Research Results
4. Results
The Results section is organized into several key subsections to present a clear narrative of findings related to threatened and endangered bird species in Sri Lanka.
4.1 Species Overview Results
The table below presents the number of unique species per IUCN Threat Category. EN (Endangered) category contains the highest number of species, while VU (Vulnerable) has the least.
Table 1_Threat Category - Species Count
| Threat_Category | Species_Count |
|---|---|
| CR | 19 |
| EN | 44 |
| VU | 15 |
The table 2 below shows total occurrence records obtained from GBIF (2000-2025), categorized by IUCN status.
The majority of records are from the EN category. VU species have notably fewer records. Also the figure 1 shows the chart of the bird occurrences.
Table 2_Threat Category - Occurrence Count
| Threat_Category | Occurence_Count |
|---|---|
| CR | 58187 |
| EN | 62497 |
| VU | 3912 |
| Total | 124596 |
Figure 1_Threat Category - Occurrence Count
Next, the table 3 lists the bird species with the highest number of occurrences.
Table 3_Top 10 Species by Occurrence
| Common Name | Occurrence_Count |
|---|---|
| Rock Pigeon | 23166 |
| Blue-tailed Bee-eater | 21397 |
| Indian Swiftlet | 9203 |
| Gull-billed Tern | 5222 |
| Sri Lanka White-eye | 4809 |
| Oriental Honey-buzzard | 4519 |
| Sri Lanka Orange-billed Babbler | 4209 |
| Little Ringed Plover | 3657 |
| Sri Lanka Crested Drongo | 3544 |
| Yellow Bittern | 352 |
The below figures illustrate species-level distribution for CR, EN, and VU categories, highlighting key contributors to total observations.
Figure 2_Registers of EN species
Figure 3_Registers of CR Species
Figure 4_Registers of VU Species
4.2 Distribution Inside vs Outside Protected Areas
4.2.1 Endangered Bird Occurrences Inside vs Outside
The below figure 5 shows the Endangered bird occurrences Inside vs Outside Protected Areas.
It shows that Endangered bird more registers were inside the protect protected areas.
Protected areas may be successfully providing habitat where endangered species can survive and be detected more frequently.
Figure 5_Endangered Bird Occurrences Inside vs Outside
The figure 6 shows the distribution of individual endangered bird species between protected areas (inside) and unprotected areas (outside).
Different species show dramatically different distribution patterns. Some species are found almost exclusively inside or outside protected areas, while others are more evenly distributed.
Several species show much higher occurrences inside protected areas, suggesting they depend heavily on these conservation zones.
Figure 6_Species-specific Distribution (EN)
4.2.2 Vulnerable Birds (VU) Inside vs Outside
The below figure 7 shows vulnerable bird occurrences between protected areas and unprotected areas.
Unlike the endangered bird data, vulnerable birds show a much more balanced distribution between protected and unprotected areas, with actually slightly higher occurrences outside protected areas.
Since these species are vulnerable rather than endangered, they may not yet be as restricted to the “last refuge” areas that protected zones often represent
Figure 7_Vulnerable Birds (VU) Inside vs Outside
Figure 8 illustrate how individual VU species are distributed inside vs. outside protected zones.
Figure 8_VU bird species distribution inside vs outside
4.2.3 Critically endangered bird (CR) Inside vs Outside
Figure 9 shows critically endangered bird occurrences between protected areas and unprotected regions.
This pattern is alarming because it shows that the majority of critically endangered birds - the species closest to extinction - are actually found outside of protected areas. This represents a significant conservation challenge.
Figure 9_CR Bird occurrences inside vs outside
Figure 10 shows how the CR Bird species distribution inside vs outside PAs.
Figure 10_CR birds distribution inside vs outside PAs.
4.2.4 Inside vs Outside for Endangered and Threatened Birds of Sri Lanka (CR+EN+VU)
When combining all threat categories, the majority of Sri Lanka’s threatened birds (nearly 54%) are found outside protected areas. This represents a significant conservation challenge for the country.
Figure 11_overall distribution of all threatened birds (Critically Endangered + Endangered + Vulnerable) in Sri Lanka.
4.3. Protected Area Effectiveness: IUCN Categories vs IBA
Figure 12 shows the distribution of Critically Endangered (CR) bird occurrences across different categories of protected areas in Sri Lanka.
Important Bird Area (IBA): By far the highest with approximately 9,000 occurrences, making it the most critical protected area category for critically endangered birds
Figure 12_CR Birds occurrences inside protected area by Protected Area Category
The below figures 13 & 14, show the distribution of Endangered (EN) and Vulnerable (VU) bird occurrences across different protected area categories in Sri Lanka, revealing consistent patterns across threat levels.
Figure 13_EN Birds Occurrences inside protected areas by protected area category
Figure 14_VU bird occurrences inside protected areas by protected area category
Across all three threat categories (CR, EN, VU), Important Bird Areas consistently contain the vast majority of threatened bird occurrences.
This consistent pattern across all threat levels strongly reinforces that IBAs are the cornerstone of threatened bird conservation in Sri Lanka, regardless of how threatened the species are.
Figure 15_Endangered and Threatened Bird Occurrences inside protected areas by protected area category
4.4. Key Regions of Concern Outside Protected Areas
Figure 16 shows the species richness (number of unique species) of threatened birds found outside protected areas across Sri Lanka’s districts, broken down by threat category.
Key Patterns:
Critically Endangered (CR) - Left Panel (Red):
Relatively low species counts across most districts (0-15 species)
Highest diversity in Matale district (~15 species)
Several districts show moderate diversity (8-12 species): Kandy, Ratnapura, Nuwara Eliya
Many districts have very few or no CR species outside protected areas.
Endangered (EN) - Middle Panel (Green):
Much higher species richness overall (0-40 species)
Matale again shows the highest diversity (~40 species)
Strong representation in central highlands: Kandy, Nuwara Eliya, Ratnapura (25-35 species)
Hambantota also shows high diversity (~30 specie)
More districts have substantial EN bird diversity compared to CR
Vulnerable (VU) - Right Panel (Blue):
Moderate species richness (0-15 species)
Hambantota and Matale show highest diversity (~15 species)
Kandy, Ratnapura also important (~12-13 species)
Central Highlands Hotspot: Districts like Matale, Kandy, Nuwara Eliya, and Ratnapura consistently show high threatened bird diversity across all categories
Figure 16_Species richness per district
The below map shows the spatial distribution of threatened bird occurrence hotspots outside protected areas in Sri Lanka, using density heat mapping to identify conservation priority areas.
Major Hotspots (Highest Density - Red/Orange):
Central-Western Region (~7°N, 80.2°E): The most intense hotspot, likely corresponding to areas around Matale/Kandy district
Central Region (~7°N, 80.5°E): Another significant hotspot in the central highlands
These align with the high species richness shown in the previous district-level chart
