Hotspot analysis of Taiwanese breeding birds to determine gaps in the protected area network

Zoological Studies

Table 1 Number of grid cells which fulfilled various hotspot criteria

	Hotspot criteria					Hotspot criteria outside of protected areas
	Top 5%	Top 10%	Top 15%	Top 20%	Top 25%	Top 5%	Top 10%	Top 15%	Top 20%	Top 25%
Total species richness
Species richness threshold of selected grid cells	≥74	≥71	≥69	≥67	≥65	≥70	≥66	≥63	≥59	≥56
Selected number of grid cells	1,472	3,245	4,856	6,583	8,373	2,201	4,006	5,560	7,697	9,190
Percent of total study area	4.1%	9.0%	13.5%	18.3%	23.2%	6.1%	11.1%	15.4%	21.4%	25.5%
Endemic species richness
Species richness threshold of selected grid cells	≥14	≥14	≥13	≥13	≥12	≥12	≥11	≥9	≥8	≥7
Selected number of grid cells	1,519	1,519	5,266	5,266	7,656	2,647	3,647	6,824	8,810	10,344
Percent of total study area	4.2%	4.2%	14.6%	14.6%	21.3%	7.4%	10.1%	18.9%	24.5%	28.7%
Threatened species richness
Species richness threshold of selected grid cells	≥23	≥22	≥21	≥20	≥19	≥21	≥18	≥16	≥14	≥12
Selected number of grid cells	1,577	3,514	5,161	6,655	8,049	2,036	4,231	6,091	7,826	9,472
Percent of total study area	4.4%	9.8%	14.3%	18.5%	22.3%	5.7%	11.8%	16.9%	21.7%	26.3%
Rare species richness
Species richness threshold of selected grid cells	≥15	≥13	≥12	≥10	≥9	≥9	≥8	≥7	≥6	≥5
Selected number of grid cells	229	3,398	4,826	6,459	7,905	2,855	4,566	6,060	7,766	9,684
Percent of total study area	0.6%	9.4%	13.4%	17.9%	21.9%	7.9%	12.7%	16.8%	21.6%	26.9%

For four different kinds of species richness, we counted the number of grid cells which fulfilled the criterion of being greater than or equal to a specific species richness threshold. We chose the various thresholds for species richness by selecting that species richness where the actual selected number of grid cells that respectively remained just below 5%, 10%, 15%, 20%, and 25% of the grid cells of the study area. For example, choosing all grid cells with a total species richness of ≥73 and ≥74 species would have respectively selected 5.42% and 4.09% of the grid cells in the entire study area. Therefore, we chose ≥74 as the species richness threshold. Note that the thresholds remained the same for different percentages when we dealt with very low number of species, e.g., endemic species richness for the entire study area.