Bird Use of Epiphyte Resources in Neotropical Trees
Total Page：16
File Type：pdf, Size：1020Kb
%LUG8VHRI(SLSK\WH5HVRXUFHVLQ1HRWURSLFDO7UHHV $XWKRU V 1DOLQL01DGNDUQLDQG7HUL-0DWHOVRQ 6RXUFH7KH&RQGRU9RO1R 1RY SS 3XEOLVKHGE\University of California PressRQEHKDOIRIWKHCooper Ornithological Society 6WDEOH85/http://www.jstor.org/stable/1368074 . $FFHVVHG Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp . JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. University of California Press and Cooper Ornithological Society are collaborating with JSTOR to digitize, preserve and extend access to The Condor. http://www.jstor.org This content downloaded from 128.171.57.189 on Mon, 13 May 2013 21:28:23 PM All use subject to JSTOR Terms and Conditions The Condor91:891-907 ? The CooperOrnithological Society 1989 BIRDUSE OF EPIPHYTERESOURCES IN NEOTROPICALTREES NALINIM. NADKARNI2AND TERIJ. MATELSON Departmentof BiologicalSciences, University of California,Santa Barbara, CA 93106 Abstract. Epiphytesare a commoncomponent of neotropicalforests, but theirimpor- tanceto birdsat thecommunity level and their role in contributingto tropicalbird diversity hasonly rarely been considered. Literature accounts from 55 studiesdocument 193 species of neotropicalbirds that take nectar, fruits, invertebrates, water, and nesting materials from epiphytes.To quantifythe amounts and types of resourcesprovided by epiphytescompared to hosttrees, we watchedbirds in 14 forestand pasture sites (1,350-1,420 m) for2 months in a lowermontane landscape of CostaRica. During our 289 hrof observationsfrom within the canopyand on the ground,33 of 56 birdspecies observed in foragingvisits foraged in resourcesprovided by epiphytes.Epiphyte resources were involved in 32%of all foraging visits.For eight bird species, 40% or moreof allforaging visits involved epiphyte use, which includedforaging for fruits, nectar, invertebrates, water, and nesting materials. Six typesof birdforaging behaviors in six typesof epiphytesare described and compared to birduse of treeresources. Some birds appeared to specializeon particularepiphyte resources such as invertebratesin crownhumus. The frequent epiphyte use by a largenumber of birdspecies indicatesthat epiphytes constitute a resourcethat has generally been overlooked in pastbird communitystudies. We discusstwo waysthat epiphytes may contribute to hightropical birdspecies diversity. Key words: Epiphytes;canopy; cloud forest; tropical forest; foraging ecology; resource; Monteverde;Costa Rica; community ecology. INTRODUCTION which supportscanopy humus invertebrates,in- Studies of relationshipsbetween tropical forest cluding earthworms, millipedes, beetles, and birdsand plantshave focusedalmost exclusively other arthropods(Lyford 1969, Nadkarni and on resourcesprovided by trees and understory Longino 1988). shrubs.Epiphytes, plants that derive supportbut Given the greatdiversity and largebiomass of not nutrients from their host trees, are a con- epiphytes in tropical and temperatewet forests spicuous component of many tropical and wet (Nadkarni1984, 1985;Gentry and Dodson 1987), temperateforests. They occupy the same phys- thereis surprisinglylittle data on their use by the ical location as their host trees and produce a animalcommunity. Only a few field studieshave diverse arrayof fruits, nectar, and foliage (Ben- mentioned(Orians 1969) or quantified(Remsen zing 1987, Gentry and Dodson 1987). Epiphyte 1985) the importance of epiphytes, (primarily biomass varies greatlyamong forest types; it is mosses) as a resourcefor tropicalbirds. Only one largestin neotropicalcloud forests,where the live study has directlycompared temperate vs. trop- and dead standingcrop can exceed 4,800 kg/ha, ical epiphyte use by birds (Thiollay 1988). A equivalent to 40% of the total tree, shrub, and numberof studiesfocusing on the use of canopy- understoryfoliar biomass (Nadkarni 1984). Many held dead-leaflitter pointed out the need to dis- tank and rosette epiphytes impound and store tinguish within-canopyresources (Remsen and water, leaf litter, and dissolved and particulate Parker 1984). However, nearly all the informa- minerals, which support populations of inver- tion is scatteredin general descriptionsof bird tebrates and vertebrates(Picado 1911, Laessle behavior and resource use. The technical diffi- 1961).The dead organicmatter that accumulates culties of observingbirds within the canopyitself beneath mats of live epiphytic cryptogams have been overcome in only very few studies by (mosses and liverworts)creates a microhabitat using towers,walkways, and mountain-climbing equipment (e.g., Perry 1978, Greenberg 1981, Loiselle 1987). Although a large body of litera- 'Received15 February1989. Final acceptance 26 ture on July1989. epiphyte taxonomy, physiology, and 2 Presentaddress: Director of Research,The Marie mineral nutrition exists (Watson et al. 1987), SelbyBotanical Gardens, 811 SouthPalm Avenue, ecological interactions of birds and canopy- Sarasota,FL 34236. dwelling plants have been almost entirely over- [891] This content downloaded from 128.171.57.189 on Mon, 13 May 2013 21:28:23 PM All use subject to JSTOR Terms and Conditions 892 NALINIM. NADKARNIAND TERI J. MATELSON looked in the literature,except for a few groups (ovenbirds, 14 species),Tyrannidae (flycatchers, such as the hummingbirds(e.g., Feinsingeret al. 14 species), Fringillidae(finches, 8 species), Pa- 1987) and several frugivorousspecies that dis- rulidae (warblers, 8 species), and Turdidae persemistletoes (e.g., Davidar 1983, Fitzpatrick (thrushes,7 species).Nesting materialsfrom epi- 1980, Parker1981, Remsen et al. 1982). phytes have been noted anecdotally for many This studyis a firststep in assessingthe overall species of birds, and are most commonly col- importanceof epiphytes to birds in the tropics. lected by Furnariidae. We summarize scatteredliterature accounts of Epiphyteresources used by birdsinclude fruits, epiphyteuse by birdswith respectto bird species, flowers, seeds, water, and invertebratesin bro- resource types, and epiphyte groups involved. meliad "ponds"and sequesteredin dead organic We then present results of a field study that fo- matterbeneath moss mats, nestingmaterials, and cused on bird and epiphyte interactionsin trees nest sites. The most frequentcitations concerned of primaryforests and pasturesin Monteverde, foragingfor epiphyticfruits and nectarin flowers Costa Rica, to ask the following questions: (1) (Table 1 and Appendix 1). The list of epiphytes What species of birds are associated with epi- used by birds includes 42 genera in 15 families phyteuse? (2) Whatis the frequencyof bird visits of vascularand nonvascularplants (Table 1).The and foragingbehavior associatedwith resources Bromeliaceae, Loranthaceae, Marcgraviaceae, createdby epiphytes comparedto those of host and Ericaceaeare the families of vascular epi- trees? (3) Which epiphyte groups and epiphyte phytes most frequentlycited for use by birds. resourcesare used by the bird community?(4) Do any birds appearto specialize on particular FIELD STUDY OF EPIPHYTE resourcesprovided by epiphytesor on particular USE BY BIRDS epiphytegroups? (5) What are community-level STUDYAREA implicationsof bird exploitationof epiphyte re- sources? Study sites were in Monteverde, Puntarenas Province, Costa Rica (10018'N, 84048'W).The LITERATUREREVIEW OF EPIPHYTE area is a mosaic of primarylower montane wet USE BY BIRDS forest and pasturesof various land-use histories We searchedthe literaturefor any referencescon- (Lawtonand Dryer 1980). The bird community cerningneotropical bird use of epiphytes(except of Monteverdehas been well studied, and bird- for field identificationguides, which almost ex- plantinteractions have receivedparticular atten- clusively describeforaging behaviors anecdotal- tion (e.g., Wheelwrightet al. 1984, Feinsingeret ly). We reviewed 55 papers that fell into four al. 1987). We selected 14 sites between 1,350 categories:(1) frugivoryin neotropicalbirds, (2) and 1,420 m in elevation and within 2 km of hummingbirdpollination, (3) bird life-histories, each other. These sites represent the range of and (4) mistletoe dispersal (Appendix 1). This habitats in the area: (a) three sites in primary compilationis usefulin identifyinggeneral trends lower montane forest,(b) five sites in "relicttree and documentingthe diversity of birds that use pastures"(pastures partially cut, leaving some epiphytes.The extentto which this summarycan primaryforest trees), and (c) six sites in "scrub be generalizedto a community level is limited, tree pastures"(pastures cut completely, with a however,as it reflectsthe purposesand geograph- similardensity of second-growthtree speciescol- ical locations of studies not specificallydesigned onizing the pastures).Differences in bird use of to assess the importanceof epiphytes to birds. epiphytesin the three habitatswill be described A total of 193 species of birds in 125 genera elsewhere(Nadkamrni and Matelson, unpubl.) and 25 familieshas been cited as using epiphytes Epiphytesof the Monteverdecommunity are (Appendix 1). Birds of the three major diet cat- describedin Nadkamrni(1986). The taxonomyand egories (frugivores, insectivores, and nectari- distributionofepiphytes are in generalonly