Habitat association of Little Grebe (Tachybaptus ruficollis) at Kallar Kahar Lake, Pakistan

1 Introduction

Habitat resources such as food, refuge and water are the basic needs of an animal species required for its survival and successful reproduction in a particular area (Leopold, 1933; Thomas, 1979). Habitat selection is a hierarchical process related with a series of innate and learned behavioral decisions made by an animal about what kind of a habitat it would select at different scales of the environment (Hutto, 1985). The Little Grebe (Tachybaptus ruficollis) or Dabchick (Order Podicipediformes; Family Podicipedidae) is one of the smallest grebes with body length of 25–29 cm and having a buoyant rounded body. The global conservation status of Little Grebe is of Least Concern (IUCN, 2009). Little grebe is widely distributed all over the world. It occurs in Europe, central and southern Asia and sub-Saharan Africa, Pacific islands and southern Africa except in Kalahari (Hockey et al., 2005). In Pakistan, Little Grebe is widespread in distribution. It is resident to large lakes, but very rarely seen in the flowing rivers and occasionally visits the estuaries and salt water bodies along the seacoast. In Punjab province, the species occurs in Salt Range lakes including Khabbeki, Nammal and Ucchali (Roberts, 1991) and Kallar Kahar Lake (Ali, 2007; Azam et al., 2009). Human activities and environmental changes are prime factors of decline in most of the waterfowl populations. Consequently, essential conservation efforts need to be taken. It is also important to have high quality baseline information on species habitat preferences and breeding biology to construct guidelines for the preservation and improvement of waterfowl habitat (Bruce et al., 1992). The data regarding biology and ecology of Little Grebe are deficient in Pakistan. Present study was, therefore, conducted to study the association of Little Grebe abundance (population density) with habitat parameters at Kallar Kahar Lake, Chakwal, Punjab.

2 Materials and methods

3 Results

We recorded two main habitat types viz. open water and marshy to swampy areas along the edges of Kallar Kahar Lake. The most dominant species of emergent hydrophytes recorded from the lake was Phragmites karka (Importance Index Value = IVI = 43.22) followed by Saccharum spontaneum (IVI = 13.86) while the most abundant submerged species was Spirogyra spp. (Relative Cover = RC = 30.79), Chara spp. (RC = 24.88) and Hydrilla verticillata (RC = 10.86) (Table 1). The strip I had similar dominant emergent species of hydrophytes while strip II also had Schoenoplectus lacustris (IV = 15.34) as important emergent species in addition to Phragmites karka (IV = 15.99), and Saccharum spontaneum (IV = 13.65) (Table 1). The strip III had only submerged and floating vegetation with Chara spp. (RC = 34.69), Spirogyra spp. (RC = 19.80) and Cladophora spp. (RC = 13.71) (Table 1). The mean water temperature was relatively higher at strip II (Table 2). The pH of the lake was slightly basic (above 8). The turbidity was the highest along strip II while strip III had the maximum depth (0.69 m) (Table 2). The studied physico-chemical parameters differed significantly (F = 3.35, df = 27, P < 0.05) among three strips. We recorded 203 individuals (N) of Little Grebes with a population density (PD) of 12.68 individuals per hectare from the lake during the study period (Table 2). The maximum number of grebes was 129, with a population density of 21.5 recorded from strip I followed by strip III (N = 60; PD = 15) and strip II (N = 14; PD = 2.33). The population density of grebe differed significantly (P < 0.05) among the strips. The maximum number of Little Grebe (N = 28) was recorded in June, 2011 while the minimum number (N = 11) was recorded in January, 2011 (Table 2). Temperature (β = −1.343, t = −3.654, P = 0.001) and turbidity (β = −0.058, t = −1.888, P = 0.001) were negatively related while pH (β = 10.537, t = 3.601, P = 0.001) and depth (β = 0.159, t = 2.845, P = 0.008) were positively related with the population density of Little Grebe. The temperature ranged from 21.2 to 25.6 °C at the lake during the present study. The maximum number of nests (06) was noted along strip I which showed that the reed vegetation such as Phragmites and Typha was preferred as shelter and nesting sites. The maximum number of dives per minute (2.6) was recorded in strip III, which is the area located at the open water. This seems to indicate that the open areas of the lake provided foraging sites for the grebes, as it had abundant planktons and crustaceans, algae such as Spirogyra spp and submerged vegetation such as Chara spp (Table 2).

4 Discussion

Little Grebes make a differential use of the available habitat. The vegetation and water physico-chemical characteristics are the main variables that govern Little Grebe distribution. Rais et al. (2011) reported 0.15 Little Grebes per hectare during 2008–09 from Kallar Kahar Lake. Our results showed increase in the population mainly due to the restoration of the ecological condition of the lake. Water level of the lake was much reduced during 2009–2010 (Rais et al., 2010) which might had affected the population of breeding birds including Little Grebe. Further, variation in the population estimation may also be contributed to differences in the observers, time and duration of the study and different sampling sites.

It is believed that site occupancy and frequency of occurrence of water bird species are strongly correlated with the presence of submerged vegetation, vegetation along the shore and pond size. The three important factors affecting site selection are pond size (area), connectivity (distance to the nearest wetland) and habitat quality (González et al., 2010a,b). We also recorded that water depth, water quality and vegetation had strong association with Little Grebe occurrence. The trophic status and/or shallowness of water also influence water bird richness and abundance (McKnight, 1998; Colwell and Taft, 2000). Little Grebe inhabits a wide range of small and shallow wetlands usually less than 1 m depth with rich vegetation (Fjeldsa, 2004). Ceccobelli and Battisti (2010) recorded Little Grebe from wetland channels with water deeper than 0.3 m. We recorded the species from areas having different water depth levels, but usually above 0.4 m. Burton (1988) reported that Little Grebe favors 20–32 °C temperature and adjusts itself accordingly in the habitat. The population of Little Grebe increases during clear stages of water, because the visibility of prey increases in low turbidity (Gregg and Rose, 1985; Kerekes, 1994). Moss and Moss (1993) reported that Little Grebe mostly preferred the habitat with reed vegetation such as Phragmites, Scirpus and Typha which are used in nest building. Little Grebe inhabits a variety of habitats including reclaimed waterfront. However, the species was found to prefer reed beds (Hattori and Mae, 2001). Our results are consistence with aforementioned studies. We concluded that the species used shallow water habitats with preponderance of reed vegetation, slightly high alkalinity but low water temperature and turbidity.

The lake enjoys legal protection under the provincial wildlife law. The main factors affecting the Little Grebe population at Kallar Kahar Lake are water eutrophication, fluctuation in the water level and litter deposition by the visitors. Several actions may be taken to improve the conservation of the lake. We suggest a proper management of the vegetation to maintain high-quality habitat for the species, but removing over growth so that the lake integrity may not be affected. Further, an educative program should also be taken to reduce littering in and around the lake by visitors. Finally, water entering the lake needs to pass through check dams to reduce the influx of excessive nutrients to reduce eutrophication and silting in the lake.