Uilkraals Situation Assessment - Anchor Environmental

For this study, a count of water‐associated birds was conducted in late February 2010, whensummer migrant numbers are usually maximal. Birds were recorded from the mouth to thesection of the estuary where the wider channel becomes a series of smaller braided channels,approximately 3 km from the mouth.Counts during this study showed a drastic decrease in bird numbers compared to previousyears, while diversity was not affected as much (Table 4). Only 435 individuals were recorded,the majority of these being Kelp Gulls (310 individuals). Most birds (89%) were found in thesandflats above the bridge (Error! Reference source not found.). Ten species were piscivoresand 12 species were invertebrate‐feeding waders. No herbivores were recorded. Compared tothe study by Barnes (1996) the proportion of invertebrate‐feeders, piscivores and herbivoreswas similar. Barnes (1996) recorded 15 species of piscivores, 18 species of invertebratefeedersand one species of herbivore (Egyptian Goose).The low numbers can be explained by the significant decrease in the numbers of CurlewSandpipers, as well as only a small number of terns being present (32 individuals) as comparedto previous counts (Error! Reference source not found.). Curlew Sandpiper has been recordedat the estuary in high numbers during every previous survey conducted (Error! Referencesource not found.). It is an Arctic‐breeding migratory species, and is found in southern Africafrom August/November to March/April. It forages for nereid worms, snails and crustaceansmainly in the intertidal area of coastal lagoons and estuaries and on sheltered open shores withmuch stranded algae (Hockey et al. 2005). The estuary was closed to the sea during the studyand had been closed for approximately two months. Therefore, the large inter‐tidal feedinghabitat which covered the entire sandflat region below and above the road bridge was lost.Most inter‐tidal invertebrates had probably desiccated and died or migrated elsewhere. Whilemany sandprawn burrows were still present, these animals are able to burrow deeper to a levelof sufficient moisture in dry times and are often found in closed systems. They are also verytolerant of varying salinities (Forbes 1974). Due to their large size and the depth of theirburrows it is unlikely that sandprawns can be utilised as prey by small invertebrate‐feedingwaders.Kelp Gulls were recorded roosting for the first time in high numbers at Uilkraals with 310individuals recorded (Table 5). Barnes (1996) recorded 67 and Ryan et al. (1988) recorded 77individuals. On the day of the count a strong south‐easterly wind was blowing and it is possiblethat this species seeks shelter in the estuary sporadically. Similar numbers of Kelp Gulls were,however, still present the following two days, even after the wind had died down. The lownumbers of terns recorded are of particular concern as this site was once a major roost forseveral tern species including the Caspian Tern, Sandwich Tern and Swift Tern, of which ithosted 6.8%, 2.8% and 6.6% respectively of the south‐western Cape’s population (Barnes1996). Whimbrel has previously been recorded in high numbers at the estuary (76 and 65individuals) making it the second largest population in the south‐western Cape after LangebaanLagoon (Barnes 1996). Only 17 individuals were recorded in this study. Whimbrel are relativelysensitive to disturbance and higher levels of recreational use of the estuary by people may be acontributing factor, in addition to the loss of intertidal feeding habitat.In addition to the changes associated with the building of the bridge and the closure of themouth, disturbance would have increased with the size of the surrounding settlements andamount of people utilizing the adjoining caravan park and estuary for recreational purposes.Uilkraals Estuary Situation Assessment30Anchor Environmental