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Hummingbirdsaresmall,oftenbrightlycoloredbirdsofthefamily TrochilidaethatliveexclusivelyintheAmericas.About12speciesarefound inNorthAmerica,butonlytheruby-throatedhummingbirdbreedsineastern NorthAmericaandisfoundfromNovaScotiatoFlorida.Thegreatestvariety andnumberofspeciesarefoundinSouthAmerica.Anotherhummingbird species is found from southeasternAlaska to northern California.

Manyhummingbirdsareminute.Buteventhegianthummingbirdfoundin westernSouthAmerica,whichisthelargestknownhummingbird,isonlyabout 8incheslongandweighsabouttwo-thirdsofanounce.Thesmallestspecies, thebeehummingbirdofCubaandtheIsleofPines,measuresslightlymore than 5.5 centimeters and weighs about two grams.

Hummingbirds'bodiesarecompact,withstrongmuscles.Theyhavewings shapedlikeblades.Unlikethewingsofotherbirds,hummingbirdwings connecttothebodyonlyattheshoulderjoint,whichallowsthemtoflynot onlyforward butalsostraightupanddown, sideways, andbackward. Because oftheirunusualwingshummingbirdscanalsohoverinfrontofflowerssothey cansucknectarandfindinsects.Thehumming-bird'sbill,adaptedforsecuring nectarfromcertaintypesof flowers, isusuallyratherlongandalwaysslender, and it is curved slightly downward in many species.

Thehummingbird’sbodyfeathersaresparseandmorelikescalesthan feathers.Theuniquecharacterofthefeathersproducesbrilliantandiridescent

colors,resultingfromtherefractionoflightbythefeathers.Pigmentationof otherfeathersalsocontributestotheuniquecolorandlook.Maleandfemale hummingbirdslookalikeinsomespeciesbutdifferentinmostspecies;males of most speciesare extremely colorful.

Therate atwhichahummingbirdbeatsitswingsdoesnotvary,regardlessof whetheritisflyingforward,flyinginanotherdirection,ormerelyhovering. Buttheratedoesvarywiththesizeofthebird-thelargerthebird,thelower therate,rangingfrom80beatspersecondforthesmallestspeciesto10times persecondforlargerspecies.Researchershavenotyetbeenabletorecordthe speedofthewingsofthebeehumming-birdbutimaginethattheybeateven faster.Mosthummingbirds,especiallythesmallerspecies,emitscratchy, twittering,orsqueakysounds.Thewings,andsometimesthetailfeathers,often producehumming,hissing,orpoppingsounds,whichapparentlyfunction much as do the songs of other birds.

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