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Papéis Avulsos de Zoologia París Avrisos Zo01., 5. PaoLo, 43 (1): 1 27. VIIL.I9TO THE COMPOSITION OF AVIAN COMMUNITIES IN REMANESCENT WOODLOTS IN SOUTBERN BRAZIL Epwin O. Wiis ABSTRACT Consuses of birds in remanescent awoodlots of 1400, 250, and 21 ha on the subtropical São Paulo pluteau in southeastern Brazil showed 202, 146, and 93 species of birds still present. Presumably all areas originally had about 280 species before forest cutting became widespread. Few species present im a small woodlots were absent from a larger one, so that the small woodiots addeá to bird preservation mainly by repeating species im ow different area. The large and medium qwoodlots had much the same numbers of individudis per 100R of observation, but the small «woodlot had fer individuals and hence did not show density compensation. Certain groups of birds and mammais were especially prone to extirpation in small woodiots: large frugivores of the canopy (parrots, cotingids, monkeys, etc.), birds eating large insects on or near the ground (antbirds, woodereepers), and smull insectivores of forest bamboo thickeis and other tangles. Frugivores were to some extent replaced by cdge-living omnivores, ground-living doves, and by ground-living mammais (apoarentiy Teading to increases in owls) in small woodiots. Small birds eating small insects. om or near the ground became more abundant, although not more diverss, tn small woodlots, Migrants, which here acere mosthy birds of the forest camopy and edges, were common in the medium-siced woodlot but not in the small one. Edge-living species became more abundant or relatively more abundant in small woodlots. These changes cause small woodloto to become more like temperate zone forests in emnhases on oscine birds of canopy and edge and on migrants, und in loss of fruit-eating birds. Losses of large hawks and of birds of the forest understory may de due to tow population numbers and occasional extinctions in small areas. Losses of canopy frugivores and of hummingbirds, tokich fly easily between aoodiots, are more Bbely due to loss of specific flowering or fruiting trees nsed at certain times of the year. The' conservation of ecosystems has received less attention over the years than has the preservation of conspicuous species. The hope has rather been that, when by diligent effort one sets aside and protects a patch of habitat that is the home of one or several species Department of Biology, Princeton University, Princeton, N.J. 08540. 2 Papéis Avulsos de Zoologia of particular interest, other species of that community will also survive. In a world increasingly preempted by agricultural and other human uses, the remaining patches of habitat have become smaller and smaller. Preston (1962) was first to point out the danger of leaving only small patches of habitat, using data from biogeographical studies oí islands. It had long been known that small islands support fewer species than do large ones; as a general rule, dividing area by 10 causes loss of half the species (Darlington, 1957). Preston noted that, since this is true for any isolated area, species must disappear from remanescent patches of habitat even if humans do not interfere inside the patches. This implies that communities will rearrange themselves internally, becoming impoverished with time, if restricted ín area. MacArthur & Wilson (1967) extended these ídeas to suggest that immigration and extinction rates set equilibria that are lower on small and isolated islands than on close and large ones. Diamond (1972) suggested that species nave been disappearing from islands off New Guinea since these islands were connected to it in the last glacial period of low sea level; and he suggested that species have disappeared fastest on the smallest islands. Censuses of birds of the protected forest reserve of Barro Colorado Island, a hilltop isolated by Gatun Lake during construction of the Panama Canal about 1914, showed that some species have disappeared over the years (Chapman, 1938; Eisenmann, 1952; Willis, 1974; Willis & Eisenmann, in press). Preston's suggestion was thus proved correct in one fairly welldocumented case. Decreases were often losses of birds of secondary woodland, but there were some losses of large forest hawks and of large and small ground birds. The Barro Colorado evidence stimulated suggestions that habitat reserves be left as large and interconnected as possible to slow down changes due to “ecological truncation” of guilds of spe (Wilson & Willis, 1975; Terborgh, 1974). Changes in the structure of communities as an ecosystem is diminished in size can perhaps indicate possible reasons for loss of species. Simberloff & Abele (1976) looked at insects on a mangrove islet that they subdivided; species numbers did not decrease, at lcast in the short term. However, thcy did not report on internal structures of the insect communities thus created nor on changes over the course of several years. Others have looked at present conditions on naturally created islands of differing sizes. Diamond (1975) found that some “forbidden” combinations of bird species never occur together on islands of different sizes off New Guinea, and that some bird species persist only on small and depauperate islands. These “supertramp” species generally are good at moving about and can persist in small areas of habitat, but do not stay when many species meve in on large islands. Johnson (1915) looked at birds of forested mountains ín the deserts of the Great Basin in the western United States. More species were present when more macrohabitats were present, even when habitat areas were limited. Like the mangrove insects of Simberloft & Abele and the supertramp birds of Diamong, these birds seem able to survive in even small patches of habitat. In a sense, nontramp species were already gone before man arrived. To look directly at changes within communities due to decrease in area of habitat in places where the natural faunas are still relatively 4 Papéis Avulsos de Zoologia Barreiro Rico, were censused for birds from February 1975 to March 1978..One, the “Santa Genebra” tract, is 250ha of forest (centered about 22º49' S and 47007 W on the Campinas quadrangle of the Carta do Brasil 1:50000) in cótton fields. In 1969, this area was reduced to its present size by cutting of about 145 ha. Another, the “Unicamp” tract, is 21ha set in pastures and cotton fields near the Universidade Estadual de Campinas, at 3.75km east (just northwest of 22º0'S and 47004 W) of the Santa Genebra tract. Small cattail (Typha. angustifolia) marshes and swamps next to both tracts were not censused. Both the Santa Genebra and Unicamp woodlots are on red and fertile “terra roxa” latosols rather than the sandy soils of Barreiro Rico, and both include swampy areas with small creeks. The Barreiro Rico tract has two small creeks arising at its north edge, but is mainly a dry hilltop woodiand. The Santa Genebra and Unicamp forests should therefore be taller and better developed than the forest at Barreiro Rico, which lies on an ecotone near areas of cerrado and cerradão, The Santa Genebra and especially Unicamp woodlots are indeed taller and more imposing at their centers, with 35m emergent Jequitibá trees (Cariniana legalis, Lecithydaceae) towering over 20-25 m guarantã (Esenbeckia leiocarpa, Rutaceae) and others. However, the edges and trail margins of both the Unicamp and Santa Genebra tracts are highly disturbed by wood cutting and therefore tend to a vinetangled appearance not greatly different from the irregular canopy at Barreiro Rico, Some trees have been removed over the years at Barreiro Rico, and removal of valuable species by colonists and even Indians must be assumed for all areas. Parts oi the Santa Genebra tract seem old second growth. Scattered coffee plants and even rows occur in both the Un'camp and Santa Genebra tracts. The rows arc remains of small nurseries in use to 35 years ago, but other plants probably do not indicate former cultivation; bird dispersion of coffee seeds occurs in many woodlots and state parks in eastem São Paulo. Occasional windfalls have created tangled zones or low woodlands in all three forests, and occasional fires (notably extensive ones at the edges of the Santa Genebra tract in 1964) have also left tangled patches. Layers of charcoal are in the soil of sandy areas at Barreiro Rico. Freezes, such as one in July 197%, temporarily defoliated Cecropia sp. but do noi seem to cause lasting changes. Drought periods, such as the «winter of 1975 and the summer oí 1978, cause much loss of canopy foliage, Barreiro Rico has an included patch of 5 ha of cerrado vegetation (censused separately), and a few ha of sandy bordering woodlands add some diversity of habitat lacking in the Santa Genebra and Unicamp tracts, However, the swampy creeks of the last two areas, with palms (mostly Arecasirum romanzojfinnum), add a diversity lacking at Barreiro Rico, as do the jequitibás and nectariferous scaitered paineira trees (Chorisia speciosa, Bombacaceae). Trees common in all the censused areas include guarantã, peroba (Aspidos- perma polgneuron, Apocynacene), guaraiuva (Segurinega guaraiuva, Euphorbiaceae), canxim (Pachystroma illicifolium, Euphorbiaceae), Vol. 33 (1), 1979 5 tapixingui (Croton sp. Euphorbiaceae), guaritá (Astroneum graveolens, Anacardiaceae), pau d'óleo (Copaifera langsdorffi, Leguminosae), jatobá (Hymenaea courbaril stilbocarpa, Leguminosae), pau-jacaré (Piptadenia gonoacantha, Leguminosae), and canjarana (Cabraiea canjarana, Meliaceae), A common understory shrub is carrapateiro (Meireodorea sp. Rutaceae). There are scattered patches of slender bambocs, and lianas are dense enough to clutter the forest understory and form tangles in the frequent treefall and other clearings. METHODS Two types of censuses were used: one-hour censuses and general censuses. In onehour censuses, 1 recorded every bird seen or heard while walking slowly along standard routes in each woodlot between 07:00 and 99:00. Some censuses at Barreiro Rico were run at less favorable hours (10:0017:00) but along alternate routes. General censuses were run by walking slowly through the woodlots, attempting to reach all parts of the areas. Usually general censuses at Unicamp and Santa Genebra were run in the favorable morning hours, but at Barreiro Rico I worked in the aíternoons as well. Birds at Barreiro Rico tended to be more active all day long than in the two smaller woodlots, so that census totals at Barreiro Rico did not seem low. The Unicamp woodlot was often visited with students at noncensus hours; seven vagrant species encountered only at such times are not included in analyses. General censuses at Barreiro Rico totaled 550.4 hours, at Santa Genebra 444.3 hours, and at Unicamp 205.0 hours. Birds were identified with 10x50 binoculars, and study skins of the Museu de Zoologia nf the Universidade de São Paulo were checked to confirm identifications. SPECIES NUMBERS These forest tracts must originally have had similar total numbers of bird species, but I found (Table 1) 202 species in the tract at Barreiro Rico (B), 146 at Santa Genebra (S), and 93 at Unicamp (U). Not counted are a few birds of open areas that occasionally visit the edges of woodlots (notably Guira guira; 5 species at B, 6 at S, and 5 at U) nor some water or marsh birds that occasionally perch atop trees (Cairina moschata at B, Donacobius atricapillus at 8; and Syrigma sibilatriz at U). Table 1. Bird species in three São Paulo woodlots Number of Species im Given Locality B' s VU Total recorded 202 146 93 Breeding species 175 119 76 Summer only 13 12 8 Wintering species 5 5 2 Vagrants 22 22 15 *B is Barreiro Rico, S is Santa Genebra, and U is Unicamp. Vol. 33 (1), 1979 7 NUMBER OF SPECIES vol E 100 so “o ot 4 GENERAL CENSUSES 2 otgg o à Ea Judo 965 TE55 NUMBER OF INDIVIDUALS Fig. 2. Cumulative numbers of species recorded for given numbers of of individuals in general censuses. Originally these and yet another 50 species should have been in all the forests of the region. Some 20 now present, mainly forestedge species, would have been lacking; totals should have been near 230 species. Lacking today are most macaws (Ara sp), large parrots CAmazona spp. other than forestedge 4. aestiva), araçaris (Ptero- glossus aracari; see Haifer, 1974:229), eagles (Spizaetus spp. etc), and several brightly colored treetop tanagers (Tangara spp. etc). BARREIRO Rico a NUMBER OF SPEGIES ONE-HOUR CENSUSES 15 NUMBER OF HOURS Fig. 3. Cumulative numbers of species recorded by given times for one-hour censuses, 8 Papéis Avulsos de Zoologia 100 Pd BARREIRO RICO qm tab g ad SANTA GENEBRA e Ê á ae pa PTC pq E 5 ONE-HOUR CENSUSES 160 560 tos [E 050 NUMBER OF INDIVIDUALS Pig. 4. Cumulative number of species recorded for given numbers of individuals in one-hour censuscs. COMPOSITIONS OP AVIFAUNAS Appendices 1-20 present the species recorded and the numbers of individuals seen or heard per 100h of field observation in the three woodlots. Only in a few cases were breeding birds recorded at Santa Genebra or Unicamp and not at Barreiro Rico; therefore, birds of Unicamp were in general a subset of those at Santa Genebra and birds of Santa Genebra a subset of those of Barreiro Rico. Woodrails (Aramides cajaneo), streamereeper (Lochmias nematuro), and a dove (Leptotila rujaxilla) were absent in Barreiro Rico primarily pecause their creekside woodlands are absent. Large owils favored the smaller woodlots (Appendix 6), perhaps for reasons cited below. A single Great Antshrike (Batara cinerea) appeared for several months in the Santa Genebra woodlot, which lacked forestedge Barred Antshrikes (Thamnophilus doliatus) for unknown reasons. The only other exception was the seeming absence of a small tyrannulet of scrub (Serpophaga subcristata) at the edge of Barreiro Rico. Some other species, such as the becard Platypsaris rufus, were very rare at Barreiro Rico. The piculet there was Picumnus minutissimus, that of Santa Genebra and Unicamp P. cirrhatus; but P. cirrhatus was in à 325-ha woodlot at Barreiro Rico. Veniliornis passerinus nearly replaced V. spilogaster in the main woodiot at Barreiro Rico, but was less common than it in the 500-ha woadlot. 1. Large Canopy Frugivores and Omnivores Large fruiteating birds, especially ones that eat large insects as well, were unusually poorly represented in both small woodlots (Appendix 1). One parrot (Pionus maximiliani) was more common in the medium-sized woodlot and to some extent took the place of other 19 Papéis Avulsos de Zoologia 10. Large Ground Insectivores Insectivores that get large insects from or near the ground were rare in small woodlots (Appendix 10). Absence of army ants (Eciton burchelli and Labidus praedator) from both small woodlots probably caused reduced numbers of antfollowing Dendrocincia turdina and Dendrocolaptes platyrostris and absence of Pyriglena leucoptera. A fourth ant-following species, Trichothraupis melanops, eats fruits as well and remained in all three woodlots (Appendix 3). 11. Small Ground Insectivores “Small ground insectivores (under 25 g) did well in small woodlots (Appendix 11), probably because large ones did not. However, some small species were absent from small woodlots. 12. Small Understory Insectivores Most small insectivores of the understory were in all woodlots (Appendix 12). None were migratory, except for a few wandering winter individuals. 13. Tangle Insectivores Forest insectivores that inhabit bamboo and vine thickets or their edges (Appendix 13) tended to drop out in small woodlots. 14. Midlevel Insectivores Some midievel insectivores (notably Piaya cayana, Hypoedaleus guttatus, and Herpsilochmus rufimarginatus) also use tangles, but most species use more open foliage than members of the preceding group. Like them, they were less diverse in small woodlots (Appendix 14). High abundance of the three that also use tangled vegetation (and of a summer species that liked edges of such tangles) in Santa Genebra was not repeated in Unicamp, although vinetangled midlevels are common in both areas. 15. Small Canopy Insectivores Small insectivores of the treetops (Appendix 15) were much like small canopy omnivores (Appendix 2) and midlevel insectivores (Appendix 14) in being more common in the medium-sized woodlots ut no more diverse there. They were uncommon but fairly diverse in the smallest woodlot. 16. Edge Insectivores Edge insectivores, which vary in foraging between tangles and midlevels and treetops, were usually present in all three woodlots (Appendix 16). High densities of some tangleforaging species (Hylophilus poicilotis, Synallaxis spp.) in Santa Genebra raised total numbers there. Presence of dead trees and cerrado-like vegetation in pastures at Barreiro Rico accounted for addition of Myiarchus tyrannulus and Troglodytes aedon at forest edges. Vol. 33 (1), 1979 8! 17. Aerial, Insectivores Aerial insectivores (Appendix 17) were generally present over al woodlots and over intervening open areas as well. Five species bred outside each woodlot and hence were local vagrants, totals surpassed onty by edge omnivores of Appendix 4 and perhaps by birds of Appendices 19 and 20. 18. Nocturnal Insectivores Nocturnal insectivores, in contrast to carnivores, were poorly represented in small woodlots (Appendix 18). 19. Nectarivores Birds that use nectar and small insects (Appendix 19) were less diverse and numerous in the small woodlot. Since most of these birds find flowering trees or sugar-water feeders even in suburbs at Campinas (Thalurania glaucopis is the only forestinterior species that does not appear outside the forest), absence in the small woodlot probably reflects undependability of flowering there. Phaethornis pretrei and Chiorostilbon aureoventris, the least dominant and most vagrant of local hummingbirds, were common in the small woodlot. 20. Edge Granivores Birds that eat seeds and small insects (Appendix 20) were mastly at forest edges. Only Haplospiza unicolor (a vagrant or winter visitor at Campinas, perhaps from the Serra do Mar) and Tiaris fuliginosa regularly wander through forests and find small trailside patches of grass seeds. Probably reduced diversity and ahundance in small woodlots reflects reduced abundance in nearby cotton fields and intensively grazed pastures; Barreiro Rico seedeaters came mostly from weecdy patches in nearby pastures. Also, many seedealers are captured for cage birds ncar Campinas. MIGRANT BIRDS Summering birds reached ali three woodiots, although the smallest wocdlot unaccountably lacked a few species (notably Myiopagis viridicata and Platypsaris rujus, midlevel to treetop insectivores common at nearby Santa Genebra). Summering species were all edge, midlevel, canopy, or aerial species; most were insectivores, though some used fruits to some extent. None, except perhaps Claravis pretiosa if it really is absent in winter, used the forest trunks or lower levels. However, Empidonax euleri of the lower levels seemed less common in winter, and may emigrate to some extent at that season. The frugivorous Tityra spp. also were less common or absent in winter, and may migrate like their smaller relatives, the becards. One pair of T. cayana appeared in Santa Genebra on 21 August 1977, as if on spring migration. Two nocturnal species, Caprimulgus rujus and Nyctibius griseus, were unrecorded in winter; but they are not easily detected when not calling. In the Campinas woodlots, many summering species disappeared by February and apparently failed to breed in the drought summer of Vol. 33 (1), 1979 13 Table 3. Wintering migrants of three São Paulo woodiots Species Individuals/100 h B s U Phibalura jlavirostris 0 Pachyramphus castaneus 1 Knipolegus cyanirostris 2 3 Contopus cinereus 5 23 3 Dendroica striata 0 Pipraeidea melanonota (U 3 ) Haplospiza unicolor 4 Total 9 33 3 Several rare birds, here considered vagrants (Basileuterus culicivorus, Pyrrhocoma ruficeps, Cranioleuca pailida, Attila rufus), probably come from the south and may represent individual wintering birds; they reached only the Campinas woodlots, which are closer to the wooded Serra do Mar than is. Barreiro Rico. A single Dendroica striata seen twice in Santa Genebra was the only migrant from North America. WANDERING SPECIES Counting only species known to be able to travel between woodlots (T” species in the Appendices), 140 of 216 or about two thirds can wander. Only for the categories of ground and tangle insectivores (Appendices 10, 11, 13) are most species unlikely to cross open areas. Large fruit-eaters, small understory insectivores, and trunk birds average about half species that can cross open areas. Diversity of nonwandering species was reduced in small woodlots: 74 species (37% of the avifauna) at Barreiro Rico, 38 at Santa Genebra (26%) and 19 at Unicamp (20%). Many of the 19 at Unicamp are small and abundant species that are likely to be resistent to extinction; but many may wander better, especially as immatures, than is known at present. Empidonax euleri and Turdus albicollis are particularly likely to be transferred to the “travelprone” category when more information is available, since both may be partially migratory. DENSITY COMPENSATION There were fewer birds per hour at Unicamp in general censuses than at Santa Genebra or Barreiro Rico (see above). In the one-hour censuses, there were 50.0, 87.5, and 79.9 birds per hour, respectively. TAXONOMIC CHANGES Passeriform birds and tyranniform birds, characteristic of forest edges and temperate-zone woodlands, both increase in small woodlots 14 Papéis Avulsos de Zoologia (Table 4). Most migrants are in these groups. Furnarioid tyranniform birds, nonmigratory insectivores of forests or of continuous vegetation, decrease in small woodlots. Other nonpasseriform birds also decrease, in part because such birds are often large (e. g., hawks) or are food spec'alists (parrots). Table 4. Taxonomic composition of three São Paulo woodlot avifaunas Taron Percentages of Avifauna B s U Passeriformes al 26 28 Tyranniformes, Tyrannoidea 27 2 32 Tyranniformes, Furnaríoidea 15 4 10 Others 37 33 30 FGOD-USE CHANGES Fruit eaters decreased from 9 to 6% of species in the two small woodlots, but omnivores were 23% in the two large woodlots compared to 27% in the smallest one. Insectivores were 51% in the largest woodlot, 54% in the two others. Carrion eaters and carnivores were 5-6% in ali woodlots, nectarivores 58%, and granivores 2-5%. An increase in omnivory was expected in small woadlots, since omnivory would buffer against fluctuations in food supply (Willis, 1976); but the evidence instead suggests a shift toward insectivory in smail woodlots, Discussion Internal structures of these three woodlot avifaunas differed considerably, since decrease in area caused greater losses in some groups of species than in others. Two groups that seemed especially to decrease in small woodlots were large frugivores and large insec- tivores. Trunk and twig foragers and tangle-living insectivores also decreased considerabiy in small woodiots, as did diurnal carnivores, carrion eaters, and nocturnal insectivores. Aerial, edge, and treetop birds decreased little. Small ground and understory insectivores also decreased less tnan the average. Reasons for high losses of large frugivores and large understory insectivores may be somewhat different. Most large frugivores fly well, and only about half the species in Appendix 1 are unlikely to fly between woodlots. Parrots and toucans could easily travel to the Campinas woodlots, and indeed a flock of Aratinga leucophthalmus has been seen to fly past Unicamp. Probably the large frugivores disappear from the small woodlots because they depend on scattered trees of different species at different seasons or years; and only large woodlots have enough tree diversity to keep populations from oceasional famine. Hummingbirds, which also disappear from small 16 Papéis Avulsos de Zoologia a niche subdivision, as well as based on the presence oi creekside woodlands, Increases in squirrel and lizard abundance in small woodlots are probably due to increased fruit on the forest floor. Nocturnal ground mammals may also increase in small woodlots, causing the presence of nocturnal large owis in these woodlots and seemingly not at Barreiro Rico. This possible chain of effects needs investigation, for owls were not studied well. They could be responding to better soil conditions and forests of the Santa Genebra and Unicamp sites, or to other factors. Small treetop and understory birds that eat fruit and insecis (Appendices 2,3) persist in small woodlots better than do large birds, although in reduced numbers in the smailest woodiot. However, the absence of small treetop Tangara tanagers from all three woodlots is puzzling, as these birds occur in large forest tracts both eastward (Serra do Mar) and westward (Iguaçu National Park). Small understory, midlevel, and treetop insectivores (Appendices 12, 14, 15) persisted better in the small woodlots than did tangle insectivores (Appendix 13). Treefalls may be too few in number in very small woodlots, or edge species may outcompete tangle species for them. Edge insectivores (Appendix 16) persisted well in all woodlots, but were as high in numbers in the medium-sized woodlot as were midlevel insectivores. Perhaps the large woodlot had increased competition from large forest omnivores (Appendix 1), large ground insectivores (Appendix 10), and from trunk and twig insectivores (Appendix 9). The generally lower numbers of insectivores of all these types in the smallest woodlot are not readily explainable, unless very small woodlots do not provide enough habitat variation to support such small insectivores al year long by local movements. If small woodlots do support dependable insect populations, edge insectivores should move to such woodlots. Instead, edge omnivores (Appendix 4) moved into the smallest woodlot and replaced to some extent both fruit eaters and insect eaters. This suggests that generalist birds that can switch from fruit to insects or vice versa are favored in small woodlots, perhaps in cold waves or other environmental “disasters” that may be as important in small woodlots as at margins of tropical forests generally (Willis, 1976). Roles of Migrants: Migrants were birds of the air, forest upper stories, and edge. No migrant species came from the categories of trunk or insectivorous understory birds. These forests lose leaves mainly in the canopy, perhaps accounting for lack of migrants from the understory. Migrants from the forest understory are a conspicuous part of the migratory avifauna in cold coniferous or deciduous forests of the northern hemisphere, which differs in at least that respect Trom the migratory avifauna in São Paulo. Migrants in São Paulo are mostly cotingas and tyrantflycatchers rather than the nine- “primaried oscines so common among North American migrants, too. Migrants that eat seeds move into many northern woodlands in winter as well as to open areas and forest edges. This component of migration is very weak on the São Paulo plateau, where only Haplospiza unicolor winters in very small numbers. Many seed-eating birds of open areas or forest edges become rate or disappear in the winter: Sporophila caerulescens, for instance. These forests seem to Vol, 33 (1), 1979 11 produce fruit-eating birds rather than seed-eating species, except that ground-living tinamous and doves probably eat seeds as well as fruits. Some summer migrants are known to eat fruits, at least in other regions (Morton, 1977 for Vireo and Legatus leucophaius). These migrants seem mostly insectivorous when on the São Paulo plateau, although detailed study is needed. Certain wintering and passage migrants of forest edge and cerrado zones are mainly frugivorous (Elaenia spp. Turdus spp), and a few thrushes move into the local woodiots when certain trees are in fruit. Pionus maximiliani moves into the Unicamp woodlot mainly in the spring, but is thought not to preed there. Local movements of fruit-cating cdge birds bring them into all woodlots (Appendix 4). The numbers of these birds in forest are rather low, even though they increase slightly in small woodlots as one might expect fram the low numbers of resident frugivores in such woodlots. Many humminghirds appear in the local woodiots only when there are certain trees in flower, notably Mabea fistulijera (Euphorbiaceae) of the sandier parts of Barreiro Rico in April and May. The necessities and numbers of nectarivorous species should depend not on the size of local «oodlots but on the presence of other woodlands in the Serra do Mar, close enough to permit altitudinal and local migrations that must be rather complex. However, the decrease in humminghird numbers in small woodlots (with a small increase in Coereba flaveola populations in the medium-sized woodlot as a partial compensation) indicates that nectarivorous migrants must find food more easily in large woodlots. Perhaps, like fruit-eating species, they can stay longer in the larger woodlois, which are likely to have a greater seasonal spread of fruit and flower resources than are small woodlots. Roles of Travelprone Species: Local wanderers of many species visit all three woodlots in very small numbers. Some are probably wintering immatures or other birds that normally winter on the lower slopes of the nearby Serra do Mar: Bosileuterus culicivorus certainly is at most accidental here, as the very similar B. hAypoleucus replaces it about 50 km southeast of Campinas, inside the Serra do Mar near São Paulo. A snail-eating kite, Chondrohierax uncinatus, once scared past but did not enter the Unicamp woodlot. The ovenbird Cramioleuca pallida appeared and sang for several months in the Santa Genebra woodlot. These vagrants could colonize the local woodlots, and may occasionally do so. Some species counted as residents in the small woodiots (notably Chiroxiphia caudata in the Unicamp woodlot, wherc I have never seen an adult male) may be birds produced in larger woodlots nearby. There is enough movement that the smail woodlots are probably enriched unduly by birds from larger tracts of forest, notably from the coastal mountains of São Paulo. Low species numbers in small woodlots may be due more to rapid extinction than to failure to immigrate. Still, one must remember (with MacArthur and Wilson, 1967) that long distances of movement reduce chances oí pairs reaching isolated woodlots. Also, not considered by MacArthur and Wilson, there is the possibility that source areas may be deforested. Gradual deforestation of the coastal ranges of São Paulo is to be expected, plus gradual loss of woodlots that now are scattered over the São Paulo plateau. When the Unicamp or Santa Genebra or Barreiro Rico Vol. 33 (1), 1979 19 Morton, E. S, 1977. Intratropical migration in the Yellow-green Vireo and Piratic Flycatcher. Auk 94: 97-106. Preston, F. W., 1982. The canonical distribution of commonness and rarity. Part IL. Ecology 48: 410-432. Simberloff, D. 8. & L. G. Abele, 1976. Island biogeographic theory and conservation practice. Science 191: 285-286. Terborgh, J. W, 1974, Preservation of natural diversity: the problem of extinction-prone species. Bioscience 24: 15-22. wWhitcomb, R. F. J. F. Lynch, P. A. Opler & C. 8. Robbins, 1976. Island biogeography and conservation: strategy and limitations. Science 198: 1030-1032, willis, E. O, 1974. Populations and loca! extinctions of birds on Barro Colorado Island, Panama. Ecol. Monogr. 44: 1583-169. Willis, E. O. 1976. Effects of a cold wave on an Amazonian avifauna in the upper Paraguay drainage, western Mata Grosso, and suggestions on oscine-suboscine relationships. Acta Amazonica 6: 8719-394. Willis, E. O. & £. Eisenmann. A revised list of birds oi Barro Colorado Tsland, Panama. Smithsonian Contr. Zo0l., in press, wilson, E. O. & E. O. Willis, 1975. Applicd biogeography. In Cody, M. L. & J. M. Diamond, eds, Ecology and Evolution of Communitics, pp. 522-584. Harvard Univ. Press, Cambridge, Mass. 545 Pp- APPENDICES 1. Forest birds eating large fruit and insects a Penelope superciliarisP Columba cayennensisFT Pionus mazimilianiFT Ara maracana-FT Aratinga leucophthalmusFT Pyrrhura frontalis-F Amazona aestivaFT Trogon rujusO surrucura-O Ramphastos toco-FT dicolurus-FT Lipaugus lanioidesO Tityra cayanaOT inquisitor-O Pyroderus seutatusF Cyanocorax chrysopsO Pitylus fuliginosus-O Total 2. Small canopy omnivores à Phibelura flavirostrisOT Camptostoma obsoletum-OT Ozyruncus eristatus-O * Vireo olivaceus-OT Dacnis cayanaoT Euphonia chioroticaOT violacea-O Nemosia pileata-OT Hemithraupis ruficapilusO Pipraeidea melanonota-OT Total 3. Small understory omnivores Chirozxiphia coudata-OT Manacus manacusO Schijfornis virescens-O Antilophia galeataOT Laniisoma elegansO Pipromorpha rufiventrisO Habia rubicaO Trichothraupis melanops-O Turdus albicoltisO Total 51 100 154 [e nã es was SAL 52 6L 3 “83 ob 7e 21 
