J. Field Ornithol., 70(1):58-70

AVIAN DISTRIBUTION IN DOMINICAN SHADE COFFEE PLANTATIONS: AREA AND RELATIONSHIPS

JOSEPHM. WUNDERLE,JR. InternationalInstitute of TropicalForestry USDA b orest Service P. O. Box 490 Palm• Puerto Rico 00721 USA

Abstract.--Residentsand wintering Nearctic migrantswere sampledby point countsin 40 smallto medium-sized(0.07-8.65 ha) shadecoffee plantations with an overstoryof Inga vera in the CordilleraCentral, DominicanRepublic. The purposeof the studywas to determine the relative importance of plantation area, isolation, and habitat structure to avian distribu- tion and abundance.Variation in abundancewas unrelated to plantation area for all migrant (n = 7), whereasthe local abundanceof four of ten resident speciesincreased significantlywith area. Elevationwas the only variablethat significantlycontributed to the total number of speciesper plantation (fewer speciesat higher elevation), and no habitat variablessignificantly contributed to variation in the total number of migrant species.In contrast,significantly higher numbers of resident specieswere found in larger and older plantationsat lower elevations,characterized by numerous stems-•3 cm DBH, little or no pruning of overstorybranches, and maximum canopycover at 12.0-15.0 m. Coffee planta- tions with high levelsof structural and floristic diversityshould be encouragedfor avian conservation,and even the smallestplantations, if not too isolated by treelessareas, can contribute to avian abundanceand diversityin tropical agricultural regions.

DISTRIBUCION DE AVES EN ALGUNAS PEANTACIONE$ DE CAF• DE $OMBRA EN LA REPI•BLICA DOMINICANA: RELACIONE$ ENTRE • Y HABITAT Sinopsis.--Enla Cordillera Central de la Reptblica Dominicana,se muestrearon(por conteo de puntos)40 plantacionesde caf• de sombra(cuyo tamafio vari6 de 0.07-8.65 ha) con un docel de Inga vera.E1 proptsito del estudiofu• determinar la importanciarelativa del •rea de la plantacitn, el aislamiento de la misma y la estructura del habitat, en relacitn a la distribucitn y abundanciade aves.La variacitn en abundanciano estuvorelacionada al frea de la plantacitn para las especiesmigratorias estudiadas (n = 7), aunquela abundancia,de cuatro de un total de diez especiesresidentes, aument6 significativamentecon el incremento en frea. La elevacitn fue la 6nica variableque contribuy6significativamente al ntmero total de especiespor plantacitn (a mayor elevacitn menos especies),y ninguna variable en el habitat contribuy6 significativamentea la variacitn en el ntmero total de especiesmigrato- rias. En contraste,un ntmero significativamentemayor de especiesresidentes fue encontra- do en plantacionesde mayor tamafioy de mflstiempo, establecidasa elevacionesmfls bajas. Estasse caracterizaronpor tener tallos > a 3 cm DBH, un sotobosquepoco alterado y un docel mSximo de 12.0-15.0 m. Deben promoverseplantaciones de caf• con altos nivelesde diversidad(tanto estructuralcomo floristico) para la conservacitnde las aves.Inclusive las plantacionesmfls pequefias,si no estan muy aisladasde otras fireascon firboles,pueden contribuir a la abundanciay diversidadde avesen las regionesagricolas del trtpico.

Traditiorial coffee plantationsthat include an overstoryof shadetrees have a relativelyrich avifauna (e.g., Wetmore 1916; Griscom1932; Augilar- Ortiz 1982; Wunderle and Latta 1996; Greenberg et al. 1997a,b). The relativelyhigh diversityof found in shade coffee plantationsand the presencethere of some forest-dwellingspecialists suggest that shade coffee may provide a valuable refugia for birds and other organismsin heavily deforested agricultural regions of the tropics (Perfecto et al.

58 Vol.70, No. 1 Birdsin CoffeePlantations [59

1996). However, not all shade coffee plantations may be equivalent in their attractivenessto birds, as variation in canopy structure and compo- sition influence avian abundance and diversity in some plantations (Greenberget al. 1997a;Calvo and Blake 1998;Johnson, in press).Dem- onstrationof the potential value of shade coffee to birds requires iden- tificationof particularhabitat characteristics of the plantationswith which variousbird speciesare associated. Plantation area should influence avian distribution in shade coffee plantations,based on other studiesof species-areaeffects on birds (re- viewedin Burgessand Sharpe1981; Williamson 1981; Harris 1984). None- theless,species differ considerablyin their responseto patch size. For instance,many Nearctic migrantsavoid small isolatedforest patcheson the breeding grounds (e.g., Lynch and Whigham 1984; Robbinset al. 1989), although they may readily inhabit similar or even smaller-sized patcheson the tropicalwintering grounds (Robbins et al. 1987; Green- berg 1992). Although most species-areastudies have been conductedin the temperateregion, the few tropical studiesindicate that many tropical residentspecies are sensitiveto habitatpatch size (e.g., Willis 1974, 1979; Lovejoyet al. 1986). Thus, smallisolated shade coffee plantations should support fewer speciesper unit area of habitat. In the Dominican Republic shade coffee plantations often constitute the only broadleaftree coverremaining in mid-elevationagricultural ar- eas.There plantationsof different sizesare typicallyisolated by pastures or croplandfrom other plantationsor forestpatches of pine or mixed pine and broadleafspecies. A varietyof residentand migrant species occupythese plantations,thereby maintainingavian diversityin an oth- erwise inhospitableagricultural landscape (Wunderle and Latta 1996). However,the relativeimportance of plantationarea, isolation, and habitat structurefor attractingdifferent speciesis unknown.The objectiveof this studywas to examinethe relativeimportance of thesevariables on species- area relationshipsin shade coffee plantations.A multivariateapproach wasused to identify the plantation characteristicsassociated with individ- ual migrant and resident species.

METHODS

Studysite.--Forty shade coffee plantations(mean = 1.1 ha, range 0.1- 8.7 ha) were sampledin the vicinityof Constanza(18ø54'N, 70ø37'W), Ebano Verde (19ø2'N, 70ø34'W), Manabao (19ø6'N, 70ø48'W) and Jara- bacoa (19ø9'N, 70ø39'W),La Vega province,at an elevationof 480-1240 m in the Cordillera Central of the Dominican Republic. The plantations are located in a zone that receivesan annual rainfall of approximately 1200 mm (Hartshorn et al. 1981) and is classifiedas subtropicalmoist forestin the Holdridge life zone system(Anonymous 1967). In this re- gion, coffee is cultivatedin areasthat were originallypine forest (Pinus occidentalis).Pine forests,most of which have been logged selectively,re- main in scatteredpatches on the steeperslopes. These relict standscon- 60] J.M. Wunderle,Jr. j. FieldOrnithol. Winter 1999 tain variableamounts of broadleafunderstory that hasbeen degradedby fire, cutting, or grazing. Broadleafcanopy trees are restrictedprimarily to shadecoffee plantations,fruit and ornamental trees along fence rows and around homes, and in arroyos lined primarily with the exotic Syzygiumjambos.Broadleaf forest or woodlandare absentand pastureand cultivatedground cropsare the predominant cover . Bird censuses.--Birdpopulations were sampled 6-19 Feb. 1992 using fixed-radiuspoint counts (Hutto et al. 1986). An observerrecorded all birds seen or heard during a 10-min period at each point. Pointswere placed in the center of the smallestplantations. In larger plantations, each point wasset at least 100 m from each other and equidistantfrom the plantation edge, at least 20 m from the edge. Each point was 100 m or more from all others. Only in the ten largestshade coffee plantations was it possibleto conduct more than one point count. Countswere ini- tiated at sunrise and terminated before 1100 h, with most counts com- pleted before 1030 h. During the count, the observerestimated the min- imum distanceto each bird detectedwithin a 25-m radius.Analyses were restricted to counts of birds detected only within a 15-m radius circle ensuringthat all plots, including those in the smallestplantations, con- tained equivalentamounts of coffee habitat. The surveysexcluded swal- lows,swifts, and raptors. Habitat measurements.mVegetationwas measured in 16-m diameter plots (0.02 ha) centered at each point. Stemsof all standingtrees and saplings->3 cm were measured 1.3 m above the base (DBH) and identi- fied to species.Stem density of coffee plantsat breastheight wasestimated along four 8-m transectsrunning in the cardinal directionscentered with- in the 0.02-hacircle. Shrub densitywas determined by an observerwalk- ing along the transectand counting all woodystems (<3 cm) touching the observer'sbody and outstretchedarms at breastheight. The contri- bution of coffee and other plant specieswas recorded separately. Foliage-heightprofiles were determined at 20 points located at 1.6-m intervalsalong the north, south,east, and westradii of each circularplot (Schemskeand Brokaw 1981). A 3-m pole (2.0-cm diameter) marked at 0.5-m intervalswas placed verticallyat each sample point. The presence or absenceof foliage touching the pole within each height classwas re- corded aswell as the identity of the foliage.For height intervalsabove 3 m, we sightedalong the pole and recorded the presence/absenceof fo- liage in each of the following height intervals:3-4, 4-6, 6-8, 8-10, 10- 12, 12-15, 15-20, and 20-25 m. Total foliage per height interval wascal- culated by summing the number of points (maximum = 20) with the presenceof foliage at a particular height interval. Foliage densitywas calculatedby adding the total number of height intervalswith foliage at the 20 points. The outer perimeter of all coffeeplantations was measured using a hip chain and a compassto obtain bearings.The amount of varioushabitat types (e.g., pasture,ground crops,road, stream,trees >2 m,) adjoining the plantation was estimatedin meters along each bearing of the plan- Vol.70, No. ! Birdsin CoffeePlantations [61 tation perimeter.Maps of all plantationswere preparedand the error of closuremeasured to determineaccuracy (all <5%) of field maps.A dig- itizer was used to estimateplantation area. As aerial photographswere unavailable, plantation isolation was estimated as either the distanceto the nearest shade coffee plantation or the nearest pine forest patch (>0.25 ha). Analysis.--In the larger plantations,where more than one point count was conductedand more than one vegetationplot was measured,the averagevalues of bird countsor vegetationmeasurements were used to representthe plantation.Hence for each plantation,only one valuewas usedfor each variable,but averagingvalues for the large plantationsad- justed for the concomitantlygreater samplingeffort. Principal component analysis(PCA) was used to assesshabitat differ- encesamong the plantations.Variables included in the analysiswere: total stems>3.0 cm DBH, foliage density,number of height intervalswith Inga foliage, total coffee stems,total number of species,and total foliage in each of the five height intervals (0-0.5 m, 1.5-2.0 m, 4.0-6.0 m, 12.0- 15.0 m, and 15.0-20.0 m). All variablesapproximated a normal distribu- tion as determined by visual inspection of normal probability plots in SYSTAT(SYSTAT 1992). The PCA wasgenerated using a correlationma- trix and four factors.A varimaxrotation was selected because it provided better separationthan did either equimax or quadramaxrotations. The significanceof each habitat variablewith respectto the PC axeswas as- certained by correlation (Pearsonproduct moment) of the original vari- ablesback to the PC scores.In addition, Pearsonproduct moment cor- relationswere used to determine the degree of associationbetween log plantation area and individual habitat variables. A forward stepwisemultiple regressionwas used to evaluatethe influ- ence of plantation area, isolation, and the suite of habitat variableson componentsof the arian community.The procedurewas run on SYSTAT usingthe default settingsfor the alpha to enter (0.15) and alpha to re- move (0.15) chosenon the basisof Monte Carlo studiesof stepwisere- gression(Bendel and Afifi 1977). Independentvariables included the 10 vegetation variables characterized in the PCA, as well as elevation, esti- mated distance (m) to nearestplantation, estimateddistance to nearest pine forest, and log of plantation area (ha). All variableswere entered into a multiple regression(forward selection) to obtainthe TypeII partial correlation coefficients to evaluate their relative contributions to R 2.

RESULTS l&getation.--Atotal of 23 plant species(height >1 m) occurred in the 0.02 ha plots in the 40 plantations.The plantationswere characterized by an overstoryof Inga vera (Mimosoideae),although mango (Mangifera indica), avocado(Persea americana), various citrus species(Citrus spp.), and banana or plantains (Musa spp.) were scattered throughout some plantations,where they providedan intermediatelayer above the coffee. In a few plantations,an occasionalpine (Pinus spp.) or palm (Roystonea 62] J.M. Wunderle,Jr. j. FieldOrnithol. Winter 1999

TABLE1. Resultsof principalcomponents analysis of vegetationstructure in 40 shadecoffee plantationsin the DominicanRepublic. Component loadings are shownwith the signif- icancelevels from Pearsonproduct moment correlationof the originalvariable back to the PC score.

Variable PC1 PC2 PC3

Stems ->3.0 cm DBH 0.733*** -0.072 -0.227 Foliagedensity 0.716'** 0.193 0.404** Categorieswith Inga 0.528** 0.089 0.371 Total coffee stems -0.526** -0.095 0.462** Total foliage 0.0-0.5 m 0.096 -0.552 0.055 Total foliage 1.5-2.0 m -0.232 0.266 0.791'** Total foliage 4.0-6.0 m 0.513 -0.702*** -0.038 Total foliage 12.0-15.0 m 0.437 0.662** 0.088 Total foliage 15.0-20.0 m 0.148 0.694*** -0.372' Total plant species -0.391 0.255 -0.353 Eigenvalue 2.30 1.91 1.47 % of variance accounted for 22.9 19.1 14.7

* 0.05 -> P > 0.01; ** 0.01 --> P > 0.001; *** P--< 0.001.

spp.) extended into the overstory.The pervasivevariety of coffee (Coffea arabica) in the shade plantationswas the traditional "tfpica" variety,al- though "catorra" predominatedin some of the larger plantationsand wasintroduced to replace "tfpica" in some of the smallerplantations. The first three principalcomponents (PC 1-3) accountedfor 56.7%of the variationin habitat structureamong the coffeeplantations (Table 1), whereasfive componentsaccounted for 78% of the variation.The first componentdistinguished plantations primarily on the basisof total stems ->3.0 cm DBH, total coffee stems,foliage density,and total foliage inter- valswith Inga, The secondaxis separatedplantations primarily on the basisof total foliage in the intervalsof 4.0-6.0 m, 12.0-15.0 m, and 15.0- 20.0 m, and the third axis separatedplantations mostly on the basisof total foliage at 1.5-2.0 m, total coffee stems,and foliage density. Most habitat variables were not correlated with log plantation area, though one variable (total foliage in 1.5-2.0 m) showeda weak, but sta- tisticallysignificant correlation (r = -0.36, P = 0.02). Correlationswere not detectedbetween plantation size and degreeof isolationas measured by distanceto nearestplantation (r = -0.12, P = 0.47), distanceto near- est pine forestpatch (r = -0.18, P = 0.27) or proportionof perimeter bounded by pastureor field (r = -0.24, P = 0.14), or elevation (r = -0.08, P = 0.62). Although considerablevariation existed among the 40 plantations in termsof different measuresof isolation,most plantations were moderately isolated from each other and from woodland suitable for birds. The median distanceto the nearest plantation was 50 m (range 10-500 m) and the median distanceto the nearest pine forest patch was 65 m (range 0-350 m). The median proportion of the plantation perimeter Vol.70, No. 1 Birdsin CoffeePlantations [63 that wasbounded by pastureor field washigh (median = 0.96, range = 0.0-1.0). Bird censuses.•A total of 28 bird species (Appendix lists scientific names)was detected during the countsincluding 17 residentspecies, 10 Nearctic migrants,and 1 Neotropical migrant that breedsin Hispaniola. The last specieswas included with residentspecies in subsequentanalyses. Examination of speciesaccumulation curves indicated that speciescom- position(i.e., richness)of the plantationswas adequately determined and recent re-surveysof 32 of theseplantations have found a similar species composition (Wunderle and Latta 1996). Plantationarea (log) did not accountfor variationin total speciesrich- nessper point in the coffeeplantations (R e = 0.01, P = 0.27). However, area did accountfor somevariation in speciesrichness of residentspecies (Re = 0.11, P = 0.04), but not migrant species(R"= 0.003, P = 0.72). Inclusionof variablesfor vegetationstructure, elevation, and measuresof plantation isolationin the stepwisemultiple regressionimproved the as- sociation between total resident speciesper point and plantation area, but not betweentotal migrant speciesper point and area (Table 2). Some variation in individual abundancewas attributable to plantation area in four of the ten resident speciesthat were adequatelysampled (found in -->5plantations), including Rufous-throatedSolitaire (Re = 0.16, P = 0.01), Hispaniolan Lizard Cuckoo (R e = 0.15, P = 0.01), His- paniolan Woodpecker(R e = 0.14, P = 0.02), and Broad-billedTody (R e = 0.13, P = 0.04). Inclusion of habitat variables and elevation in the stepwisemultiple regressionslightly improved the regressionof abun- dance and plantation area only in the Broad-billedTody (Table 2). Thus, plantation area had a slight effect on abundancefor a few resident spe- cies,but <25% of the variationin abundancewas explained by area even for thesespecies. Of the 14 variables included in the multiple regressions,elevation showedthe mostconsistent relationship with abundance.Among the 17 bird speciesthat were analyzed,this variablewas significant for only six (Table 2). The next most important variableswere the number of foliage intervalscontaining Inga, total foliage in 0.0-0.5 m, and plantationarea, each of which were significantpredictors of abundancein four species. The next most common predictorsof abundancewere total stems>3 cm DBH (3 bird species),total foliage 4.0-6.0 m (3), distanceto nearestpine forest (2), total foliage 1.5-2.0 m (2), and total foliage 12.0-15.0 m (2). Eachof the other five variableswas a significantpredictor in only a single specieseach. Residentspecies differed from migrantsin their responsesto elevation (five residentspecies vs. one migrant speciessignificantly correlated) and plantation area (four vs. zero). For migrants,at least one of the foliage height intervalswas a significantpredictor in six of the sevenspecies, in contrastonly three of sevenresidents were significantlycorrelated with the densityof foliage at one or more height intervals. 64] J.M. Wunderle,Jr. j. FieldOrnithol. Winter 1999

TABLE2. Variablesidentified as significantpredictors of avian speciesrichness or relative abundancefor 17 speciessampled by point countsin shadecoffee plantations in the DonfinicanRepublic. Variables were selectedby usingforward stepwise multiple regres- sionand partialcorrelations calculated to indicatethe importanceof eachvariable to the overallmodel. Only partialcorrelations which are significant(P -< 0.05) are shown, and negativepartial correlationsare indicatedby (-).

Dependentvariable t•2 P Independentvariable Partial Total species 0.25 0.005 Elevation -0.13 Total residentspecies 0.56 0.001 Stems 0.38 Log plantation area 0.21 Foliagedensity 0.18 Elevation -0.16 Total foliage 12.0-15.0 m 0.14 Total nilgrant species 0.00 N.S. Residents HispaniolanLizard Cuckoo 0.10 0.01 Log plantationarea 0.15 HispaniolanEmerald 0.46 0.001 Total foliage0.0-0.5 m 0.40 Total coffee stems -0.39 Distanceto pine forest -0.32 Narrow-billedTody 0.20 0.04 Stems -0.15 Broad-billedTody 0.56 0.001 Elevation -0.43 Categorieswith Inga -0.26 Log plantationarea 0.24 HispaniolanWoodpecker 0.31 0.004 Elevation -0.20 Log planm0on area 0.12 Red-leggedThrush 0.51 0.001 Elevation -0.29 Distanceto plantation 0.21 Total foliage0.0-0.5 m 0.19 Categorieswith Inga -0.16 Plant species 0.09 Rufous-throated Solitaire 0.22 0.01 Log plantationarea 0.17 Black-whiskered Vireo 0.13 0.02 Elevation - 0.13 HispaniolanStripe-headed 0.11 0.04 Elevation - 0.11 Tanager 0.28 0.007 Categorieswith Inga 0.20 Black-cowled Oriole Migrants Black-and-White Warbler 0.33 0.007 Total foliage 12.0-15.0 m 0.23 Total foliage 4.0-6.0 m 0.19 Foliagedensity - 0.13 Cape May Warbler 0.58 0.001 Stems 0.42 Total foliage 0.0-0.5 m 0.18 Total foliage 12.0-15.0 m -0.13 Total plant species -0.13 Black-throated Blue Warbler 0.26 0.004 Total foliage 1.5-2.0 m -0.20 Black-throated Green Warbler 0.15 0.02 Total foliage 4.0-6.0 m 0.15 Ovenbird 0.17 0.04 Elevation - 0.12 Common Yellowthroat 0.37 0.001 Dist. to pine forest 0.30 Categorieswith Inga -0.18 Total foliage 1.5-2.0 m -0.11 American Redstart 0.31 0.01 Total foliage 4.0-6.0 m 0.22 Stems - 0.19 Vol.70, No. 1 Birdsin CoffeePlantations [65

DISCUSSION

Plantation age and intensity of management contributed to variation in the structure and composition of vegetation among the plantations. Although exact plantation ages were unavailable for most plantations, younger plantations appeared to differ from older plantationsby having coffee bushesof lower stature but with denser foliage, lower overstory canopieswith fewer foliage layers,and fewer stemsof all species>--3 cm. Many of these age-relateddifferences were reflected in the first principal component. Younger plantations appeared to show lessstructural varia- tion resulting from managementdifferences than did the older planta- tions. The effectsof intensivepruning of the shade overstorywere most evident in older plantations,in which more foliage layerscould poten- tially be eliminated,than in the young plantationswith low statureover- stories.The second principal component reflected many of these man- agementdifferences among plantationsby contrastingplantations mostly on the basisof the presenceof foliage in different height intervalsin the overstory.Older plantationswere found at both extremesof the second principal component axis representing either intensivemanagement or abandonment, in contrast to younger plantationswhere relativelylittle variationwas observed among plantations. Despite somevariation in vegetationstructure attributable to plantation age and management,the Dominican plantationsI studiedwere relatively homogeneousin structure and compositionin comparisonto those that havebeen studiedin Meso-America(Greenberg et al. 1997a,b).Although overstoryheight and distribution of foliage layersdiffered among plan- tations,all the Dominican plantationshad an overstorycomposed mostly of Inga vera,which shadedalmost all of the coffee plants (Wunderle and Latta 1996, 1998). The Dominican coffee plantations were clearly separatedfrom other areasof continuousforest or woodlands,as measured by distanceto near- est pine forest or nearest plantation, but ! did not quantify the possible "stepping stone" effects of scatteredtrees or small groups of trees in the vicinity of plantations.These scatteredtrees were used by variousspecies to move between plantations and forest patches (Wunderle and Latta, unpublished) presumablyfacilitating immigration. In addition, the scat- tered trees between coffee plantations and woodlotsmay increase the likelihood that individual birds could incorporate more than one plan- tation or clump of trees into a single territory (e.g., Howe 1984). More- over,the presenceof nearby scatteredtrees may enable an individualto inhabit a plantation that by itself is too small to support a territory, as documented in some of these plantations for severalspecies of Nearctic migrants (Wunderle and Latta, ms). Thus, scatteredtrees likely facilitated immigration and enabled somespecies to inhabit plantationssmaller than their average territory size, thereby inflating species(and individual) numbers in small plantations above the values that would be expected, assumingcomplete isolation of plantations. 66] J.M. Wunderle,Jr. j. FieldOrnithol. Winter 1999

Scattered trees effectivelydiminished the isolation of some plantations and presumablycontributed to the weak species-areaeffect: area account- ed for only 11% of the variationin the number of residentspecies per point and none of the variation in total speciesor migrant speciesper point. In addition, the plantations were only moderately isolated from each other or nearby woodlandsand it is likely that if the plantations were more widely separatedfrom these sourcesthe area effects would have been much greater. In addition, a stronger area effect is expected if a wider range of plantation sizeshad been available,particularly with the addition of plantationsgreater than 10 ha. It is conceivablethat some area-sensitivespecies (trogons, quail-doves) were absentor poorly repre- sented in the studybecause even the largestsampled plantations were of insufficient size (maximum 8.65 ha). The absenceof an area effect on the number of Nearcftc migrant spe- cies or number of individuals is consistentwith some previousfindings on the winteringgrounds (Robbins et al. 1987, Greenberg1992, but see Askinset al. 1992) despite the sensitivityof many of these speciesto area effectson the breeding ground (e.g., Lynch and Whigham 1984, Robbins et al. 1989). Even wintering migrants typical of Caribbean forests (Wun- derle and Waide 1993), such as Ovenbird, Black-and-white Warbler, Amer- ican Redstart, Black-throated Blue Warbler, and Black-throated Green Warbler appearedto be unaffectedby the abrupt plantation-pastureedg- es.Additional evidencethat most migrantsare not adverseto usingsmall isolated (•5 ha) woodlotsis noted each spring in North America where smallpatches attract numerous passage migrants (e.g., Martin 1980,Blake 1986). The migrantsin this studywere a much more homogenousgroup of speciesthan the residentsin terms of taxonomic diversity(1 family vs. 7 families) and foraging ecology(mostly insectivorous, 2 highly nectari- vorous vs. 4 insectivorous,5 frugivorous, I nectarivorous). Therefore, it wasnot surprisingthat migrantsas a group were more consistentin their responseto area than were resident species. Plantation area did influence the total number of resident species,and for four resident species,the number of individualsdetected at a point. Some of this area effect may be attributed to the fact that a relativelyhigh proportion of the plantationswere undoubtedlysmaller (30% lessthan 0.5 ha) than the averagehome range size of some of the larger resident species (Hispaniolan Lizard Cuckoo, Hispaniolan Woodpecker). For these species,some small plantationsmay have alsobeen sufficientlyiso- lated by inappropriatehabitats so as not to be incorporatedwithin a home range. In addition, habitat diversityusually increases with area (e.g., Wil- liamson 1981) so that larger plantationsare more likely to have a greater diversityof essentialresources than do smallerplantations. In the present study, larger plantations were more likely to contain fruiting palms or shrubs attractive to frugivores (e.g., Hispaniolan Woodpecker, Rufous- throated Solitaire). Thus, some of the area effect in residentsmay be attributed to the extremely small size of many of the plantationsrelative Vol.70, No. 1 Birdsin CoffeePlantations [67 to the larger home range sizesof someresident species and the greater likelihood that larger plantationscontained critical resources. As found in previousstudies of aviandistribution in coffeeplantations (Greenberget al. 1997b), speciesrichness decreased with elevation.Six individualspecies significantly declined in abundancewith elevation(one migrant, five residents)and none increasedwith elevation.Although a few plantationcharacteristics varied with elevation(total foliage0-0.5 m, r -- 0.48; coffee stemsr = -0.37) thesefactors unlikely are directlyre- sponsiblefor observedelevational declines. More likely, the observed changesin abundanceare associatedwith elevationalchanges in climate which affect the distributionof individualspecies directly or indirectlyby affecting resourcedistributions in the plantationsor in nearby habitats. Elevationalmigration or seasonalmovements of some residentsand win- tering migrants,which are evidentin someCentral American coffee plan- tations(Greenberg et al. 1997b), are unlikelyto be importantfactors in theseplantations where little seasonalvariation was detected, at leastdur- ing October to April (Wunderle and Latta, in prep.). From previousobservations in theseplantations (Wunderle and Latta 1996, 1998) and elsewhere(Greenberg et al. 1997a,b),it was expected that avian speciesrichness and abundancewould infrequentlybe associ- ated with coffee understory characteristics.This was expected because coffee is a resource-poorhabitat (i.e., low in nectar, fruit, and inverte- brates) relative to the Inga overstory(Wunderle and Latta 1996; Green- berg et al. 1997a) and, not surprisingly,most birds forage in the planta- tion canopyand rarelyin the understory(Greenberg et al. 1997b;Wun- derle and Latta 1998). Therefore, coffee layerfeatures were expectedto be lessfrequently correlated with avianabundance than featuresrelating to the shadeoverstory alone or shadeand understorytogether. As expected,features of the coffee layer were of limited utility as pre- dictors of avian abundance, as abundance was correlated with these fea- turesin only 6 of 17 species.In four species,abundance was positively correlated with the presenceof foliage at ground-level(total foliage 0- 0.5 m), which was mostlyan indication of weed abundance.This feature might be of direct importanceto the ground-nestingBroad-billed Tody and to the Red-leggedThrush which occasionally forages on the ground, but of indirect importanceto nectarivores(Hispaniolan Emerald, Cape May Warbler) whichforage above this zone (foragingheights in Wunderle and Latta 1998). Abundancewas negatively correlated with measuresof coffee density in the two specieswhich mostly forage above this layer (Hispaniolan Emerald, coffee stems;Black-throated Blue Warbler, total foliage 1.5-2.0 m), and in Common Yellowthroatwhich foragesmostly below this level. Featuresof the plantation overstoryor thosecombining overstory and understorywere predictors of avian abundancefor only a few species. Neither total number of speciesnor total number of migrant specieswas correlated with vegetationfeatures, in contrast to the total number of residentspecies. Plantations with high numbersof residentspecies tended 68] J.M. Wunderle,Jr. j. FieldOrnithol. Winter 1999 to occur at low elevation,were large and relativelyold, characterizedby numerousstems ->3 cm DBH, showedlittle or no pruning of overstory branches,and had their maximum canopycover at 12-15 m. Similarly, Greenberget al. (1997a) found that residentbirds in contrastto migrants in Guatemalancoffee groves showed the strongestcorrelation with habitat variablesbased on multiple regressionanalysis. Specifically, variables re- lated to vertical structure and taxonomic diversityof the canopycontrib- uted most to variation in total resident species. From a conservationstandpoint, the traits that characterizeplantations with large numbers of resident speciesshould be encouraged.Although larger plantationstend to have more resident species,smaller plantations still attractsome resident species as well as a full complementof migrant species,which as a group are unaffected by area in these plantations. Therefore, small plantationsshould be included in conservationefforts, particularlyin areaswhere plantationsare not extremelyisolated by pas- tures, fields, or other treelessareas. In addition, small coffee producers are more likely to grow a diversityof crops in their plantations and are lesslikely to manage intensivelyfor coffee production (see also Green- berg et al. 1997a),thereby providing better development of the structural and floristic diversitywhich is attractiveto birds.

ACKNOWLEDGMENTS

EstebanTerranova provided invaluable assistance measuring vegetation plots and wasre- sponsiblefor measuringplantation areas. The manuscriptbenefited from the criticalcon- structivecomments of Robert A. Askins,Russell Greenberg, Steven C. Latta,James F. Lynch and Michael R. Willig. This paper is dedicatedto the memory of JamesF. Lynch, a pioneer in fragmentationand migrant studies,who contributedvaluable advice to our migrant and coffeestudies. Funding was provided in part from the NationalFish and Wildlife Foundation and theJohn T. and CatherineC. MacArthurFoundation. This work was done in cooperation with the Universityof Puerto Rico.

LITERATURE CITED

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APPENDIX. Summary of birds detected in point counts conducted in 40 shade coffee plan- tations in the Cordillera Central of the Dominican Republic in February 1992. Shown are the range of plantation sizes,number of plantations detected, and status (M = Nearctic migrant; R = Resident). Asteriskindicates a speciestreated as a resident al- though it migratesto SouthAmerica after breedingin the Dominican Republic.

Num- Range of ber of plantation planta- Species sizes(ha) tions Status Hispaniolan Parrot (Amazona ventralis) 0.59-8.65 2 R HispaniolanLizard Cuckoo (Saurotheralongirostris) 1.36-8.65 6 R Hispaniolan Emerald ( Chlorostilbonswainsonii) 0.22-1.40 6 R Antillean Mango (Anthrocothorax dominicus) 0.09-8.65 30 R Vervain ( minima) 0.11-8.65 26 R Narrow-billed Tody ( Todusangustirostris) 0.09-8.65 8 R Broad-billedTody ( Todussubulatus) 1.36-8.65 10 R HispaniolanWoodpecker ( Melanerpesstriatus) 1.36-8.65 9 R Hispaniolan Pewee ( Contopushispaniolensis) 0.23-8.65 7 R Red-leggedThrush ( Turdusplumbeus) 0.23-4.56 6 R Rufous-throatedSolitaire ( Myadestesgenibarbis) 2.29-8.65 5 R Palmchat (Dulus dominicus) 0.09-1.89 3 R Black-whiskeredVireo ( Vireoatiloquus) 0.10-2.45 8 R* Black-and-whiteWarbler ( Mniotilta varia) 0.10-2.29 16 M Northern Parula (Parula americana) 0.18-0.59 5 M Magnolia Warbler (Dendroica magnolia) 0.09-0.64 4 M Cape May Warbler (Dendroicatigrina) 0.09-8.65 29 M Black-throated Blue Warbler (Dendroica caerulescens) 0.09-8.65 31 M Black-throated Green Warbler (Dendroica virens) 1.40-4.36 6 M Ovenbird (Seiurusaurocapillus) 0.09-8.65 24 M Common Yellowthroat( Geothlypistrichas) 0.09-3.83 11 M Green-tailedGround Warbler (Microligiapalustris) 0.87-1.40 2 R Hooded Warbler ( Wilsonia citrina) 0.59 1 M American Redstart ( Setophagaruticilla) 0.09-8.65 27 M Bananaquit( Coerebaflaveola) 0.09-8.65 40 R Hispaniolan Stripe-headedTanager (Spindalisdominicensis) 0.10-8.65 9 R Black-crownedPalm Tanager (Phaenicophiluspalmarum) 0.09-8.65 25 R Black-cowled Oriole ( Icteris dominicensis) 0.26-8.65 8 R