THE JOURNAL OF RAPTOR RESEARCH A QUARTERLY PUBLICATION OF THE RAPTOR RESEARCHFOUNDATION, INC.

VOL. 22 SUMMER 1988 No. 2 j. RaptorRes. 22(2):37-43 ¸ 1988 The Raptor ResearchFoundation, Inc.

ATYPICAL NESTING HABITAT OF THE PEREGRINE FALCON (Falcoperegrinus) IN VICTORIA, AUSTRALIA

CLAYTON M. WHITE, WILLIAM B. EMISON AND WILLIAM M. BREN

ABSTR^CT.--Nestingof the PeregrineFalcon (Falcoperegrinus) in disusedstone quarries is not unusual, but occupancyof activelyworked quarries represents a departurefrom typicalnesting behavior. In Victoria, Australia, sevenof 11 stonequarries occupiedwere activelyworking quarries. In one casethe eyrie was 50 m from quarrying operations,rock crushingequipment and machinery.In 1982 Peregrinesoccupied a hydroelectricdam within 3 yrs of its completion.They also occupieda gravel loading silo in use and nestedabout 20 m above a truck loading area. Such exploitationof seemingly"unsuitable" or "disturbed"sites could be expectedin an expandingPeregrine population containing a high percentage of youngerinexperienced adults. In Victoria the populationis stableand somequarries have been occupied in excessof 20 yrs. We suggestsuch quarry use in Australia reflectsa large, numericallyhealthy falcon populationwith a large vulnerablefood supply in areasotherwise limited in natural nestingsites.

The PeregrineFalcon (Falcoperegrinus) can and Herein, we describe five of these sites. The structure doesnaturally nest in closeproximity to human ac- of worked quarries was similar in all regardsto those tivity (i.e. urban building, bridges,etc.). Such situ- in disuse. ationsdepart from the normally isolatedand remote

cliff sitescharacteristic of the species(Hickey 1969). METHODS Indeed, with the reintroductionof the Peregrinein Studieson Peregrinesin Victoria (ca. 227 300 km2) the easternUnited States,use of bridgeshas become started in 1975, continuedthrough 1984, and thereafter frequent(Cade and Dague 1985). Overall, however, occurredas opportunity presented (see Emison et al. 1988). suchnestings are uncommon.One of the more com- No attempt was made to examine intensivelyall known monlyused man-made structures is the stonequarry stonequarries in Victoria. Rather, disusedquarries were and in fact it shouldbe, as a quarry is nothingother examinedas they were found or reported;working quar- ries were examinedwhen a report of falconswas received than a man-made cliff or rock face. Many quarries at the Arthur Rylah Institute (Victoria has an extensive providenew nestinghabitat in regionswhere oth- bird watchingcommunity; between 1977 and 1981 nearly erwiseno nestingsubstratum exists and mostquarry 800 observersreported data and the Peregrineresearch useis of disusedquarries. Fischer (1973) indicated program receivedattention in the public media). Each quarry examinedwas visitedon foot and frequently the that disusedquarries along the Main, Necker and "high walls" were climbed. Absenceof suitable nesting Weserrivers in the Unstrut Valley, Germany,opened ledgeswas usually noted. Measurementsof prey density up an entirelynew area for nesting.Likewise, Rat- were not made in a systematicmanner, but impressions cliffe (1980) documentedthat many quarriesin Brit- of prey densitynear eyrieswere casuallynoted. Compar- ain providenew cragsfor nestingin regionswhere isonsbetween Peregrine distribution and the distribution of four major prey groups (Rock Dove [Columbalivia], noneotherwise existed. We suggestthat quarry use Galah [Cacatuaroseicapilla], rosellas [Playtcercus sp.], and in Victoria functioned in the same fashion and is EuropeanStarling [Sturnus vulgaris]) were madeusing the related to food supply. Atlas of Victoria Birds (Emison et al. 1987). For the Atlas We currently know of 11 quarry eyries among the state was divided into blocksof 10 min (ca. 18 km) of more than 79 natural cliff sites studied (see Pruett- E. Lat. by 10 min (ca. 15 km) of S. Long. of area, resulting in 918 blocks in Victoria. Bird speciesoccurrence was Joneset al. 1981; White et al. 1981). Of these 11 recordedfor each block during the Atlas period (1973- quarries, seven are being excavatedcontinuously. 1986) which gavedistribution and an index of frequency.

37 38 WHITE ET AL. VOL. 22, NO. 2

...

.-.

• . ..;•

Figure 1. Sitenumber 1•panoramic •iew of quar•. •ote •ra•el1oa•er in leftcenter of photo• arrow indicates e•rie location.

tween two vehicles.The Peregrinelanded on the RESULTS roofof the vibratingloader amidst rising dust. Un- The Eyries. The only thingmost quarry eyries ableto locatethe pigeon,the falconleft within about had in commonwas their placementon high walls. one rain but at no time seemeddisturbed by the Eachsite had particularfeatures of interestand it commotion. is instructiveto describea sampleto presenta clear b) Site #2 is a verysmall, active quarry (30 x pictureof the variablesat thesesites. 75 m) in the shapeof a quartercircle. While we do a) Site #1 is in the largestactive stone quarry not havea historyof falconuse of the site,in 1977 in Victoria(ca. 80 ha) (Fig. 1). The quarry started and 1978 nestingoccurred about 50 m froma section operationin 1929and Peregrines began nesting there of the quarry beingworked (Fig. 2). at leastin theearly 1960s (Max Parker,pers. comm.). ½) Site #3 is aboutthe samedimensions as #2 Pairs haveused five or six different walls depending but more U-shapedand locatedabout 12 km in a onwhere quarrying occurred but normallyselected straightline from #2. We haveno history of useof less disturbed areas. Falcons were so accustomedto the quarry.The quarry is inactiveand servesas a quarryingoperation that on oneoccasion we sawa firingrange on weekendsfor a localrifle andpistol Peregrinechase a FeralPigeon past the office build- club.In 1977 a Peregrineeyrie was located opposite ing andtoward a 10 m highgravel loader in oper- and at a 90ø anglefrom the targetsand about60 m ationfilling vehicles. The pigeonflew into dust gen- from benchrests and the area housingshooters. On eratedby the loaderand seemed to slamwith total 29 October 1977 we were at the site when shooting abandoninto the loader and fell to the ground be- startedat 1300 H. The femaleleft her perchbeside SUMMER 1988 ATYPICAL NESTING OF AUSTRALIAN PEREGRINES 39

Figure 2. Site number 2--arrow indicateseyrie location.Work is being doneabout 50 m to the left of the eyrie.

a single 3« wk old nestlingwhen shootingstarted, in 1976 (Peter Shanahan,pers. comm.). The quarry screameda few times and perched in a tree about representedthe only vertical rock faceswithin a 13 100 m away. She remainedperched until the shoot- km radius,and the closestrock face is anotherquarry ing was over.We were told by localsthat the female in the city of Geelong.Workmen frequently watched laid eggsand startedincubation after weekendshoot- the pair cooperativelyhunting above the quarry pur- ing had already started. suing flocksof Feral Pigeons(about 15-30 individ- d) Site #4 is dug as a long, shallow pit into uals) or CommonStarling flocks of > 100 individuals otherwiselevel ground (Fig. 3) rather than into a (John Russell,pers. comm.). Although four young hillside as with mostquarries. Vertical facesof high fledgedin 1977 (four young is an unusually high walls are about 15 m high and faceeach other about number of young in Victoria), successof the pair 150 m apart. The long axis is about 350 m. The was apparently not good becauseof the open and eyrie was actually below the level of surrounding unshelterednature of nestingledges. In 1978 water land. As desired rock was removed,the quarry was gathered on the nesting ledge and eggs were in a filled in at one end and new ground was openedat pool of mud when checked.The pair may have been the other end. The quarry was in essencemoving in youngeradults as the quarry had beenused <5 yrs one direction. Filled areas were then reclaimed and by Peregrinesin 1978. replanted.As new high walls were created,the fal- In 1986 and 1987 a pair of Peregrinesfledged cons moved and the actual wall used for nesting youngfrom a nest on top of a 30 m gravel loading seemedto dependupon which one was being mined silo (Fig. 4) locatedat this quarry. The silo had a duringegg laying. The wall usedin 1978 was opened coveredconveyor belt housing that, becauseof its 40 WHITE ET AL. VOL. 22, NO. 2

Figure 3. Site number 4--panoramic view of quarry. Arrow indicateseyrie location. position,left a gap of about 0.3 m high covering6 where the structuremet the dam wall proper a con- m2. This platform, 20 m abovethe trucks, provided ical "pot-hole" of 1.3 m3 was formed that provided a nest scrapemade in powdery dust from years of the nestingledge. The eyrie was within 20 m of a operation. serviceroad and car park usedby reservoirstaff. A, e) Site #5 has one main face of limestone 150 service walkway along the "draw-off" structure rn long and 35 m high with only one suitablenesting passeddirectly over top of the eyrie and within 0.6 ledge,a cut about 25 m from the ground.This ledge m. While this sitewas only successfulin raisingtwo was usedfor at least 20 yrs (Neville Holland, pers. young in 1982, there were signsof falcon presence comm.)and during 8 yrs of monitoringby us, 17 at the dam in subsequentyears. young fledged.The quarry has been continuously Assessmentof Prey. While we have no direct worked and the eyrie was only 50 m from heavy measure of prey density or vulnerability we have machineryand a rock crusher.The falconsshowed attemptedto derive an index basedon speciesoc- no concernas long as humansdid not approachthe currence.The four majorbird prey groupsmade up, eyrie too closelyin a direct manner. on average,62% (of 65 species)of prey. Pigeons f) Dam Site. Like quarries,dams form cliff-like were found in 72% (av.) of the Peregrineeyries, structuresthat have beenused by nestingfalcons. In Galahsin 54%, rosellasin 29%, and starlingsin 65% Zambia, for example,where the Peregrineis a scarce (see Pruett-Jones et al. 1981). Of the 84 blocksin breeder at best, nesting has occurredon a buttress which Peregrineswere recordedbreeding in the At- of the Kariba Dam wall (Osborne and Colebrook- las period(Emison et al. 1987), starlingsand Galahs Robjent 1980). A dam 35 km from Melbourne was occurredin 82 (the blockin which either speciesdid completedin 1979. The front wall of the dam rises not occur was different), rosellas in 74, and while about 95 m high at the highest point, whereas the pigeons were not seen in about 15 blocks where back of the dam wall rose about 10 m above the Peregrinesbred they nonethelesswere found in ey- water's surface during years of average rainfall. ries as food. Domesticpigeons are releasedby the Peregrinesnested on the backwall in 1982. A "draw- thousandsin racingcontests and thusoccur through- off" structureprotruded over the water surfaceand out Victoria during theseraces. Lost pigeonsfrom SUMMER 1988 ATYPICAL NESTING OF AUSTRALIAN PEREGRINES 41 these racesare seen in unlikely placesnearly any time of the year. As an indication of distribution (commonness?) of thesemajor prey speciesGalahs were seenin about 84% of the blockswithin Victoria and were present in about 50% of the statein any givenmonth except February. Starlings were seenin about 91% of the blocksand presentin over 60% of the statein any givenmonth. The mostwidespread bird in Victoria, by comparison,is the Australian Magpie (Gymno- rhina tibicen) reported in about 98% of the blocks within nearly 85% of the state in any given month. By contrast,two raptors,the Peregrineand the rel- ativelywidespread and abundantAustralian Kestrel (Falco cenchroides),have values that are 38% and 83% of the blocks and about 5% and 35% of Victoria in any given month, respectively. As a relativeindex of density,Galahs are reported on 48% of the bird lists in blockswhere they occur. Comparativevalues are 60% of lists for the starlings and 7% of lists for the Peregrines.The proportion of Galahsto starlingsin reportingrates was the same as the proportion found as prey in eyries.

DISCUSSION In regionsof high Peregrine population pressure younger breeding members, usually part of the "floatingpopulation," may use nestsites that older Figure 4. Gravel loadingsilo site--arrow indicateseyrie establishedpairs would not. In Britain where there location on silo. are currently about 1100 pairs in the 229 900 km2 region, about 25 disusedquarries have been used and 11 of these are in areas where no other suitable were first-timenesters from the "floater" population cliffs exist (Ratcliffe 1980). However, in 1979 in a as the nearest known historical sites more than 20 departurefrom the occupancyof disusedquarries, km away were also occupied. one British eyrie was in an unusedportion of a Expansionof Peregrinesinto new situationsand quarry where work was underway and a second their useof more "unorthodox"nesting sites is seem- eyrie was abovean excavationsite in progress(Rat- ingly related to, among other things, an abundant cliffe 1980). Similarly, in the German Democratic food supply that can be adequatelyexploited. Rat- Republic, where the Peregrine population is cur- cliffe (1980) did not have a direct measure of the rently (1986) in a rapid recolonizationphase, an foodbase but suggestedthat the expansionof Pere- actively worked quarry was recently occupiedby grines in Britain into new areas and their use of nesting Peregrines (H. Richter, via D. J. Brimm, cliffs for nesting heretoforeunoccupied by falcons pers.comm.). We alsoknow of a sitein Alaskawhere was a functionof the combinationof an expanding in 1980 a presumablyyounger pair of adults suc- population(many young enteringinto the adult co- cessfullynested on a cliff sonear a road construction hort so densitydependent) and abundantfood sup- site that concussionof dynamite blasting was seen plies(so densityindependent with domesticpigeons to ruffle featherson the perchedmale. The falcons as a dominantpart of that foodsupply). Nelson and moved onto the cliff, that over the past 30 yrs had Myres (1976) suggestedthat the reversealso hap- only been used by the Golden Eagle (Aquila chrys- pens and interpreted the reduction of Peregrinesin aetos), after constructionhad already started (D. the Queen Charlotte Islands,Canada, to be a func- Roseneau,pers. comm.). We presumethe Peregrines tion, in part, of reduced prey. Certainly the 42 WHITEET AL. VOL.22, NO. 2 reintroductionof Peregrinesback into North Amer- by thefact that more than half of thequarries used ica has been as successfulas it has by initially se- by Peregrinesin Victoriaare in continualoperation. lectingsites with abundant food supplies nearby (e.g., The fact that a few disusedquarries in Victoria erectingtowers in marshes). with seeminglyadequate ledges and food supply Like Europeanquarries at leasttwo of thosewe nearbyare unoccupiedby falconswhile somein havediscussed (Site 1 andSite 4) providenew habitat operationare used is alsosomething that we arenot in regionswhere no other naturally occurring rock fullyable to explain.However, we cansuggest that facesexist within 15-20 km. The rapid occupancy at leastthe followingconditions may be responsible. byPeregrines ofrecently exposed rock faces at some 1) Localfood supplies may be efficientlyexploited quarriesin Victoriasuggests that a largepopulation only from certain quarries. 2) Peregrinepopulation of "floating,"non-breeding birds is present.Of fur- pressureis suchthat whatwe wouldcategorize as therinterest is thatquarries in general,and quarries "marginal"habitat (in the sensethat disturbances •nactive operation especially, became occupied while are frequentand severe)becomes used in spiteof other areasof Victoria with seeminglyexcellent nat- less desirable conditions because an abundant food ural rock faceswere unused.This suggestedthat not supplymore than compensates for the disturbance onlywas there a numericallyhealthy surplus pop- factor.3) There is someassociation of bioticand ulationof Peregrinesavailable to exploitthese quar- abioticfactors in concertat quarriesthat we have tersbut that thosequarries occupied were in areas not been able to identify. 4) Falconsthat occupy of a highfood base that helped to overridethe neg- such sitesare more tolerant of disturbancesthan the ative effect of disturbanceand thus providedthe normof thespecies. If thelatter is thecase it would properset of conditionsconsisting of •tn essentialbe interestingto determineif suchtolerance is a balancebetween nesting and foraginghabitat. In heritable factor or learned becauseof previous ex- essencequarries provided something that nesting on periencesearly in their lives. natural cliffsdid not (we haveseveral examples of eggsbeing laid annually and subsequently broken LITERATURE CITED becauseno adequate ledges exist on particular cliffs). CADE,T. J. ANDP. R. DAGUE.1985. The Peregrine Rapidoccupancy of the dam site once it wascom- Fund. Cornell Univ. Lab. of Ornith., Special Spring pletedcorroborates thisnotion. We suggestthat the Report,Spring 1985. Peregrinepopulation in Victoriamay be nearsat- EMISON,W. B., C. M. BEARDSELL,F. I. NORMANAND uration and that unoccupiednatural cliffs in areas R. H. LOYN. 1987. Atlas of Victorian birds. Dept distantfrom the nearest used e.yrie have some biotic Cons.Forests and Lands, and Royal Aust. Ornithol. deficiencysuch as lack of a nearbyexploitable food Union, Melbourne, Australia. EMISON,W. B., W. M. BRENAND H. F. ARCHER.1988 supply.We arenot yet able to explain why all seem- Victoria-Agricultural,and Victoria-Mallee. Pages 267- •nglyoptimal environments are not exploited at the 268. In T. J. Cade,J. H. Enderson,C. Thelander, samefrequency. For example, Peregrines do not nest and C. M. White, EDS.Peregrine Falcon populations in citiesin Victoria where there is an abundanceof theirmanagement and recovery. The PeregrineFund, nestinglocations and an enormousfood supply, es- Inc., Boise, ID. peciallyFetal Pigeons. This becomes even more of FISCHER,W. 1973. Der wanderfalke;Falco peregrinus an enigmabecause where cliffs or quarriesare not undFalco pelegrinoides. Die NeueBrehm-Bucherie, A. available,Peregrines in Victoriause trees for nest ZiemsenVerlag, Wittenberg Lutherstadt, G.D.R. sites(see White et al. 1981).We wereinterested in Hm}CE¾,J. J. (ED.). 1969. PeregrineFalcon popula- thefact that of the data presented by Ratcliffe (1980) tions;their biology and decline. Univ. Wisconsin Press, Madison. about2.5% of theeyries in Britainwere in quarries, NELSON,R. W. ANDM. T. MYRES. 1976. Declinesin whilein Victorianearly 14% were in quarries.Hav- populationsofPeregrine Falcons and their seabird prey ing seenmany sub-optimal eyries in Britain,we at LangaraIsland, British Columbia. Condor 78:281- wonderwhy more quarries there are not used. Use 293. ofquarries inVictoria becomes more interesting when OSBORNE,T. O. ANDJ. F. R. COLBROOK-ROBJENT.1980 one realizes that Britain and Victoria have similar The statusof the genus Falco in Zambia.Proc. IV Pan- land area, but about 10 timesmore cliff eyriesare Aft. Ornith. Congr. 301-306. knownin Britain than in Victoria. We are impressed PRUETT-JONES,S. G., C. M. WHITEAND W. R. DEVINE. SUMMER 1988 ATYPICAL NESTING OF AUSTRALIAN PEREGRINES 43

1981. Breeding of the Peregrine Falcon in Victoria, Department of Zoology, Brigham Young University, Australia. Ernu 80:253-269. Provo, UT 84602, USA; Address of second and third R^TCLIFFE,D. 1980. The PeregripeFalcon. Buteo Books, authors: The Arthur Rylah Institute for Environ- Vermillion, SD. mental Research, Department of Conservation, WHITE, C. M., S. G. PRUETT-JONESAND W. B. EMISON. Forestsand Lands, 123 Brown Street, Heidelberg, 1981. The status and distribution of the Peregrine Victoria 3084, AUSTRALIA. Falcon in Victoria, Australia. Ernu 80:270-280. Received30 August 1987; accepted21 April 1988

The 1987 Annual Meeting of The Raptor ResearchFoundation, Inc.--More than 400 were in attendanceat the 21st annual meeting of The Raptor ResearchFoundation, Inc., held on 28-31 October 1987 in Boise, Idaho. The scientificprogram included 74 paper presentationsand 18 posterpresentations. Gary Duke was electedas the Foun- dation'snew President,succeeding Jeffrey L. Lincer, while Richard J. Clark, James E. Fraser and Jim Fitzpatrick will continueas Vice President,Secretary, and Treasurer, respectively.Newly electeddirectors included Bernd Meyburg, Keith Bildstein, and Jeffrey L. Lincer. Thomas Hamer of Western Washington University was presentedwith the William C. AndersenMemorial Award for 1987 for the best studentpaper presentation.The paper was co-authored by Fred Samson.The LeslieH. Brown Memorial Award for 1987 was presentedto Geoff and Hilary Welch for their raptor researchand conservationefforts in Djibouti. The StephenR. Tully Grant for 1987 was awarded to Kelly F. Hogan for a study of Prairie Falcon foragingecology in the Chihuahuan Desert. The 22nd annual meeting of the Foundationwill be held on 26-29 October 1988 at the Crowne Plaza Holiday Inn Metrodome in Minneapolis, Minnesota.