Bird Survey Methodologies and Analysis: A Case Study of Pulau Breuh

 

Observing birds on  Breuh Island.

* Heri Tarmizi, Yuri Gagarin, Samsul Muarif, Ahmad Muhjir, Pijar Habibi.

A total of 34 bird species from 19 families were recorded during the surveys on Pulau Breuh. The highest species richness was observed in the forest habitats, followed by the coastal and semi-montane regions. 

Introduction

Bird surveys are crucial for understanding avian diversity, population dynamics, and conservation needs. In this essay, we explore the methodologies for conducting bird surveys, with a focus on Pulau Breuh.

Pulau Breuh, nestled within Aceh Besar, Indonesia, boasts a varied landscape encompassing both lowland and highland environments. The island's lowland areas lie near sea level, featuring gently sloping terrains that support rich coastal ecosystems. These habitats are vital for numerous bird species adapted to coastal environments, showcasing diverse avian communities influenced by proximity to the sea.

In contrast, Pulau Breuh's highland areas ascend to semi-montane elevations, reaching approximately 600 meters above sea level. Here, the terrain becomes more rugged, characterized by hills and mountains that create distinct microclimates and vegetation zones. These semi-montane regions serve as a transitional zone between lowland and full montane habitats, offering unique habitats for various bird species adapted to higher elevations.

The geographic location of Pulau Breuh, situated off the coast of Aceh Besar, further enhances its ecological significance. This positioning not only influences the island's diverse topography but also plays a crucial role in shaping the distribution patterns and foraging behaviors of its avian inhabitants. Understanding these geographical nuances is essential for assessing bird species diversity and conservation needs across Pulau Breuh's distinct landscapes.

Methodologies for Bird Surveys

1. Point Count Surveys

Point count surveys are a widely used method for estimating bird populations. Observers stand at fixed points and record all birds seen or heard within a specific radius over a set period. This method is effective for surveying a wide range of habitats and can be adapted to various environmental conditions (Bibby et al., 2000).

2. Transect Surveys

Transect surveys involve walking along a fixed path and recording all birds encountered along the way. This method is particularly useful for covering large areas and varying habitats. Observers typically record the distance from the transect line to the bird, which helps in estimating bird density (Gregory et al., 2004).

3. Mist Netting

Mist netting is a technique used to capture birds for detailed study. Fine nets are set up in areas where birds are likely to fly through, and captured birds are carefully extracted, identified, measured, and then released. This method provides valuable data on bird morphology, age, and health (Proctor & Lynch, 1993).

4. Playback Surveys

Playback surveys involve playing recorded bird calls to elicit responses from birds in the area. This method is particularly useful for detecting elusive or cryptic species that might not be easily observed otherwise (Sutherland et al., 2004).

 5. Nest Monitoring

Nest monitoring involves locating and regularly checking bird nests to gather data on breeding success, clutch size, and nest predation. This method provides insights into the reproductive biology and success rates of bird species (Newton, 1979).

Methodology for Pulau Breuh Survey

To assess the bird diversity on Pulau Breuh, we employed a combination of point count and transect surveys. The island's varied habitats, including coastal areas, forests, and semi-montane regions, were systematically surveyed to capture a comprehensive picture of the avian population.

Point Count Surveys

We established 20-point count locations across different habitats on Pulau Breuh. Each location was surveyed for 10 minutes, during which all birds seen or heard within a 50-meter radius were recorded. Surveys were conducted during peak bird activity times, early morning and late afternoon (Bibby et al., 2000).

Transect Surveys

Four 1-kilometer transects were established in different habitats, including coastal, forest, and semi-montane regions. Observers walked each transect at a slow, steady pace, recording all birds observed within 25 meters on either side of the transect line. Transects were surveyed twice, once in the morning and once in the afternoon, to account for diurnal variations in bird activity (Gregory et al., 2004).

Results

A total of 34 bird species from 19 families were recorded during the surveys on Pulau Breuh. The highest species richness was observed in the forest habitats, followed by the coastal and semi-montane regions. Notable species included the Pied Hornbill (Anthracoceros albirostris), Bronze Drongo (Dicrurus aeneus), Ruby-throated Bulbul (Pycnonotus dispar), Thick-billed Green Pigeon (Treron curvirostra), Black-naped Oriole (Oriolus chinensis), Greater Racket-tailed Drongo (Dicrurus paradiseus), Pale Blue Flycatcher (Cyornis unicolor), White-bellied Sea Eagle (Haliaeetus leucogaster), Changeable Hawk-Eagle (Nisaetus cirrhatus), Shikra (Accipiter badius), Crested Serpent Eagle (Spilornis cheela), and Japanese Sparrowhawk (Accipiter gularis).

Species Richness and Abundance

- Forest Habitats: 13 species

- Coastal Areas: 11 species

- Semi-Montane Regions: 10 species

Shannon Diversity Index

The Shannon diversity index (H') was calculated to assess species diversity in each habitat. The index values were:

- Forest Habitats: H' = 2.53

- Coastal Areas: H' = 2.32

- Semi-Montane Regions: H' = 2.10

These values indicate a higher diversity of bird species in the forest habitats compared to coastal and semi-montane areas.

Analysis

The results suggest that forest habitats on Pulau Breuh support a higher diversity of bird species compared to coastal and semi-montane regions. This could be attributed to the varied microhabitats and abundant food resources available in these areas. The presence of unique and endemic species highlights the ecological importance of these forest habitats.

Theories on Montane and Lowland Bird Diversity and Foraging Behavior

Bird Diversity in Montane vs. Lowland Regions

Montane and lowland regions offer distinct environments that influence bird species composition and diversity.

Montane Regions

1. Habitat Heterogeneity: Montane regions often have diverse microhabitats due to variations in altitude, slope, and vegetation. This habitat heterogeneity can support a higher diversity of bird species by providing multiple niches (Rahbek, 1997).

2. Climate: The cooler, more stable climate of montane regions can reduce the competition and predation pressures found in lower, more variable environments, thus supporting a different set of bird species (McCain, 2009).

3. Endemism: Montane regions frequently act as refuges for endemic species that have adapted to specific conditions and are not found in lowland areas. This isolation can lead to higher endemism and unique biodiversity (Price et al., 2014).

Lowland Regions

1. Resource Abundance: Lowland regions typically have more abundant and diverse food resources due to higher primary productivity. This can support larger populations and a higher number of species (Terborgh, 1977).

2. Habitat Complexity: Dense vegetation in lowland forests provides a complex structure that supports a variety of foraging strategies and nesting sites, promoting species richness (MacArthur & MacArthur, 1961).

3. Seasonal Variation: Lowland regions often experience greater seasonal variations, which can influence bird migration patterns and seasonal diversity (Karr, 1976).

Foraging Behavior in Montane vs. Lowland Birds

Foraging behavior is shaped by the availability of food resources and habitat structure.

Montane Birds

1. Specialized Diets: Montane birds often have specialized diets adapted to the specific resources available in higher elevations. This can include insects, fruits, or seeds unique to montane flora (Remsen, 1994).

2. Vertical Stratification: Birds in montane regions may exhibit vertical stratification in foraging, utilizing different vegetation layers to reduce competition (Terborgh & Weske, 1975).

3. Energy Conservation: Due to cooler temperatures, montane birds may adopt foraging strategies that minimize energy expenditure, such as perch-and-wait tactics or foraging in sheltered areas (Walsberg, 1983).

Lowland Birds

1. Generalist Diets: Many lowland birds are generalists, capable of exploiting a wide range of food resources. This dietary flexibility can be advantageous in dynamic lowland environments (Greenberg, 1981).

2. High Activity Levels: The warmer climate and abundant food resources in lowland regions can support high activity levels and more frequent foraging bouts (Pearson, 1971).

3. Diverse Foraging Techniques: Lowland birds often display a variety of foraging techniques, including gleaning, probing, and sallying, to exploit different food types and reduce interspecific competition (Morrison, 1984).

Conservation Implications

Understanding the differences in bird diversity and foraging behavior between montane and lowland regions is crucial for conservation planning.

1. Habitat Protection: Protecting diverse habitats in both montane and lowland regions is essential to preserve the full spectrum of bird diversity. This includes maintaining connectivity between habitats to support migratory species (BirdLife International, 2024).

2. Climate Change Adaptation: Climate change poses a significant threat to montane species adapted to specific temperature ranges. Conservation strategies should include monitoring and mitigating the impacts of climate change on these vulnerable populations (Forero-Medina et al., 2011).

3. Sustainable Land Use: In lowland regions, sustainable land-use practices can help preserve critical habitats and resources for bird species. This includes managing agriculture and forestry to minimize habitat fragmentation and degradation (Sekercioglu, 2002).

Conclusion

The bird survey on Pulau Breuh reveals significant variation in species diversity across different habitats, with forest habitats showing the highest diversity. By employing a combination of point count and transect surveys, we obtained comprehensive data on the island's avian population. These findings highlight the ecological value of forest habitats and the need for focused conservation efforts to protect the rich bird diversity on Pulau Breuh. The differences in bird diversity and foraging behavior between montane and lowland regions underscore the importance of tailored conservation strategies to address the unique needs of these environments.

References

1. Bibby, C. J., Burgess, N. D., Hill, D. A., & Mustoe, S. H. (2000). Bird Census Techniques (2nd ed.). Academic Press.

2. Forero-Medina, G., Joppa, L., & Pimm, S. L. (2011). Constraints to species' elevational range shifts as climate changes. Conservation Biology, 25(1), 163-171.

3. Gregory, R. D., Gibbons, D. W., & Donald, P. F. (2004). Bird census and survey techniques. In W. J. Sutherland, I. Newton, & R. E. Green (Eds.), Bird Ecology and Conservation: A Handbook of Techniques (pp. 17-56). Oxford University Press.

4. Greenberg, R. (1981). The abundance and seasonality of forest canopy birds on Barro Colorado Island, Panama. Biotropica, 13(4), 241-251.

5. Karr, J. R. (1976). Seasonality, resource availability, and community diversity in tropical bird communities. American Naturalist, 110(976), 973-994.

6. MacArthur, R. H., & MacArthur, J. W. (1961). On bird species diversity. Ecology, 42(3), 594-598.

7. McCain, C. M. (2009). Vertebrate range sizes indicate that mountains may be ‘higher’ in the tropics. Ecology Letters, 12(6), 550-560.

8. Morrison, M. L. (1984). Influence of sample size and sampling design on analysis of avian foraging behavior. Condor, 86(2), 146-150.

9. Newton, I. (1979). Population Ecology of Raptors. T & AD Poyser.

10. Pearson, D. L. (1971). Vertical stratification of birds in a tropical dry forest. Condor, 73(1), 46-55.

11. Price, T. D., Hooper, D. M., Buchanan, C. D., Johansson, U. S., Tietze, D. T., Alström, P., & Olsson, U. (2014). Niche filling slows the diversification of Himalayan songbirds. Nature, 509(7499), 222-225.

12. Proctor, N. S., & Lynch, P. J. (1993). Manual of Ornithology: Avian Structure & Function. Yale University Press.

13. Rahbek, C. (1997). The relationship among area, elevation, and regional species richness in Neotropical birds. American Naturalist, 149(5), 875-902.

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

15. Sekercioglu, C. H. (2002). Effects of forestry practices on vegetation structure and bird community composition in two tropical forest reserves, Veracruz, Mexico. Biological Conservation, 107(2), 133-144.

16. Sutherland, W. J., Newton, I., & Green, R. E. (2004). Bird Ecology and Conservation: A Handbook of Techniques. Oxford University Press.

17. Terborgh, J. (1977). Bird species diversity on an Andean elevational gradient. Ecology, 58(5), 1007-1019.

18. Terborgh, J., & Weske, J. S. (1975). The role of competition in the distribution of Andean birds. Ecology, 56(3), 562-576.

19. Walsberg, G. E. (1983). Avian ecological energetics. In D. S. Farner, J. R. King, & K. C. Parkes (Eds.), Avian Biology (Vol. 7, pp. 161-220). Academic Press.