THE JOIYRNAL OF RAPTOR RESEARCH A QUARTERLY PUBLICATION OF THE RAPTOR RESEARCH FOUNDATION, INC.

VOL. 25 SPRING 1991 NO. 1

J. RaptorRes. 25(1):1-8 ¸ 1991 The Raptor ResearchFoundation, Inc.

ALTITUDINAL DISTRIBUTION AND CONSERVATION OF RAPTORS IN SOUTHWESTERN

JEAN-MARC THIOLLAY Laboratoired'Ecologie, Ecole Normale Supgrieure, 46 rue d'Ulm, 75230Paris, Cedex05, France

ABSTP•CT.--Diurnal raptors were surveyedduring four weeks along a gradient from sea level to 4000 m on the Pacific slopesof the in southwesternColombia. However, most of the work on habitat selection,density estimates and conservationproblems was donewithin the subtropicallevel (1200-2400 m) in the 3200-haforest reserve of La Planadaand its surroundingmosaic of pastures,cultivated fields and disturbedforest. Twenty-two raptor specieswere recorded.Forest richness does not change noticeablyat successivelevels between 0 and 1000 m, but this richnessdecreases rapidly above1500 m. The numberof opengrassland species tends to increasewith elevation.Extensive deforestation is a major threat to the survivalof severalforest raptors, including endemics from the humid westernslope of the Andes.Some sufficiently large areasof relativelyundisturbed forest, suitable for raptor conservation,still remain between500 and 2000 m but very few can be found aboveor below this level.

Distribuci6ny conservaci6nde avesde rapifia en diversosniveles de altitud en el sudoestede Colombia EXTg^½TO.--Raptorasdiurnas fueron inspeccionadasdurante 4 semanasa 1o largo de una gradiente comprendidaentre el nivel del mar y los4000 metros,en las pendientesandinas del Pacificoen el sudoeste de Colombia.Sin embargo,la mayor parte del trabajo de selecci6nde habitat, estimacionesde densidad y problemasde conservaci6n,ha sidohecho dentro del nivel subtropical(1200-2400 m) en las 3200-ha. de la reservaforestal La Planada,y el mosaicode susalrededores con pastos, campos cultivados y alterada floresta.22 especiesde avesde rapifia han sidoregistradas. La riqueza de las especiesraptoras de floresta no cambianotablemente en los sucesivosniveles entre 0 y 1000 m, pero sl decrecerapidamente a partir de los 1500 m. E1 nfimero de las especiesde las areas de pastostiende a crecer con la elevaci6n.La extensivadeforestaci6n constituye el mayorpeligro para la supervivenciade las avesraptoras de floresta; estoes cierto tambi•n para las especiesde las hfimedaspendientes occidentales de los Andes. Areas suficientementegrandes de florestarelativamente inalterada, apropiadaspara la conservaci6nde aves raptoras,afin se encuentranentre los 500 y los 2000 m, pero muy pocaspueden encontrarse por encima o por debajode estenivel. [Traducci6n de Eudoxio Paredes-Ruiz]

Colombia is ornithologicallyone of the richest vey methodsare required to establishthe presence, countriesin the world with at least 1695 speciesof or to assessthe relative abundance,of many species. birdsreliably recorded,including 75 , These methodsare time consumingand are often as summarizedby Hilty and Brown (1986). The appropriatefor only a particularsubset of the raptor extreme southwesternpart of the countryis among assemblage(Thiollay 1989a).The birdsin this study the least studiedareas. Yet this Pacificslope of the area provedto be no exception. Andes, called southern Choco, which extends into The presentstudy of the distributionof raptors northwestern , is both rich in endemic taxa along a gradientfrom sealevel to 4000 m was of and threatenedthroughout by rapid deforestation, interest for several reasons. Little was known about especiallyin the lowlands.Moreover, diurnal rap- the area and its endemicspecies; the gradient had a torsare usually poorly surveyed because specific sur- wide altitudinalrange but within a relativelynarrow 2 JEAN-MARCTHIOLLAY VOL. 25, NO. I

,,/'

TUMALCO C_•MBIA

ECUADOR

•,...,L.•,...,

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1,0 2,0

Figure 1. Map of the studyarea in southwesternNarino, Colombia.Dots representvillages or smalltowns and trianglesthe highestpeaks (volcanoes). strip; comparativedata were drawn in 1987 from a (Holdridge 1967). 1) The Paramo extendsfrom the tree personalsurvey of raptorsin nearby northwestern line (3200-3400m) to theupper limit of vegetation(around Ecuador; this was among the first usesof raptors as 4500 m). The RosetteShrub (Espeletiasp.) was charac- teristicof the lower part of this wet alpine grasslandwhere sensitiveindicators for the managementof a Bio- some patchesof low, densePolylepis woodland still re- sphereReserve (UNESCO-MAB) proposedin the mained in the ravines.The upper part of the Paramowas area; severalspecies may soonbecome extinct be- dominatedby grasslands.Strong winds, cool temperatures, moderate rains and extensive cloud cover occurred almost causeof the current high rate of deforestation. daily. 2) The temperateor montaneforest was found main- ly from 2500-3500 m betweenE1 Espino,Miraflores and STUDY AREA AND METHODS Piedrancha.Trees were usually under 20 m tall and cov- The southwesterncorner of Colombia(Narino), along ered with epiphytes.Stunted trees and shrubsdominated the Ecuadorian border, providesa 115-km-wide gradient a so-calledelfin forest near the tree line. 3) From 2400 m from the upper ridge of the westernAndes, dominated by down to 1200 m, a subtropical,humid or premontane the Cumbal Volcano (4764 m), down to the Pacific coast. forestwas found. Many treesreached 25-30 m in height It is crossedby the Pasto-Tumaco road of which the E1 and were heavilycovered by epiphytes(e.g., ferns, mosses, Espino-Altaquersection has been the mostintensively sur- bromeliads).Trees were dominatedby the generaCassza, veyedduring this study(Fig. 1). Clusia,Ficus, Miconia, as well as palms. The denseand This Pacific slopeof the northern Andes (Choco) has wet undergrowthhad many tree ferns. 4) From 1200 m the heaviestrainfall in the Americas (Hilty and Brown to 500 m, in the Altaquer-Junin-Barbacoas-E1Diviso area, 1986), ranging from over 3000 mm on the coastto an the foothillsbore a tropicalwet forest(rain forestof Hold- averageof 10 000 mm in the foothills (500-1000 m) and ridge 1967). It was the elevationwith the heaviestrainfall, decreasingto about 4-5000 mm at the subtropicaland coveredby a dense,evergreen forest, with treesreaching montane levels. The heavy cloud covertends to increase 30-35 m. The highesttree speciesdiversity may be found with altitude. The mean temperaturedrops by about 6øC at this level (G. Samper,pers. comm.).5) Below 500 m, with each 1000-meter increase in elevation. the lowland wet forest was the tallest (35-45 m) with The altitudinalgradient was dividedinto fivemain zones comparativelyless undergrowth and still high tree species SPRING 1991 RAPTORSIN SOUTHWESTERN COLOMBIA 3 richness.A wide belt of mangrovesfringed the coast.All servations and the behavior of adult monitored. This alongthe gradient,much of the originalforest cover has minimum number of pairs of eachspecies is probably too beenconverted to cattle pastures and cultivated fields; shrubs low for the secretivesmall forest speciesbut much more predominatedon lightly grazedor abandonedareas. accuratefor the conspicuouslarge soaring species.Pairs Most of my observationswere madein and aroundLa of displayingLeucopternis or Leptodonand even calling Planada Natural Reserve, within the subtropicalzone. Micrasturwere widely separatedand thus easyto distin- This 3200-ha reserve was at an altitude of 1500 to 2200 guishfrom eachother without a completemapping of their m and coveredwith primary forest. Over 200 ha were territory. regenerating,after being either convertedinto pastureor Around the 3000-ha forest of La Planada, an additional loggedfor valuabletimber 10-20 yearsago. The mature area of about 7000 ha of mixed pastures,cultivated fields, forestwas on average20-30 m high with a dense,very old clearingsand disturbedforests was surveyedmainly wet undergrowthand a discontinuouscanopy. Palms and for easilydetectable (soaring) species. A minimumnumber treeferns were numerous and epiphytes were omnipresent. of pairs was estimatedfor this total area of approximately Two hundredresident specieshave been identified 10 000 ha (seespecies status). The aim of the censuswas (unpubl.list from numerous observers), including 25 Cho- to provide somebasic data about the ecologicalrequire- co endemics.Mammals (squirrels,monkeys, carnivores) mentsof suchspecies if their survivalis to be considered usuallyexisted at lowdensities. The largestmammals were in a future managementplan for this part of the western the SpectacledBear, Tremarctosornatus and the Brocket Andes. More details about census are given elsewhere Deer, Mazama americana. (Thiollay 1989a). On the easternborder of the reserve,the deepvalley of ?ialapi waspartly clearedfor shiftingcultivation and the RESULTS remainingforest patches were often disturbed.Along the northeasternside, the slopesof the Rio Miraflores valley Altitudinal Distribution. The distribution of were used for cattle ranching,but substantialareas of raptorsalong the altitudinal gradientis presentedin foreststill coveredthe upper slopes.The large valley of Figure 2. It was not possibleto give a more quan- the Rio Guiza was denselypopulated and cultivated,with titativepicture of the species'distribution because of pastureson the upper slopes.Some patches of forestre- mainedonly on the steepest slopes, ridges and ravines. The the brevityof the surveyin the foothillsand lowlands. lower and upperparts of the valley are heredefined from Table 1 emphasizesthe relative abundance of species the positionof La Planada(at the level of Chucunes- in the subtropical-temperatezone where most of the R•caurte) 25-30 km downstreamto Altaquer and up- work was carried out. Below I describethe raptor streamto Mallama. The uppervalley was more deforested but less cultivated than the lower section. assemblagein each successivealtitudinal zone but The entire area of La ?lanada-?ialapi and the valley specieswill be citedonly in the upper level of their fromAltaquer to Mallama weresurveyed on footbetween rangeand not repeatedin eachof the followingones 24 June and 26 July 1988. Three additionaldays were (seeFig. 1). Especiallyin the least surveyedareas, spentin the montanezone (around Cumbal and Azufral Volcanoes)and two daysin the lowlands.Rain and fog somespecies may havebeen overlooked. This is why were of almostdaily occurrenceand loweredthe detect- I mention the speciesthat I have not seenbut that abilityof raptors.Using all availabletrails and roads,I have beenrecorded by J. Orejuela (pets. comm.)or searchedthe area for raptorsfrom dawn to dusk,making that were knownformerly and are still likely to exist intensiveuse of clear late morning hours. I spent more at similar levelin westernNarino (Hilty and Brown time in openings(treefall gaps,landslides, clearings, ridg- es) from where most raptorscould be seenin flight. The 1986). secretiveforest falcons (Micrastur sp.) were mostlylocated In the Paramo zone, the Carunculated by their callsin early and late hours. (Phalcoboenuscarunculatus) was still common and The data were expressedas the mean number of in- widespreadin the highestgrasslands and oftencame dividualsrecorded per hour spentunder three different down to 3000 m or lower into ploughedfields.•The conditionsaffecting raptor detectability and defined as op- timal, suboptimaland unsuitable.Based on prior expeJ Red-backedHawk (Buteopolyosoma) was evenmore rience(Thiollay 1989a), and according to the behaviorof common,but was mostlyassociated with the lower eachspecies, these conditions included: habitat (i.e., inside paramo(up to 3800 m) and the montanegrasslands or outsidethe forest),time of day and weather. A mean down to 1800 m and even 1600 m in the La Planada frequencyof occurrenceper hour was then calculated, usingonly optimalconditions. This index of abundance area. Although consideredmerely a non-breeding was comparablewithin a givenspecies between different migrant in Colombiaby Hilty and Brown (1986), localitiesbut not between species, which usually vary widely I found this speciesbreeding on the slopesof the in their behaviorand conspicuousness. Azufral Volcano,above E1 Espino.An adult brought Most of La Planada Reservewas coveredin this survey and all residentspecies are thoughtto havebeen recorded prey to a nestnear the tree line at 3400 m on 7 July or confirmedby previousrecords. Conservative density and another adult was followed by a calling, newly estimatesare presentedbased on the mappingof all ob- fledgedyoung. Two CinereousHarriers (Circusci- 4 JEAN-MARCTHIOLLAY VOL. 25, No. 1

TROPICAL MONTANE

i Lowlandl Foothill Subtropical Temperate Paramo Altitude (meters) o I lOOO 2000 3000 4000

! ! Cathartes aura Coragyps atratus Leptodon cayanensis Chondrohierax uncinatus Elanoides forficatus Elanus leucurus Circus cinereus striatus Accipiter collaris Accipiter superciliosus Accipiter bicolor princeps Leucopternis semiplumbea melanoleucus magnirostris Buteo brachyurus Buteo polyosoma Oroaetus isidori carunculatus Herpetotheres cachinnans Micrastur ruficollis Falco sparverius ,

Figure 2. Altitudinal distributionof Falconiformesrecorded in July 1988 alongthe Pacificslope of the Andesin southernColombia. Solid lines representregular observations. Dashed lines are rangescited by Hilty and Brown (1986) but not confirmedduring this study,or personalobservations that are out of the knownbreeding level given by theseauthors. Fifteen additional species were formerly reported and are still likely to occurin the area,mainly in lowland forest.

Table 1. Raptor populationof the subtropicalzone in southwesternNarino, Colombia.Numbers represent the percentageof optimaldetectability hours in which the specieswere recorded.Mean numberof individualsseen per hr are in parentheses.The five habitatsare arrangedin increasingorder of visuallyestimated deforestation. The total numberof suitablecensus hrs rangedfrom 11-101.

LA PLANADA PIALAPI RIO LOWER UPPER RESERVE VALLEY MIRAFLORES RIO GUIZA RIO GUIZA 1500-2200 m 1200-1900 m 1500-3300 m 1200-1500 m 1600-2500 m

Coragypsatratus 14 (2.0) 72 (4.2) 82 (4.1) 75 (5.3) Cathartes aura 14 (1.0) 24 (1.0) 55 (1.8) 12 (4.0) Leptodoncayanensis 28 (1.0) 20 (1.0) Chondrohierax uncinatus 2o (2.o) Elanoidesforficatus 30 (1.0) 43 (6.7) 24 (5.6) 37 (18.3) Accipitercollaris 6 (1.0) 3 (1.0) Accipiterbicolor 4 (1.0) Leucopternisprinceps 30 (1.5) 72 (1.8) 73 (2.2) Leucopternissemiplumbea I (t.0) Geranoaetus melanoleucus 25 (2.0) Buteomagnirostris 14 (1.0) 57 (2.2) 79 (2.2) 45 (1.8) 12 (2.0) Buteobrachyurus 9 (1.0) 12 (2.0) Buteopolyosoma 27 (1.3) 14 (1.0) Oroaetus isidori 14(1.0) Micrastur ruficollis 17(1.1) Falcosparverius 38 (1.3) Speciesrichness 10 7 7 5 6 Diversity index (H') 2.150 1.376 1.582 1.143 1.106 SPRING 1991 RAPTORS IN SOUTHWESTERN GOLOMBIA 5 nereus)were seenin the lower paramo and meadows frequent. I saw a pair of Barred down to of the samearea. The Andean Condor (Vultur gry- 800 m below Junin. The Semi-collared is phus) formerly widespread(Goodfellow 1902), is also known to extend down to the foothills (Hilty now very rare in Narino (Orejuela, pers. comm.) and Brown 1986). I observedboth speciesup to 2200 and was not seen. It is still present in northern m. The BicoloredHawk (Accipiterbicolor) probably Ecuador (pers. obs.). reachesits upper limit at La Planada Reservewhere In the temperatemontane zone, numerous Black I recorded it several times around 1700 m. I saw it Vultures(Coragyps atratus) were foraging in the cat- also in the lowlands and thus its range overlaps tle pasturesand cultivatedfields. They occurredup completelywith that of Accipitersuperciliosus and to 3300 m in the Cumbal-Espino-Tuquerresvalley with most of that of A. collaris. The and were commonin denselypopulated areas all (Buteomagnirostris) was the mostcommon hawk in alongthe gradientdown to the coast.The American the clearedsemi-wooded areas, from sealevel to 1900 Kestrel (Falcosparverius) was locallycommon from m. It overlappedwith the American Kestrel in the 3200 m downto 1600 m. Two pairs of Black-chested upper 200-300 m of its range. Individuals of the -(Geranoaetus melanoleucus) were lo- Short-tailed Hawk (Buteo brachyurus)were occa- catedin the upper Rio Guiza valley around2500 m sionally seenhunting up to 1900 m, but the highest and 2900 m. The nestof oneof them, on a cliff ledge, establishedpair was recordedat 1300-1400 m. The containeda fully featheredfledgling on 17 July. I White-rumped Hawk (Buteoleucorrhous) has been saw other pairs in similar grassyand rocky slopes recorded in the La Planada area, but was not seen near cliffs above E1 Pedregal and in the Rio Pasto during this study. The Black-and-chestnutEagle Canyonnear Chachagui.The only temperateforest (Oroaetusisidori) is a rare, spottily distributedand raptor recordedwas the Sharp-shinnedHawk (Ac- threatenedspecies, typically associatedwith the un- c•piterstriatus) between 3000 m and 3500 m. Three disturbed,wet, subtropicalforest of this level. I iden- individuals,including one in dark phase,were hunt- tified it six times, only in the La Planada area. The ing around a 200-ha forest remnant, along edges, Barred-forest Falcon (Micrastur ruficollis) was the shrubbyareas, pasturesand lower paramo at the only commonand widespreadforest falcon, seen be- foot of the Azufral Volcano. A feather was even tween 1500-2200 m, and may be the mostabundant foundby C. Samper(pers. comm.)at 4000 m. The raptor in the natural forest undergrowth. White-throatedHawk (Buteoalbigula) which is a In the tropical foothills, no new specieswere re- typical speciesof similar temperateforests in north- corded.However, two presumablyrare Chocoforest ern Ecuador, has not been observedhere and is not endemics,the PlumbeousHawk (Leucopternisplum- citedfrom Narino (Hilty and Brown 1986). bea) and the Plumbeous Forest-falcon (Micrastur In the subtropicalzone, the Turkey Vulture (Ca- plumbeus)are known from this area, which several thartesaura), which was more common in the low- lowland speciesalso may reach (Hilty and Brown lands,extended here up to 2200 m and occasionally 1986). 2600 m but it was less numerous at this elevation The lowlandswere visitedonly briefly. This area than the Black Vulture. The Gray-headed Kite was almostentirely deforestedand devotedto cattle (Leptodoncayanensis) reached its upper limit at this raising and cultivation.,The only remainingforest level (2100-2200 m). It may breed up to 1900 m patchwas too smallto includea representativesam- wherea displayflight was recorded,but it was more ple of the natural raptor community.The species commonin the coastalplain. The Hook-billed Kite not previouslyrecorded on the gradient were the (Chondrohieraxuncinatus) which was seenat 1800- Black-shouldered Kite (Elanus leucurus) and the 2000 m, may not be breedingat this upper limit of LaughingFalcon (Herpetotheres cachinnans) in open its range. The Swallow-tailedKite (Elanoidesforfi- pasturesand secondary woodlands. Both may extend catus)was seencommonly between 1200 and 2400 to 1000 m and more. The semiplumbeousHawk m, sometimesin flocks of 11 to 32 individuals. It (Leucopternissemiplumbea) and the (Ac- was less abundant in the deforested lowlands. The cipitersuperciliosus) were seenin and around forest little-known SemicollaredHawk (Accipitercollaris) fragments.I alsorecorded the former onceat 1600 and the muchmore conspicuousBarred Hawk (Leu- m in La PlanadaReserve but it may not be resident copternisprinceps) were the two most characteristic at that altitude. Up to 10 additional forest species speciesof this altitudinal level and amongthe most were known (Hilty and Brown 1986), and are still 6 JV,^N-M^P,cTHIOLLAY VOL. 25, NO. 1

SPECIES NUMBER laris,A. bicolorand probablyChondrohierax uncinatus are representativesof this category.They may sur- viveforest disturbance and fragmentationbetter than obligateforest species, but theydo not take advantage of it and cannotpersist in heavily deforestedareas.

GRASSLAND Sp. Other forestspecies, such as Leucopternisprinceps, are readilyusing, or evenconsistently associated with, natural or man-made openingsinside the forest, includinglarge woodedpastures along edges.Elan- oidesforficatus hunts for insectsover the canopyof bothunbroken and fragmentedforest, as well asover openwoodlands. They appearto benefitfrom a mod- erateamount of deforestation(at leastL. princepsis

ALTITUDINAL rarer or absentin large unbroken tracts of forest) LOWLAND• 'SUBTROPIC.'• • •PARAMO FOREST• LEVELSSp. but theystill avoidareas that are extensivelycleared. FOOTHILLS TEMPERATE Originally nonforestspecies are still associated Figure 3. Highestnumber of primarily forest(hatched) with partly woodedareas, forest edges and clearings and grasslandor open-woodlandspecies (cross-hatched) (e.g., Cathartesaura, Buteomagnirostris, B. brach- recordedin this study,or likely to occur(Hilty and Brown yurus).They increasetheir huntingand/or breeding 1986), along the altitudinal gradientin SW Narino. All regularspecies are included,regardless of their abundance range at least in the early stagesof deforestation, or breedingstatus. Occasional vagrants are excluded. sincethey readily colonizenewly deforestedareas. Most opengrassland species invade formerly wooded areas in advancedstages of deforestation(Fig. 3). likely to occur in the coastalplain. These include Geranoaetusmelanoleucus, Buteo polyosoma and Falco the Double-toothed Kite (Harpagus bidentatus), sparveriuswere here typical representativesof the PlumbeousKite (Ictinia plumbea),Common Black fauna replacingthat of the former temperateforest. Hawk (Buteogallusanthracinus), Crested The numberof pairs of eachspecies recorded dur- (Morphnusguianensis), Black-and--ea- ing this one-monthsurvey is probably too conser- gle (Spizasturmelanoleucus), Ornate Hawk-eagle vative.Some pairs may havebeen overlooked. How- (Spizaetusornatus), Red-throated Caracara (Dapo ever, the difference between the actual and observed trius americanus),Slaty-backed Forest-falcon (Mi- densitiescannot be great and is likely to provide a crasturmirandollei), Collared Forest-falcon (Micras- reasonableestimate of the currentcarrying capacity tur semitorquatus)and Bat Falcon(Falco rufigularis). of the area. Two different pairs of Leptodoncaya- Some of them may survivein the area but at least hensiswere locatedon oppositesides of the 3000-ha the eaglesrequire large areas of relatively undis- La Planada Reserve.Their home ranges extended turbed forest (Thiollay 1989b) that may no longer beyondthe reserve'slimits. An additionalrecord may exist at low elevation. have representeda third pair within the 10 000-ha Habitat Selection in the La Planada Area. The area. Only one pair of Chondrohieraxuncinatus was raptorsstudied may be dividedinto severalcategories seenflying over the reserve.One flock including 2 accordingto their natural habitatand their observed to 13 Elanoidesforficatus, and sometimesadditional susceptibilityto deforestation.Obligate forest species isolatedbirds, were seenevery day moving all over occuronly in sufficientlylarge areasof primary or the area. The residentpopulation within the 10 000 old secondaryforest. Micrastur ruficollishas never ha may not have exceeded15 birds. beenseen outside dense forest undergrowth. Oroaetus I made several observations within the reserve of isidoriwas apparentlyhunting only over large tracts Accipitercollaris, including individuals carrying prey. of forest,flying directlyand high aboveclearings and The existenceof a minimum of two pairs can be secondgrowth. Both speciesare likely to be the most assumed.This specieswas not seenoutside the re- sensitiveto forestdegradation or fragmentation. serve.Similarly the presenceof onepair of Accipiter Someprimary forestspecies may hunt regularly bicolorwas inferred from the spatialgrouping of the along edges,in someopenings, second growth and six different recordswithin the 3000-ha protected disturbedforest. Leptodoncayanensis, Accipiter col- forest. However, thesetwo secretivelittle hawks are SPRING 1991 RAPTORS IN SOUTHWESTERN COLOMBIA 7 easily overlookedand their actual populationmay invasionof speciesoriginating from grasslandsand have been higher. upper levels. At this elevation,the grasslandcom- LeucoJoternisprinceps was the only commonlarge munity becamericher than that of the forestalone. hawk. Six pairs were locatedon the 10 000-ha area. But the overall man-induced richness of the forest- Three of the home rangesoverlapped the limits of grasslandmosaic was still 26% lower than that of the 3000-ha reservebut probablynone of them was the tropical forest alone. At higher elevation,more completelyincluded in it. At least sevenpairs of raptor specieswere favoredthan were lost when the Buteomagnirostris were identified,always associated forestcover was destroyed.Conversely, below about with clearings.Only one pair was on the reserve. 1500 m, many more specieswere lost than gained One pair of Buteopolyosorna with a fledgedyoung through large scaledeforestation. The bird assem- was hunting regularly in the northern part of the blagesof smalldegraded patches of woodlandsamong study area, outsidethe reserve.One adult Oroaetus fieldsand pastureswere probablymuch poorerthan zszdori was seen several times over the western and thoseof the original forest.These patternsmay be southwesternparts of the reserve,often ranging well explainedby the formerrarity of openhabitats below outside the boundary of the protectedarea. It is the temperatezone and the evolutionof few species unlikely that more than one pair of this rare eagle adaptedto openareas in the humid lowlands.More- occurredwithin the 10 000-ha study area and the over, apart from paramo specialists,most of grass- protectedforest zone was apparently not large or land speciesbenefiting from deforestationwere geo- suitableenough to meet all of its requirements. graphicallywidespread and often commonspecies, At least, three well separatedpairs of Micrastur whereasthe disappearingforest birds were poten- ruficolliswere located(direct observationsand dawn tially threatened everywhere and are therefore in or dusk calls),within the central part of the reserve. more urgent need of conservation. It was probablythe mostabundant forest raptor and ConservationProblems. Raptors face a major the only one for which the 3000-ha reservemay be threat from the extensiveand rapid deforestationat large enoughto support a significant,if not self- all altitudinal levels,for cattle grazing more than for sustainable,population. cultivation. Logging is now very important every- where (first for valuable timber, then for fuelwood DISCUSSION and charcoal) and it often precedesand prompts Community Composition. Twenty-two raptor forest clearing. Erosion preventsregeneration and specieswere recordedand at leastfourteen additional further aggravates deforestation. Pollution and onesare expected.Altogether, two-thirds (24) are hunting pressureseemed to have only a local and forest species,and only 12 are grasslandor very minor impact. open-woodlandspecies. The markedsuccession and No comparablecensuses, with statisticallytestable turnoverof communitiesfound alongaltitudinal gra- results, have been made in different forest types. dientsin the Andes (seeTerborgh 1971, Terborgh However, at least within the best studied area, both and Walker 1975) were also found here, although abundanceand diversityof forest raptors decreased the incompletecensuses at lower levelspreclude a with the reductionand degradationof forestpatches detailed analysis.Some specieshad narrow altitu- (Table 1). A higher proportion of recordsper unit dinal distributions,replacing each other along the of time or distancecovered was obtained from high gradientswhile others had wider and overlapping primary forest in the reserve,on moderate slopes distributionranges (Figure 1). The genusAccipiter with deep, well-drained soils.Unfortunately these offersstriking examplesof three altitudinal special- areas are also the most accessible and are said to be ists, with A. su1•erciliosusunder 1000 m, A. collaris the most valuable for timber production and agri- between 1000 and 2500 m and A. striatus above 2500 culture.Therefore they are the first to be loggedand m. The range of a larger species,A. bicolor,over- cleared. The remaining forest patchestend to be of lappedwith that of collarisand su1•erciliosus. the pooresttype, i.e., on steepslopes, at high eleva- The total speciesrichness, and the number of for- tions, in ravines,on narrow ridgesor swampy flats. estspecies, quickly decreased with altitude,but only The wet Pacific slopeof the Andes of Colombia above1000 m (Figs. 2 and 5). At mid-level of the and western Ecuador is well known for its numerous gradient (subtropical),the loss of forest species endemicbird species.Among the Falconiformes alone, through deforestationwas partly balancedby the several specieshave restricted ranges (Micrastur 8 JE^N-M^gc THIOLL^Y VOL. 25, No. 1 plumbeus,and to a lesserextent, Leucopternisplum- ofthe easily accessible timber has already been logged. beaand L. princeps)or very scattereddistributions It is the last opportunityto take conservationmea- (e.g., Accipitercollaris, Oroaetus isidori). Moreover, suresin an area that probablyharbors most of the they are very little-knownforest species whose long- speciesof the lower and upper levels, as well as term conservationmay be dependenton national endemics of its own. parksin Colombiaand Ecuadorwhich are currently ACKOWLEDGMENTS in small number and understaffed. Althoughthe minimum sizeof a viablepopulation The studywas fundedby the UNESCO-MAB project (Paris). It hasbeen made possible thanks to the help and of raptors is still debated,it can hardly be lower logisticsupport of the team of the La Planada Reserve, than severalpairs. Thus the sizeof an isolatedforest especiallyits director Jorge Orejuela and its manager patchrequired for the long-termsurvival of a raptor Guillermo Cantillo. D. and B. Snowas well as C. Samper populationmust be large. The 3200-ha reserveof were also helpful both in the field and through their com- La Planadaharbors at besta few pairs of the most mentson a first draft of the manuscript,which was typed by F. Thiolla¾. To all of them, I am very grateful. abundant speciesand not a single completehome range of the rarestones. Fortunately, several species LITERATURE CITED here use edges,clearings or secondaryvegetation GOODFELLOW,W. 1902. Results of an ornithological aroundthe forest(all Accipiterand Leucopternisspe- journey through Colombia and Ecuador. Ibis 8:207- cies) or can crosswide expansesof degradedwood- 233. landsbetween primary forest patches (Oroaetus). The HILTY, S.L. AND W.L. BROWN. 1986. A guide to the small forestfalcons (Micrastur), althoughrestricted birds of Colombia. PrincetonUniversity Press,Prince- to forest undergrowth,may have small territories ton, NJ. (under 100 ha) and reach relativelyhigh densities HOLDRIDGE,L.R. 1967. Life zone ecology.Tropical (this study, Klein & Bierreõaard 1988, Thiollay ScienceCenter, San Jose, Costa Rica. 1989b). Thesebehavioral traits may reducethe area KLEIN, B.C. AND R.O. BIERREGAARD.1988. Movement and calling behavior of the Lined Forest-Falcon of forestreserves necessary for the survivalof viable crasturgilvicollis) in the Brazilian Amazon.Condor 90. populationsof thesespecies. 497-499. Within the study area, both the lowland and the TERBORGH,J. 1971. Distribution on environmentalgra- temperatezones are so deforestedthat there is little dients:theory and a preliminary interpretationof dis- hope of preservinga viable natural communityof tributional patterns in the avifauna of the Cordillera forest raptors or even to afford the persistenceof Vilcabamba, Peru. Ecology52:23-40. everyforest species. In the La Planada-Pialapiarea, -- ANDJ.S. WALKER. 1975. The role of competition significantexpanses of suitableforest still remain. in the distributionof Andean birds. Ecology56:562- If deforestationcan be stopped(e.g., through a man- 576. agementplan of the proposedBiosphere Reserve), TIIIOLLAY,J.M. 1989a. The censusof diurnal raptors in a primary rain forest: comparativemethods and the original raptor communitymay survive. How- speciesdetectability. ]. Raptor Res. 23:72-84. ever,the bestprospects for conservationlie with the 1989b. Area requirementsfor the conservation large tracts of little-disturbedforest that still remain of rain forestraptors and gamebirds in FrenchGuiana. on lower slopes(500-1000 m, notably the Junin- ConservationBiology 3:128-137. Barbacoasarea). The very heavyrainfall may pre- vent large scaleagricultural developmentand most Received19 May 1989; accepted25 September1990