62 NATIVE ANI> INTRODUCED

dominated by Allolobophora caliginosa orA. terrestris, were found.

These examples can be taken as typicalof what has happened wherever native vege-tation has been cleared and replaced bypasture. There has been no competitionbetween native and introduced species,either for food or for living space. All butsubsoil species among the native earthwormshave died out before the introduced lumbri-cids became established, and the few subsoilearthworms that have remained do notcompete with the lumbricids, as the latterare confined to the topsoil.

Where native vegetation has not beeninterfered with introduced earthworms areusually absent, and if present they areusually rare. An exception to this generalisa-tion is found at Raoul Island, where thedominant earthworm of forest litter andtopsoil is Eisenia foetida, an introduced lum-bricid. E. foetida is usually found in NewZealand, and in Europe, in compost andmanure heaps, and is rare in agriculturalsoils. Its presence in forest soils at RaoulIsland probably results from the high rateof decomposition of forest litter in a warmclimate. producing conditions that wouldnot be found in forests in the cooler climateof New Zealand. In addition to the higherrate of litter breakdown. the spread of E.foetida has apparently been facilitated bythe absence of native topsoil earthworms onRaoul Island. The native earthworm fauna

SPECIES IN Nmv ZEALAND

of Raoul consists of only two species of verysmall leaf mould earthworms. So in thiscase too, there has apparently been no com-petition either for food or for living spacebetween introduced and native species.

The introduction of European earthwormshas been accompanied by far reachingchanges in the soil environment, broughtabout by man. The result has been that thenative earthworm fauna has been destroyed,but its destruction stems directly from theman-induced environmental changes, and isnot a result of interaction between intro-duced and native species. The same can besaid of many groups of soil invertebrates, andmay well be true of other animal groups.

REFERENCES

CERNOSVITOV, L. and EVANS,A. c., 1947. The LinnaeanSociety of London Synopses of the British Fauna.No.6. Lumbricidae (Annelida). London, 1947.

DARLINGTON,P. J., 1959. Area, climate and evolution.EvoJwiOfl t 3: 488-510.

LEE.K. E., 1959. The earthwonn fauna of New Zealand.N.Z. Dept. Sci, Industr. Res. Bull. 130.

MILLER, R. B., STOUT, J. D. and LEE, K. E., 1955. Biologi~cal and chemical changes following scrub burning ona New Zealand hill soil. N.Z. J. Sci. Tech. 37:290--313.

SMITH, W. W., 1894. Further notes on New Zealandearthworms. Trans. N.Z. Ins!. 26: 155-175.

WATERS,R. A. S., 1955. Numbers and weights of earth~worms under a highly productive pasture. N.Z. J.Sci. Tech. A.36: 516-26.

THE INTERACTION OF NATIVE AND INTRODUCED BIRDS

IN NEW ZEALAND

E. G. TURBOTT

Canterbury Museum

The purpose of this paper is to outline thefactors which are believed to influence thestatus of native and introduced birds-including their interaction - and as a back-ground it will be necessary to re-examine thehistory of settlement. Some effects of settle-

ment are obvious: the clearing of forest andthe acclimatisation of birds from overseaswere major events transforming certainaspects of the environment. Other events,especially the arrival of mammalian preda-tors and probably of avian diseases, did not

TURBOTT: Bums 63

at first seem unduly important and are stilllittle understood. All these events moved so

rapidly that any form of scientifi~ record, ifattempted, would have been dillicult; and,today, the opportunities for research arerestricted to investigations of bird popula-tions that are already modified. The extent ofmodification, is however, largely unknown.

It is necessary, in attempting to assess theeffect of settlement upon native and intro-duced birds, to consider the history of modi-fication in some detail, both from contem-porary accounts of the course taken bysettlement and through what is known ofchanges in the bird fauna. Intensive settle-ment began in about 1850 (there had beenlocal settlement for several decades earlier),and from this date until approximately 1920there was rapid and extensive change: forestwas cleared and other environments (especi-ally swamp) were changed or eliminated.Introduced birds became established whilethese changes were in progress.

In the writer's opinion too much impor-tance has been attached to the total effect ofenvironmental modification. Too little con-sideration has been given to the fact that thecountry was, indeed, settled in an irregular,or "patchwork", pattern. Comparativelysoon after the establishment of the firstsettlers, a certain amount of tree and shrubcover which could be used by forest specieswould probably be available. The settlers'gardens and orchards and their hedgerows,shelter belts and plantations were becomingestablished as the forest was destroyed.Much would have depended upon the extentof nearby forest clearing, but certainly inmost districts there were remnants, at least,of forest even though much was cleared.

The modification of the environment Wasnot simultaneously in progress throughoutthe country. In 1880 settlement in the SouthIsland was advanced, while the forests ofthe centre and south of the North Islandwere still little touched. The plains of theSouth Island - clothed in tussock and scrub- were especially tractable, and the com-paratively small areas of bush were readilycleared. In the North Island, the main periodof forest clearing in the lowlands of Tara-naki and the Manawatu did not occur until1880-1910; the forests of the hill lands of theNorth Island were still being destroyed

actively up to 1925 (Masters, Holloway &McKelvey 1957, Cumberland 1949).

It is only possible to surmise the effect ofthis pattern of environmental change uponthe native species: early accoun1s at leastmake it clear that some evidently adaptableforest birds appeared in settled environ-ments from the first-fantail (Rhipidurafuliginosa), grey warbler (Gerygone igata),silvereye (Zosterops lateralis) and morepork(Ninox novaeseelandiae); the silvereye, anAustralian self-introduced arrival of theearly settlement period, is a special case.The kingfisher (Halcyon sancta), an inhabi-tant of both forest and open areas, also ex-panded into modified habitats. These arestill common species in modified as well asunmodified habitats. For a further species,the falcon (Falco novaeseelandiae), theintroduced birds represented a new sourceof prey, but shooting prevented it from ex-panding into settled areas.

J. Kikkawa, who is at present studyingforest bird populations, suggests that fantail,grey warbler and silvereye may prefer theforest edge habitat, and may thus havereadily entered the newly established exoticvegetation, and even regenerating nativevegetation, soon after settlement (pers.comm.).

It seems reasonable to believe that thoseforest species which were slower to adoptmodified environments found at least somefood in the newly settled districts. These arespecies which now appear to be increasing(discussed below, under present trends).

Open country produced by settlement wasprobably acceptable from the first to harrier(Circus approximans) and pipit (Anthusnovaeseelandiae): the harrier now includesin its range strictly pastoral country, but thepipit is found in rough pasture and wasteland, avoiding pure pasture. (An extensionof habitat was also provided for certainwaders, not discussed here.)

Introduced species were liberated in thenew settlements. It is notable that of 125species brought to New Zealand, some 90species were liberated during the period1860-1880 (Wodzicki 1950). They thus arrivedat a comparatively early stage, doubtlessspreading in the wake of settlement. Inform-

64 NATIVE AND iNTRODUCED

ation on the introduction and spread ofevery species is given by Thomson (1922)and Guthrie-Smith (1921). Of the total, only25 are now established species.

. .

.As mentioned above, certain native forest

birds from the first appear to have enteredmodified environments where there weretrees. Tree cover is also one of the require-.ments of most of the introduced species,and this may have meant some interspecificcompetition between native and introducedspecies. Whatever its extent, this did not pre-clude the establishment of certain species,both native and introduced. The presentblend of native and introduced species inmodified environments seems stable, but theincrease in the number of native species insuch environments possibly may upset thebalance.

It is noteworthy that only a few intro-duced species now occur in forest: blackbird(Turdus merula), song thrush (Turdus erice-torum) and chaffinch (Fringilla coelehs)are the only species within the forest; thehedge sparrow (Prunella l11odularis) occursin forest edges; and the redpoll (Cardue/isflammea) at the subalpine level in both opencountry and forest. Whether there was inter-specific competition when these introducedspecies became established cannot now bcdetermined, for the forest bird populationsmay already have changed. Certainly therenow appear to be stable, or increasing, popu-lations of these introduced species in forest.So far there has been no indication thatintroduced species" drive out" native species,as is often popularly supposed.

Certain partly seed-eating introducedspecies probably spread rapidly into nativegrasslands; and several species, notably theredpoll, are at present well established inthe remaining relatively unmodified grass-lands now limited to the alpine zone. Asmentioned earlier, most of these are specieswhich may feed in the grassland but requiresbrubs or trees for sheJter and nest sites;the skylark (Alauda arvensis) is the mainexception. The appcarance of introducedseed-eating birds in grassland might haveaffected only one native species, the NewZealand quail (Coturnix novaezeelandiae);but it was extinct by 1870.

.SPECIES IN NEw IEALANb

In summary, this account has dwelt par-ticularly upon the native forest birds whichwere able to become established in the en-vironment produced by settlement. It shouldbe stressed that the destruction of forest

meant violent transformation of the en.vironment over large areas. Relatively fewforest birds adopted the modified environ-ment, but these - together with introducedbirds - produced the mixture of native andintroduced species now found throughoutsettled districts. Native forest and grasslandhabitats were entered by a few introduced

.

speCIes.

It is not intended to suggest that theecological results of settlement are over. Itis possible to be more specific, for there isa record of increasing occupation, sinceabout 1920, of the modified environment bynative birds. One reason for this may be thatthere has been little change in the extent ofnative vegetation in most areas for sometime. In addition, exotic trees and shrubshave reached maturity: shelter belts, hedges,plantations and orchards are now wellgrown, and are in established positions. Thetendency of native species to enter suchvegetation is especially marked in planta-tions of pines and other exotics, which nowhave vigorous populations, native and intro-duced (Gibb 1961); the adoption of planta-tions of mature age by forest species inBri tain has been recorded by Lack (1933,1939).

.

Of other factors which may havc causedthis increase, legal prot_ection probably hashad considerable effect. Up to 1895, legisla-tion was entirely devoted to the introducedbirds - more especially game species - anda comprehensive and effective bird protec-tion Act did not appear until 1921. It isperhaps significant that this so closely coin-cided with the last stages of intensive de-forestation. Writings of the succeedingperioclform a direct contrast with those of thebeginning of the century: thus Myers (1923)was already speaking hopefully of the posi-tion of a range of native species, in contrastwith Buller (1905) who expressed the widelyheld opinion that the extinction of a largeproportion of native forest birds must inevit-ablyrcsult from settlement. Thc la! IeI' opinionwas so widely prevalent during the period ofsettlement that it must, in a number of ways,

TURBOTT: BIRDS 65

have aggravated the adverse effect of manupon the native birds.

For certain species, e.g. the bellbird (An-thorn is melanura), apparently the only fac-tor which could have caused the acutereduction in population was disease. Re-invasion of areas from which species wereeliminated by disease would probably lateroccur, and for the bellbird this is, in fact,taking place in one area (Turbott 1953).

The principal species that appear to beincreasing in settled habitats are the kiwi(Apteryx australis), weka (Gallirallus aus-tralis), pigeon (Hemiphaga novaeseelan-diae), bell bird and tui (Prosthemaderanovaeseelandiae). Others, especially tit(Petroica macrocephala), rifleman (Acan-thisitta chloris), brown creeper (Finschianovaeseelandiae) and kaka (Nestor meri-dionalis), may appear in modified habitats,but probably require an adjacent forest area.The extent to which the latter requirementapplies to the other species listed is notkncwn. An investigation of the presentstatus, and history as far as known, of eachof these species would be of the greatestinterest. As pointed out by the writer (Tur-bott 1957) such species contrast markedlywith those forest birds which cling to thenative forests that remain, and show no ten-

. dency to appear in environments to anyextent modified.

The writer believes that populationchanges of native birds such as those men-tioned provide an opportunity to obtaininformation on the ecology of these birds,and especially their interaction with intro-duced birds. There is also the possibility offurther changes in the populations of intro-duced birds, such as the recent northwardexpansion of the myna (Acridotheres tristis)in the Auckland district.

Specifically, interaction between nativeand introduced birds may occur in fourways:

(1) Competition for food.(2) Competition for nest sites.(3) Aggressive behaviour.( 4) Predation.

Of these, interaction through competitionfor food is indirect, but information on foodcan be compared and might prove to be cor-

related with population changes. However,there has been little detailed investigation offoods of native and introduced birds so far.A notable exception is that of Marples (1942)on the little owl (Athene noctua). Everyopportunity should be taken to develop suchstudies, if possible in relation to populationchange, e.g. investigation of competition insettled districts by bellbird for insects, andby pigeon for fruits and buds. The intro-duced cha/linch is numerous, and possiblyincreasing, in most native forest areas andmay compete for insects with native birds.

Competition for nest sites, most readilyobserved in hole-nesting species, has beenrecorded frequently between introducedstarling (sturnus vulgaris) and native king-fisher. An additional report, which is likelyto be of similar competition, refers to thedisappearance of the more pork in the Christ-church suburban area simultaneously withthe increase of the little owl (L. W. McCaskill,pers. comm.). However, these species nowoccur together in other parts of the SouthIsland. Recently chasing of one species bythe other was reported to the wri ter in thefoothills of Canterbury.

Aggressive behaviour (which may includeterritorial behaviour) is exemplified by theAustralian magpie (Gymnorhina hypoleuca),which frequently chases both native andintroduced species, although this is some-times actually predation. While it is doubtfulwhether aggressive behaviour alone wouldresult in the exclusion of a species (d. theinteraction of the red and introduced greysquirrels in Britain), strongly aggressiveand/or territorial introduced species mayhave this effect. Specially interesting wereearly observations on the Australian magpieby Moon (1956), who recorded the destruc-tion of two successive clutches in a nest ofthe Australian white-faced heron (Nolophoyxnovaehollandiae) soon after the arrival of thelatter species in North Auckland. Yet, sub-sequently, the heron has had a history ofsuccessful establishment throughout NewZealand, in areas with large populations ofmagpies, and it seems possible that the inci-den ts recorded by Moon were competitionfor a nest site.

Predation of introduced species by thenative falcon was mentioned earlier: theAustralian magpie has been recorded killing

66 NATIVE AND INTRODUCED SPECIES IN NEW ZEALAND

native species on various occasions; and thefood of both native morepork and intro-duced little owl includes small birds, eithernative or introduced.

REFERENCES

BULLER, W., 1905. Supplement to Birds of Ncw Zealand.,

The Author, London.

CUMBERLAND,K. B., 1949. This is New Zealand. Whit~combe & Tombs, ChristChurch.

Gum, J. A., 1961. Ecology of the birds of KaingaroaForest. Proc. N.Z. Eco/. Soc. 8: 29-38.

GUTHRIE-SMITH, H., 1921 and later editions. Tlaira.Blackwood, London.

LA<:K, D., 1933. Habitat selection in birds. with specialreference to the effects of afforestation on the Rreck-land avifauna. J. Anim. Ecol. 2: 239-262.

LACK,D., 1939. Further changes in the Breckland avi~fauna caused by afforestation. J. Anim. Ecof. 8:277-285.

RELATIONS BETWEEN SALMONIDAE THE

FRESHWATER FAUNA

K. RADWAY

MARPLES, B. L 1942. A study of the little owl, Alhenenoctua, in New Zealand. Tran.~. Rov. Soc. N.Z. 72:

-237-252.

MASTERS, S. E., HOLLOWAY,J. T. and McKELVEY, P. 1.,1957. The national forest survey of New Zealand,1955. VoL I. Govt. Printer, Wel1ington.

MOON, G. J. H., 1956. White-faced heron nesting inNorth Auckland. Notornis 6: 244.

MYERS,J. G., 1923. The present position of the endemicbirds of New Zealand. NZ. Journ. Sci. Tech. 6: 65-99.

THOM'SON,G. M., 1922. The lIafllralisation of animahand plants in New Zealand. Cambridge UniversityPress.

TURBon, E. G., 1953. Notes on the occurrence of thebellbird in North Auckland. Notornis 5: 175-17&.

TURBOIT,E. G., 1957. Native and introduced birds. InScience in New Zealand. Reed, Wellington.

WODZICKI, K. A., 1950. Introduced mammals of NewZealand: an ecological and economic survey. Bull.Dept. ScL Ind. Re,~. 9&.

AND NA TIVE

IN NEW ZEALAND

ALLEN

Fisheries Laboratory, N.Z. Marine

Department

The freshwaters of New Zealand providean environment into which relatively fewexotic species have penetra ted, partly be-cause the problems of survival duringtransportation are so difficult for a fresh-water animal as to make accidental immi-gration very unlikely, and partly because themotives which may stimulate deliberateimportation by man are so few in this case.So much remains to be done in the studvof our freshwater fauna that a number ofexotic species of the smaller invertebratesmay exist unrecorded in this country, butthe known freshwater fauna of non-nativeorigin is limited to one snail and some dozenspecies of fish all deliberately introduced.

Most of the fish were introduced to providesport, and it is not surprising that a largeproportion of them belong to the Salmoni-

dae since in its native Northern Hemispherethis family contains the majority of the mosthighly regarded game species. Of the speciesthat were introduced, two have establishedthemselves successfully over a large part ofthe country, and a third in a more restrictedarea. These are the brown and rainbowtrouts (Salina trutta and S. gairdnerii) andthe quinn at salmon (Oncorhynchus tscha-wytcha) respectively. A few other speciesexist in small numbers in limited areas. Forsimplicity, I propose to limit considerationof the introduced freshwater fauna largelyto these few highly successful species ofSalmonidae; both because of their wide-spread abundance and because, on accountof their popular esteem, they have beenrelatively intensively studied.

It should be realised that fresh waters