NESTING HABITAT AND NEST SITE CHARACTERISTICS OF THE WHITE-BELLIED SEA-EAGLE IN THE GIPPSLAND LAKES REGION OF VICTORIA, AUSTRALIA by William B. Emison Fisheries and Wildlife Division ArthurRylah Institute for EnvironmentalResearch 123 Brown Street Heidelberg,Victoria, 3984, Australia and RogerJ. Bilney Fisheries and Wildlife Division McMillan Chambers Main Street Bairnsdale,Victoria, 3875, Australia

Abstract Thirteennesting territories and 16 nestingtrees used by the White-belliedSea-Eagle (Haliaeetusleucogaster) in the GippslandLakes region of Victoria, Australia,are de- scribed.Concern is expressedabout previous losses of nestinghabitat and the insecurity of overhalf of the nestingterritories presently active in the area.

Introduction The White-belliedSea-Eagle (Haliaeetus leucogaster) is well-knownaround the coast- al lakesin the GippslandLakes region (Fig. 1), but its biologyin the regionhas never

Lake King, Lake LakeVictoria Wellington Sale o

BASS STRAIT Traralgon

147 ø 148 ø

Figure1. GippslandLakes region of Victoria,Australia.

54 RaptorResearch 16(2):54-58 Summer1982 Emisonand Bilney--White-bellied Sea Eagle 55 been studied.The only substantialwork conductedon the speciesin Victoria hasBeen along the Murray River (Favaloro 1944); little work has been done elsewherein Australia. During 1978 and 1979 we made a concertedeffort to find the nestingterritories of sea-eaglesin the GippslandLakes region (excluding Lake Tyers)by searchingfor nests on the groundand from aircraft,and by obtaininginformation from local inhabitants. Aerial surveysof knownnests were conductedtwice duringboth 1979 and 1980. Here we describethe vegetationin the territoriesand somecharacteristics of nestingsites.

Results Thirteenactive (eggs or youngor both were presentduring one or morebreeding sea- sons)nesting territories were foundin the GippslandLakes region during the 1978-1980 breedingseasons (Table 1). Nine of the 13 territorieswere within i km of one of the coastallakes in the GippslandLakes region. The other four territorieswere between2 km and 13 km from the nearestcoastal lake, but all were within i km of either a large swampor a river. Seventerritories were on private land, anotherfive on public land and onewas partially on private and public land.

Table 1. Breedingactivity in sea-eagleterritories during 1978-1980

Active* during: Number of different treesused for nesting Territory 1978 1979 1980 during the 3 seasons

i Yes Yes Yes 2 2 Yes Yes Yes 1 3 Yes No No 1 4 Yes Yes No 1 5 Yes Yes ? 1 6 Yes ? No 1 7 Yes Yes Yes 2 8 Yes No No 1 9 Yes Yes No 1 10 ? Yes Yes 1 11 ? Yes No 1 12 ? Yes No 1 13 ? Yes Yes 2

*Eggsor youngor both observed

The 13 territorieswere locatedin 5 vegetationformations comprising eight vegeta- tion unitseach dominated by I or 2 differentspecies of trees(Table 2). In 3 of the nest- ing territories2 differenttrees were used for nestingduring the 3 seasons(Table 1). Thus from the 13 territorieswe havedata on 16 differentactive nest sites (Table 3). The aver- age heightof treessupporting nests was 27.8 m and the averagediameter at breast heightwas 1.1 m. Nestswere at an averageheight of 18.9 m. All treesexcept two E. te- reticorniswere alive, although one E. botryoideshad been recently burnt and epicormic growthwas occurring. One nestmeasured in situ was2.4 m deepand 1.2 m x 2.1 m wide; the nestingcup was0.3 m deep,0.6 m x 0.8 rn wide andlined with fresheucalypt leaves. 56 RAPTOR RESEARCH Vol. 16, No. 2

Table2. Vegetationunits where active sea-eagle nests were found at leastonce in 1978,1979 and 1980.

Formation •.•. • Dominantspecies ß .• Characteristic features

Tall open-forest Eucalyptuspseudoglobulus 30•40 In shelteredgullies and slopes.Dense 2 layerof Pittosporumundulatum to 12 m. E. cypellocarpacommon at one site.

E. camaldulensis 30-40 On marginof largeriver. Shrublayer of Acacia dealbata to 12 m.

Open-forest E. globoidea 25-30 Denselayer of Pteridiumesculentum to 1.5 m. ScatteredE. cypellocarpato 45 m.

E. bosistoana 20-25 ScatteredE. globoidea,E. pseudoglobulus and E. ovata. A few E. bosistoana to 45 m.

Open-forestto woodland E. bosistoana and 20-30 Denselayer of Leptospermumphyllocoides 1 E. melliodora to 3 m. E. viminalison adjacentsandy areas.

E. botryoidesand 10-25 Usuallywith a denselayer of Pteridium 3 Banksiaintegrifolia esculentum to 1 m. Banksia serrata and Leptospermumlaevigatum also present.

Closed-scrub Melaleucaericifolia 3-7 In waterloggedand low-lyingareas. 2 ScatteredE. tereticornis.Leptospermum juniperinumwas co-dominant at onesite.

Pasture Introducedgrasses and 0.5 Scattered E. tereticornis. 2 crops

Discussion The total numberof White-belliedSea-Eagles nesting in the GippslandLakes region is unknown,but we are suremore nesting territories will be foundas our studypro- gresses.The presentdistribution of nestingpairs suggests that the removalof forests frommany of theareas along the northern shores of LakesKing, Victoria and Welling- ton has resultedeither in the lossof sea-eaglenests or in somepairs attempting to nest in sub-optimalhabitats. Seven species of treeswere used to supportnests, but one of the 2 mostcommonly used, E. tereticornis,has been extensively cleared from the Gippsland Summer1982 Emisonand Bilney-White-belliedSea Eagle 57

Table 3. Characteristicsof activenest sites of the White-belliedSea-Eagle.

Eucalyptustereticornis 4 22 15 1.0 E. botryoides 4 23 18 0.8 E. bosistoana 2 34 25 1.2 E. cypellocarpa 2 40 23 1.2 E. camaldulensis 2 32 20 1.7 E. pseudoglobulus I 27 23 1.4 E. melliodora i 25 12 0.9 Totals 16 27.8 18.9 1.1 Standard error 2.1 1.4 0.1

Lakesregion (Fell 1972)and today there remain only smallremnant populations and oc- casionalindividual trees growing in other plant communities.We foundsea-eagles nest- ing in surprisinglysmall remnants of forest(some pairs even nest in treesin pastures), but the needfor moreforest reserves, particularly those containing some E. tereticornis, is evident. White-belliedSea-Eagles usually build their nestsin the taller trees,and generally 8-10 m belowthe top of the tree, althoughin our sample,one waslocated at the very top. The Bald Eagle (Haliaeetusleucocephalus) of North Americais closelyrelated to the White-belliedc.•. rv..•.• ....• comparison•.r •r •..•; .... • site characteristics is of interest.A recent studyof the Bald Eagle in Florida (McEwan and Hirth 1979) showedthat of 18 nesttrees all were Pinus (all 16 nest treesin our studywere Eu- calyptus),their averageheight was 26.3 m (comparedto 27.8 m in our study),their av- eragediameter at breastheight was 0.6 m (1.1 m in our study)and the averageheight of nestswas 22.4 m (ourswas 18.9 m). Thus the averageheights of the trees and of the nestswere remarkablysimilar in the two studies.Further, while the heightof the Acacia tree usedin Africaby the Africa FishEagle (Haliaeetus vocifer) was not givenby Brown andHopcraft (1973), they mentionedthat nestswere about20-30 m abovethe ground, onceagain similar to abovedata. The diversityof habitatsand of the typesof treesused to supportthe nestssuggest that sea-eaglesattempt to build their nestsin whateveris availableprovided they have readyaccess to a foodsource (mainly aquatic vertebrates) and providedtheir territory does not encroachupon that of another nesting pair. In areas which have little groundcoverand which are easilyaccessible to man, human interferencebecomes a problem;although the sea-eaglesmay attemptto nest,they are unlikelyto be successful (bothof the nestsin treesin pasturesfailed in 1979 and 1980). We are concernedthat more than half (7 out of 13) of the nestingterritories in our studyis on private land. While mostlandholders are sympathetictoward the conservationof sea-eagles,econom- ic pressuresto clearthe land for farming,for developmentor for timber will resultin the destructionof someof thesenesting habitats. 58 RAPTOR RESEARCH Vol. 16, No. 2

Acknowledgments Our studyof the White-belliedSea-Eagle is continuingand we wouldbe gratefulfor reportsof possiblenest sites in the GippslandLakes region. We thankC. M. Beardsell for hisi•lentifications of vegetation at the nestsites; D. D. Evansand F. I. Normanfor their commentson draftsof the manuscript;A. Withersand R. Medlingfor their help in the field; and the manypeople who providedinformation on possiblelocations of sea- eagleterritories.

References Brown,L. H. andJ. B. O. Hopcraft.1973. Population structure and dynamicsin the Af- rican fish eagle Haliaeetusvocifer (Daudin) at Lake Naivaska,Kenya. E. Aft. Wildl. ]. 11:255-269. Favaloro, N. 1944. The White-breastedSea-Eagle along the Murray Valley. Emu 43:233-242. Fell, L. A. 1972. Ecologyof someeucalypts of the GippslandLakes district. 100 years after Dr. Howitt. Victorian Nat. 89:320-325. McEwan,L. C. and D. H. Hirth. 1979. SouthernBald eagleproductivity and nestsite selection.J. Wildl. Manage.43:585-594.

EGG LAYING IN A TWENTY-EIGHT YEAR OLD GOLDEN EAGLE by David M. Bird and StephenTinker MacdonaldRaptor Research Centre MacdonaldCampus of McGill University Ste. Anne de Bellevue, Quebec H9X 1C0, Canada

Longevityof wild and captivebirds of preyhas been reviewedby Brownand Areadon(1968) and Newton (1979),but little or no mentionis madeof durationof reproductivecapacity in raptors.The onlyinformation existingin aviculturalliterature is the suggestionthat the captive Bald Eagle (Haliaeetusleucocephalus) shouldhave a productivelife spanof 20 to 30 years(Hancock 1973). At what age do birdsof prey ceaseto produceeggs or sperm? In 1981,a tetheredcaptive 28-year old GoldenEagle (Aquila chrysaetos), originally taken as a nestlingin 1953at WatsonLake, Yukonby F. Reinruler,produced 2 eggs.This bird washeld captivesince 1973 at the RaptorResearch facilities, McGill University,Montreal. It had apparentlyproduced eggs previously, but the ownerdid not keepany records.No eggswere laid at McGill Universityuntil 1977,when the eaglewas han- dledregularly by the juniorauthor. Courtship behaviour towards people and subsequentegg-laying without a normalmate stronglysuggests that this eaglewas imprinted on man. The eggswere generallyremoved within 1 or 2 daysof laying. The pigmentation,length (mean = 7.33 cm) and breadth(mean = 5.32 cm) of eggswere quite uniformand similarto that reportedfor eggsof thisspecies by Reed(1965) and Brownand Areadon(1968). Eggs were gen- erallylaid in the first2 weeksof April, 4 in 1977,none in 1978,2 in 1979,and 3 in 1980. The longevityrecords summarized in Table 47, p. 367, by Newton (1979)indicate that someraptors can surviveat leastup to 26 yearsin the wild andup to 55 yearsin captivity.He furtherreported that eggsfrom an agingPeregrl-fi• Falcon (Falco peregrinus) tended to be smallerand paler than the normal.We havealso observedthis in a very old captiveRed-tailed Hawk (Buteojamaicensis). However, the role of old agein the potentialreproductive output of anyavian species will notbe clearlyunderstood until furtherinformation be- comesavailable from both banding and captive breeding programs.

Raptor Research16(2):58-59