**3.1 Birds in** *Commiphora* **spp. compared with those in** *Vachellia***-dominated vegetations**

A total of 171 species in 103 genera, 12 orders, and 54 families of birds were recorded. The results show that *V. tortilis*-dominated vegetation supported the highest species richness of ground-feeding birds, followed by the *Commiphora spp.* vegetations. In contrast, *V. robusta* remained with lower bird species richness (**Table 1**). In terms of abundance, *Commiphora*-dominated vegetation supported a higher abundance of birds followed by *V. tortilis* and then *V. robusta*-dominated vegetations (**Table 1**). There was no significant difference in the abundance of bird species between *Commiphora* and *V. tortilis* (*U* = 8896.5, *n*1 = 34, *n*2 = 29, *P* = 0.246). However, the difference in abundance between *Commiphora-* and *V. robusta*dominated vegetations was significant (*U* = 8085.5, *n*1 = 34, *n*2 = 30, *P* = 0.017, **Table 1**). The Shannon-Wiener index shows that *V. tortilis* and *Commiphora* accommodated higher bird species diversity values than *V. robusta*-dominated habitat and the randomization test showed that these values of diversity were significantly different (*P* = 0.0001, **Table 1**).

The result from tree-feeding bird species shows that *V. tortilis*-dominated vegetation has the highest bird species richness with 102 species, followed by *Commiphora spp.* with 66 species and *V. robusta*-dominated vegetation with 59 species (**Table 2**). Bird abundance of tree-feeding species in *V. tortilis*-dominated vegetation showed the highest value of 25 individual birds. The *V. robusta*-dominated vegetation remained with 20 individual birds when compared with *Commiphora* spp. which had 19 individual birds, the difference of individual birds between the two vegetations was not significant (*U* = 5151, *n*1 = 28, *n*2 = 24, *P* = 0.905, **Table 2**). The abundance of birds in *V. tortilis*-dominated vegetation was significantly higher than that in *Commiphora* spp. (*U* = 4123, *n*1 = 28, *n*2 = 22, *P* = 0.0102). The randomization test results showed that the index of diversity for birds was higher in *V. tortilis* than that for *V. robusta*- and *Commiphora spp.*-dominated vegetations (*P* = 0.0001, **Table 2**).


#### **Table 1.**

*Richness, abundance, and diversity of ground-feeding birds in V. tortilis, Commiphora spp., and V. robusta of the Serengeti National Park.*


#### **Table 2.**

*Richness, abundance, and diversity of tree-feeding birds in V. tortilis, Commiphora spp., and V. robusta of the Serengeti National Park.*

## **3.2 Grassland compared with** *V. drepanolobium* **and** *V. seyal*

*V. drepanolobium* and *V. seyal*-dominated vegetations supported higher groundfeeding bird species richness but lower overall abundance compared with that of grassland vegetation (**Table 3**). The difference in abundance between *V. seyal* and the western grasslands was significantly different (*U* = 7684.0, *n*1 = 48, *n*2 = 40, *P* = 0.003), but not between *V. drepanolobium*-dominated vegetation and the northern grasslands (*U* = 8791.5, *n*1 = 44, *n*2 = 42, *P* = 0.186, **Table 3**). However, the results from the randomization test showed that there was a significant difference in diversity between both the *V. drepanolobium* and *V. seyal*-dominated vegetations and their adjacent grassland plots (**Table 3**).

#### **3.3 Tree-feeding bird species in** *V. drepanolobium* **and** *Acacia seyal*

Concerning tree-feeding bird species both *V. drepanolobium* and *V. seyal*dominated vegetations accommodated higher bird species richness compared with that in grassland habitats (**Table 4**). However, the abundance of birds showed a different pattern: abundance of tree-feeding birds was higher in grassland than in *V. drepanolobium*-dominated vegetations, *V. seyal*-dominated habitats supported a higher abundance of birds when compared with that of grassland vegetation (**Table 4**).


#### **Table 3.**

*Abundance of birds, species richness, and diversity of ground foraging birds in V. drepanolobium, V. seyal, and grasslands of western and northern Serengeti National Park.*


#### **Table 4.**

*Estimation of richness, abundance, and diversity of tree-feeding birds in V. drepanolobium, V. seyal, and grassland in the western and northern Serengeti National Park.*


#### **Table 5.**

*Abundance of ground feeding birds in different habitat types relative to grass height in the Serengeti National Park (n = 6, standard error in brackets).*

#### **3.4 The effect of grass height on the abundance of ground-feeding bird species**

The abundance of ground-feeding birds in *Commiphora spp.*-dominated vegetations was higher in short grass height and declined consistently as the grass grew taller (from 75 to >100 cm). The abundance of birds in short grass (≤25 cm) in *Commiphora* spp. was significantly higher than that in *V. tortilis* and *V. robusta*-dominated vegetations. In contrast, the abundance of birds in tall grass in *Commiphora spp.*-dominated vegetations was lower than those in *V. tortilis* and *V. robusta*dominated habitats (**Table 5**). The highest abundance of birds in *V. tortilis* and *V. robusta*-dominated habitats were at the intermediate level of grass heights (10–25 and 25–50 cm levels, **Table 5**). However, the abundance of birds did not decrease linearly with grass height; it reached a peak at the intermediate level of grass heights (10–25 cm, **Figure 7**).

*Vegetation and Avifauna Distribution in the Serengeti National Park DOI: http://dx.doi.org/10.5772/intechopen.106165*

**Figure 7.** *Linear estimate of birds' abundance in different grass height interval in the Serengeti National Park habitats.*
