Breeding and Foraging Behaviour and Habitat Characteristics of the Scaly Ground-Roller Geobrasfes Sgua Migerus in Madagascar
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Ostrich 2004, 75(1&2): 25-31 Copynght @ NISC Pty Ltd Printed in South Afnca All ights reseNed OSTRICH /ssN 0030 6525 Breedingand foragingbehaviour and habitatcharacteristics of the ScalyGround-roller Geobrasfes sgua migerus in Madagascar Jean Eric Rakotoarisoal,2'3*and Berthin Bel 1 ThePeregrine Fund, PO Box4113, Antananaivo 101, Madagascar ' Facultedes Sclences,PO Box 906,Antananarivo 101 , Universityof Antananarivo,Madagascar 3 Currentaddress: l inois StateUniversitv. PO Box4120. Normal. lL 61761.United States of America * Correspondingauthor, e-mail: [email protected] The endemicScaly Ground-roller Geobrasfes squamigerus was studiedduring two breedingseasons from October1997 to January1999 in MasoalaNational Park, Madagascar. Several vocalisations were associatedwith territorialdefence, contact, excitement,and aggressivenesstowards intruding conspecifics. Of the 269 prey itemsobserved, 71.5o/o werc invertebrates, 7.5%vertebrates, and 21 .0Vo unidentified. Earthworms and centipedesrepresented the most numerousprey-types taken, rep- resenting55% and 21o/oof the identifiedprey, respectively. Three nests were locatedin valleysand nearstreams. Nests were placedin groundburrows with tunnelsthat measuredless than 1Ocmin diameterand less than 1m in depth.A singleegg clutchwas laidin each nest,and incubationand the nestlingperiods lasted 18 daysand 24 days,respectively. Nesting began in late October,and one youngfrom each nest successfullyfledged in mid-December.Only the femaleincubated and brood- ed the young.Both male and female provided food for the nestling,and feeding rates did not differbetween the sexes.Nesting habitatdiffered significantly from randomplots sampled. Herbaceous coverage density was higherin nestingareas than ran- dom Dlots. c'l+ Ln (^, lntroduction The Scaly Ground-rollerGeobrasfes squamigerus (sensu of slash-and-burnclearings, secondary growth, and largely Kirchmanet al. 2001) is a burrow-nestingspecies (Benson intactforests. The maturelowland rain forest of the Masoala et al. 1976,Goodman 1994) whose rangeextends from the Peninsulahas a canopy height less than 30m with few northto the centreof the easternrain forestof Madagascar emergenttrees, high floristic diversity, and steep mountain- (Langrand1990). lt belongsto the endemicfamily of ous topography(Guillaumet 1984), and elevationsrange Brachypteraciidaeand was formerly placed in the genus from 0-1 200m. Average rainfall recorded at AFS from Brachypteraciasuntil a recent phylogeneticstudy of the fam- 1992-1996was 6 049mm(Thorstrom et al. 1997),making it ily (Kirchmanet al. 2001).The Scaly Ground-rolleris cate- one of the wettestregions on the island.Monsoon rains and gorisedas vulnerable(a taxonfacing a highrisk of extinction cyclones occur between December and April (Donque in the wild in the medium-termfuture) in the recentlyupdat- 1972).September through November is normallythe driest ed Red Data List (Collaret al. 1994).The speciesis known periodof the year.Annual temperatures vary from a low of to inhabitundisturbed evergreen primary rain forest with a 18"Cto a highof 33"C. preference for relatively dark undergroMh that offers fairly We located Scaly Ground-rollersby their calls. low herbaceousvegetation and a carpetof dead leavesand Vocalisationswere recordedand analysedwith Spectrogram branches(Langrand 1990). Little information is availableon 3.2.1software (Horne 1994). Behaviours associated with the its behaviouralecology and breedingbiology and this paper callwere notedfor furtheridentification of eachcall type. We presentsthe firstsystematic study of this species. capturedadufts with mist nets (2.6mx 12.2m,36mmmesh) installednear nestsor where oairs had often been encoun- Methods and study area tered. Capturedground-rollers were measuredwith vernier calipers(nearest 1 .Omm), weighed with Pesola3009 spring ScalyGround-rollers were studiedduring two breedingsea- scale (nearest1 .09), and fittedwith colouredplastic rings. sons, coveringthe periodsOctober 1997 to January 1998 Morphologicalmeasurements include bill lengthtaken from and October1998 to January1999, in the MasoalaNational the end of featheringon the top mid-lineto the tip (Palmer Park, northeasternMadagascar. The study was conducted 1962);unflattened wing chord taken from the front of the at two sites,both below600m above sealevel. The firstsite folded wrist to the tip of the longestprimary (Biggs et ai. '1978); was situatednear AndranobeField Station(AFS) on the tarsus lengthtaken from the posteriorcentre of the west coast of the Masoala Peninsula(15'41'S, 49"57'E). tibiotarsal-tarsometatarsaljoint to the dorsalbase of the cen- The secondsite, also on the peninsula,was 3km east and tre toe (Biggs et al. 1978)iand tail length taken from the up slope from the villageof Ambanizana,7km north of the pointof insertionof the centralfeather to the tiD. AFS. The peninsulais road lessand composedof a mosaic Scalv Ground-rollernests were located in two wavs. Rakotoarisoaand Be First,in order to solicitresponse from breedingadults, we Results playedtape recordingsof their calls.We followedadults to the oresumednest areas and searchedfor Dotentialnest We located three nests for which observationtime totalled sites. We then monitoredDotential burrows and recorded 483h,with an averageof 10h + SD of 1.8h per day in 1997 observationsof Scaly Ground-rollernesting activitiesat (n = 22 days),and 7h t SD of 1.3hper day in 1998(n = 39 these sites. Second, we attached a 2.19 back-mounted days). transmitter(Holohil Systems Ltd, Canada) to a captured adultand monitoredits movementsand behavioursDrior to Vocalisations the nestingactivities. The transmitterweighed less than 3% Several vocalisationswere identified.These calls were of the weight of the individualand lastedtwo weeks. The associatedwith differentbehaviours. Territorial calls were 'whoop' nesting behaviourof Scaly Ground-rollerswas observed represented by a sequence of notes that were from blinds or other camouflagedlocations at about 30m uttered with various frequencies according to circum- from nest. Observationswere made using 10 x 40 binocu- stances.Frequency of notes(number of notesper time unit) lars and datawere recordedin a continuouswritten log that was seen to increasewhen two neighbouringbirds were in includedthe time of day, frequency,and durationof their close proximityto each other while defendingtheir respec- nestingactivities at and aroundnest sites. tive territories(from 7-10 call min-1,duration = 22min).Most We recordeddata for each pair usingthe colouredplas- territorial calis were given early in the morning tic rings and assignedsex based on behaviourduring the (05h00-06h00)and late in the afternoon(16h00-17h00) nestingperiod. As only one individualwas seen to perform (Figure1). Territorial calls were broadcastfrom percheswith all the incubationduties and brooding in each pair, we an averageheight of 1.2m (range0.8-2m) and drameterof assumedthat individualwas the female. 2.5cm(range 1-4cm, n = 5 perches). For nestingphenology, egg layingwas assumedto have A second type of vocalisation,the contact call, was occurredand incubationbegan when the femalestarted to associatedwith communicationbetween a pair as they spend more than three hours a day in the nest. Hatching movedthrough the forest.The call consistedof a hollowsin- 'whoop' was assumedto have occurredinside and broodingbegun gle and deep note similar to the territorialcall. when the male startedto deliverprey to the nest while the Spectrogram analyses of the territorial and contact calls femaleremained inside. Nests were checkedabout every 10 showeda differencebetween them in frequencyand dura- daysto followthe developmentof the young.Prey itemsfed tion of notes.Territorial call notes had a seeminglyhigher to the nestlingby adultswere visuallyidentified and sizes frequency(mean = 43.23kH2,SD = 0.04kH2,n = 10 notes) estimated.Nest chamberswere excavatedand measured and lasteda shorterperiod of time (mean= 312.9ms,SD = the followingbreeding season after confirmationthat they 67.8ms, n = 10 notes) than the contact call (25.73k{z. had been abandoned. 372ms,n=1call). 'kwek' Severalparameters were consideredwithin an area of A third type of vocalisation,a sharp,harsh alarm 100m2around the nestto characterisethe site.Saplings and call was made when the bird becameexcited (e.9. during herbaceouscoverage were categorisedinto ranges of size. preycapture) or when threatened(e.9. when trappedin mist Data recordedincluded herbaceous coverage density, tree density,and distancefrom water,slope, and canopydensity. The same parameterswere measuredon 10 randomlysam- pled plotsof 100m'within the same forestblocks. Location Territorialcalls of the plots(distance from the nest,direction and angle)was Contactcalls determinedby randomlydrawing numbers in a bag contain- I ing numberedpapers. We then comparednest sites with randomplots in orderto detectany uniquecharacteristics of the nest site. Data referring to nest site characteristicswere first test- ed for normalityusing the Shapiro-Wilktest (Shapiroand Wilk 1965).All variablesexcept number of tree species,dis- tance from water, and distancefrom valley bottom were nor- mallydistributed. The Student'st-test was usedto compare nest sites and random plots for herbaceousvegetation, saplingdensity, tree density,slope of the nest,slope of the site, number of liana, ferns, tree height,tree diameterat (dbh), foliagedensity. The Wilcoxontwo breastheight and 99| sampletest (Sokaland Rohlf1995) was usedfor numberof vqtqt ,.Fo.q*s*$glss*6$*lr--d,_dS${)*v*b*dS