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

State of Saldanha Bay & Langebaan Lagoon 2011
Birds
In Saldanha Bay the declines are mainly attributed to scarcity of their main prey, the rock
lobster which in turn has reduced recruitment to the colonies (Crawford 2007; Crawford et al.
2008c). Bank Cormorants are also very susceptible to human disturbance and eggs and chicks are
taken by Kelp Gulls and Great White Pelicans. Increased predation has been attributed to the loss of
four colonies in other parts of South Africa and Namibia (Hockey et al. 2005). Smaller breeding
colonies are more vulnerable to predation which would further accelerate their decline. Birds are
also known to occasionally drown in rock-lobster traps, and nests are often lost to rough seas.
local water quality (Hockey et al. 2005).
The White-breasted Cormorant
Phalacrocorax carbo lucidus, also known as
Great Cormorant, occurs along the entire
southern African coastline, and is common in
the eastern and southern interior, but occurs
only along major river systems and wetlands in
the arid western interior. The coastal
population breeds from Ilha dos Tigres in
southern Angola, to Morgan Bay in the Eastern
Cape. Along the coast, White-breasted
Cormorants forage offshore, mainly within 10
km of the coast, and often near reefs. Whitebreasted
Cormorants that forage in the marine
environment feed on bottom-living, mid-water
and surface-dwelling prey, such as sparid fishes
(e.g. Steentjies and White stumpnose, du Toit
2004). This species forages in Saldanha Bay and
Langebaan Lagoon, making it susceptible to
Within Saldanha Bay, breeding effort has occasionally shifted between islands. Whitebreasted
Cormorant bred on Malgas Island in the 1920’s, and low numbers of breeding pairs were
counted on Marcus and Jutten Islands intermittently between 1973 and 1987 when they stopped
breeding there and colonized Schaapen, Meeuw and Vondeling islands (Crawford et al. 1994). Most
of the breeding population was on Meeuw in the early 1990s, but shifted to Schaapen in about 1995.
By 2000, the breeding numbers at Schaapen had started to decline and the breeding population had
shifted entirely back to Meeuw by 2004, where it has remained since (Figure 10.8). Overall numbers
have increased recently and there is no long term declining trend.
Human disturbance poses a threat at breeding sites. These cormorants are more susceptible
to disturbance than the other marine cormorants, and leave their nests for extended periods if
disturbed, exposing eggs and chicks to Kelp Gull predation. Other mortality factors include Avian
Cholera, oil pollution, discarded fishing line and hunting inland (du Toit 2004). Due to Schaapen
Islands’ close proximity to the town of Langebaan, the high boating, kite-boarding and other
recreational use of the area may pose a threat to these birds.
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