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For this study, a count of water-associated birds was conducted in late February 2010, when
summer migrant numbers are usually maximal. Birds were recorded from the mouth to the
section 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 previous
years, 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 the
sandflats above the bridge (Error! Reference source not found.). Ten species were piscivores
nd 12 species were invertebrate-feeding waders. No herbivores were recorded. Compared to
the study by Barnes (1996) the proportion of invertebrate-feeders, piscivores and herbivores
was similar. Barnes (1996) recorded 15 species of piscivores, 18 species of invertebratefeeders
and one species of herbivore (Egyptian Goose).
The low numbers can be explained by the significant decrease in the numbers of Curlew
Sandpipers, as well as only a small number of terns being present (32 individuals) as compared
to previous counts (Error! Reference source not found.). Curlew Sandpiper has been recorded
t the estuary in high numbers during every previous survey conducted (Error! Reference source
not found.). It is an Arctic-breeding migratory species, and is found in southern Africa from
August/November to March/April. It forages for nereid worms, snails and crustaceans mainly
in the intertidal area of coastal lagoons and estuaries and on sheltered open shores with much
stranded algae (Hockey et al. 2005). The estuary was closed to the sea during the study and
had been closed for approximately two months. Therefore, the large inter-tidal feeding habitat
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. While many
sandprawn burrows were still present, these animals are able to burrow deeper to a level of
sufficient moisture in dry times and are often found in closed systems. They are also very
tolerant of varying salinities (Forbes 1974). Due to their large size and the depth of their
burrows it is unlikely that sandprawns can be utilised as prey by small invertebrate-feeding
waders.
Kelp Gulls were recorded roosting for the first time in high numbers at Uilkraals with 310
individuals recorded (Table 5). Barnes (1996) recorded 67 and Ryan et al. (1988) recorded 77
individuals. On the day of the count a strong south-easterly wind was blowing and it is possible
that 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 low
numbers of terns recorded are of particular concern as this site was once a major roost for
several tern species including the Caspian Tern, Sandwich Tern and Swift Tern, of which it
hosted 6.8%, 2.8% and 6.6% respectively of the south-western Cape’s population (Barnes
1996). Whimbrel has previously been recorded in high numbers at the estuary (76 and 65
individuals) making it the second largest population in the south-western Cape after Langebaan
Lagoon (Barnes 1996). Only 17 individuals were recorded in this study. Whimbrel are relatively
sensitive to disturbance and higher levels of recreational use of the estuary by people may be a
contributing factor, in addition to the loss of intertidal feeding habitat.
Uilkraals Estuary Situation Assessment
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