Page 84 - Atlas Sea Birds Ver1

Species and numbers breeding:

African Penguin
Year No. of pairs
1951 a 2
1988 b 1
a Rand (1952a)
b Williams and Dyer (1990)

Cape Cormorant
Year No. of pairs
1956 a 215
1976 a 152
1977 a 14
1978 a 109
1988 b 45

a Cooper et al. (1982)
b Williams and Dyer (1990)
Bank Cormorant
Year No. of pairs African Penguins breeding at Mercury Island, 1993 (photo RJM
Crawford)
1977 a 18
ly a disturbance programme conducted outside the seal
1988 b 13 breeding season successfully ousted seals from the island
1996 c 19 and it was re-manned. The seals colonised Dolphin Head
on the mainland opposite the island and many displaced
2020 d 7 birds returned to their nesting areas.
a Cooper (1981) African Penguins, Cape Gannets, Cape and Bank cor-
b Williams and Dyer (1990) morants have bred on the surface of the islands, mostly on
c Crawford et al. (1999) their leeward sides, Bank and White-breasted cormorants
d MFMR (unpublished information) on jetties and Crowned Cormorants in the main cave of the
main island (Williams 1987, Crawford et al. 1989, Sherley
White-breasted Cormorant et al. 2012). Gannets used the more level portions of the
islands and some less-steep slopes.
Year No. of pairs Seabird guano was collected at Mercury Island in
1988 a 2 87 years between 1896 and 1984, the total quantity
removed in this period being 22,864 metric tons (Tom et
a Williams and Dyer (1990) al. 2024).
Conservation status: It falls within NIMPA and has
Mercury Island restricted access (Currie et al. 2009).
Coordinates: 25.72 S; 14.83 E Species, numbers breeding and sources of informa-
Description: This precipitous island lies in Spencer Bay tion: Nine seabird species have bred at Mercury Island.
c. 800 m from Dolphin Head. It comprises the main island Estimates of numbers of seven of the species breeding
and North Islet, which are connected by a wooden bridge, in different years from 1956–2022 are shown on the table
and Black Rock (Crawford et al. 1989). It has a surface area applicable to Mercury Island. They were from the follow-
of c. 3 ha, rises to a height of c. 38 m above sea level and was ing sources, which were updated by unpublished records
formerly manned (Rand 1963). Cape Fur Seals became of Namibia’s Ministry of Fisheries and Marine Resources
extinct at the island following a large depletion in their pop- (MFMR): African Penguin (Crawford et al. 1995, 2013,
ulation in the 19th century caused by indiscriminate and Kemper 2015a); Cape Gannet (Crawford et al. 2007a,
uncontrolled harvesting (Shaughnessy 1984). They under- Kemper 2015b, Sherley et al. 2019); Cape Cormorant
took a major recolonisation of the island from 1981–1986 (Crawford et al. 2007b, Kemper and Simmons 2015);
after the removal of permanent staff from the island. The Bank Cormorant (Crawford et al. 1999, Kemper et al. 2007,
recolonisation may have been precipitated by intense har- Roux and Kemper 2015); White-breasted Cormorant
vesting of seals at the mainland colonies of Wolf and Atlas (Brooke et al. 1982; Crawford et al. 1989); Crowned
bays farther south. It resulted in substantial displacement Cormorant (Williams 1987, Kemper et al. 2007, Kemper
from their nest sites of three threatened seabirds (African 2015c); Kelp Gull (Kemper et al. 2007). Additionally, in
Penguin, Cape and Bank cormorants) that are endemic to 2012, 25 pairs of Hartlaub’s Gull and 35 pairs of Greater
the Benguela system (Crawford et al. 1989). Subsequent- Crested Tern bred at the island (MFMR unpublished data).

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