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The National Audubon Society Christmas Bird Count

The National Audubon Society Christmas Bird Count (CBC) is an early-winter survey of birds. Although counts occur in Central and South America, most CBCs occur in North America. The sample area for a count is a circle that is 15 miles in diameter, and varying numbers of volunteers count all birds they see in the circle during a single day, which is within 2 weeks of 25 December. (Butcher 1990)

Although this analysis only considers the interval 1959 - 1988, the CBC was begun in 1900. The number of circles and participants has changed dramatically since the early years. Butcher (1990) notes that 1,508 circles were surveyed in 1986-1987. Unfortunately, the number of birds counted is a function of effort, and analysis of change over time must incorporate some effort adjustment (Butcher and McCulloch 1990). In this analysis, we standardized the counts to birds/100 party hours, but we acknowledge that more research is needed into methods of adjusting counts.

Each year, American Birds publishes a summary of the previous years count (e.g., American Birds 47(4):1-1026) that notes interesting features of the counts and summarizes birds, effort, and volunteers for each circle. Also, numerous articles have appeared in American Birds that summarize data for individual species and groups of species. Root (1988) has summarized patterns of regional relative abundance for wintering North American birds.

Taxonomic problems with the database

Several species are grouped in the database, and several transcription errors have occurred in collating the data. In Table 1, we note species that are incorrectly grouped in the database. Also, many categories exist for rare or unidentified birds. In Table 2, we list the taxa that we have eliminated because of possible taxonomic problems.

Species with small sample sizes

Because the CBC is an early winter survey, many migrant species appear in the database. Because species seen on few circles could provide misleading views of population trends, we have eliminated species with small sample sizes (fewer than 40) from display.

These species are listed in Table 3.

Literature Cited

Butcher, G. S.  1990. Audubon Christmas Bird Counts. Pp. 5-13 in 
     J. R. Sauer and S. Droege, eds. Survey designs and statistical
     methods for the estimation of avian population trends. U.S.
     Fish Wildl. Serv. Biol. Rep. 90(1).

Butcher, G. S., and C. E. McCulloch  1990. The influence of
     observer effort on the number of individual birds recorded on
     Christmas Bird Counts. Pp. 120-129 in J. R. Sauer and S.
     Droege, eds. Survey designs and statistical methods for the
     estimation of avian population trends. U.S. Fish Wildl. Serv.
     Biol. Rep. 90(1).

Root, T.  1988.  Atlas of wintering North American birds. 
     University of Chicago Press, Chicago, Il.

Table 1. Species that are incorrectly grouped in the database. A '*' indicates that the combined data appears under that name.

            Grouped Species                                  

1.  Western grebe, Clark's grebe. 
2.  Red-breasted sapsucker, Yellow-bell. sapsucker, 
      Red-naped sapsucker.
3.  Gilded flicker, Yellow-shafted flicker, Red-shafted 
      flicker, Northern Flicker*.
4.  Tufted titmouse*, Black-crested titmouse.
5.  Canyon towhee, Brown towhee.
6.  Great-tailed grackle, Boat-tailed grackle.
7.  Myrtle warbler, Audubon's warbler, Yellow-rumped warbler.

Table 2. Taxonomic groups that are found in the CBC database, but are of questionably validity for trend analysis. These groups include birds not identified to species, some species not commonly found in North America during the breeding season, and species with taxonomic changes that have not been consistently identified in the database.

       "AOU"         Taxon identifier         Number of Circles

        3333    unidentified_accipiter_ unac          853
          12    aechmophorus_spp_______ ****           27
        5769    aimophila_spp__________ ****            6
         345    alcidae_spp____________ ****           68
        5509    ammodramus_spp_________ ****            4
        4289    archilochus_spp________ ****           26
        3669    asio_spp_______________ ****           23
       51830    nanday_(black-hooded)_p ****           22
         930    black-vented_shearwater bvsh           15
        4989    emberizidae/blackbird_s bkbd          487
        5971    blue_bunting___________ blbu            4
        7669    sialia/bluebird_spp____ ****           14
        4832    brown_jay______________ brja            4
        3822    budgerigar_____________ budg           26
        3451    unidentified_buteo_spp_ bute          687
        1326    anus/black_x_mallard_sp ****          134
        5911    california_towhee______ calt          111
        2211    caribbean_coot_________ cact           16
        5169    carpodacus_spp_________ ****           66
        7559    catharus_spp___________ ****           15
       64239    chaetura_spp___________ ****            6
        7351    chickadee_species______ chic           94
        7621    clay-colored_robin_____ ccro            3
        3095    common_peafowl_________ cope            4
        1207    phalacrocorax/cormor_sp corm          139
        4879    corvus_spp_____________ ****            6
        5219    loxia/crossbill_spp____ ****           33
        4889    corvus/crow_spp________ ****          116
        4689    empidonaz/d_or_h_flycat ****           15
        1339    anatidae/dabbling_duck_ ****            3
         909    procellariidae/d-backed ****           29
        1639    melanitta/d-winged_scot ****            4
        6509    dendroica_spp__________ ****           21
        1499    anatidae/diving_duck_sp ****            6
        2327    limnodromus/dowitcher_s dowi          191
        1327    unidentified_duck______ duck          581
        3499    accipitridae/eagle_spp_ ****          121
        1579    anatidae/eider_spp_____ ****           18
        4679    empidonax_spp__________ empi          131
        3154    european_collared_dove_ ****            8
        5099    euphagus_spp___________ ****            8
        3559    falco/falcon_spp_______ ****          302
        5189    emberizidae/finch_spp__ ****           64
        5742    five-striped_sparrow___ fssp            2
        4449    tyrannidae/flycatcher_s ****           12
        7519    polioptila/gnat-catch_s ****           23
        4169    caprimulgidae/goatsucke ****           12
        1519    bucephala/goldeneye_spp ****           52
        5299    carduelis/goldfinch_spp ****           26
        1697    unidentified_goose_____ goos           69
          37    podicipedidae/grebe_spp greb           74
       11230    green_parakeet_________ ****            8
        2979    phasianidae/grouse_spp_ ****           16
         534    larus/gull_spp_________ gull          578
        3333    accipitridae/hawk_spp__ hawk          853
        6224    hawaii_oo______________ haoo           33
       17520    hill_mynah_____________ himy            6
        3271    hook-billed_kite_______ hbki            3
        4401    unidentified_hummingbir humm          114
        4123    hybrid_flicker_________ ****            8
        1326    hybrid_mallard_________ hybm          134
        1861    threskiornithidae_spp__ ****           25
         387    stercorarius/jaeger_spp jaeg           65
        4779    corvidae/jay_SPP_______ ****            9
        5677    junco/junco_spp________ junc           97
        7489    regulus/kinglet_spp____ ****           25
        3333    accipiter/large_spp____ ****          853
         349    alcidae/large_spp______ ****           11
        3559    falco/large_spp________ ****          302
         534    larus/large_spp________ ****          578
        3669    strigiformes/large_spp_ ****           23
        2089    rallus/large_spp_______ ****           28
         909    procellariidae/l-backed ****           29
        5387    calcarius/longspur_spp_ long           74
          77    gavia/loon_spp_________ loon          128
        5012    unident._meadowlark____ unme          326
        1299    anatidae/merganser_spp_ ****          168
        4891    mexican_crow___________ tacr            6
        3824    monk_parakeet__________ mopa           72
         309    uria/murre_spp_________ ****           23
         219    alcidae/murrelet_spp___ ****           20
       10210    muscovy_duck___________ mudu            3
        4529    myiarchus_spp__________ ****           15
        2029    nycticorax/night_heron_ ****           12
        4207    chordeiles/nighthawk_sp nigh           14
        7279    sitta/nuthatch_spp_____ ****           16
        6799    oporornis_spp__________ ****           21
       11290    orange-fronted_parakeet ofpa            6
        5039    emberizidae/oriole_spp_ ****            9
        3687    strigiformes/owl_spp___ owl.          308
        3829    psittacideae/parakeet_s ****           17
        3829    psittacidaee/parrot_spp ****           17
        2477    scolopacidae/peep_spp__ peep          216
        2247    phalaropus_spp_________ phal           22
        5959    pheucticus_spp_________ ****           12
        1861    plegadis_spp___________ ****           25
        2709    charadriidae/plover_spp ****           13
        2929    phasianidae/quail_spp__ ****           15
        2089    rallus/rail_spp________ ****           28
        2089    rallus_spp_____________ ****           28
        4869    corvus/raven_spp_______ ****           33
        5279    carduelis/redpole_spp__ ****           37
       11580    red-lored_parrot_______ ****            4
        3823    rose-ringed_parakeet___ rrpa           17
        7622    rufous-backed_robin____ rbro           11
        4123    redxyellow_shafted_flic ****            8
        2567    scolopacidae/sandpiper_ spip          166
        4022    sphyrapicus/sapsucker_s ****           27
        1489    aythya/scaup_spp_______ scau          472
        1657    melanitta/scoter_spp___ scot          189
        3737    otus/screech-owl_spp___ sowl          981
        4329    selasphorus_spp________ ****           61
         909    charadriiformes/shorebi ****           29
        6227    lanius/shrike_spp______ shri           92
        3333    accipiter/small________ ****          853
        3559    falco/small____________ ****          302
        3669    strigidae/small________ ****           23
         634    sterna/small___________ ****           85
        5409    sparrow_spp____________ ****          400
        5599    spizella_spp___________ ****            9
         634    sterna_spp_____________ ster           85
        6101    stripe-headed_tanager__ shta            3
        6149    hirundinidae/swallow_sp ****           83
        1799    cygnus/swan_spp________ ****           35
        4229    apodidae/swift_________ ****            6
        6099    emberizidae/tanager_spp ****            4
        1389    anas/teal_spp__________ ****           60
         634    sterna/tern_spp________ tern           85
         431    thayer's_gull__________ thgu          195
        7029    mimidae/thrasher_spp___ ****           13
        7599    muscicapidae/thrush____ ****           65
        7319    parus/titmouse_spp_____ ****            6
        7029    toxostoma_spp__________ ****           13
        1491    tufted_duck____________ tudu           22
        4459    tyrannus_spp___________ ****            3
        6409    vermivora_spp__________ ****            5
        6249    vireo_spp______________ ****            9
        3269    cathartidae_spp________ ****            6
        6399    emberizidae/warbler_spp ****          105
        6199    bombycilla/waxwing_spp_ ****           30
        4642    w._flycatcher_complex__ wefl           48
        0011    clarks_grebe___________ clgr           --
          12    western_grebe__________ ****           27
        4401    unident._hummingbird___ unhu          114
         534    larus/white-winged_gull ****          578
        4660    traill's_flycatcher____ trfl            4
        4089    woodpecker_spp_________ ****           83
        7139    troglodytidae/wren_spp_ ****           66
       11600    yellow-headed_parrot___ ****            9
        2549    yellow_leg_spp_________ ****           87
        2549    tringa/yellowlegs_spp__ ****           87
        3131    rock_dove______________ rodo         1709

Table 3. Species seen on fewer than 40 CBC circles.


       "AOU"         Species name             Number of Circles

        5920    abert's_towhee_________ abto          35
        4650    acadian_flycatcher_____ acfl           2
        4340    allen's_hummingbird____ alhu          24
        5031    altamira_oriole________ alor           7
        1820    greater_flamingo_______ gflm          10
        3980    strickland's_woodpecker stwo          12
        1080    ashy_storm-petrel______ aspe           5
        1080    ashy_storm-petrel______ aspe           5
         130    atlantic_puffin________ atpu          19
        5030    audubon's_oriole_______ auor           7
         920    audubon's_shearwater___ aush           3
        2410    baird's_sandpiper______ basa          26
        5450    baird's_sparrow________ brds          34
        6160    bank_swallow___________ bnks          24
        1770    black-bell._whist._duck bbwd          37
        1770    black-bell._whist._duck bbwd          37
        4720    n._beardless-tyrannulet nbty           9
        6330    bell's_vireo___________ bevi          26
        7080    bendire's_thrasher_____ beth          33
        1140    masked_booby___________ mabo           5
        3880    black-billed_cuckoo____ bbcu           4
        6620    blackburnian_warbler___ blbw          18
         810    black-foot._albatross__ bfal           5
        5030    audubon's_oriole_______ auor           7
        6610    blackpoll_warbler______ bplw          10
        1070    black_storm-petrel_____ bspe           5
        3450    common_black-hawk______ cbha           9
         770    black_tern_____________ blte          23
        4530    brown-crest._flycatcher bcfl          15
        4940    bobolink_______________ bobo          16
        3710    boreal_owl_____________ boow          18
        5760    botteri's_sparrow______ bosp           3
        4410    broad-bill._hummingbird brbh          16
        7340    bridled_titmouse_______ brti          26
        1150    brown_booby____________ brbo           9
        4320    broad-tail._hummingbird btlh          13
        4390    buff-bel._hummingbird__ bubh          22
        4270    blue-thr._hummingbird__ bthh           4
        6410    blue-winged_warbler____ bwwa           8
        3240    california_condor______ caco           2
        6860    canada_warbler_________ cawa          11
        6121    cave_swallow___________ casw           5
        3825    canary-winged_parakeet_ cwpa          14
        3110    plain_chachalaca_______ plch          10
        4230    chimney_swift__________ chsw           4
        6590    chestnut-sided_warbler_ cswa          24
        6120    cliff_swallow__________ clsw          15
        3450    common_black-hawk______ cbha           9
        4200    common_nighthawk_______ coni          32
        4190    common_pauraque________ copa          21
         130    atlantic_puffin________ atpu          19
        6780    connecticut_warbler____ conw           8
        4600    greater_pewee__________ grpe          15
        4461    couch's_kingbird_______ coki          25
        4931    crested_mynah__________ crmy           7
        4550    dusky-capped_flycatcher dcfl           8
        4690    dusky_flycatcher_______ dufl          17
        4610    eastern_wood-pewee_____ ewpe          33
         660    elegant_tern___________ elte          10
        3890    elegant_trogon_________ eltr           4
        3810    elf_owl________________ elow           2
        1760    emperor_goose__________ emgo          13
        5261    european_goldfinch_____ eugo           6
        4730    eurasian_skylark_______ eusk           6
        6883    eurasian_tree_sparrow__ etsp          26
        3300    snail_kite_____________ snki          10
        3800    ferruginous_pygmy-owl__ fpow           5
        3800    ferruginous_pygmy-owl__ fpow           5
         951    flesh-footed_shearwater flfs           6
        1050    fork-tail._storm-petrel ftsp           3
        1050    fork-tail._storm-petrel ftsp           3
        4110    gila_woodpecker________ giwo          37
        1820    greater_flamingo_______ gflm          10
        4490    great_kiskadee_________ gkis          20
        4600    greater_pewee__________ grpe          15
         890    greater_shearwater_____ grsh           6
        4830    green_jay______________ grnj          14
        3910    green_kingfisher_______ gkgf          27
        3092    green_pheasant_________ ****           2
        3460    gray_hawk______________ grha           8
        4450    gray_kingbird__________ gknb           8
        6340    gray_vireo_____________ grvi           8
        4820    gray-breasted_jay______ gbja          22
        4680    hammond's_flycatcher___ hafl          17
        6090    hepatic_tanager________ heta          13
        6840    hooded_warbler_________ howa          15
         390    ivory_gull_____________ ivgu          12
        2880    northern_jacana________ noja           4
        6770    kentucky_warbler_______ kewa          13
        4490    great_kiskadee_________ gkis          20
        5990    lazuli_bunting_________ lazb          19
        4670    least_flycatcher_______ lefl          30
          50    least_grebe____________ legr          34
         740    least_tern_____________ lete          29
        7110    le_conte's_thrasher____ lcth          18
        3070    lesser_prairie_chicken_ lpch           6
        4210    lesser_nighthawk_______ leni          22
        5031    altamira_oriole________ alor           7
        7060    long-billed_thrasher___ lbth          27
        6760    louisiana_waterthrush__ lowa          26
        6430    lucy's_warbler_________ luwa           8
        6800    macgillivray's_warbler_ macw          31
        4260    magnificent_hummingbird mahu           7
        3860    mangrove_cuckoo________ macu           7
         900    manx_shearwater________ mash          22
        1140    masked_booby___________ mabo           5
        1680    masked_duck____________ madu           9
        4820    gray-breasted_jay______ gbja          22
        5700    yellow-eyed_junco______ yeju          13
        3290    mississippi_kite_______ miki           4
        2960    montezuma_quail________ mtzq          20
        2810    mountain_plover________ moup          38
        6790    mourning_warbler_______ mowa           3
        4720    n._beardless-tyrannulet nbty           9
        2880    northern_jacana________ noja           4
        2230    red-necked_phalarope___ rpha          37
        6490    tropical_parula________ trpa           5
        5860    olive_sparrow__________ olsp          20
        6510    olive_warbler__________ olwa          11
        4590    olive-sided_flycatcher_ osfl          10
        5060    orchard_oriole_________ oror          35
         951    flesh-footed_shearwater flfs           6
        6880    painted_redstart_______ pare          15
        4190    common_pauraque________ copa          21
        6260    philadelphia_vireo_____ phvi          15
         910    pink-footed_shearwater_ pkfs          15
        3110    plain_chachalaca_______ plch          10
        6370    prothonotary_warbler___ prow          30
        6110    purple_martin__________ puma          26
        3130    red-billed_pigeon______ rbpi           3
        3826    red-crowned_parrot_____ rcpa          16
        6240    red-eyed_vireo_________ revi          22
        2230    red-necked_phalarope___ rpha          37
        3901    ringed_kingfisher______ riki          17
        4260    magnificent_hummingbird mahu           7
        2356    rock_sandpiper_________ rosa          34
         720    roseate_tern___________ rost           6
        4411    rose-throated_becard___ rtbe           4
        2600    ruff___________________ ruff          15
        5790    rufous-winged_sparrow__ rwsp          24
        3090    sage_grouse____________ sagr          39
        1850    scarlet_ibis___________ scib           4
        6080    scarlet_tanager________ scta          10
        5040    scott's_oriole_________ scor          36
        3440    short-tailed_hawk______ stha          19
         960    short-tailed_shearwater stsh          27
        4730    eurasian_skylark_______ eusk           6
         960    short-tailed_shearwater sbsh          27
        3830    smooth-billed_ani______ sban          27
        5370    smith's_longspur_______ smlo          37
        3300    snail_kite_____________ snki          10
         950    sooty_shearwater_______ sosh          34
        5032    spot-breasted_oriole___ sbor           5
        3151    spotted_dove___________ spdo          32
        3980    strickland's_woodpecker stwo          12
        4451    thick-billed_kingbird__ tbki           7
        4460    tropical_kingbird______ trki          26
        6490    tropical_parula________ trpa           5
         120    tufted_puffin__________ tupu          12
        6000    varied_bunting_________ vabu           2
        4240    vaux's_swift___________ vasw          17
        7560    veery__________________ veer          28
        6440    virginia's_warbler_____ viwa           9
        2590    wandering_tattler______ wata          39
        6270    warbling_vireo_________ wavi          17
        4620    western_wood-pewee_____ wwpe          12
        3140    white-crowned_pigeon___ wcpi           7
        6020    white-collar._seedeater wcse           4
        3180    white-tipped_dove______ wtdo          10
        3731    whiskered_screech-owl__ whso           6
        2040    whooping_crane_________ whcr           5
        2400    white-rumped_sandpiper_ wrsa          25
        3731    whiskered_screech-owl__ whso           6
        3180    white-tipped_dove______ wtdo          10
        3410    white-tailed_hawk______ wtha          31
        3040    white-tailed_ptarmigan_ wtpt           7
        4530    brown-crest._flycatcher bcfl          15
        3010    willow_ptarmigan_______ wipt          12
        6390    worm-eating_warbler____ wewa          24
         250    xantus'_murrelet_______ xamu           9
        4630    yellow-bell._flycatcher ybfl           4
          80    yellow-billed_loon_____ yblo          38
        5700    yellow-eyed_junco______ yeju          13
         491    yellow-footed_gull_____ yfgu           2
        2150    yellow_rail____________ yera          24
        3400    zone-tailed_hawk_______ ztha           8