Human-Altered Tree-Based Habitats and Their Value in Conserving Bird and Bat Diversity in Northeast Luzon, The Philippines - Smallholder Tree Growing for Rural Development and Environmental Services - page 349

16.3.2 Observed and Estimated Species Richness

The mean estimated species richness for resident birds in the three habitats was
12 to 30 percent higher than observed species richness (Table 16.4). The pattern in
observed species richness was however maintained: shrub-land was most species
rich in resident birds followed by Gmelina forest and homegardens. The mean esti-
mated forest species richness was considerably higher for shrub-land (49 percent),
homegardens (39 percent) and Gmelina forest (28 percent) than the observed rich-
ness. Gmelina forest had the most observed and estimated forest bird species fol-
lowed by shrub-land. Homegardens had the least number of forest bird species.
For bats, 65 to 78 percent of the estimated species richness was detected.
Gmelina forest was least well sampled in this respect, with 65 percent detection.
Shrub-land emerged as the species richest habitat type, with 12 observed and 15 to
16 estimated bat species. Gmelina forest followed with nine observed and 13 to 15
estimated species, whereas homegardens were least rich with nine observed and 11
to 13 estimated species. Fruit bats attained much higher detection proportions. Both
Gmelina forest and homegardens had six fruit bat species, i.e., 84 percent and 88
percent of the estimated fruit bat species richness. Shrub-land had five fruit bat
species, a figure not likely to increase with continued sampling effort (99 percent
of estimated species richness).

Table 16.4 Non-parametric species richness estimators and observed species richness
Species richness estimators

Gmelina forest Homegardens Shrub-land

Birds
Mean estimated species richness a 43.35 ± 0.84 36.21 ± 1.19 66.30 ± 3.50

Observed species richness 38 27 47

Proportion of estimated species 88% 75% 71%

richness detected
Mean estimated forest species 13.98 ± 0.75 8.20 ± 0.71 11.83 ± 1.49

richness a
Observed forest species richness 10 5 6

Proportion of estimated forest species 72% 61% 51%

richness detected
Bats
Mean estimated species richness a 13.95 ± 1.22 11.87 ± 0.88 15.41 ± 0.88

Observed species richness 9 9 12

Proportion of estimated species 65% 76% 78%

richness detected
Mean estimated fruit bat species 7.12 ± 0.34 6.83 ± 0.32 5.05 ± 0.24

richness a
Observed fruit bat species richness 6 6 5

Proportion of estimated fruit bat species 84% 88% 99%

richness detected
a The mean of nine non-parametric species richness estimators: ACE, ICE, Chao1, Chao2,
Jackknife1, Jackknife2, Bootstrap, MMMeans and MMRuns and the standard error of this mean.
Percentages show the proportion observed species of estimated species richness