Feb 4, 1994 - season south of the Tropic of Cancer (e.g. Hagan and. Johnston 1992a, b, Finch and Stangel 1993), a view which excludes austral (southern) ...
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521
DAWSON,D. G. 1981. Counting birds for a relative measure (index) of density. Pages 12-16 in Estimating numbersof terrestrialbirds (C. J. Ralph
LAWTON,J. H. 1989. What is the relationship between population density and body size in ani-
and J. M. Scott, Eds.). Stud. Avian Biol. 6. INOUYE,D. W., W. A. CALDER,AND N.M. WASER. 1991.
PERRINS,C. g., AND T. R. BIRKHEAD. 1983. Avian
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ecology. Blackie and Son, Glasgow. TERnORGI-I, J. 1989. Where have all the birds gone? of hummingbirdpopulations. Condor93:279-285. Princeton Univ. Press,New Jersey. JOHNSTON, D. W., AND E. P. ODUM. 1956. Breeding WHITTAKER, R. H. 1970. Communities and ecosysThe effect of floral abundance
on feeder censuses
tems. Macmillan, New York. bird populationsin relation to plant succession on the Piedmontof Georgia.Ecology37:50-62. JUANES, F. 1986. Populationdensityand body size Received4 February1994, accepted27 May 1994. in birds.
Am. Nat.
128:921-929.
The Auk 112(2):521-523, 1995
Definitions for Migrant Birds:What is a Neotropical Migrant? FLOYD E. HAYES
Department of Biology, Caribbean UnionCollege, P.O. Box175, Port of Spain,Trinidadand Tobago As a North American who has spent three years long agreed that most of North America (north of living in the TemperateZoneof the Neotropics(Par- centralMexico)belongsto the Nearcticrealm,whereaguay), I often have wondered what the term "Neotropical migrant" refers to. Although some authors
define a Neotropicalmigrant as any speciesof bird that migrateswithin the Neotropicalbiogeographical realm(Stangel1992,Kofordet al. 1994),the prevailing view of a Neotropicalmigrant is a speciesthat breedsin North Americaand spendsthe nonbreeding seasonsouthof the Tropicof Cancer(e.g.Haganand Johnston1992a,b, Finch and Stangel 1993), a view which excludesaustral (southern)and intratropical migrants(Levey 1994).Levey (1994)adopteda broader view of the term "Neotropicalmigrants"by including the latter two groupsof migrantsin the definition. I agreewith Levey'sargumentsthat austral and intratropicalmigrantsneed to be studiedfor both scientific and conservation reasons. However, by lurepingall of thesebirdsinto the samecategory,we blur the already obscuredefinition of what a Neotropicalmigrantisand is not,which leavesusbegging for a more precisesetof termsand definitionsfor the
as Central America, the Caribbean and all of South
America (south to Tierra del Fuego) belong to the Neotropical realm (e.g. Brown and Gibson 1983;see Fig. 1). In my mind, the two groupsof migrantscould logically be referred to as: (1) "Nearctic migrants," which breedin temperateNorth Americaand migrate southward;and (2) "Neotropical migrants,"which breedin temperateSouthAmericaand migratenorthward. But instead, North Americans have persisted in selectivelyapplying the term "Neotropical migrants"to the speciesbreedingon the North American continent and wintering to the south of the Tropic of Cancer,which all but precludesthe useof the term for migrant speciesbreedingin temperateSouth America.
The use of this term in this context
is so
pervasivethat it frequently gracesthe titlesof articles in the majorNorth Americanornithologicaljournals, as well as the titles of two recently publishedsymposium volumes (Hagan and Johnston 1992b, Finch and Stangel 1993). The term has been echoed revarious groups of migrants. peatedlyby conservationorganizationsand alliances, In the New World, there are two fundamentally suchasPartnersin Flight. As a consequence, workers distinct systemsof long-distancelatitudinal migra- suchas myself have been forced to use the term "austion: (1) breeding birds in temperateNorth America tral migrants"in referenceto migrant speciesbreedthat migratesouthwardto spendthe winter in warm- ing in SouthAmerica (e.g. Chesser1994,Hayes et al. er climates, often in Central and South America; and 1994, Hayes 1995). (2) breeding birds in temperate South America that As Levey(1994)andothershaveproposed, we could migrate northward to spend the winter in warmer simply refer to all of thesemigrantsas "Neotropical climates,but only rarely in North America. The dis- migrants," which is certainly logical becausethese tinctivenessof these two groups of migrants is ac- speciesall winter in the Neotropicsand their ancescentuatedby the timingof their seasonal cycles,which tors probablyevolved in the New World tropics(e.g. are essentiallyhalf a year apart. Biogeographershave Brown and Gibson 1983). But then what definitions
522
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[Auk, Vol. 112
Fig. 1. The biogeographicalrealmsof the world recognizedby mostbiogeographers (basedon Brownand Gibson 1983).
shouldwe useto distinguishbetweenthe two major
Ethiopian migrant.--Anyspeciesof bird or population of the species breedingin Africathatregularlymition betweenthesegroupsis where theybreedrather gratesnorthwardduring the nonbreedingseason. than where they winter. Haganand Johnston(1992a) Intratropicalmigrant.--Any speciesof bird or popuand Levey (1994) referred to Neotropical migrants lation of the speciesthat breedsin the tropicsand breedingin North Americaas"Nearctic-Neotropical regularly migratesto another areaof the tropicson an annual basis. migrants,"a preciseand accurateterm, but usedthe vagueterm "australmigrants"for speciesbreeding Nearcticmigrant.--Anyspeciesof bird or population in SouthAmerica.Thesetwo termsare hardly comof the species breedingin North Americathat regparable.The term "australmigrants"could equally ularlymigratessouthwardduringthe nonbreeding season. apply to migrant speciesthat breed in Africa, Australia or Antartica, which are also in the Southern Neotropical migrant.--Anyspeciesof bird or populaHemisphere.Likewise, the term "boreal migrants" tion of the speciesbreedingin SouthAmericathat (northern migrants)could apply to migrant species regularly migrates northward during the nonbreedingin either or both the Nearcticand Palearctic. breedingseason. To avoid confusionand ambiguity in the use of Palearctic migrant.--Any speciesof bird or population these terms, I recommendthat a more preciseterof the speciesbreedingin Europeor Asiathat regminologybe standardized.I proposethat the followularly migratessouthwardduring the nonbreeding
groupsof migrants? The majorgeographical distinc-
ing setof termsand definitionsbe adoptedby ornithologists:
Altitudinalmigrant.--Any speciesof bird or population of the species thatregularlymigratesfromone altitude
to another
on an annual
basis within
a
biogeographicalrealm. Australmigrant.--Any speciesof bird or population of the speciesbreeding in the Southern Hemi-
spherethat regularlymigratesnorthwardduring the nonbreeding season.
Australian migrant.--Anyspeciesof bird or population of thespecies breedingin Australiaor New Zealand that regularlymigratesnorthwardduring the nonbreedingseason. Borealmigrant.--Any speciesof bird or population of the speciesbreedingin the Northern Hemisphere that regularlymigratessouthwardduring the nonbreeding season.
season.
Theseterms are not mutually exclusive.With this setof definitions,borealmigrantswould includeboth Nearcticand Palearcticmigrants,whereasaustralmigrantswould includeAustralian,Ethiopian,and Neotropical migrants.To give an example,the Peregrine Falcon(Falcoperegrinus) asa specieswould fit mostof these definitions; the North American populations would be consideredNearctic migrants as well as borealmigrants,and the SouthAmericanpopulations would be consideredNeotropicalmigrantsaswell as australmigrants. I realize that sucha drasticchangein the meaning of the term "Neotropicalmigrant" will be resisted initially and will take time to be accepted.However, if the statusquo continues,we will continue to be confusedby a plethora of impreciseterms. Science demands precision and logic in both our terms and
April1995]
Short Communications andCommentaries
definitions.In the caseof naming different groupsof migrants, the names should be based on long-acceptedtermsand definitionsof biogeographical realms (e.g. Brown and Gibson 1983;Fig. 1). Given the above definitions
of Nearctic
and Neo-
523
An overview of the australsystem.Bird Conserv. Int. 4:91-107.
FINCH, D. M., AND P. W. STANGEL(Eds.). 1993. Status
and managementof Neotropicalmigratorybirds. U.S.Dep. Agric. ForestServ.Gen. Tech.Rep.RM-
229, Fort Collins, Colorado. tropicalmigrants,how dowe distinguishbetween(1) Nearcticmigrantsthat migrateentirely within the HAGAN, J. M., III AND D. W. JOHNSTON. 1992a. Introduction. Pages1-3 in Ecologyand conservaNearctic,and (2) thosethatmigrateto the Neotropics? The distinctionbetweenthesetwo groupsof migrants tion of Neotropicalmigrantlandbirds.Smithson-
is important for both scientificand conservationrea-
ian Institution Press,Washington, D.C.
sons.I suggestthat the mostpreciseterms,awkward HAG•a•, J. M., III AND D. W. JOHNSTON(Eds.). 1992b. Ecologyand conservationof Neotropical migrant astheymaybe,are "Nearctic-Nearctic migrants"and landbirds. Smithsonian Institution Press, Wash"Nearctic-Neotropical migrants,"respectively.An alington, D.C. ternative(but lessprecise)setof termsmight be "temperateNearcticmigrants"and "tropicalNearcticmi- HAYES,F. E. 1995. Status,distribution and biogeographyof the birds of Paraguay.Monogr. Field grants,"which couldbe simplifiedas"temperatemiOrnithol. No. 1. American Birding Association, grants" and "tropical migrants," respectively.The ColoradoSprings,Colorado. sameprincipleof combiningtermscouldbe usedfor speciesmigratingwithin or betweenother biogeo- HAYES,F. E., P. A. SCHARF,AND R. S. RIDGELY. 1994. Austral bird migrants in Paraguay.Condor 96: graphicalrealms (e.g. Palearctic-Palearctic migrants, 83-97. Palearctic-Ethiopian migrants,Palearctic-Oriental migrants,Palearctic-Australianmigrants). Acknowledgments.--I thank J. M. Hagan III, D. W. Johnston,D. J. Levey,and G. D. Schnellfor valuable commentsand suggestions on an earlier draft of this commentary.
KOFORD,R. R., J. B. DVNNING, C. A. RInIC,•D D. M. FINCH. 1994. A glossaryfor avian conservation
biology. Wilson Bull. 106:121-137.
LEVEY, D.J. 1994. Why we shouldadopta broader view of Neotropicalmigrants.Auk 111:233-236. STANGEL, P.W. 1992. Justwhat is a Neotropical mi-
LITERATURE CITED
grant?Partnersin FlightNewsl.2(1):29.National
Fish and Wildlife Foundation, Washington, D.C. BROWN, J.H., ANDA. C. GInSON.1983. Biogeography. Received 9 August1994,accepted 27 January1995. C. V. Mosby, St. Louis,Missouri. CHESSER, R. T. 1994. Migration in South America:
