Effect of a major highway on the spatial and temporal variation in the structure and diversity of the avifauna of a tropical premontane rain forest

Abstract

Roads immersed in conservation areas will increase in number, size, and traffic over the next decade, and thus, understanding their effects on forest-dependent wildlife is crucial for improving current management practices and reducing the negative impacts of roads on sensitive species. We examined the influence of route 32 (a.k.a. Guápiles Highway) on temporal and spatial changes in the structure of the avifauna of Braulio Carrillo National Park, Costa Rica, a site crossed by this road along 25 km. The highway connects the capital city of San José with the Harbor of Limón in the Caribbean Sea (142 km). Although the road is narrow (12 m in width and comprised by two lanes along most of the route) it services over 1.5 million motor vehicles per year, 12 % are heavy trucks and trailers. We expected the highway to divide the avifauna, and thus to observe significant differences in species structure on opposite sides of the road. We described changes in bird diversity between wet and dry seasons at Las Palmas and Ceibo trails located on opposite sides of the highway (14 point counts per trail), and evaluated how abundance and diversity varied with road distance. Censuses took place during wet and dry seasons from 2002 to 2005. We listed 245 species and 6 035 observations during the 4-yr survey. Rare species dominated the avifauna (65 % of species < 5 observations), and species overlap between trails was high (Sorensen= 71 %; Morisita= 0.96). Species accumulation curves varied little among trails, yielding 190 species. Resident species represented 70 % of observations, followed by elevational (15 %) and long-distance migrants (1-2 %). Understory species were the most abundant (60 %) followed by canopy birds (30 %). Species turnover rate was 55 % between seasons, but species composition between trails remained homogeneous. Overall, birds were avoiding the road (abundance increased away from the road) although other diversity parameters (richness, dominance, Shannon index, and equitability) were not influenced by road proximity. Although the avifauna remained homogeneous on both sides of the road, which did not support the fragmentation hypothesis, the highway reduced the abundance and diversity of specialized understory insectivores associated with primary forests near the road. This highway will expand outside the National Park (from 2 to 4 lanes along 107 km from Río Frío to Limón) in the next years, which will increase traffic volume and road impacts within the Park. Roads are increasing across highly diverse tropical areas justifying the need for management practices based on the identification of sensitive groups. Rev. Biol. Trop. 64 (4): 1383-1399. Epub 2016 December 01.

Interactive effects of elevation and newly paved road on avian community composition in a scientific reserve, Bioko Island, Equatorial Guinea

“…Species accumulation curves exhibited similar trends between road and interior forest transects at 300 and 1200 m elevations; however, slightly higher richness values were observed for each transect type at 1200 m. Overall, differences in species richness between road and interior transects were minimal for each elevation. These findings are consistent with a recent study showing little variation in species accumulation curves regardless of road proximity among bird populations in Costa Rica (Avalos & Bermúdez, 2016). Lastly, higher species richness was observed along the road edge at the mid elevation site (800 m).…”

“…Understory insectivores (mixed‐flock followers, ant‐followers, and insectivores) exhibited higher proportional capture rates among interior transects as compared to road edge transects at 300 m. Specialist bird species are particularly susceptible to habitat alteration (Habel et al, 2019) and more specifically, insectivorous birds can be highly sensitive to anthropogenic disturbance exemplified by severe declines among this guild within logged versus unlogged forest in Ghana (Arcilla et al, 2015). Similar results were found among understory insectivores in Costa Rica and Thailand, where negative correlations were observed between overall abundance and road proximity (Avalos & Bermúdez, 2016; Khamcha et al, 2018). This observation may be attributed to a lack of road‐crossing behavior seen among these guilds.…”

“…Elevation was the most significant factor governing community composition based on NMDS plots in the present study area, as indicated by clustering of communities at 300, 800, and 1200 m irrespective of transect type or sampling season. Similar associations have previously been found between bird species distributions and elevation (Blake & Loiselle, 2000;Young et al, 1998), however, one must exercise caution when interpreting these results as a multitude of variables are likely responsible for species distributions across elevations (Avalos & Bermúdez, 2016;Lomolino, 2001;Rahbek & Graves, 2001). Indeed, elevation is often closely linked with other explanatory variables (e.g., temperature, precipitation, vegetation) influencing species range limits, particularly in tropical montane regions where niche partitioning is common (Lundberg & Moberg, 2003;McCain, 2009;Young et al, 1998).…”

“…In the Neotropics, negative consequences related to road disturbances are, especially pronounced among terrestrial insectivores (birds that walk on the forest floor), and birds associated with insectivorous mixed‐species flocks (Mokross et al, 2014; Powell et al, 2015); conversely, species with diverse dietary preferences are often capable of persisting in degraded forests and forest edges (Wolfe et al, 2015). Understory birds are negatively impacted by habitat fragmentation caused by road construction, which may act as a barrier to flock movement (Avalos & Bermúdez, 2016; Develey & Stouffer, 2001). Although birds are capable of long‐distance movement based on the ability of flight, experimental evidence suggests that many rainforest birds are incapable of traveling >100 m in a single flight (Moore et al, 2008), and even common rainforest species can become genetically isolated by disturbance over relatively short distances (Woltmann et al, 2012).…”

Impact of longevity and wettability of fern leaves on epiphyll colonization in a Mexican lowland rainforest

“…In two other studies from Costa Rica, rough, horizontally placed plastics were covered already by liverworts within nine months to 11.5% (Monge‐Nájera & Blanco, 1995) and were colonized within 12 months by 32 lichen species (Lücking & Bernecker‐Lücking, 2002), respectively. Both locations have an annual rainfall (4000–4500 mm) slightly less than at our study site (5000 mm), but lack a pronounced dry season (Monge‐Nájera & Blanco, 1995; Enríquez & Rangel‐Salazar, 2001; Avalos & Bermúdez, 2016), which should clearly favor epiphyll colonization in those studies. Although patterns in epiphyll diversity have been similar between artificial and natural leaves in other studies (Lücking & Bernecker‐Lücking, 2002), our artificial substrates were less colonized than the fern leaves, mainly because we installed them more flexibly and at a less favorable angle for epiphyll colonization and perhaps because of their smoother surface.…”