Abundance and species richness (spot diversity)

During the 528 h that the 102 m mist-net line was opened, a total of 1,307 individuals (recaptured specimens are excluded) belonging to 93 species, were trapped. The number of individuals was not significantly affected by habitat type (one-way ANOVA, F 3,20 = 0.65, P

= 0.59): the numbers of individuals per sampling station were highest in SF (59.0 ± 11.9;

mean ± SD), slightly lower in AC (57.8 ± 23.5) and CF (54.5 ± 17.1), and lowest in NF (46.5

± 13.6).

When excluding most abundant species from the analysis i.e. species with more than 100 individuals each (Little Greenbul, Yellow-whiskered Greenbul and Olive Sunbird), the number of individuals becomes significantly affected by habitat types (one-way ANOVA, F

3,20 = 3.19, P = 0.046): the number of individuals per sampling station is highest in AC (41.0

± 20.1), slightly lower in NF (39.7 ± 11.1) and SF (37.2 ± 7.4), and significantly lower in CF (20.7 ± 9.5).

Based on rarefaction analyses and data pooled per habitat (pooled data from six study sites each), overall understorey birds, even when most abundant species are excluded, biome-restricted, Nectariniidae, insectivores, lower stratum and small foliage gleaners showed steady increase species richness with increasing habitat modification: At standard sample size n = 270 individuals, overall species richness was highest in AC (47.7 ± 1.6), a bit lower in CF (44.2 ± 1.7), intermediate in SF (38.2 ± 1.5) and lowest in NF (30.7 ± 0.5) (see Figs. V.1. and V.2A.).

Overall observed species richness per sampling station was significantly affected by habitat types (On-way ANOVA, F3,20 = 3.40, p = 0.038), and no clear defined was found: Highest species richness was found in AC (mean ± SD; 22.5 ± 6.0); it was slightly lower in SF (20.0 ± 2.1) and CF (17.3 ± 3.2), and was significantly lower in NF (16.3 ± 2.0) (Tukeys Honest Significant difference-Test, p = 0.041, see also Fig. V.11.).

0

Figure V.1.: Sample- A) and individual- B) based accumulation of understorey bird species from mist-net samples in different habitat types. Habitats are: near-primary forest (NF), secondary forest (SF), agroforestry systems (CF) and annual cultures (AC).

Observed and estimated species richness and Fisher’s α-diversity showed similar trend; other diversity indices (Simpson, Shannon and Evenness) per habitat were also highest in AC, followed by NF/SF, but lowest in CF (see Table V.2.). When most abundant species are excluded from the analysis, the largest shared sample size between habitat types n = 125 individuals resulted in a highest expected species number of CF (45.0 ± 0.0), slightly lower in AC (38.7 ± 2.2), intermediate in SF (31.9 ± 1.9) and lowest in NF (22.8 ± 1.7) (see Fig.

V.2B.). Similar results were obtained with almost all diversity parameters except the observed species richness, which showed highest species richness in AC (see Table V.2.). Biome-restricted species, at n = 100 individuals, showed lowest species richness in NF (18.6 ± 1.5), intermediate in SF (27.0 ± 1.9) and AC (27.9 ± 1.5), and highest in CF (33.5 ± 0.7) (Fig.

V.2J.). Similar trend was observed with most diversity parameters (see Table V.2). In Nectariniidae, at n = 25 individuals, highest species richness was found in AC (4.9 ± 1.1); it was lower in CF (2.9 ± 0.9) and SF (1.8 ± 0.4) and lowest in NF (1.0 ± 0.0) (see Fig. V.2D.).

Similar trend was observed with other diversity parameters (see Table V.2.). In insectivores, at n = 90 individuals, highest species richness was found in CF (30.0 ± 0.9); it was slightly lower in AC (27.6 ± 1.5) and SF (25.6 ± 1.9) and lowest in NF (18.3 ± 1.6) (Fig. V.2I.).

Fisher’s α-diversity showed similar trend. Observed and estimated species richness were highest in SF, slightly lower in CF and AC and lowest in NF. The other diversity parameters also showed lowest species richness in NF, but which increase with increasing habitat

modifications (see Table V.2.). Lower stratum bird group, at n = 140 individuals, showed highest species richness in AC (26.4 ± 1.4), intermediate in CF (21.0 ± 0.0) and SF (17.8 ± 1.0), and lowest in NF (14.5 ± 0.6) (Fig. V.2G.). Fisher’s α-diversity, observed and estimated species richness showed similar trend. The other diversity parameters showed lowest species richness in CF (see Table V.2.). Small foliage gleaners, at n = 50 individuals, showed highest species richness in CF (15.8 ± 0.5) and AC (13.8 ± 0.9) and lowest in SF (11.7 ± 0.9) and NF (10.7 ± 1.2) (Fig. V.2M.). Almost all the diversity parameters indicated similar trends (see Table V.2.).

Species richness in Pycnonotidae, based on largest shared sample size between habitat types n

= 85 individuals, were similar between habitat types: however it seems to be highest in SF (8.7 ± 0.9), almost equal to AC (8.6 ± 0.6), slightly lower in NF (8.0 ± 0.0) and CF (7.8 ± 0.9) (Fig. V.2C.). The same result was observed for mid-stratum bird group at n = 60 individuals:

however it seems to be highest in AC (12.7 ± 1.1), almost equal to SF (12.5 ± 1.4), NF (12.4 ± 0.7) and slightly lower in CF (10.9 ± 1.6) (Fig. V.2F.). At n = 20 individuals, species richness of omnivorous birds was highest in AC (3.2 ± 0.6), almost equal to NF (3.0 ± 0.0) and slightly lower in SF (2.2 ± 0.4) and CF (2.1 ± 0.4) (see Fig. V.2E.). In ant–following birds, at n = 10 individuals, species richness was highest in SF (5.2 ± 1.0), almost equal to AC (5.0 ± 0.0) and slightly lower in CF (4.6 ± 0.9) and NF (4.5 ± 0.9) (see Fig. V.2H.). For each of these bird groups, each diversity index showed a different unclear trend along the gradient of forest disturbance (see Table V.2.).

There were no clear defined patterns in large and medium-sized foliage gleaners: At n = 9 individuals, species richness of large foliage gleaners was highest in CF (5.0 ± 0.0), intermediate in SF (3.7 ± 0.8) and AC (3.4 ± 0.9), and lowest in NF (2.5 ± 0.5) (Fig. V.2K.).

At n = 30 individuals, species richness of medium-sized foliage gleaners was highest in SF (10.3 ± 1.3) and in AC (10.2 ± 0.8), and lowest in NF (7.1 ± 0.8) and in CF (6.9 ± 1.1) (Fig.

V.2L.). All diversity indices revealed similar results (see Table V.2.).

Although it was not possible to compute rarefied species richness of frugivorous, granivorous, carnivorous and upper-stratum birds, it is evident, from data presented in Table V.1., that annual cultures or degraded habitats in general are richer than natural habitats, except carnivorous birds that seem to show highest richness in NF.

Figure V.2.: Rarefaction curves (Hurlbert 1971) for understorey bird data, pooled by habitat type for A) all species, B) all species excluding most abundant ones (i.e. species with more than 100 individuals each), C) Pycnonotidae, D) Nectariniidae, E) Omnivorous, F) Mid-strata, G) Lower strata, H) Ant-followers, I) Insectivorous, J) Biome Restricted species, K) Large foliage gleaners (> 40 g), L) Medium-sized foliage gleaners (20-40 g), M) Small foliage gleaners (< 20 g). The standard deviation for each expected species number estimate is given as measure of variation. See Fig. V.1. for abbreviations of habitats.

Table V.2.: Observed species richness, diversity indices and first order Jackknife species richness ± SD per habitat for all understorey bird species and for different groups/guilds separately.

Understorey bird

groups/guilds Diversity parameters Near-primary

forest Secondary

Forest Agroforestry

systems Annual cultures All species Observed species (S)

Diversity Fisher’s α Diversity Shannon (Hs) Diversity Simpson (1/D) Evenness Hs/In S All species* Observed species (S)

Diversity Fisher’s α Diversity Shannon (Hs) Diversity Simpson (1/D) Evenness Hs/In S Biome restricted species Observed species (S)

Diversity Fisher’s α Diversity Shannon (Hs) Diversity Simpson (1/D) Evenness Hs/In S Insectivorous Observed species (S)

Diversity Fisher’s α Diversity Shannon (Hs) Diversity Simpson (1/D) Evenness Hs/In S Ant-followers Observed species (S)

Diversity Fisher’s α Diversity Shannon (Hs) Diversity Simpson (1/D) Evenness Hs/In S Pycnonotidae Observed species (S)

Diversity Fisher’s α Diversity Shannon (Hs) Diversity Simpson (1/D) Evenness Hs/In S Nectariniidae Observed species (S)

Diversity Fisher’s α Diversity Shannon (Hs) Diversity Simpson (1/D) Evenness Hs/In S Omnivorous Observed species (S)

Diversity Fisher’s α Diversity Shannon (Hs) Diversity Simpson (1/D) Evenness Hs/In S

Mid-strata Observed species (S) Diversity Fisher’s α Diversity Shannon (Hs) Diversity Simpson (1/D) Evenness Hs/In S Lower strata Observed species (S)

Diversity Fisher’s α Diversity Shannon (Hs) Diversity Simpson (1/D) Evenness Hs/In S Large foliage gleaners Observed species (S)

Diversity Fisher’s α Diversity Shannon (Hs) Diversity Simpson (1/D) Evenness Hs/In S

gleaners Observed species (S) Diversity Fisher’s α Diversity Shannon (Hs) Diversity Simpson (1/D) Evenness Hs/In S Small foliage gleaners Observed species (S)

Diversity Fisher’s α Diversity Shannon (Hs) Diversity Simpson (1/D) Evenness Hs/In S

Notes: * Overall rarefied species richness when species with more than 100 individuals each (i.e. Little Greenbul, Yellow-whiskered Greenbul and Olive Sunbird) are excluded.