The Scale of Community Structure: Habitat Variation and Avian Guilds in Tropical Forest Understory

Abstract

The scale of community structure: habitat variation and avian guilds in tropical forest understory The scale of community structure: habitat variation and avian guilds in tropical forest understory AbstractBoth local and regional habitat characteristics influence species richness and community structure. The scale at which communities are studied, however, affects the detection of relationships between habitat characteristics and patterns of habitat selection, species diversity, and species composition, and may obscure observation of differences in how species perceive the scale of environmental variation. To determine how environmental variation at different scales is related to species occurrence and richness, I analyze mist net sampling data on several guilds of forest understory birds. Bird capture, vegetation, and physical environment data come from 23 0.5-ha study sites in primary and secondary forest in Amazonian Ecuador. The percentages of primary forest within concentric circles around each site form forest imbeddedness measures (FIMs), which are evaluated using satellite imagery. Variation in FIM size represents different measurement scales for determining forest cover. Primary forest cover is also analyzed in successively larger tori surrounding sites and is used, after variable reduction with Principal Components Analysis, to summarize variation in forest cover around sites. Linear regression, surface trend analysis, and ordination help to quantify how variation in guild composition and species richness is explained by forest cover, vegetation structure, and physical environment. Species composition is related to variation in primary forest cover, primarily within 200-600 m of study sites. Canonical Correspondence Analysis (CCA) indicates that nectarivores, shrub-layer frugivores, and ant-following birds are captured in areas with relatively low primary forest cover. In contrast, shrub-layer insectivores, shrub-layer omnivores, and birds probing dead foliage for large insects tend to be captured in areas of relatively high primary forest cover. The species richness of insect gleaners, ant followers, and omnivores is statistically related to the percent cover of primary forest within hundreds of meters from the study sites. This suggests that some mechanisms that influence guild composition act over substantial distances. Nonetheless, the small radii of FIMs related to the species richness of dead-leaf probers suggests that local conditions and variation in forest cover over short (<200 m) distances directly or indirectly influence species richness of some primary forest birds. The significant relationship between temperature variation among capture sites and species richness of ant-following birds suggests that these species choose among habitats in a temperature range at which physiological constraints operate, either directly on the birds themselves or on the ants they follow. Species richness within the nectarivores, in contrast, shows no relationship with large-scale variation in primary forest c...

A spatial scale assessment of habitat effects on arthropod communities of an oceanic island

“…The spatial scale dependence of species richness or abundance can be analysed using a multiple scale approach (Pearman, 2002). In arthropods (see Chust et al, 2004;Holland et al, 2004;Clough et al, 2005;Gaucherel et al, 2007;Gonzá lez-Mejias et al, 2007;Hendrickx et al, 2007;Driscoll, 2008), such analysis can help to identify the spatial scales at which a predictor variable influences species richness and abundance of local communities.…”

Bird Pollinator Visitation is Equivalent in Island and Plantation Planting Designs in Tropical Forest Restoration Sites

“…These results may be explained by the fact that most of the pollinator visits were by hummingbirds which often travel widely in search of food. Previous work indicates that hummingbirds as a group show few abundance or species richness effects to landscape characteristics [23][24][25] although individual species may vary in their responses to land cover patterns [26]. Neotropical migratory birds also follow food supplies in some cases [34,35] and the migrants who visited I. edulis are found in a variety of land cover types in Costa Rica [32].…”

“…Several studies have shown that tropical hummingbirds (who we assumed would be the most common pollinators) are less affected by landscape characteristics than other groups such as understory insectivores [23][24][25]. Amazonian forest hummingbird abundance did not change after forest fragmentation [23].…”

Review article: Thirty years of analysing and modelling avian habitat relationships using satellite imagery data: a review

“…While more than half of the studies were based on Landsat Thematic Mapper (TM) images, Landsat Multi-Spectral Scanner (MSS) scenes were used in 11 studies, sometimes along with Landsat TM scenes. Analyses of the higher spatial resolution French SPOT satellite were performed nine times (Miller and Conroy 1990, Andries et al 1994, Green and Griffiths 1994, Guinet et al 1995, Thibault et al 1998, Debinski et al 2000, 2002, Klaus et al 2001, Saveraid et al 2001) and the newer Indian Remote Sensing (IRS) two times (Debinski et al 2002, Kastdalen et al 2003. The Advanced Very High Resolution Radiometer (AVHRR) from the National Oceanic and Atmospheric Administration (NOAA) was applied in 22 studies; six times it was used together with other satellite sensors.…”