Background
Long-term ecological studies are critical to understanding the dynamics of environmental change on ecosystems. Birds are a model system for studying the long-term responses of ecosystems to environmental change, such as changes in land use. Birds are also important providers of ecosystem services, including pollination, seed dispersal and top-down controls on lower trophic levels. Birds can move freely between habitats with a diversity of body sizes, feeding preferences, and behavioral traits. Changes in bird community composition and structure can also indicate habitat type (e.g. high quality miombo woodland vs. human dominated cultivation areas). Bird community composition can also quickly change in response to perturbations, and any changes in bird community composition has the potential to alter ecosystems.
What’s in this report
In this report we
- present the most up to date results from the Bird Diversity Surveys in Ruvuma, including
- Unique species by year broken down in and out of WMAs
- Map showing survey effort
- Cumulative species curves for all plots
- Number of unique species by survey site by year, broken down in and out of WMAs
- Number of unique endangered and range restricted species by survey site by year, broken down in and out of WMAs
- Tables which list all species sighted inside and outside WMAs
- Suggestions of next steps in terms of analysis.
- provide an update to the methodology for 2024, including how to:
- Include protocols for bird abundance in the project area with point counts the inclusion of sampling points in Chingoli WMA, and Muhuwesi Forest Reserve
- Calculate spatial patterns using adespatial package
- Calculate species richness using vegan
- Calculate compositional dissimilarity of beta diversity using vegdist {vegan} or GDM
- Calculate Pielou’s evenness using vegan
- Calculate GLMs to understand how bird diversity metrics change over time and whether these changes are varying by land use (WMA vs outside WMA), using year as a continuous fixed variable, land use as a categorical fixed variable, and interaction term between them to see whether temporal trends varied by land-use type.
- Calculate GLMs to understand the same for gamma diversity and total beta diversity as response variables, this would have year as a continuous fixed variable as the single factor.
Improvements in sampling effort
In 2023, the target was to conduct surveys before 10am or after 4pm. However, this was not always possible. In 2024, the target changed to conducting surveys before 10am. The figure below shows this was achieved.
Map of survey efforts for each year with project area boundaries
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Map showing distinct species for each sample location
Changes in bird richness over time
Cumulative Species curves
Review whether we are collecting data from a sufficient number of sites.
Number of unique species by plot
At present it appears that there are a greater number of unique species in sites that are outside the WMA. However, as the next figure shows, this could potentially be due to edge effects.
Number of endangered or range restricted species by plot
Sites inside WMAs are more likely to be of higher habitat quality and therefore it is perhaps unsurprising that a greater number of endangered or range restricted species are found in sites inside WMAs.
Further potential analysis that can be conducted:
As described above, based on the results of the 2023 and 2024 surveys, we suggest that the following further analyses could be carried out:
- Include protocols for bird abundance in the project area with point counts the inclusion of sampling points in Chingoli WMA, and Muhuwesi Forest Reserve
- Calculate spatial patterns using adespatial package
- Calculate species richness using vegan
- Calculate compositional dissimilarity of beta diversity using vegdist {vegan} or GDM
- Calculate Pielou’s evenness using vegan
- Calculate GLMs to understand how bird diversity metrics change over time and whether these changes are varying by land use (WMA vs outside WMA), using year as a continuous fixed variable, land use as a categorical fixed variable, and interaction term between them to see whether temporal trends varied by land-use type.
- Calculate GLMs to understand the same for gamma diversity and total beta diversity as response variables, this would have year as a continuous fixed variable as the single factor.