State of the Bay Report 2011-Final.pdf - Anchor Environmental

Number of birds
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2011
State of Saldanha Bay & Langebaan Lagoon 2011
Birds
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0
Figure 10.13. Long term trends in the numbers of winter resident waders on Langebaan Lagoon
Year
10.4 Overall status of birds in Saldanha Bay and Langebaan Lagoon
Populations of two cormorant species, namely Bank Cormorants and White-breasted Cormorants,
that utilise islands within the Saldanha Bay region for shelter and breeding, have decreased since
early to mid-1990. This has been attributed to the construction of the causeway linking Marcus
Island to the mainland, and to increased human disturbance. The Cape Gannet population on
Malgas Island has also undergone increased decline due mainly to predation by Cape fur seals and
more recently by Great White Pelicans. Predation by the seals was responsible for a 25% reduction
in the size of the colony at Malgas Island, between 2001 and 2006. Management measures have
been put in place, through selective culling of seals, which has improved conditions for the gannets
at Malgas Island. The African Penguin populations are also under considerable pressure, partially
due to causes unrelated to conditions on the island such as the eastward shift of the sardines, one of
their main prey species. However, because populations are so depressed, conditions at the islands
in Saldanha have now become an additional factor in driving current population decreases. Direct
amelioration actions to decrease these impacts at the islands are difficult to find, however, support
for conservation activities that improve penguin conservation, as a means to offset these impacts,
should be considered. All other species of seabirds investigated in this study in the Saldanha Bay
region appear to have healthy populations with either stable numbers or increasing numbers.
Decreasing numbers of migrant waders utilising Langebaan Lagoon reflects a global trend of
this nature, largely due to increasing disturbance to breeding grounds of many species. The
decreasing populations of resident waterbirds present in Langebaan Lagoon, a concern in itself,
suggests that local conditions may be partly to blame for the decrease in migratory birds. This longterm
trend is most likely due to unfavourable conditions persisting in Langebaan Lagoon as a result
of anthropogenic impacts. It is highly recommended that the status of key species be monitored and
used as an indication of environmental conditions in the area.
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