Land use and conservation value for forest birds in Central Sulawesi (Indonesia)

Unprecedented deforestation is currently underway in Southeast Asia. Since this trend is likely to continue, it is critical to determine the value of human-modified habitats (e.g., mixed-rural habitat) for conserving the regional native forest avifauna. The impacts of ongoing deforestation on the highly endemic avifauna (33%) of Sulawesi (Indonesia) are poorly understood. We sampled birds in primary and secondary forests in the Lore Lindu National Park in central Sulawesi, as well as the surrounding plantation and mixed-rural habitats. Species richness, species density and population density of forest birds showed a consistent decreasing trend in the following order: primary forests > secondary forests > mixed-rural habitat > plantations. Although primary forests contained the highest proportion (85%) of a total of 34 forest species recorded from our point count surveys, 40-yr old secondary forests and the mixed-rural habitat showed high conservation potential, containing 82% and 76% of the forest species, respectively. Plantations recorded only 32% of the forest bird species. Fifteen forest species had the highest abundance in primary forests, while two species had higher abundance outside primary forests. Our simulations revealed that all forest birds that were sensitive to native tree cover could be found in areas with at least 20% continuous native tree cover. Our study shows that although primary forests have the highest conservation value for forest avifauna, the potential of degraded habitats, such as secondary forests and the mixed-rural habitat, for conserving forest species can be enhanced with appropriate land use and management decisions.     

Bird species richness in a Bornean exotic tree plantation: A long-term perspective

To provide sustainable income from forestlands, large areas in the tropics are planted with “agricultural” trees, such as oil palm and rubber, and “industrial” trees, such as Acacia mangium and Gmelina arborea. To examine how native forest birds use such plantations, we surveyed in 2005 the avifauna at Sabah Softwoods, a plantation in southeastern Sabah, Malaysian Borneo. We focused on A. mangium, Albizia (Paraserianthes falcataria), oil palm (Elaeis guineensis), and logged native forest, and compared our results to those of a study conducted at the same plantation in 1982. The number of forest species in the industrial groves did not change dramatically between 1982 and 2005, even though the trees had been cropped several times and the plantation was, by 2005, completely surrounded by cleared land and far removed from primary forest. However, as is common in logged or isolated forests throughout the world, certain primary forest groups (e.g., muscicapine flycatchers) have been extirpated from the entire plantation area. The industrial groves also lacked some larger species of kingfisher, woodpeckers, and canopy frugivores. Nevertheless, numerous primary forest taxa (ca. 50% of species) were found in mature industrial tree groves. Albizia attracted the most species of birds, followed closely by Acacia. Both tree types underpinned relatively complex secondary forests that attracted forest birds. In contrast, younger groves of Acacia and Albizia held mainly open country and scrub species. Oil palm, as a remarkably simple and unusual habitat, attracted few bird species. Sustained occurrence of forest birds in all groves of exotic trees at Sabah Softwoods was substantially enhanced by the relatively rich avifauna of the logged native forest remaining in substantial stands throughout the plantation.     

The effects of extreme forest fragmentation on the bird community of Singapore Island

Singapore Island suffered one of the highest known deforestation rates in the tropics from the mid-to-late 19th century when over 95% of its native lowland forest was cleared. We compared the current bird community structure and composition among three habitat types, i.e., old (>50 years, 7-935 ha) and young (?50 years, 29-49 ha) naturally regenerating secondary forests and abandoned wooded plantations (27-102 ha) dominated by exotic species. Forest patch area had the strongest influence on the current species richness. The overall bird richness was not greater in most mature forest patches, but 20 species were only found in the old secondary forests and five of these were found in <50% of these patches. The rapid decrease in the number of forest species in plantations was offset by an increase in the number of open habitat species. Comparisons with current bird communities in nearby mainland forest sites (Peninsular Malaysia) suggest that the forest avifauna of Singapore is depauperate. The preservation of larger mature and maturing forests is therefore required for conserving the extant forest avifauna in Singapore. Connecting isolated patches can also be envisioned to facilitate movements of forest birds that have low densities and restricted distribution.     

Bryophytes on tree trunks in natural forests, selectively logged forests and cacao agroforests in Central Sulawesi, Indonesia

Forest disturbance and transformations into agricultural land alter tropical landscapes at drastic rates. Here, we investigate bryophyte assemblages on trunk bases in natural forest, selectively logged forest and cacao agroforests that are shaded by remnants of natural forest in Central Sulawesi. Overall, bryophyte richness per site did not differ between forest types. However, mosses and liverworts reacted differently in that moss richness was lowest in cacao agroforests, whereas liverwort communities were equally rich in all forest types. In terms of cover, mosses remained unaffected while liverwort cover decreased significantly in disturbed forest. Species composition of bryophytes clearly changed in cacao agroforests as compared to natural forests and selectively logged forests. In particular some drought-sensitive species were rare or absent in cacao agroforests and were replaced by drought-tolerant ones, thus underlining the importance of microclimatic changes. Moreover, differences in bryophyte species composition between large and small trees were only pronounced in cacao agroforests, presumably due to concomitant changes in stemflow of precipitation water. In conclusion, the bryophyte assemblages of selectively logged forests and cacao agroforests were as rich as in natural forest, but species turn-over was particularly high towards cacao agroforests probably due to microclimatic changes. Maintenance of shade cover is crucial to the conservation of the drought-sensitive forest species.     

Comparison of breeding bird and vegetation communities in primary and secondary forests of Great Smoky Mountains National Park

We compared breeding bird communities and vegetation characteristics at paired point locations in primary (undisturbed) and mature secondary forest (70-100 years old) sites in Great Smoky Mountains National Park, USA to understand how sites logged prior to creation of the park compare to undisturbed sites following 70 years of protection from human disturbance. We found that bird and vegetation communities are currently similar, but retain some differences in species composition. Rank abundance curves for primary and secondary forest bird communities showed very similar patterns of species dominance. Species composition was also similar on the two sites which shared 24 of the 25 most frequently recorded species. Nonetheless, comparisons of density estimates derived from distance sampling showed three bird species were more abundant on primary forest sites and that one bird species was significantly more abundant on secondary forest sites. Notably, comparisons based on raw counts (unadjusted for potential differences in detectability) produced somewhat different results. Analyses of vegetation samples for the paired sites also showed relative similarity, but with some differences between primary and secondary forests. Primary forest sites had more large trees (trees greater than 50 cm diameter at breast height) and late successional species. Primary forest sites had a denser tall shrub layer while secondary forest sites had a denser canopy layer. Nonetheless, tree species richness, basal area of live trees and number of standing snags did not differ between primary and secondary forest sites. Results indicate that breeding bird communities on sites within the park that were logged commercially 70 years ago are currently quite similar to bird communities on sites with no history of human disturbance. Similarities between the bird communities on previously disturbed and undisturbed sites in Great Smoky Mountains National Park may exceed those on more fragmented landscapes because large patches of primary forest, adjacent to commercially logged sites, remained in the park when it was established in 1935. These patches of primary forest may have served as source areas for commercially logged sites.     

The effects of human disturbance on a stingless bee community in a tropical rainforest

Human disturbance of tropical rainforests may change pollinator communities indirectly as a result of changes in resource availability. We studied the mechanisms by which human disturbance affects a community of major pollinators, stingless bees, in Sarawak, Malaysia. We surveyed forest structure and flowering activity, and conducted a nest census and a bait-trap survey of stingless bees, both in primary forests and in forests disturbed by logging and shifting cultivation. The densities of late successional trees and large trees (diameter at breast height >50 cm) were higher in the primary forests than in the disturbed forests. The density of flowering trees was lower one year after logging, but recovered in old disturbed forests because of the active flowering of pioneer trees that became established after the disturbance. Stingless bees nest only in large trees, and nest density was positively correlated with the density of large trees. However, we found no relationship between the numbers of foragers and floristic parameters. Some species preferred nesting in dipterocarps, while others preferred dead trees. The results of the bait-trap survey also indicated that some species were abundant in the primary forests, whereas other species were abundant in the disturbed forests. These results suggest that human disturbance alters the species composition of the stingless bee community. Such changes in the bee community may affect the reproductive success of plants, and ultimately forest composition.     

Supply of tree-holes limits nest density of cavity-nesting birds in primary and logged subtropical Atlantic forest

Tree cavities are proposed to limit populations and structure communities of cavity-nesting birds. Although the greatest diversity of cavity-nesting birds is found in tropical and subtropical moist forests, little is known about how tropical logging affects the abundance of cavities or cavity-nesting birds. We compared the abundance of cavities and cavity nests between primary and selectively-logged subtropical moist Atlantic forest in Argentina, and conducted the first before-after controlled nest-box addition experiment to determine whether nest sites limit the breeding density of cavity-nesting birds in tropical or subtropical moist forest. Visual inspection of 86 cavities identified through ground-surveys revealed that only 19% were suitable for nesting birds, suggesting that cavity abundance may be overestimated in the literature on tropical forests. Suitable cavities were found in fewer than 1% of 1156 trees <60 cm dbh but 20% of 20 trees >100 cm dbh. Logged forest had half the basal area of primary forest, one third the density of large trees, nine times fewer cavities suitable for nesting birds, and 17 times fewer active nests. When we added nest boxes, nesting density increased on treatment plots but not on control plots in both logged and primary forest, suggesting that cavity supply can limit nest density even in relatively undisturbed forest. This is the first experiment to show how reduced cavity supply in logged tropical forest can limit breeding density of cavity-nesting birds. International initiatives such as forest certification should promote tropical timber management strategies that conserve large live cavity-bearing trees.     

Effects of habitat disturbance on mixed species bird flocks in a tropical sub-montane rainforest

Despite their vulnerability to forest disturbances in the Neotropics, the consequences of forest perturbation on mixed species flocks are poorly understood in the threatened Southeast Asian rainforests. We examined the effects of local-scale habitat disturbance on mixed species flocks along an escalating gradient of anthropogenic modification (i.e., forest interior, forest edge, and urban) in a sub-montane tropical rainforest in Peninsular Malaysia that is presently experiencing low intensity development. Mixed species flocks in the forest interior and forest edge habitats (9.3 ± 2.3 and 8.4 ± 2.3, respectively) had significantly higher number of species than those observed in the urban habitat (5.1 ± 1.7). Flock participation was influenced by environmental characteristics (e.g., canopy cover). Flocking species sensitive to habitat disturbance were likely to be from the Families Corvidae, Nectariniidae, and Sylviidae; had narrow to restricted altitudinal ranges; and were exclusively dependent on primary forest and understory microhabitats. We conclude that sub-montane mixed species flocks are affected by even small scale urbanization and that they, particularly with species richness as a parameter, can be used as effective ecological indicators. With the looming development pressure on the sub-montane/montane habitats in Peninsular Malaysia and the Southeast Asian region, urgent conservation actions are needed for the preservation of their biotas.     

Bird community responses to reduced-impact logging in a certified forestry concession in lowland Bolivia

We studied bird community composition and abundance within the logged and unlogged forest areas of a certified forestry concession in lowland Bolivia. The logged forest was harvested using reduced-impact logging techniques between one and four years previously. We used canonical correspondence analysis to describe the relationship between selected environmental variables and bird species abundance data, and the Indicator Value procedure to test for associations between bird species and the logged and unlogged habitats. Approximately one-third of birds were restricted to either the logged or unlogged areas, with 20% of all species only encountered in, or significantly more abundant in, the unlogged areas of the concession. The majority of birds found in significantly higher abundance in the unlogged areas of the concession were associated with forest habitats dominated by large trees, or a high diversity of trees, providing dense canopy cover and deep leaf litter, with an understorey dominated by ferns. Over 40% of bird species that were significantly associated with the unlogged areas of the concession are of conservation concern. In contrast, the majority of birds associated with the logged areas of the concession are known to be relatively resilient to human disturbance. The majority of species which exhibited significant lower abundances in the logged areas of the concession belonged to insectivorous or frugivorous feeding guilds. We discuss whether current management practices within this certified concession are sustainable and how our results can be used to guide future research and inform better practice.     

Effects of anthropogenic land use on forest birds and butterflies in Subic Bay, Philippines

Despite the loss of 83% of native forests in the Philippines, little is known on the effects of this massive habitat loss and degradation on its forest biotas. This is a cause for concern because of the threat posed to the country’s large number of endemic taxa. To investigate the impacts of anthropogenic disturbance, forest birds and butterflies were surveyed in closed and open canopy forests, as well as suburban, rural and urban areas within the Subic Bay Watershed Reserve and Olongapo City in western Luzon. Measures of forest species richness and population densities for both taxa were similar in the two forest types, but showed different patterns in the other habitats. Indirect gradient analysis showed that forest bird species were positively correlated with vegetation variables (i.e., canopy cover, tree density, height to inversion and ground cover), while forest butterflies were not strongly correlated to any of the measured habitat variables. Community composition of birds in forests was distinct from those in modified habitats, while butterfly communities were more similar. A simulation showed that canopy cover of 60% or higher was required by 24 of the 26 bird species that were sensitive to canopy loss. Endemicity and nesting strata were the significant predictors of vulnerability to habitat disturbance for birds, while endemicity and larval hostplant specificity were significant for butterflies. Both taxa were negatively affected by anthropogenic disturbance but may respond to different components in the habitat (i.e., structure and resources), and thus cannot be used as surrogates of each other. Conservation of forests with contiguous canopy cover should be prioritized, and more ecological research is needed to improve the knowledge on the effects of disturbance on Philippine biodiversity.     

Bat activity on riparian zones and upper slopes in Australian timber production forests and the effectiveness of riparian buffers

Unlogged buffers are used to ameliorate impacts to riparian areas in timber production forests. One function of these buffers is to protect the biodiversity of riparian areas. We measured bat activity in buffered streams with ultrasonic detectors across four different stream orders in logged, regrowth and mature forests (60 sites). Bat activity, foraging rates and species richness were similar in buffered streams surrounded by logged, regrowth and mature forests, suggesting that riparian areas effectively provide habitat for foraging and commuting bats in selectively logged forests. Vespadelus pumilus was the only species that responded to logging history, with decreased activity in mature forests. We found higher activity on larger rather than smaller order streams, a pattern also not affected by logging history. Bat activity along paired forest trail flyways on upper slopes (60 sites) was measured simultaneously with riparian flyway activity (for a total of 120 sites) to determine the importance of riparian areas relative to other available flyways. Activity was higher on upper slopes than on small streams, but similar to levels on larger streams. Total foraging activity was similar between riparian zones and upper slopes. Upper slopes contained higher species diversity, with Chalinolobus gouldii, Miniopterus schreibersii, Mormopterus norfolkensis, Scotorepens sp., Vespadelus pumilus and, to a lesser extent, Vespadelus darlingtoni detected more often than along streams. Other species (Rhinolophus megaphyllus, Nyctophilus spp. and Miniopterus australis) were not affected by topography. Estimates of total vegetation cover and, in particular, rainforest cover, were negatively associated with bat activity, highlighting the need for management of forest ‘clutter’ in regrowth forests for a suite of bat species. Streams and forest trails provide areas of lower clutter, which assist in maintaining high species diversity in regrowth forests. Our results support the use of riparian buffers, and point to the need for greater recognition of tracks on upper slopes as important habitat.     

High sensitivity of montane bird communities to habitat disturbance in Peninsular Malaysia

Over the past few decades, the montane forests of Peninsula Malaysia have been severely impacted by the cultivation of exotic crops and urban sprawl. To guide conservation initiatives, montane bird communities were studied to determine their response along a disturbance gradient with the aim of identifying key factors influencing their distribution. Habitat types surveyed included primary and secondary montane forests, a tea plantation, rural, and urban areas in Cameron Highlands and Fraser’s Hill. Response variables included species richness and density quantified via point counts and mistnet surveys. Explanatory variables measured were related to vegetation structure, food abundance and land-use cover. Estimated ‘true’ species richness was higher for pristine and minimally disturbed sites, lower in tea plantation and lowest in heavily developed town centres. Nonmetric multidimensional scaling revealed that both vegetation structure (e.g. canopy density) and land-use cover (e.g. proportion of forest cover) influence species distribution; certain invasive lowland birds were tolerant of extreme development and native montane birds, in general, endured only slight habitat disturbances. A simulation indicated that montane forest dependant species richness started to decline when more than 20% of the canopy cover was lost. Less than a third of the species richness remained when more than 40% of the canopy cover was cleared. The logistic regression model suggested that sensitive species nested lower, were restricted to montane habitats and foraged in mid or high canopy. The dominance of lowland invasives in highly developed urban sites reveals that homogenisation of bird communities can occur even at higher altitudes (>1400 m a.s.l.). The results indicated that native montane birds communities are sensitive to habitat loss and degradation. Thus, any development in the highlands must proceed with minimal disturbance to montane forests, of which, keeping the canopy cover intact should be a crucial consideration.     

The responses of understorey birds to forest fragmentation, logging and wildfires: An Amazonian synthesis

We combine mist-net data from 24 disturbance treatments taken from seven studies on the responses of understorey Amazonian birds to selective logging, single and recurrent wildfires, and habitat fragmentation. The different disturbance treatments had distinct effects on avian guild structure, and fire disturbance and the isolation of forest patches resulted in bird communities that were most divergent from those in continuous, undisturbed forest in terms of their species composition. Although low-intensity logging treatments had the least noticeable effects, the composition of understorey birds was still markedly different from the composition in undisturbed forest. This analysis demonstrates the importance of preventing habitat fragmentation and the spread of fires in humid tropical forests, and highlights the need for more research to determine the long-term suitability of large areas of degraded forest for forest birds.     

Home range, movement and activity patterns, and bedding sites of Malayan sun bears Helarctos malayanus in the Rainforest of Borneo

Six Malayan sun bears were captured and radio-collared from June 1999 to December 2001 in Ulu Segama Forest Reserve, Sabah, Malaysia Borneo to study home-range characteristics, movement patterns, activity patterns, population density, and bedding sites. A total of 343 locations were recorded. Home range sizes, calculated by the 95% adaptive kernel method, averaged 14.8 ± 6.1 (SD) km². Bears were found in both primary and logged forests. Daily movement distances from these bears averaged 1.45 ± 0.24 (SD) km, and were affected by food availability, especially availability of figs. Male Malayan sun bears were primarily diurnal, but a few individuals were active at night for short periods. The majority of the 26 bedding sites consisted of fallen hollow logs. Other bedding sites included standing trees with cavities, cavities underneath fallen logs or tree roots, and tree branches high above the ground. Malayan sun bears exist in primary and logged forests. Well-designed logging practices, maintenance of large trees with cavities, protection of fig trees, and strict control of poaching should be incorporated into forest management practices in logged forests.     

Diversity and abundance of selected animal species in undisturbed forest,selectively logged forest and plantations in East Kalimantan,Indonesia

Animal surveys were conducted in six habitat types within the timber concession of PT International Timber Corporation Indonesia, East Kalimantan. Species diversity was found to be similar in undisturbed forest and in 3- to 5-year-old selectively logged forest, although densities in the latter were considerably less. Both diversity and density declined drastically in forestry plantations, but certain of the species remaining caused significant damage to young trees. Although few animals were observed in areas where there was active road construction and timber felling, their densities in adjacent undisturbed forest areas did not increase, suggesting that the level of local migration actually is low. It is suggested that recolonisation of old logged forest can occur successfully provide that the level of hunting is low and that adjacent areas of undisturbed forest remain to provide a population pool from which colonists can spread.     

Rethinking the ‘back to wilderness’ concept for Sundaland’s forests

Traditional biodiversity conservation approaches emphasize the protection of pristine forests. However, it has become increasingly difficult to secure large tracts of undisturbed forests, particularly in the developing tropics. This has led some conservation scientists and organizations to explore the conservation potential of human-modified habitats, such as selectively logged forests. On the other hand, other scientists have highlighted the perils of overselling the conservation value of degraded habitats and advocate for re-focusing of efforts and resources on protecting primary forests. While there are merits to both contentions, we argue that the “back to wilderness” paradigm has limited relevance in the Sundaland region. This is because: (1) primary forest only makes up a small minority of the remaining forest in the region and most of it is already protected by law; (2) vast areas of selectively logged forest are still susceptible to plantation conversion; and (3) selectively logged forest are important habitats for some of the world’s most endangered species. To meet both conservation and development goals, we suggest that tracts of selectively logged forest be assessed for their ecological value and forests of high conservation value be prioritized for better protection through their inclusion into existing protected area networks and/or improved sustainable forestry management.     

Impacts of selective logging on canopy and ground assemblages of tropical forest butterflies: Implications for sampling

Commercial selective logging is a major cause of habitat disturbance in Southeast Asian rainforests, yet despite much research there is little consensus on impacts of disturbance on biodiversity. There is also little consensus on the most appropriate methods for sampling tropical species, making it difficult to draw general conclusions from published studies. For example, many studies have used butterflies to assess impacts of selective logging but sampling has usually been conducted at ground level and the canopy fauna has often been ignored. In this study, we investigate the importance of sampling in the canopy by using fruit-baited traps to investigate impacts of selective logging on Nymphalid butterflies in primary forest and forest selectively logged 15 years previously in Sabah (Malaysian Borneo). Analysing combined data from canopy (≈25 m above ground level) and ground-level traps showed significantly lower diversity in selectively logged forest. However, this difference was not observed when data from only ground traps were analysed. Primary forest supported a butterfly assemblage comprising species with more restricted geographical ranges, and thus higher conservation value, compared with selectively logged forest. This result was observed regardless of whether or not canopy data were included in this analysis. We conclude that sampling in the canopy is critical when producing species inventories, but of little importance when determining the impacts of selective logging on restricted-range species.     

Effects of forestry practices on vegetation structure and bird community of Kibale National Park, Uganda

I examined the lingering effects of past timber management practices on the vegetation structure and bird community of Kibale National Park, Uganda. I compared four forest treatments: unlogged native forest (UL), two that were selectively logged at low (LL) and high (HL) intensities in the 1960s, and a conifer plantation (PL). Forest-dependent birds were best represented at UL. LL was similar to UL in both vegetation structure and bird community composition, although some forest-dependent bird species were missing from the former. HL had significantly less canopy closure and lower tree density than other plots as a result of the combination of extensive secondary damage and natural disturbance patterns that prevented the reclosure of the forest canopy. Thirty-one percent of the forest-dependent bird species observed during the study were not detected at HL. At PL, bird species richness and bird abundance were about a third of those observed in other plots. There were significant correlations between heterogeneity of tree distribution (horizontal heterogeneity) and abundance and species richness of birds across plots. Abundance and species richness of all, forest-dependent, and forest generalist birds were highest in plots with intermediate measures of horizontal heterogeneity, which were mostly unlogged or lightly logged. If reduced-impact logging practices are not implemented during selective logging operations in tropical forests, consequent long-term changes in vegetation structure may result in significant declines in the populations of some forest-dependent species, as was observed in Kibale National Park.     

Global population decline of the Great Slaty Woodpecker (Mulleripicus pulverulentus)

The Great Slaty Woodpecker (Mulleripicus pulverulentus) of South and Southeast Asia, the third largest woodpecker species in the world, is currently in the IUCN Red List category of Least Concern. This woodpecker appears associated with old-growth forests, and the rapid reductions in forest cover and old-growth area in Southeast Asia urged examination of its global population trends. We assessed population densities, tree diameter use by the woodpecker, and logging disturbance at 21 transects in four regions across the range of the species: west Borneo, Lingga Island (Riau Archipelago, Indonesia), Tenasserim (Myanmar), and west-central Myanmar. Transect survey effort was 937 km. We assessed rates of deforestation and loss of old-growth forest in the range of the species from expert review reports. By combining population density and forest cover data sets we calculated the global population trend of the species. We found a preference for large diameter trees by foraging and nesting Great Slaty Woodpeckers, and a reduction of the frequency of such trees in logged forests. Across the four study regions, between old-growth forests and logged forests, densities of Great Slaty Woodpeckers were reduced by 80-94%. Although Great Slaty Woodpeckers occur in 15 countries, ca. 70% of the global population occurs in just four countries (Myanmar, Indonesia, Cambodia, and Malaysia), three of which have high annual rates of deforestation and loss of old-growth forest. Our population calculations show that over the past century at least 90% of the global population of the Great Slaty Woodpecker has been lost. At present 26,000-550,000 individuals remain. The current global decline rate of ca. 59% ± SD 17% in three generations justifies IUCN Vulnerable or Endangered status. Contributing factors to the steep decline rate of the species are a long generation time of 5.9-8.2 years and an association with old-growth, lower elevation forests. The Great Slaty Woodpecker case adds an Asian example to a global pattern of specialized woodpeckers that are associated with old or natural forests.     

Forest fragmentation and the distribution, abundance and conservation of the Tana river red colobus (Procolobus rufomitratus)

Evidence suggests that habitat heterogeneity, disturbance, disease, predation and food resources influence primate population abundance. However, few studies have focused on what habitat factors determine the probability that a primate species will occur in a habitat fragment. We analysed forest habitat and colobus population attributes to determine factors that influenced occurrence and abundance of the critically endangered Tana River red colobus. The probability of colobus inhabiting forests was positively related to the relative amount of habitat edge and canopy tree species composition. Most of the variance in the density of colobus monkeys was explained by basal area of food trees (per ha), basal area per food tree, density of food trees, and basal area per tree for all trees. We conclude that effective conservation of primates in fragmented habitats may require strategies that consider factors that influence both the occurrence of a species and its relative abundance.