Sérgio Henrique Borges 1* André Carvalhaes 2 Luiza Magali Henriques 3

1 Fundação Vitória Amazônica, Manaus, Amazonas; 2 Universidade Estadual Paulista - Campus de Botucatu, Botucatu, São Paulo; 3 Museu Paraense Emílio Goeldi, Belém - Pará



To investigate the influence of local topography on the understory bird community in the "terra firme" forest of the Central Amazon (Jaú National Park), we captured birds with mist nets at different topographic sites: upland and near stream sites. In 1680 net hours we captured 461 individuals of 64 species at seven study sites. More species and individuals were captured in the uplands, but the difference was not significant. Polar ordination showed that the two topographic levels were quite distinct in terms of bird species composition. Some species seemed to show habitat preference related to local topography, but the number of captures was too small for statistical analyses. The only exception was the species pair Hylophylax poecilinota and H. naevia. The antbird H. poecilinota was captured more often in upland (n= 20 captures) than near stream sites (n= 3 captures) and the congeneric H. naevia was more captured near stream sites (n= 22 captures) than in upland (n= 6 captures). Even with small samples and short duration this study suggests that local topography can affect the understory bird distribution in "terra firme" forest.

Key words: Amazon birds, topography, vegetation structure, Hylophylax naevia, Hylophylax poecilinota.



Previous studies in tropical areas have demonstrated the importance of local topography for habitat use by birds, both for individual species (4) as well as for the entire community (2). At the local level, topography can affect the organisms distribution by influencing the understory microclimate, resource availability and soil type (2,10).

Here we present the results of a short-term study on the influence of local topography in the understory bird community in a Central Amazonian site. Specifically we asked the following questions: Does the number of species and individuals captured in mist nets differ between sites located in upland and near stream habitats? Is the species composition affected by local topography? Which species show association with a particular topographic level?





Study sites

We selected seven independent sites to sample birds distributed in two regions of "terra firme" forest separated by more than 100km in Jaú National Park: three sites near Miratucu Lake (61o 49’ W and 1o 57’ S) and and four in the Tambor (62o 26’ W and 2o 14’ S), a small village at middle Jaú river. Jaú National Park (JNP) includes an area of 2,272,000ha and is one of the largest tropical forest reserves in the world. The major habitats in JNP include unflooded "terra firme" forest and forest inundated by black water rivers (igapó forest). The rainfall in the region is seasonal with the dry season extending from June to December and the wet season from February to June. The water level in rivers and streams in JNP also varies seasonally with low waters occurring from September to January and flooded periods from March to August. The field work was conducted in March, April and June of 1995.

Two habitat types were sampled at each study site: plateau (PS) and near stream (NS). The plant species composition differs between these topographic levels (Leandro V. Ferreira, pers. comm.). Some palm species (especially Jessenia pataua) and thickets as Heliconia spp. were more common in near stream sites. In some places the streams were dry during the sampling period.

Field procedures

We sampled birds with mist nets (12x2m and 36mm mesh) with one net-line of 10 nets in each habitat type. The two habitat types were sampled simultaneously. The sampling effort was identical in these two topographic levels. The PS and NS sites were separated by distances varying between 30 and 50 meters. The net-lines were open between 6:00 AM and 12:00. Each site was sampled on two consecutive days; all birds captured were banded.

For the description of the vegetation structure of study sites, four measurements of canopy cover were taken on each side of every net using a spherical densiometer.

Data analysis

Because the number of captures differed between habitats we compared species richness between PS and NS sites by a rarefaction method. Rarefaction generates an expected number of species in a sample with standard size using the following formula (3):

E(Sn)= å { 1- [ (N-Ni/ n) / (N/n)] }


E(Sn) = The number of species expected in a standardized sample

n = The standard size of the sample

N = The total number of individuals in the sample



Ni = The number of individuals of each species i in the sample.

Bray Curtis polar ordination based on Sorensen’s similarity coefficient as distance measure was undertaken to compare species assemblages between the study sites. As there are larger numbers of zeros in the matrix species by sites we transformed the original data using a Beals Smoothing that reduces the noise in the data matrix (5). Species captured only once were not considered in the ordination. Detailed descriptions of this ordination method can be found in (3, 5). As a method of capture, nets present problems including biological and environmental variables that can affect the data interpretation (1, 8). In order to minimize these problems, we performed an ordination eliminating from the samples the species highly mobile (hummingbirds, ant-followers and manakins) which tend to have their abundance overestimated by mist nets, and the species that tend to forage above the nets (Appendix). This procedure has as a consequence a substantial reduction of the sample size: 36% of species and 43% of the captures were not considered.


In 1680 net hours we captured 461 birds representing 64 species (Appendix). The cumulative curve of species by captures showed that new species can be added to local lists with increased sampling effort (Figure 1). However, field observations in the study sites both by sight and song detection indicated that the nuclear species (sensu 7) of the understory bird community were sampled.

Figure 1 - Cumulative curve of species by captures in near stream sites (NS) and plateau sites (PS).


Measurements of canopy cover as an index of vegetation structure show that NS sites are more open (mean = 15% of openness ± 6,52) than PS sites (mean = 11,6 % ± 4,11) (Mann Whitney U-test, p < 0,05).


More species and individuals were captured in PS than in NS sites (Table I), but the difference was not significant (Mann Whitney U- test, p > 0,05). Similarly, using a standard sample of 180 captures more species were captured in PS sites, but the difference was very small (Table I).

Table 1 - Sumary of the species richness and abundance of birds in two topographic levels. PS are plateau sites and NS are near stream sites.

* Number of species expected by a standard sample of 180 captures.

Appendix - Numbers of captures in NS and PS sites in Jaú National Park. Asterisks indicate species not considered in ordination analyses (see Methods).

* Not included in analyses because spacing system highly mobile (see Remsen 1996)

** Not included because foraging above net level.

Some bird species apparently showed preference for habitats related to local topography (Table II). Unfortunately, the number of captures was too small to confirmed the statistical accuracy of these tendencies. The only exception was the species pair Hylophylax poecilinota and H. naevia with good sample size. H. naevia was significantly more captured in NS than in PS sites (Mann Whitney U-test, p < 0,05). On the other hand, H. poecilinota was more abundant in PS sites (Mann Whitney U-test, p < 0,05).

Table 2 - Numbers of captures of some bird species with some tendency in habitat preference. PS are plateau sites and NS are near stream sites


The ordination results show that the two topographic levels are quite distinct in species composition (Figure 2a,b). When all species are analysed (Fig 2a) the bird communities are clearly separated in two groups. Similar results were obtained when some selected species were eliminated from the samples (see methods) (Figure 2b). The ordinations suggested that net-lines placed in PS and NS sites captured different "sub-groups" of understory birds.

Figure 2 - Ordinations of the net-lines in near stream (NS) and plateau sites (PS) including all species (a) and excluding high mobiles species and those that foraging above nets (b). In parenthesis are percents of variation in the original matrix explained by each axis.



During this study no consistent effect of local topography in the abundance and species richness of understory birds was found. However, our results indicated that two topographic levels contain distinct understory bird communities. Habitat selection associated with local topography also has been reported in plants (Melastomataceae and Ferns - 10 and Palms - 6), frogs (9) and Basileuterus warblers (4).

What environmental features related to topography are important to understory birds? Classically the vegetation structure is considered an important factor in determining the habitat use by birds. Additionally, it suggested that microclimate gradients of humidity, clearly related to topography, can influenced habitat selection directly through the impact on bird physiology or indirectly in food resources availability (2). In fact, activity patterns of birds are correlated with microclimate gradients (2). We did not measure microclimate parameters or food resources available for birds, but the vegetation structure measured by canopy openness is different between the two habitats sampled. This differences probably results from the greater incidence of treefall gaps in NS sites. The antbird H. naevia, one of the species with more tendency to selected habitats in NS sites, was frequently observed in gaps. On the other hand, H. poecilinota follow army ants (11 and pers. obs.) and apparently avoid NS sites. These results suggest that vegetation structure associated with local topography can be an important factor in habitat selection for understory birds.


We thank Lindomar Alves Moreira for help in field work with nets and Claude Gascon, Susan Laurence and José Gomes for critical comments and help in the English version. Field work was supported by WWF (World Wildlife Fund), PNMA ( Plano Nacional do Meio Ambiente), CAPES and CNPq (though the grant to the senior author). This publication represents nº 3 of the Jaú Project technical series.



Topografia local e a distribuição de aves de sub-bosque num sítio da Amazônia Central, Brazil. Para verificar a influência da topografia local na comunidade de aves de sub-bosque numa mata de terra firme da Amazônia Central (Parque Nacional do Jaú) foram capturadas aves usando-se redes em dois níveis topográficos: platôs e baixios (locais próximos a igarapés). Após 1.680 horas/rede foram capturados 461 indivíduos de 64 espécies de aves em sete sítios de estudo. Mais espécies e indivíduos foram capturados nos platôs, mas a diferença não foi significativa. Uma análise ao nível de comunidade utilizando-se ordenação polar parece demonstrar que os dois níveis topográficos são distintos em termos de composição de espécies. Algumas espécies parecem demonstrar preferência de habitats relacionada à topografia local, mas o número de capturas destas espécies é muito pequeno para análises estatísticas. A única exceção é o par de espécies Hylophylax poecilinota e H. naevia. O formicarídeo H. poecilinota foi mais capturado em platôs (n= 20 capturas) do que em baixios (n = 3 capturas), enquanto H. naevia foi mais capturado em baixios (n= 22 capturas ) do que em platôs (n= 6 capturas). Mesmo com amostras pequenas e sendo de curta duração, este estudo sugere que a topografia local pode influenciar a distribuição de aves de sub-bosque em matas de terra firme.


Palavras-chave: aves amazônicas, topografia, estrutura da vegetação, Hylophylax naevia, Hylophylax poecilinota




Karr, J. Surveying birds with mist nets. Studies in Avian Biology 6: 62-67, 1981.

_____; Freemark, K. Habitat selection and environmental gradients: dynamics in the "stable" tropics. Ecology 64 (6): 1481-1494, 1983.

Ludwig, J.A. and Reynolds, J.F. Statistical ecology - a primer on the methods and computing. Wiley Interscience publication,1988, 337 pp.

Marini, M. A.; Cavalcanti, R.B. Habitat and foraging substrate use of three Basileuterus warblers from Central Brazil. Ornitologia Neotropical 4: 69-76, 1993.

McCune, B; Mefford, M.J. PC-ORD. Multivariate analysis of ecological data. Version 2.0. MjM Software Design, Gleneden Beach, Oregon, USA, 1995, 126 pp.

Peres, C. Composition, density, and fruiting phenology of arborescent palms in an Amazonian terra firme forest. Biotropica 26 (3): 285-294, 1994.

Remsen, J.V. Jr. Use and misuse of bird lists in community ecology and conservation. Auk 111(1): 225-227, 1994.

_____________ Misuse of data from mist-net captures to assess relative abundance in bird populations. Auk 113 (2): 381-398, 1996.


Toft, C.A. Seasonal variation in populations of Panamanian litter frogs and their prey: a comparison of wetter and drier sites. Oecologia 47:34-38, 1980.

Tuomisto, H., Ruokolainen, K., Kalliola, R. Linna, A., Danjoy, W.; Rodriques, Z.. Dissecting Amazonian biodiversity. Science 269: 63-66, 1995.

Willis, E.O. The behavior of Scale-backed Antbirds. Wilson Bull. 94(4): 447-462, 1982.