sandhills —A term for the longleaf pine–wiregrass ecosystem that once covered 90 million acres from the coastal plain of the Carolinas to eastern Texas but is now reduced to fewer than 3 million acres.
Carpal joint —The forward-projecting “wrist” of the wing, characterized by an obvious bend; a carpal bar is an area of contrastingly pigmented plumage that extends, usually diagonally, from this joint along the upperwing coverts toward the body (as in storm-petrels); a carpal patch is a distinct area of plumage near the joint, often on the underwing (as in Rough-legged Hawk).
Cere —Raised, fleshy area at the base of the maxilla, naked in diurnal raptors (Falconiformes), feathered in parrots, and covered with an operculum (flap) in pigeons.
Chaparral —Habitat dominated by a dense growth of mostly small-leaved evergreen shrubs that is found mainly in the West and Southwest and is characterized by hot, dry summers and cool, moist winters.
Cheek —Informal term for the area of a bird’s head that includes the auriculars and surrounding feather tracts.
Chin —Informal term for the uppermost part of a bird’s throat, adjacent to the mandible.
Clear-cut —Tract of woodland in which all trees have been removed.
Clinal —Showing gradual change in a character from one end of a species’ (or population’s) range to the other; this change typically is correlated with an environmental gradient, and forms at the endpoints may appear strikingly different.
Closed forest —Relatively dense forest that has a well-developed canopy (compare “open woodland”).
Coastal plain —Area of flatland adjacent to a seacoast; the Atlantic Coastal Plain stretches some 2,200 miles (3,540km) from Cape Cod, Massachusetts, southward through the southeastern United States and Mexico to the Yucatán Peninsula.
Coast Ranges —Mountain ranges that stretch along the western coast of North America from southeastern Alaska to Mexico.
Collar —Informal term for a distinctly pigmented area of plumage that encircles the neck and/or breast.
Colony —In birds, usually a group of the same species nesting together in close proximity; some birds, especially terns, herons, and egrets, nest in colonies comprised of several species, and some birds nest in widely scattered colonies.
Coniferous forest —Woodland composed of mostly evergreen, cone-bearing trees or shrubs with needlelike or scalelike leaves, including pines, spruces, and junipers.
Contour feathers —Feathers that form the outer layer of a bird’s plumage, including remiges and rectrices.
Corvid —A bird of the family Corvidae.
Cosmopolitan —Having a nearly worldwide distribution.
Coverts —Contour feathers that lie over (or partly cover) other feathers and serve to protect them and to streamline the bird. Uppertail and undertail coverts cover the base of the tail on the upperside and underside of the body, respectively. Wing coverts are arranged in distinct tiers in many birds, especially larger species: greater coverts are the largest and closest to the remiges, median coverts form the next tier, lesser coverts the next, and marginal coverts are found along the very edge of the wing. Wing covert feathers may be further distinguished according to whether they cover primaries or secondaries and/or the upperside (upperwing coverts) or underside (underwing coverts): greater underprimary coverts are the greater coverts that cover the bases of the primaries (but not the secondaries).
Covey —Group of game birds, especially smaller species such as quail.
Cowl —Informal term for a distinctly pigmented area of plumage that appears to drape from the upperparts to the sides of the breast.
Crake —Term for a small rail with a small bill.
Crèche —Group of precocial young birds of the same age from multiple nests in a colony; pelicans, terns, cormorants, and eiders of some species “pool” their young in crèches at an early stage.
Crest —Group of crown feathers that show a peak or elongation; adults of some species are always obviously crested, while others may raise a small crest only when alarmed.
Crissum —Area of feathers between the vent and rectrices that includes the undertail coverts.
Crop —In some birds, a saclike area between the throat and esophagus used to store food before regurgitation or digestion.
Crown —Area of feathers on top of the head above the eyes, bordered by the forehead and nape (less extensive than a “cap”); a crown patch is an area of distinctly pigmented feathers in the center of the crown; a crown stripe extends along the length of the crown, either down the center (median crown stripe) or along the sides of the center (lateral crown stripes).
Culmen —Ridge of the maxilla from base to tip.
Culminicorn —In albatrosses and some tubenose allies, a distinct bill plate that lies along the culmen up to the nail (as in Yellow-nosed Albatross).
Deciduous woodland —Woodland comprising mostly or solely trees that shed their foliage at the end of the growing season, usually autumn or winter.
Decurved —Curved downward; many birds’ bills are decurved.
Desert wash —A usually dry desert streambed that flows only after periods of heavy rain.
Dimorphic —In a population or species, occurring in two forms that differ in size, shape, or coloration, frequently involving differences between male and female (sexual dimorphism) or color morphs.
Dispersal —Movement away from breeding areas by adults or young; usually distinguished from “migration” in being less regular or predictable.
Display —Innate, stylized activity or signal through which birds communicate.
Diurnal —Active by day.
Dorsal —Pertaining to the upperside of the body; in birds, refers especially to the tail, back, and wings.
Dredge-spoil island —Shoal or small island created by the deposition of sediment from dredging operations, usually in connection with the maintenance of ship channels.
Early successional —Referring to the first stages of regeneration of a (usually forested) disturbed habitat, during which grasses, shrubs, forbs, and saplings dominate.
Eclipse plumage —Plumage worn briefly by male waterfowl just after mating or after the breeding season; more muted than the plumage worn through most of the year and sometimes resembling that of the female.
Endemic —Native to or confined to a certain region and found nowhere else.
Estuary —Passage of the lower course of a river where its current meets the tides and the water is brackish.
Eye arc —Area of pale, arc-shaped plumage above and/or below the eye (as in macgillivray’s Warbler); thicker than “eye crescent.”
eyebrowStripe on the side of the head immediately above the eye.
Eye-comb —Thick, fleshy growth above the eye in certain galliforms; most noticeable when males are displaying or agitated but also seen in females of many species.
Eye crescent —Narrow area of contrasting plumage above and/or below the eye, of almost even thickness (as in Franklin’s Gull).
Eye line —Line formed by dark plumage that extends through or behind the eye; also called an “eye stripe” (a term some sources use to indicate a thicker line).
Eye patch —Area of dark plumage around the eye.
Eye ring —Area of contrasting plumage encircling the eye (compare “orbital ring”).
Facial disc —Group of feathers that surround the eyes of certain birds, particularly owls, in which the disc is often clearly defined.
Facultative movements —In birds, movements made in response to pressures or stresses in the immediate environment, such as food crop failures, drought, cold, or snow cover (compare “migration”).
Fen —Low-lying, wet land with grassy vegetation; usually a flat, transitional area between land and water.
First-year bird —Bird in its first 12 months of life; a first-winter bird is in its first winter, a first-fall bird in its first fall.
Flanks —Rear portion of the sides, from about the midpoint of the folded wing to the tail coverts.
Fledge —To grow a first set of contour feathers (as opposed to a coat of downy feathers), or juvenal plumage.
Fledgling —Bird that has fledged (acquired juvenal plumage) and left the nest; most birds begin to become independent of their parents at this time (compare “nestling”), although precocial birds leave the nest as downy chicks, long before acquiring their first set of contour feathers.
Flight call —Call used chiefly by flying birds, thought to function as a contact call among members of the same species, especially during nocturnal migration.
Flycatch —To capture flying insects while in flight.
Forecrown —Foremost part of the crown; a smaller area than the forehead.
Forehead —Front of the head, above the maxilla.
Frontal shield —Featherless, fleshy plate on the forehead, often brightly colored (as in Purple Gallinule).
Frontlet —Small area of distinctly delineated plumage near the foremost portion of the forehead.
Furcular sac —Pouch of skin lying just in front of the sternum that can be inflated to produce sounds in a few species (such as Brown Jay).
Gadfly petrel —Seabird of the genus Pterodroma, often simply called a “petrel,” intermediate in size between storm-petrels and most shearwaters.
Gape —Angle of the bill where the maxilla meets the mandible.
Glean —To pick small food items singly, usually with delicate movements; warblers glean insects from leaves or needle clusters.
Gonydeal angle —Cusp on the outer portion of the mandible along the gonys; prominent on some birds, such as gulls.
Gonys —Ridge formed by the fusion of the two outer ridges of the mandible.
Gorget —Patch of brightly colored feathers on a hummingbird’s throat.
Grassland —Area with extensive grass or grasslike vegetation, such as a prairie or meadow.
Greenland Current —Ocean current that flows from the Arctic Ocean down the east side of Greenland, merging with the Labrador Current at the southern tip of Greenland.
Grin patch —Informal term for the appearance of the contrastingly dark cutting edges (tomia) near the base of the bill in Snow Goose.
Gular pouch —Patch, often colorful, of bare skin on the throat that may be distensible or inflatable (as in Magnificent Frigatebird).
Gular skin —Bare skin that surrounds the throat in some birds.
Hammock —Tract of forested land that rises above adjacent marshland, usually in the southeastern United States.
Hand —Informal term for the outer portion of the wing past the carpal joint; typically used by hawk-watchers.
High Arctic —Area above the Low Arctic, where tundra vegetation is replaced by cushion plants, rock-brake ferns (Cryptogramma), prostrate shrubs, and rosette-forming herbs.
Hindcrown —Rear part of the crown, just forward of (above) the nape.
Hover-glean —To forage while fluttering in the air; kinglets often hover-glean insect larvae from the outer needle clusters of spruce trees.
Humerals —Feathers of the inner portion of the wing that lie along the humerus (wing bone nearest the body).
Hybrid —Offspring resulting from the breeding of different species (compare “intergrade”); certain bird species, including gulls, orioles, hummingbirds, and sapsuckers, regularly or occasionally hybridize.
Icterid —A bird of the family Icteridae.
Immature —Bird that is not yet an adult in plumage. (In this book, “immature” does not refer to a bird’s ability to breed, as many species can breed in plumages other than definitive adult plumage.)
Impoundment —Body of water, such as a reservoir or marsh, contained by manmade boundaries, especially earthen dams.
Intergrade —Offspring resulting from the breeding of different subspecies (compare “hybrid”).
Interior West —Area of the western United States south of Canada that lies east of the Sierra Nevada and west of the Great Plains.
Intertidal zone —Area of a shoreline between the low- and high-tide points.
Irruption —Large-scale movement of a species outside its typical range, usually in autumn or winter; such movements do not occur in regular, predictable patterns, unlike migration.
Juvenal plumage —A bird’s first covering of contour feathers; it is often brown or streaked.
Juvenile —Bird in juvenal plumage.
Kite —In bird flight, to hang in one position while facing into the wind with minimal or no flapping.
Kleptoparasite —Bird that forages by stealing food from other birds (such as Parasitic Jaeger).
Labrador Current —Ocean current that flows southward between Canada and Greenland, extending down the U.S. East Coast to North Carolina, where its flow deflects the Gulf Stream eastward.
Lagoon —Sheltered, shallow body of water separated from deeper, more open water.
Lek —Site where males of some species (such as prairie-chickens) gather to perform group courtship displays for females; the term can also refer to the group of displaying males.
Leucism —Condition of plumage resulting from reduced pigment in feathers; leucistic birds vary from having a few stray whitish feathers to being nearly all white with just a trace of normal pigmentation (the latter resembling albino birds but with normally pigmented eyes).
Lift —Upward force exerted on a wing due to air flow across its surface.
Lore —Area between the eye and the base of the bill; some species have distinctively colored lores (such as White-throated Sparrow).
Lowland —Area of level land that is lower in elevation than surrounding land.
Malar —Small group of feathers, sometimes distinctively colored, that extends from the base of the bill downward and slightly backward along the throat (see “submalar stripe”).
Mandible —Lower part of a bird’s bill; sometimes called “lower mandible” (compare “maxilla”).
Mangrove forest —Or mangrove swamp; low, dense woodland of tropical evergreen trees or shrubs that grow in coastal tropical and subtropical areas (of southern Florida and Texas in the scope of this guide); these plants, which grow in salt water, have stiltlike roots and stems and are important roosting and nesting sites for birds.
Mantle —In this guide, feathers of the upper back, not including the scapulars; in other publications, the term may also be used to include the scapulars and all visible upperwing coverts of the folded wing.
Mask —Informal term for an area of dark plumage extending from the base of the bill through and beyond the eyes (as in Loggerhead Shrike).
Mast —The nuts of forest trees accumulated on the ground.
Maxilla —Upper part of a bird’s bill; sometimes called “upper mandible” (compare “mandible”).
Melanism —In birds, a condition involving unusual dark pigmentation in the plumage.
Mesquite —Small, spiny trees or shrubs (genus Prosopis) that grow in hot, dry climates.
Migration —Regular movement of birds between nesting and wintering areas, generally stimulated by changes in the duration of daylight rather than a weather event or food shortage (compare “facultative movements”).
Mimid —A bird of the family Mimidae.
Mirror —In gulls’ remiges, an area of white plumage near the feather tip that is surrounded by dark plumage.
Mob —In birds, to gather around a perched predator (or pursue a flying predator) while calling vigorously (“scolding”) and sometimes making swooping flights to strike; mixed flocks of small birds will often mob an owl in daylight.
Molt —The process of shedding old feathers and replacing them with new feathers, whether all or part of the plumage; most species have regular, predictable molts.
Monogamy —The condition of having only one mate during a breeding season or during the breeding life of a pair.
Montane —Of or found in mountainous environments.
Morph —In birds, a variation, usually in plumage, found within a population or an entire species; often called “color morph” (formerly “plumage phase,” although the condition is permanent).
Motte —Copse or small stand of trees on a prairie, such as the oak mottes found on the coastal prairie of eastern Texas.
Moustachial crescent —Distinct area of dark plumage forming a curve along the lower border of the auriculars above the malar and somewhat resembling a mustache (as in Prairie Warbler).
Mudflat —Area of mud along rivers, lakes, or other water bodies usually exposed by receding tides or by drought; often important habitat for foraging shorebirds and waterbirds.
Muskeg —Habitat characterized by an acidic, very moist soil type common in Arctic and boreal areas that is made up of dead plants in various states of decomposition and often includes sphagnum moss and sedge peat; often found along the uneven interface of taiga and tundra, where there are few and stunted trees.
Nail —Distinct horny plate at the end of the maxilla or mandible, most pronounced and obvious in larger tubenoses (in the order Procellariiformes).
Nape —The back of the head, including the hindneck, just below the hindcrown.
Nearshore waters —Ocean waters between the low-tide point and a depth of about a hundred fathoms (200m).
Neotropical —Of the New World tropics, which extend from southern Mexico through Central America into South America; a “Neotropical migrant” passes the nonbreeding season in this area.
Nest box —Box with an entrance hole set out specifically for cavity-nesting birds, such as wrens, woodpeckers, owls, and parids.
Nestling —Young bird that has not yet left the nest.
Nominate subspecies —In a species, the first subspecies to be described (“named”) to science; nominate subspecies have the same scientific species and subspecies names (the nominate subspecies of Bell’s Vireo is Vireo bellii bellii).
Nonpasserine —Any bird that is not in the order Passeriformes (passerines).
Northern tier —In the lower 48 United States, the states that border Canada.
Oak scrub —Open, fairly dry habitat consisting of shrubby, thicket-forming oaks.
Offshore waters —Open ocean waters, rather than nearshore waters; also called “pelagic waters” (see also “pelagic”).
Old-growth forest —Mature woodland ecosystem characterized by the presence of old woody plants, especially old trees, and the wildlife and smaller plants associated with them.
Open woodland —Woodland community characterized by widely spaced trees or an open, broken canopy (such as a pine savanna).
Orbital ring —Ring of often brightly colored bare skin encircling the eye (as in Black-billed Cuckoo).
Ornithologist —Scientist who studies birds.
Oscines —Collective term for a suborder (Passeri) of the songbirds (passerines); see also “suboscines.”
Pacific Slope —The part of western North America that drains to the Pacific Ocean.
Pack ice —Floating sea ice that has been driven together into a mass.
Parid —A bird of the family Paridae.
Passerine —Any bird in the order Passeriformes; passerines are often called “perching birds.”
Peep —Small shorebird of the genus Calidris, usually applied only to Least, Semipalmated, Western, Baird’s, and White-rumped Sandpipers and not to larger Calidris.
Pelagic —Relating to deepwater ocean regions (see also “offshore waters”).
Permanent resident —Nonmigratory species found year-round in a given area; sometimes refers to a species that makes short-distance (and/or facultative) movements, replacing local birds with birds of the same species from other areas in the nonbreeding months.
Phenotype —Observable physical properties of an organism.
Phylogenetic —Based on evolutionary history; used in the context of evolutionary relationships among taxa.
Pine barren —Area of infertile land that is dominated by pines and has limited understory vegetation (found in eastern North America).
Pinyon-juniper woodland —Habitat found on the lower slopes of mountains, consisting of short evergreen trees—mostly one or more species of pinyon pine (Pinus) and juniper (Juniperus)—mixed with desert and upland shrubs or open grasslands.
Pishing —Giving vocal imitations of parid calls (that sound a bit like steam escaping in quick bursts) to attract woodland birds.
Plunge-dive —To dive on aquatic prey from the air.
Pocosin —Freshwater bay swamp (bays are broadleaf evergreen trees of various families) in the Atlantic Coastal Plain.
Polyandry —The condition of a female having more than one mate in a breeding cycle.
Polygyny —The condition of a male having more than one mate in a breeding cycle.
Polymorphic —Having one or more distinct types within a population, usually referring to plumage types (or “morphs”).
Polynya —Area of open water surrounded by sea ice.
Prairie —Extensive area of flat or rolling, mostly treeless grassland, especially the large tract or plain of central North America known as the Great Plains.
Prairie pothole —Depressional lake or pond formed by a stranded block of glacier and dependent for its water on rain or snow; these lakes are scattered through the northern Great Plains and into Canada and are important nesting areas as well as stopover sites for migrating waterfowl.
Precocial —Referring to chicks that are covered with down and capable of moving about when hatched, such as those of most shorebirds and galliforms (compare “altricial”).
Primaries —The outermost and longest remiges, usually numbering between 9 and 12, that with their coverts form the outer portion of the wing.
Primary projection —The length of the primaries that projects past the tertials when the wing is folded (of particular use in the identification of certain passerines).
Primary shaft —The stiff central axis of the primary feather, sometimes distinctly visible in flying birds if the feather color is contrastingly dark (as in jaegers).
Range —Geographic area typically occupied by a species.
Raptor —Bird of prey, usually referring to a falcon, hawk, or owl.
Rectrices — (singular: rectrix)Tail feathers, not including the tail coverts.
Recurved —Curved upward (as in the bill of American Avocet).
Remiges —Flight feathers, including the primaries and secondaries but not their coverts.
Resaca —In southern Texas, a local name for an oxbow lake (formed when a meander of a river is cut off to form a crescent-shaped lake) of the Rio Grande.
Resident —Usually nonmigratory and present throughout the year.
Rictal bristles —Hairlike feathers that project from the gape area and are thought to aid in the capture of aerial insects by trapping them or serving a tactile function.
Riparian —Along the banks of a flowing natural watercourse such as a river; a riparian forest is found along a stream or river and does not extend far from the banks.
Riverbottom swamp —Bottomland hardwood forest with a river that moves very slowly through it (mostly southern United States); “bayou” is sometimes a local synonym.
Rump —Lower back above the uppertail coverts and below the mantle.
Sage scrub —Arid, mostly treeless habitat of the American West that is dominated by sage (Salvia, Artemisia, and other genera) and other low-growing plants; coastal sage scrub, found mostly in southern California, is a particular habitat that features species of sage and various shrubs, cacti, and grasses adapted to the semiarid climate of that region.
Saltpan —Shallow basin in a desert region containing salt and gypsum deposited by an evaporated salt lake; also a flat area of dry or drying salt water that opens or once opened onto tidal water.
Savanna —Ecosystem characterized by widely spaced overstory trees (often pines) and open expanses in the understory, which is usually grassy or herbaceous in patches; in this book, mostly refers to habitats of the southeastern United States involving loblolly and longleaf pines.
Scansorial —Adapted to or specialized for locomotion by climbing, especially on tree trunks.
Scapulars —Group of feathers that lies along the margins of the mantle or back and also overlaps the folded wing.
Scree —Loose rock debris covering a slope.
Scrub —Dry habitat (also called “scrubland”) characterized by short or stunted vegetation, sometimes but not always with heavy undergrowth.
Scrub oak —Informal term applied to several species of thicket-forming shrubby oaks.
Secondaries —The remiges of the inner part of the wing.
Second-growth woodland —Trees that grow to cover an area after the original stand has been removed.
Semi-precocial —Referring to chicks that hatch open-eyed, covered with down, and capable of leaving the nest soon, but which stay at the nest and are fed by parents (as in tern and gull chicks).
Shortgrass prairie —Arid habitat of the western Great Plains, just east of the Rocky Mountains, characterized by sparse, low vegetation, little rainfall, and periods of severe drought.
Shrub-steppe —Habitat, found from eastern Washington and Oregon to western Wyoming and Colorado, characterized by grasses and shrubs, including big sagebrush, rabbitbrush, greasewood, bitterbrush, buckwheat, and hopsage.
Sinkhole —Natural depression that connects with a subterranean passage, generally occurring in limestone regions.
Slough —(Pronounced “slew” or “slou.”) Marshy area, lake, or pond that lacks inflowing water; can be locally synonymous with “bayou” and “backwater.”
Song —Vocalization used mostly by male birds to attract a mate or to define and defend a territory (compare “call”).
Spatulate —Shaped like a spoon or a spatula.
Speciation —The process through which new species evolve from those in existence.
Spectacles —Informal term for a combination of contrastingly pigmented lores and eye rings, which resemble eyeglass frames (as in Plumbeous Vireo).
Speculum —Distinctively pigmented area on the upper surface of the secondaries, particularly in dabbling ducks (such as American Black Duck).
Sphagnum moss —Any of several mosses of the genus Sphagnum that grow in wet, acidic areas and whose decomposed remains form peat.
Staging area —Place where large numbers of birds traditionally gather en route to breeding or sometimes wintering areas, where they feed and/or roost before continuing onward.
Stoop —Characteristic aerial plunge of some falcons onto prey below.
Subadult —A bird that has not yet acquired definitive adult plumage but no longer has juvenal plumage.
Subarctic —Area just below the Arctic Circle characterized by acidic soils and taiga forest vegetation.
Submalar mark —Or submalar stripe; mark or line of contrastingly dark plumage between the malar and the throat feathers.
Suboscines —Birds in the order Passeriformes other than those in the suborder Passeri (oscines); in North America (north of Mexico), flycatchers (suborder Tyranni) are the only representatives of the suboscines.
Subterminal band —The next-to-last tail band, adjacent to the terminal band.
Subtropical —Relating to areas adjacent to the tropics where summers are hot but winters are nontropical (southernmost Florida and southernmost Texas are the only subtropical regions in the United States).
Succession —The gradual development of an ecosystem caused by changes in community composition.
Supercilium —Area between the lower edge of the crown and the eye line, often contrasting in color with both.
Swamp woods —Type of freshwater wetland, often found along the floodplains of large rivers, that is filled with water most or all of the year.
Taiga —Also called “boreal forest”; continuous belt of subarctic coniferous forest just below the tundra, in North America extending mostly from Alaska to eastern Canada.
Tailband —Contrastingly pigmented area of the tail, perpendicular to the axis of the tail.
Tallgrass prairie —Grassland ecosystem of tall grasses (such as big bluestem, little bluestem, indiangrass, and switchgrass), once extending for tens of millions of acres from the Dakotas to Texas and east through Illinois, but now found only in tiny remnants.
Talon —Claw of a bird of prey.
Tamaulipan brushlands —Ecosystem of the lower Rio Grande valley delta of southern Texas and northeastern Mexico (state of Tamaulipas), characterized by dense, thorny vegetation, mostly stunted trees and spiny shrubs.
Taxon — (plural: taxa)Broadly, a taxonomic category or group, such as a phylum, order, family, genus, or species; in this guide, “taxa” is often used as shorthand to refer to different subspecies.
Terminal band —Outermost tail band, at the tail’s tip.
Territoriality —Behavior pattern in birds concerned with the occupation and defense of a territory, often characterized by intensive singing and clashes with rivals.
Territory —Area occupied by a single bird, mated pair, or group and often vigorously defended against intruders, especially those of the same species.
Tertials —Innermost secondaries (normally 3) that often have a different shape than other secondaries and are sometimes molted on a different schedule.
Thorn scrub —Dry habitat characterized by low-growing thorny vegetation.
Thorn woods —Any habitat where thorny trees dominate, usually in arid regions.
Throat —Area of the underparts bounded by the malars and the breast.
Tideline —Area where two different water masses or currents meet, often concentrating nutrients, prey items, and flotsam.
Tomial notch —Toothlike serration in the edge of the maxilla, as seen in shrikes and vireos.
Tree line —The elevation in a mountainous region above which trees do not grow or the northern (or southern) latitude beyond which trees do not grow; also called “timberline.”
Tremolo —Rapid repetition of a single tone with a tremulous quality, similar to vibrato in human singing.
Tropics —The region of earth centered on the equator and lying between the Tropics of Capricorn and Cancer.
Tundra —In North America, the area north of the tree line in Canada and Alaska vegetated with low shrubs, dwarf heath shrubs, cottongrass communities, and various wetlands.
Ulnar bar —Area of dark plumage in the underwing coverts that extends from the humerals to the carpal joint, as seen in many gadfly petrel species.
Vagrant —Bird found outside its normal range, especially one quite far out of range.
Vent —Opening through which waste and reproductive products pass in birds; also the plumage located around this area between the legs.
Ventral —In birds, relating to the lower surface of the body from chin to undertail coverts.
Wetland —Low-lying area, such as a marsh or swamp, that is saturated with moisture for at least some period of time during a year or cycle.
Wing bar —Line of contrastingly pigmented (usually pale) plumage formed by the tips of the upperwing coverts, usually the median and/or greater coverts; many species of birds have two wing bars per wing.
Wing-loading —The weight of a bird divided by its wing area.
Wing stripe —Contrastingly pigmented (usually pale) lengthwise stripe on the upper surface of the extended wing, usually formed by the bases of the remiges (compare “carpal bar”).
Wrist —Synonym for “carpal joint.”
