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~ b t t E a ~ m a n i a n j l } a t u r a l i ~ tTHE JOURNAL OF THE

Tasmanian Field Naturalists' ClubNew Series-Vo!. 1. DECEMBER, 1925. No. IV.

Nomadic Migration 0/ Birds.Just as the, nomad savage wanders toand fro about his wilderness. pitchinJ[ his

tent here one day, miles away the next,acoording to his ever-fluCltunting supply ofthe bare necessaries of 1ife. so do certainbirds pass the! greater part of their exist~ n c e moving round. Few birds are reallystationary throughout the year; in fact,i t jR rather the exception fo r a speeicRto be absolutely sedentary, Many, if notall. young birds are great wandercl'Is, being(lriYcn from their birthplace their Prt-'f!nts. or deserting i t voluntarily as soonas parental care becomes unnecessary.while seY-era.1 nelCtar-feeding species ar1('onstant1y on the m()ve. At one time wemay no-tice a flock of a certa.in variety in aparticu1ar district. and at another timenot a bird is there. the food supply ofthe area pnrhaps having failed, as it oftendoes. or the e x i s t i n ~ climatic conditionsbeing f.ound unsllitwbIe. The bird:s. there_fore. have found it necessary to move toothf'r diRtrictR where thn t h i n ~ R they re,...,.;re fire obtainable' but. so soon as t b e ~fail. or ('bange. they are on tbp. movf'[lOlrrin. aTmeal'ti."fJ' hPTP one wepk flnel ~ O n t P . where else th .. next. ann on. Thislocal movement of hirdR 1

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'l'HE TASMANIAN NATURALISTof other birds, are purely in se!arch offood, and as this in the case of lorikeets,found in the flowers of the eucalypts,we find the birds following up the irregular flowering periods of the tre":s_ T ~ e yperiodically sweep over Hobart wIth nmAYcry! hunting out every" garden, park and

r ~ e r v e where the flowering treels are tobe found, and after exhausting the supplyof nectar for the time are off to the couutry to seek for more. They may ~ e described as birds at the mercy of CIrcumstance-here one day, gone the next, asit were. During t11e 1(',Qurse of the yearthey move. round the country very extensively, each district being visited inturn and they seem to breed in any suitable 'place when s'pring comes upon them.The rasella and other kinds of parrots arcbirds that 3100 roam. though not to thesame extent as those species, which arealmost entire1y dependent upon a supplyof nectar for their food. When thel natural food supply of the parrots becomesRenrC'''' n ,diet of frnit is often n ~ s u r t e d to.the birds making raids on orchards or gardens for the T'lllrnnse. and i t is because orthi::; thnt they :U'p bnk('fl npon with ;:TIneh

d i s f a , ~ o r by some frllitgrowers.Other Nomads_

Birds of the j'Jigeon tri:be are notoric,us wanderers as is ins,tanced by theeasp of two or three mainland varietiesnf'rur!"tng m Tasmania. from time totime. So are martins. and to someextent. swallows, though these speciess u b j ~ c t to seasonal mlgra,uon aswell. and cannot. clorrectly speaking. heclasserl as nomadic migrants. But.strangely enough the swift, whichvisits us from Japan. combines in avery marked manner examples of bothregu1ar and nomadic forms of migration. Its lengthy journeys from landswell above the {'quator h, the extremesouth of Tasmania and back againthe f('l1owing season. which compel ustn admire thiR wonderful flyer. is oneof the best and most advanced examplesof, regular migration; its cc.nstant w'an'":."erintre on the wing in search of foodduring the time it is with us in the

Bummer also render i t an outstandingspe-cics of t.he nomadic class of feR thered migrants.Other nomads of tbe avian world arethe little white-eyes. gronnd 1ark. cbats.n&tive hens and slome varieties of thehoney'nters. Swans and ducks are veryirrelimlar in theIr habits, for they winbe found in thousands on a swamp oneyear; and then for no apparent reason(2)

they will desert it. During the periodof a drought in one par,t of the countrythere is an extensive IDlovem.ent in progress to o t h e r s ~ and at such times weSE'e birds in our districts that perhapshave never come before. When thereis a dry spell in Victoria or New Sc.uthWales, for e:x;ample, as there is from timeto tim, many kinds of water blrd8,ducks e ~ p e c i a l l y , migrate southward. toTasmania and flock to the marshes andlaglool1s there where they feed, A t thattime nomadic migration is a t its height.and mnny interesting things can blP. observed by the outdoor ornithologist.Such birds as the black magpie, eagleand jay, seem to be fairly stationaryin the hills, h o w e v e t ~ cold i.t is, far theirforJd supply is not affected by the wint { ' l ' to the same extent as that of insectivorous or granivorous birde; but attimes, even these are compelled to moveas the food may fluctuate. and comedown to the lowlands close to bumanhahitation during spells of unusuallyinclement weather, hastening bark again,however, as Soon as easier climatic conditions reCur. This also applies towhi.te and black cockatoos ,which arf>usually only to be seen away fromtheir wlldnesses when severe weathp.l'drives them to the open country.

Movements of RobIn .Were it not for the fact that we arein possession of a certain amount ofevidence lof their regular movements,I might refer to the robins as otherblrd!1l with nomadic tendencies. But. a ~

,It gf'llf'ral rule, the robillB move from thehIghlands to the lowlauQs, and vice versa,fit r e g l l l a l ~ periods of the year. [ , t hasheen observed that at the approach ofwinter the birds leave their haunts inthe mountains, which they have inhabitf!d an the summer, and make 'dc.wn the'tul1lcs to the warmer regionb on the( ~ a ~ t E ' r n coalSt. where they stay for twoor thrE'e months of the year. Then,

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THE TASMANIAN NATURALISTwe have evidence of a distinct infiuxof ,the birds in eastern. coastal district.

What we Learn.fhe study of the nomadic movementsuf birds is to the naturalist highly a t 1 active, as i t is from such migratioJlI.hat the wonderful flight.. of the swift.t.he curlew, the turnstone, and goldenplover, which literally travel from polet(.o pole have originated. Ordinary seaMonal migration has sprung from it aswell. Furthennore, i t goes to prover.hat the great initiating cause CIf allmigratioH was food. That, of course, iaHtill the underlying motive of today,ror hirds, in order to secure a proper

diet, not merely for themselves, but fOl"their yc..ung, travel the wide world tortnd H. Tha t is why so many millionsHock to the tundras of Siberia and)oJ"orth America every year to nest. Theylilld there -absolutely countless hordell ofmosqUitoes and insects ou the edge of the.

~ I 1 u " ' , as well as berries and other fruits,

and have only ,to open their beaks to"et a meal. ThSe nomadic migrationsr e J . l r e s c n ~ iIlCipient migratU,on in the pastwhicl:: never developed in these speciesor their ancestors to any greater extentthan what we now witness. But, inthe great majority of birds throughc..utthe world, the practice of migrationgradually became a function fraught withgreat importance -to avian life, and necessary eVen for the preSrvation of th,eraces. For it s origin We must 10vkback to a very remote past, when theglobe was subject to mighty climatic(:hanges and physical disturbances, withvast -alterations in the rela,tive level ofland and sea, and remarkable volcanicactivity; and such glimpses into theages are dear to the heaxt of everyscientist. At whatever period of theworld's histury the migration of birdscommenced there cannot, however, beany other conclusion but that the under_lying cause of the movement was the failure of food supply. M. S. R Sharland.

Outlines 0/ Tasmanian GeologySECTION 17EXTRAORDINARY LANDSCAPESThere are t.hree types or landscapes.

' ~ ( ) m m o n in certain localities, but by nomeans usual when the whole s11rface of theglobe is c