ExoticPigeonsby Michael Mace, Curator of Birds

San Diego Wild Animal Park

ronments they inhabit. Typically, boththe eed-eating and fruit-eating groupsare arboreal roosting, feeding, andnesting in the canopies of the world'sforest. Some tnay never spend morethan hort periods of time on theground. This applies to species such asthe tTIulti-colored Black-naped FruitDove Ptilinopus melanospila of south­eastern Asia. Such arboreal forms mustadapt in order to coexist with poten­tially harmful specie '. Monkeys, forexample, would certainly be a threat tothe adult birds and catastrophic tosquabs and egg '.

Some birds that live in regions withprimates have developed differentstrategies for propagation. The adap­tive strategy was to become more ter­restrial; feeding habits were influencedand the birds eat fallen fruits andseeds. The terre 'trial pigeons evenbegan to nest on the ground or in low,inconspicuous shrubs and bushes. Afew species such as the WongaColumba melanoleuca of easternAustralia and the Victoria CrownedPigeon Goura victoria of Papua NewGuinea have al 0 adapted to a moreterrestrial life-styl .

Pigeon are unique in the avianworld. The late Frenchornithologist Dr. Jean Delacour

de cribed the pigeon as "one of themost intriguing and beautiful group' ofbirds in the world. For year' Delacourhimself kept a large private collectionin Clere, ormandy France.

The many shapes and form ofpigeon and their various color , fromoft tans and grays to a pectrum of

hlues, red , and yello ' ar breath­taking. Pigeons and dov ' belong tothe order Columbiforme', whichincludes the now extinct dodo.

There are approximately 300species divided into two main groups,the seed-eating pigeon and the fruit­eating pigeon . They are a fairly hardyand diver e family of bird , and theirability to adapt has been u ed to mea­sure how a taxon of animal' acclima­tizes to different environment.Pigeons are more wide pread thanparrots ranging throughout the majorcontinents.

They al 0 re ide on the 'maIler iso­lated i lands, particularly in the tropicalregions. The only place' on the planetthat do not host at lea t one specie' ofpigeon are the frozen polar cap . Themost familiar to us of cour e are theordinary feral pigeons found in ourcity parks, al 0 commonly called RockDoves Columba livia.

In addition to species diver ity, vari­ation can exi t ithin a pigeon species,according to geographical location. Forexample the Rock Dove of penin ularIndia is darker in color than the samespecies in Europe. The unique differ­ence between pecie of do es andpigeons are determined by the envi-

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Wonga Pigeon u ith chick.

Other differences in the pigeoncharacteristics affected by evolutionare the various plumage. Pigeons andthe maIler dove display many b au­tiful colors and patterns. The vivid col­or " as well as the duller hades ofgrays and browns, provide crypticcover for the birds. OrnithologistDerek Goodwin explain that"because they are usually preyed uponby avian predators uch as hawks andfalcons, smaller species of pigeonst nd to be tnore cryptic in color thanthe larger specie ." The inconspicuousgray and browns of such specie ath insular Mauritius Pink PigeonColumba mayeri aid in the crypticcamouflage that is important for theirsurvival. Other adaptations volv d inspecies such as the extinct Pas 'eng rPigeon Ectopistes migratori'us of thAmericas, which d veloped long inaand tail feathers. Goodwin th oriz 'that 'The purpose of th elongat dwing and tail feath r of pig ons i a ~

a direct correlation to regular migra­tions and bird with enlarged territorie 'that are defended. "

In contra t to the Ie' colorfulColumbiformes are the pecie' thatinhabit the deep forests of the world,particularly Asia and Australia. Manyornithologi ts consider these pigeonsth very es ence of color. For eachspecies, the colors are used a' aInethod of recognition. Color are alsoutilized in aggres 'iv po 'turing amongand between sp ci s and in court hipdi 'plays. Markings and colors are alsoa forn1 of de~ nse against unwelcon1e Green-naped Pigeon.

intruders. By flashing bright colors andpatterns, pigeons can tattle a predatorfor a split second, allowing the bird toescape. Aggressive displays can alsobe u 'ed to intimidat con- pecificmales that are pur uing the samt lnale. With lnale color used forcourtship and aggressive di 'plays thfelnales are usually less colorful. Thilack of coloration is, in itself, a defenselnechanism. It would be a poor adap­tation if an incubating female were toocolorful and caught the attention of ahungry predator.

Additional adaptations are seen inpigeon eggs. All species of pigeons layfrom one to two eggs in a clutch. Eggcolor is typically white or cream. Theconspicuous white eggs are a liability Compare the large Green-naped PigeoJl egg to a quarter.

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Western Beautiful Fntit Dove.

if spotted by a predator, however, thehen will not easily flush from anattended nest to reveal the egg.Incubation periods vary from specieto species, but u ually the eggs hatchin 14 to 18 days. Altricial chicks are feda diet of crop milk' by the parents.While the parents are incubating theegg(s), prolactin is released. Lipid­engorged epithelial cells lining thecrop lough off and are used as nour­ishment for the chicks' first few days oflife. After that, the rapidly growingchicks are fed a diet of seeds and/orfruits, depending on the pecies.

The number of clutches produced

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yearly by a pair in the wild is normal­ly one if they are successful in raisinga brood. However, double clutchingfrom a pair is oft~n accomplished ifsome other factor has taken place: aninfertile clutch, predation of eggs or'quabs, or inexperienced birds that donot lay egg in the nest. By doubleclutching a pair still has the opportu­nity to rai e chicks after the first clutchha failed.

The way the pigeon family hasadapted to a wide range of climates,habitat , and disturbances, includingmankind, shows their re ilience. Infact, throughout history pigeons and

doves have often occupied a positionof cultural significance. One of the ear­liest known archaeological recordsconcerning pigeons was their domesti­cation by the first Egyptian dynasty in3,000 B.C. Biblical references havenoted in the 600th year of Noah's life,a dove was used to determine the levelof the flood waters covering the earth(Genesis 8:8).

Today, however, pigeons anddoves are only recognized as a plague,particularly in this country. They areconsidered pests, which deposit guanoon the famous buildings and land­lnarks of cultural Mecca the worldover and contribute to the spread ofsuch diseases as ornithosis which canbe transmitted to humans. Even thedove depicted as a symbol of peaceand love, is presently hunted for sportduring a designated season in thewestern United States. Yet these mar­velou ly adaptive birds have mademany contributions to human history.

Neolithic people were the firstrecorded to domesticate and usepigeons as a food source in the formof eggs and squab. Early culturessoon discovered the prolific nature andhoming instincts characteristic ofpigeons. The homing instinct was usedas a means of keeping a constant, reli­able food source, upon release thepigeons would continue to return tothe crudely con tructed pigeon lofts.

The abilities of the homing pigeonhave been studied extensively byethologiSts for centuries. Two maintheories SeelTI to prevail: that the birdsnavigate by the positioning of the sunand that they utilize the earth's mag­netic fields. Research has proven thesun to be the primary factor in naviga­tion, which is similar to the methodemployed by the honeybee.Researcher Charles Walcott proved hisnavigational theory by altering themagnetic field of some pigeons, eitherby strapping magnets to the birds orby outfitting them ith helmets thatconsisted of a battery-poweredHelmholtz coil. Dr. Walcott reportedthat upon release the birds were dis­oriented but only on overcast orcloudy days. Additional researchinvolving the Rock Dove indicates thatpigeons may also be sensitive to infra-onic waves, slight changes in baro-

metric pressure, polarized light, andeven, perhaps, area-specific odors.

Owning pigeons was once consid­ered a sign of wealth by Europeannoblemen. Emperors would issueorders to the effect that "only the lordsof the manors can build and maintaindovecotes." Meat was scarce, but thebirds were an effective source of pro­tein. The flocks, easy to care for, werereleased into the fields to forage on theweed seeds of the grounds owned byroyalty. Non breeding stock waslaughtered, and the meat was smoked

and alted and stored for the long, coldwinters. The monasteries of the Britishwere famou for their ability to raisedomesticated pigeons. The orders wereespecially ambitious in the number ofbirds they housed, sometimes in excessof 2,000 breeding pairs. Alternativesource of protein were eventuallydev loped in Europe, and dome ticpigeon wa gradually replaced. Thebirds then became an agricultural pe tbecau e of the feeding habits.

By the 18th century, the dovecoteBlack-collared bnpenal Pigeon.

]ambu Fruit Dove.

system was obsolete. However, arenewed interest in the pigeon devel­oped because of Messenger or CarrierPigeons. The Messenger Pigeon hadbeen u ed by Genghis Khan as a reli­able and swift means of communica­tion. The birds were used to exchangeinformation between his mightyarmies, particularly when the bordersof this empire began to expand intoother regions of the continent. CarrierPigeons were used by NapoleonBonaparte's armies in the late 18thcentury during the French Revolution.Even as recently a World War II, theCarrier Pigeon has been employed forthe transport of U. S. military docu­ments.

Competitions evolved to determinethe fa test birds in the lands. Thesecompetitions led to other types ofshoWings: pigeon with elaborateplume , tumblers, and various sizes ofbirds. Charles Darwin, a local residentof London, kept a pigeon house thathe used for research and amu ement.Francis Darwin tated about hi father"In the cour e of my father s pigeon­fancying enterprise he necessarilybecame acquainted with breeders, andwa fond of relating his experience aa member of the Columbarian andPhiloperistera Clubs and learnt muchof the mystery of their art."

Before writing hi cIa sic book TheOrigin of Species (1859), CharlesDarwin rai ed pigeon a supportingevidence for his exten ive works. TheZoological Society of San Diego itselfha . had a long hi tory with Columbids,dating back to 1926 with the acquisi­tion of a Galapagos Dove Zenaidagalapagoensis. From 1926 to 1998,more than 145 specie of pigeons havebeen kept in the collection. Our expe­rience has revealed that pigeons anddoves are easily integrated with otherpecies. If utilized correctly they can fill

niches that may have been underuti­lized in aviaries and exhibits. Many ofthe species are in peril and researchersand aviculturists alike need to continueworking with the family - in particularthe insular species where changes inhabitat are at an ever increasing rate.Presently, the Society is working withmore than 80 species, and many ofthem are on exhibit at the Zoo and theWild Animal Park. .,..

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