Four-letter bird codes (FLBCs)

Four-letter codes are commonly (and too often incorrectly) used as a short-hand way to write a bird name. Two different sets of codes are in use. The first codes were created by the Bird Banding Laboratory (BBL) for use by bird banders in submitting data; consequently the codes are frequently referred to as “banding codes”. A slightly different set of codes has been published by the Institute for Bird Populations (IBP).

The basic codes were derived from a simple set of rules for reducing a name to four letters. A major problem is that the rules can create “collisions”; cases where two (or more) different names reduce to the same four letters. In these cases, different codes had to be created ad hoc. Unfortunately, if you want to use the codes, you simply must memorize the special cases; there is no way around it. Worse, the BBL and IBP code sets differ in some of these ad hoc codes.

Here is a summary of the basic rules:

  1. If the name is one word, the code is the first four letters.
       DICK Dickcissel
       SORA Sora
    
  2. If the name is two unhyphenated words, the code is the first two letters of each word.
       MODO Mourning Dove
       AMRO American Robin
    
  3. If the name is two words, with the last word hyphenated, the code is the first two letters of the first word and the first letter of each part of the hyphenation.
       EASO Eastern Screech-Owl
       EAWP Eastern Wood-Pewee
    
  4. If the name is two words, with the first word hyphenated, or simply three words, the first two letters of the code are the first letter of each of the first two parts of the hyphenation or of each of the first two words, and the second two letters of the code are the first two letters of the last word, or the third part of the hyphenation.
       GCFL Great Crested Flycatcher
       GTGR Great-tailed Grackle
       RTHU Ruby-throated Hummingbird
       RTHA Red-tailed Hawk
       CWWI Chuck-will's-widow
    
  5. If the name has four parts, either separate words or hyphenated parts, the code is the first letter of each part
       BCNH Black-crowned Night-Heron
       NRWS Northern Rough-winged Swallow
    

A footnote: The above rules describe how today's BBL codes were generated. I went back and read the 1978 paper by Klimkiewicz and Robbins where the first rules for banding codes were published, and those rules are slightly different. However, nomenclature was quite different then as well. I don't know the source of today's rules.

There are no published rules for resolving collisions in the BBL system, but I have observed the patterns below. First, note that the basic rules for two- or three-word names divide the name into a “first name” and “last name”, or specific name and group name, and the specific name always gets two letters and the group name two letters. Most of the ad hoc cases deviate from this equal division between specific name and group name.

When codes collide, usually all of the involved species take ad hoc codes. But in some cases where one species is rare or has a limited distribution, and the other is commoner or more widely distributed, the ad hoc code may be only used for the less common species. This is illustrated by the last example above, where Barrow's Goldeneye keeps the basic code BAGO even though it could be confused with Barnacle Goose, which gets an ad hoc code.

Some specific problems with the BBL codes relate to their primary purpose for banding. For some species, no official code is provided. For example, the BBL does not oversee banding of gallinaceous birds, so it provides no code for them. Also, they tend to retain established codes rather than update them as nomenclature changes. For example, they retain CAGO for Canada Goose even though Cackling Goose is now recognized as a species. And sometimes they provide only specific codes for recognizable forms rather than an over-all code for a species. For example, they have several codes for various forms of Snow Goose, but SNGO is not an official code for the species. The codes from the IBP address these problems.

As you can see, there are many reasons not to use these codes. The foremost reason is that they are a barrier to communication with people who do not know the codes. Another reason is that you are likely to make mistakes, and years later when you refer back to your notes you may find yourself unsure which species you actually meant. Nevertheless, you can't stop people from using the codes so it's best to try to learn them. I suggest that the most appropriate use of the codes is for quick taking of field notes that you will transcribe before you forget what you meant. If you are already a user of the codes, I predict that if you study the table carefully, you will discover at least a couple of species for which you've been using the wrong codes.

The table below lists a suggested code for each species that might be recorded in the Carolinas. This code is either the BBL code; or if none is provided, the IBP code. If the code is an ad hoc code rather than one that comes from application of the basic rules, there is an asterisk in the Exception column. If the IBP ad hoc code differs from the one from BBL, it is listed in the Alt. code column. For ad hoc codes, the reason that the basic code cannot be used is explained in the Conflict with column. The code for the conflicting species is also given there.

Both BBL and IBP list numerous codes for recognizable forms other than species. A few of these are listed in a second table; see the original sources for others.

NameExceptionCodeAlt. CodeConflict withComment
Black-bellied Whistling-DuckBBWD
Fulvous Whistling-DuckFUWD
Greater White-fronted GooseGWFG
Snow GooseSNGOBBL uses specific codes for different forms of Snow Goose
Ross's GooseROGO
BrantBRANBBL uses ATBR for Atlantic Brant
Barnacle Goose*BRNGBARGBarrow's Goldeneye BAGO
Cackling Goose*CACGCanada Goose CANG
Canada Goose*CAGOCANGCackling Goose CACG
Mute SwanMUSW
Trumpeter Swan*TRUSTree Swallow TRES
Tundra SwanTUSWBBL uses WHSW for Whistling Swan
Wood DuckWODU
GadwallGADW
Eurasian WigeonEUWI
American WigeonAMWI
American Black DuckABDU
MallardMALL
Mottled DuckMODU
Blue-winged TealBWTE
Cinnamon TealCITE
Northern Shoveler*NSHONorthern Shrike NSHR
Northern PintailNOPI
GarganeyGARG
Green-winged TealGWTEBBL uses AGWT for American Green-winged Teal
CanvasbackCANV
RedheadREDH
Ring-necked DuckRNDU
Tufted DuckTUDU
Greater ScaupGRSC
Lesser ScaupLESC
King EiderKIEI
Common EiderCOEI
Harlequin Duck*HARDHADUHawaiian Duck HAWD
Surf ScoterSUSC
White-winged ScoterWWSC
Black ScoterBLSC
Long-tailed DuckLTDU
BuffleheadBUFF
Common GoldeneyeCOGO
Hooded MerganserHOME
Common MerganserCOME
Red-breasted MerganserRBME
Masked DuckMADU
Ruddy DuckRUDU
Northern BobwhiteNOBOBBL provides no codes for gallinaceous birds
Ring-necked Pheasant*RNEPRed-necked Phalarope RNPHBBL provides no codes for gallinaceous birds
Ruffed GrouseRUGRBBL provides no codes for gallinaceous birds
Wild TurkeyWITUBBL provides no codes for gallinaceous birds
Red-throated LoonRTLO
Pacific LoonPALO
Common LoonCOLO
Pied-billed GrebePBGR
Horned GrebeHOGR
Red-necked GrebeRNGR
Eared GrebeEAGR
Western GrebeWEGR
Clark's GrebeCLGR
Yellow-nosed AlbatrossYNAL
Black-browed AlbatrossBBAL
Northern FulmarNOFU
Herald PetrelHEPEBBL provides no code
Fea's PetrelFEPEBBL provides no code
Bermuda PetrelBEPEBBL provides no code
Black-capped PetrelBCPE
Bulwer's PetrelBUPE
Cory's ShearwaterCOSH
Cape Verde ShearwaterCVSHBBL provides no code
Great ShearwaterGRSH
Sooty ShearwaterSOSH
Manx ShearwaterMASH
Audubon's ShearwaterAUSH
Little ShearwaterLISH
Wilson's Storm-PetrelWISP
White-faced Storm-PetrelWFSP
European Storm-PetrelEUSPBBL provides no code
Black-bellied Storm-PetrelBBSPBBL provides no code
Swinhoe's Storm-Petrel*SSTPSwamp Sparrow SWSPBBL provides no code
Leach's Storm-Petrel*LHSPLESPLeast Storm-Petrel LTSP
Band-rumped Storm-Petrel*BANPBSTPBrewer's Sparrow BRSP
White-tailed TropicbirdWTTR
Red-billed TropicbirdRBTR
Masked BoobyMABO
Brown BoobyBRBO
Red-footed BoobyRFBO
Northern GannetNOGA
American White PelicanAWPE
Brown PelicanBRPE
Double-crested CormorantDCCO
Great CormorantGRCO
AnhingaANHI
Magnificent FrigatebirdMAFR
American BitternAMBI
Least BitternLEBI
Great Blue HeronGBHE
Great EgretGREG
Snowy EgretSNEG
Little Blue HeronLBHE
Tricolored HeronTRHE
Reddish EgretREEG
Cattle EgretCAEG
Green HeronGRHE
Black-crowned Night-HeronBCNH
Yellow-crowned Night-HeronYCNH
White IbisWHIB
Glossy IbisGLIB
White-faced IbisWFIB
Roseate SpoonbillROSP
Wood StorkWOST
Black VultureBLVU
Turkey VultureTUVU
OspreyOSPR
Swallow-tailed KiteSTKI
White-tailed KiteWTKI
Snail KiteSNKI
Mississippi KiteMIKI
Bald EagleBAEA
Northern HarrierNOHA
Sharp-shinned HawkSSHA
Cooper's HawkCOHA
Northern GoshawkNOGO
Red-shouldered HawkRSHA
Broad-winged HawkBWHA
Swainson's HawkSWHA
Red-tailed HawkRTHA
Rough-legged HawkRLHA
Golden EagleGOEA
American KestrelAMKE
MerlinMERL
GyrfalconGYRF
Peregrine FalconPEFA
Yellow RailYERA
Black RailBLRA
Clapper RailCLRA
King RailKIRA
Virginia RailVIRA
SoraSORA
Purple GallinulePUGA
Common GallinuleCOGA Recently split from Common Moorhen (COMO).
American CootAMCO
LimpkinLIMP
Sandhill CraneSACR
Whooping CraneWHCR
Northern LapwingNOLA
Black-bellied PloverBBPL
American Golden-PloverAMGP
Snowy PloverSNPL
Wilson's PloverWIPL
Semipalmated PloverSEPL
Piping PloverPIPL
KilldeerKILL
Mountain PloverMOPLFormerly MOUP because of conflict with Mongolian Plover, which is now called Lesser Sand-Plover
American OystercatcherAMOY
Black-necked StiltBNST
American AvocetAMAV
Spotted SandpiperSPSA
Solitary SandpiperSOSA
Spotted RedshankSPREBBL provides no code
Greater YellowlegsGRYE
WilletWILL
Lesser YellowlegsLEYE
Upland SandpiperUPSA
Eskimo CurlewESCUBBL provides no code
WhimbrelWHIM
Long-billed CurlewLBCU
Black-tailed Godwit*BLAGBTGDBar-tailed Godwit BARG
Hudsonian GodwitHUGO
Bar-tailed Godwit*BARGBTGOBlack-tailed Godwit BTGO
Marbled GodwitMAGO
Ruddy TurnstoneRUTU
Red KnotREKN
SanderlingSAND
Semipalmated SandpiperSESA
Western SandpiperWESA
Red-necked StintRNST
Little StintLISTBBL provides no code
Least SandpiperLESA
White-rumped SandpiperWRSA
Baird's SandpiperBASA
Pectoral SandpiperPESA
Sharp-tailed Sandpiper*SHASSPTSStilt Sandpiper STSA
Purple SandpiperPUSA
DunlinDUNL
Curlew SandpiperCUSA
Stilt SandpiperSTSA
Buff-breasted SandpiperBBSA
RuffRUFF
Short-billed DowitcherSBDO
Long-billed DowitcherLBDO
Wilson's SnipeWISNFormerly COSN for Common Snipe
American WoodcockAMWO
Wilson's PhalaropeWIPH
Red-necked PhalaropeRNPH
Red PhalaropeREPH
Black-legged KittiwakeBLKI
Sabine's GullSAGU
Bonaparte's GullBOGU
Black-headed GullBHGU
Little GullLIGU
Laughing GullLAGU
Franklin's GullFRGU
Black-tailed GullBTGUBand-tailed Gull BTGU (now called Belcher's Gull)
Mew GullMEGU
Ring-billed GullRBGU
California GullCAGU
Herring Gull*HERGHeermann's Gull HEEG
Yellow-legged GullYLGUBBL provides no code
Thayer's GullTHGU
Iceland GullICGU
Lesser Black-backed GullLBBG
Slaty-backed GullSBGU
Glaucous GullGLGU
Great Black-backed GullGBBG
Brown NoddyBRNO
Sooty TernSOTE
Bridled TernBRTE
Least TernLETE
Gull-billed TernGBTE
Caspian TernCATE
Black TernBLTE
White-winged TernWWTE
Roseate Tern*ROSTRoyal Tern ROYT
Common TernCOTE
Arctic TernARTE
Forster's TernFOTE
Royal Tern*ROYTRoseate Tern ROST
Sandwich TernSATE
Black SkimmerBLSK
Great SkuaGRSK
South Polar SkuaSPSK
Pomarine JaegerPOJA
Parasitic JaegerPAJA
Long-tailed JaegerLTJA
DovekieDOVE
Common MurreCOMU
Thick-billed MurreTBMU
RazorbillRAZO
Black GuillemotBLGU
Long-billed MurreletLBMU
Atlantic PuffinATPU
Rock PigeonROPI
Band-tailed PigeonBTPI
Eurasian Collared-Dove*ECDOEUCDECDO does not follow the rules for forming a code
White-winged DoveWWDO
Mourning DoveMODO
Passenger PigeonPAPI
Common Ground-DoveCOGD
Monk ParakeetMOPA
Carolina ParakeetCAPA
Yellow-billed CuckooYBCU
Black-billed CuckooBBCU
Smooth-billed AniSBAN
Groove-billed AniGBAN
Barn Owl*BNOWBANOBarred Owl BDOW
Eastern Screech-OwlEASO
Great Horned OwlGHOW
Snowy OwlSNOW
Burrowing OwlBUOW
Barred Owl*BDOWBADOBarn Owl BNOW
Long-eared OwlLEOW
Short-eared OwlSEOW
Northern Saw-whet OwlNSWO
Lesser NighthawkLENI
Common NighthawkCONI
Antillean NighthawkANNI
Chuck-will's-widowCWWI
Eastern Whip-poor-willEWPWFormerly WPWI before the qualifier “Eastern” was added.
Chimney SwiftCHSW
Green Violetear*GVIOGREVGray Vireo GRVIFormerly GRVE before the hyphen was removed from “Violet-ear”.
Green-breasted Mango*GREMGNBMGray-breasted Martin GBMA
Broad-billed Hummingbird*BBLHBBIHBuff-bellied Hummingbird BUFH
Buff-bellied Hummingbird*BUFHBBEHBroad-billed Hummingbird BBLH
Blue-throated Hummingbird*BLUHBTHHBroad-tailed Hummingbird BTLH
Ruby-throated HummingbirdRTHU
Black-chinned HummingbirdBCHU
Anna's HummingbirdANHU
Calliope HummingbirdCAHU
Broad-tailed Hummingbird*BTLHBTAHBlue-throated Hummingbird BLUH
Rufous HummingbirdRUHU
Allen's HummingbirdALHU
Belted KingfisherBEKI
Red-headed WoodpeckerRHWO
Red-bellied WoodpeckerRBWO
Yellow-bellied SapsuckerYBSA
Downy WoodpeckerDOWO
Hairy WoodpeckerHAWO
Red-cockaded WoodpeckerRCWO
Northern FlickerNOFLBBL uses YSFL for Yellow-shafted Flicker
Pileated WoodpeckerPIWO
Ivory-billed WoodpeckerIBWO
Olive-sided FlycatcherOSFL
Eastern Wood-PeweeEAWP
Yellow-bellied FlycatcherYBFL
Acadian FlycatcherACFL
Alder FlycatcherALFL
Willow FlycatcherWIFL
Least FlycatcherLEFL
Gray FlycatcherGRFL
Pacific-slope FlycatcherPSFL
Cordilleran FlycatcherCOFL
Eastern PhoebeEAPH
Say's PhoebeSAPH
Vermilion FlycatcherVEFL
Ash-throated FlycatcherATFL
Great Crested FlycatcherGCFL
Tropical KingbirdTRKI
Couch's KingbirdCOKI
Western KingbirdWEKI
Eastern KingbirdEAKI
Gray Kingbird*GRAK Great Kiskadee GKIS, Green Kingfisher GKIN
Scissor-tailed FlycatcherSTFL
Fork-tailed FlycatcherFTFL
Loggerhead ShrikeLOSH
Northern Shrike*NSHR Northern Shoveler NSHO
White-eyed VireoWEVI
Bell's VireoBEVI
Yellow-throated VireoYTVI
Blue-headed VireoBHVI
Warbling VireoWAVI
Philadelphia VireoPHVI
Red-eyed VireoREVI
Black-whiskered VireoBWVI
Blue JayBLJA
American CrowAMCR
Fish CrowFICR
Common RavenCORA
Horned LarkHOLA
Purple MartinPUMA
Tree Swallow*TRESTrumpeter Swan TRUS
Violet-green SwallowVGSW
Northern Rough-winged SwallowNRWS
Bank Swallow*BANS Barn Swallow BARS, Bahama Swallow BAHS
Cliff SwallowCLSW
Cave SwallowCASW
Barn Swallow*BARSBank Swallow BANS, Bahama Swallow BAHS
Carolina ChickadeeCACH
Black-capped ChickadeeBCCH
Tufted TitmouseTUTI
Red-breasted NuthatchRBNU
White-breasted NuthatchWBNU
Brown-headed NuthatchBHNU
Brown CreeperBRCR
Carolina Wren*CARWCanyon Wren CANW, Cactus Wren CACW
Bewick's WrenBEWR
House WrenHOWR
Winter WrenWIWR
Sedge WrenSEWR
Marsh WrenMAWR
Blue-gray GnatcatcherBGGN
Golden-crowned KingletGCKI
Ruby-crowned KingletRCKI
Northern WheatearNOWH
Eastern BluebirdEABL
Mountain BluebirdMOBL
Townsend's SolitaireTOSO
VeeryVEER
Gray-cheeked ThrushGCTH
Bicknell's ThrushBITH
Swainson's ThrushSWTH
Hermit ThrushHETH
Wood ThrushWOTH
American RobinAMRO
Varied ThrushVATH
Gray CatbirdGRCA
Northern MockingbirdNOMO
Sage ThrasherSATH
Brown ThrasherBRTH
European StarlingEUST
White WagtailWHWA
American PipitAMPI
Sprague's PipitSPPI
Cedar Waxwing*CEDWCerulean Warbler CERW
Lapland LongspurLALO
Chestnut-collared LongspurCCLO
Smith's LongspurSMLO
Snow BuntingSNBU
Bachman's WarblerBAWABBL provides no code
Blue-winged WarblerBWWA
Golden-winged WarblerGWWA
Tennessee WarblerTEWA
Orange-crowned WarblerOCWA
Nashville WarblerNAWA
Northern ParulaNOPA
Yellow WarblerYEWA Formerly YWAR because of conflict with Yellow Wagtail (now called Eastern Yellow Wagtail)
Chestnut-sided WarblerCSWA
Magnolia WarblerMAWA MacGillivray's Warbler MGWA
Cape May WarblerCMWA
Black-throated Blue WarblerBTBW
Yellow-rumped WarblerYRWA
Black-throated Gray Warbler*BTYWBlack-throated Green Warbler BTNW
Black-throated Green Warbler*BTNWBlack-throated Gray Warbler BTYW
Townsend's WarblerTOWA
Blackburnian Warbler*BLBWBlackpoll Warbler BLPW
Yellow-throated WarblerYTWA
Pine WarblerPIWA
Kirtland's WarblerKIWA
Prairie Warbler*PRAWProthonotary Warbler PROW
Palm WarblerPAWABBL uses YPWA for Yellow Palm Warbler and WPWA for Western Palm Warbler
Bay-breasted WarblerBBWA
Blackpoll Warbler*BLPWBlackburnian Warbler BLBW
Cerulean Warbler*CERWCedar Waxwing CEDW
Black-and-white WarblerBAWW
American RedstartAMRE
Prothonotary Warbler*PROWPrairie Warbler PRAW
Worm-eating WarblerWEWA
Swainson's WarblerSWWA
OvenbirdOVEN
Northern WaterthrushNOWA
Louisiana WaterthrushLOWA
Kentucky WarblerKEWA
Connecticut Warbler*CONWColima Warbler COLW
Mourning WarblerMOWA
MacGillivray's Warbler*MGWAMagnolia Warbler MAWA
Common YellowthroatCOYE
Hooded WarblerHOWA
Wilson's WarblerWIWA
Canada WarblerCAWA
Yellow-breasted ChatYBCH
Green-tailed TowheeGTTO
Spotted TowheeSPTO
Eastern TowheeEATO
Cassin's SparrowCASP
Bachman's Sparrow*BACSBaird's Sparrow BAIS
American Tree SparrowATSP
Chipping SparrowCHSP
Clay-colored SparrowCCSP
Field SparrowFISP
Vesper SparrowVESP
Lark SparrowLASP
Lark Bunting*LARBLazuli Bunting LAZB
Savannah Sparrow*SAVS Sage Sparrow SAGS, Saltmarsh Sparrow SALS
Grasshopper SparrowGRSP
Henslow's SparrowHESP
Le Conte's SparrowLCSP
Nelson's SparrowNESPFormerly NSTS for Nelson's Sharp-tailed Sparrow
Saltmarsh Sparrow*SALS Sage Sparrow SAGS, Savannah Sparrow SAVSFormerly SSTS for Saltmarsh Sharp-tailed Sparrow
Seaside SparrowSESP
Fox SparrowFOSP
Song SparrowSOSP
Lincoln's SparrowLISP
Swamp SparrowSWSPSwinhoe's Storm-Petrel SSTP
White-throated SparrowWTSP
Harris's SparrowHASP
White-crowned SparrowWCSP
Golden-crowned SparrowGCSP
Dark-eyed JuncoDEJUBBL uses SCJU for Slate-colored Junco
Summer TanagerSUTA
Scarlet TanagerSCTA
Western TanagerWETA
Northern CardinalNOCA
Rose-breasted GrosbeakRBGR
Black-headed GrosbeakBHGR
Blue GrosbeakBLGR
Lazuli Bunting*LAZBLark Bunting LARB
Indigo BuntingINBU
Painted BuntingPABU
DickcisselDICK
BobolinkBOBO
Red-winged BlackbirdRWBL
Eastern MeadowlarkEAME
Western MeadowlarkWEME
Yellow-headed BlackbirdYHBL
Rusty BlackbirdRUBL
Brewer's BlackbirdBRBL
Common GrackleCOGR
Boat-tailed GrackleBTGR
Shiny CowbirdSHCO
Brown-headed CowbirdBHCO
Orchard OrioleOROR
Bullock's OrioleBUOR
Baltimore OrioleBAOR
Scott's OrioleSCOR
BramblingBRAM
Pine GrosbeakPIGR
Purple FinchPUFI
House FinchHOFI
Red CrossbillRECR
White-winged CrossbillWWCR
Common RedpollCORE
Pine SiskinPISI
Lesser GoldfinchLEGO
American GoldfinchAMGO
Evening GrosbeakEVGR
House SparrowHOSP

The table below lists a sample of codes that are defined for forms that are not species. See the original sources for others.

Blue Greater Snow GooseBGSG
Lesser Snow Goose (intermediate phase)SBGI
Lesser Snow Goose (white phase)LSGO
Greater Snow GooseGSGO
Lesser Snow Goose (blue phase)BLGO
Eurasian Green-winged TealEGWT
Great White HeronGWHE
Traill's FlycatcherTRFL
Gray-cheeked/Bicknell's ThrushGCBT
Brewster's WarblerBRWA
Lawrence's WarblerLAWA
Myrtle WarblerMYWA
Audubon's WarblerAUWA
Ipswich SparrowIPSP
Sharp-tailed SparrowSTSP


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