Page 267 - Atlas Sea Birds Ver1

Great White Pelican or too high and thought that pelican numbers may rather
4 000 be indicative of food availability. At Lake St Lucia, Great
White Pelicans nest on islands or protected shores. Should
3 000 these be flooded (Berruti 1980), or joined to the mainland
through falling water levels or deposits of silt, suitable habi-
2 000 tat for breeding will be lost (Bowker and Downs 2008c).
For example, no breeding occurred in 1995 because all
1 000 islands were flooded, and flooding caused pelicans to
abandon breeding in 1997 (Bowker and Downs 2008a).
Human activities such as firing missiles or building towers
2 000 4 000 6 000 also caused Great White Pelicans to abandon breeding
White-breasted Cormorant attempts (Berruti 1980, Bowker and Downs 2008a).
Counts of White-breasted Cormorants at Lake
300 St Lucia were made in 43 of the years between 1976 and
2021 (Table 1). Reported maxima ranged from six birds
200 in 1983 to 1,710 birds in 2014. The average of all annual
maxima was 260 birds (sd ± 380). Maxima were usually
lower from 1975–2006 than subsequently; the ten highest
100 counts were recorded from 2007–2021.The maximum
Number of pairs Grey-headed Gull 1 000 1 500 breeding in the Lake St Lucia system was of about
estimate of numbers of White-breasted Cormorants
500
300 pairs in 1964 (Berruti 1980). In four recent years
> 200 pairs bred there (2007, 2008, 2014, 2021;
600
Table 2). In north and central Zululand, it is likely that White-
breasted Cormorants move between different breeding
localities (Crawford et al. 2013).
400 Counts of Grey-headed Gulls at Lake St Lucia were
made in 44 of the years between 1976 and 2021
200 (Table 1). Annual maxima showed no discernible trend and
fluctuated around a mean of 984 birds (sd ± 741). The
highest count of 3,650 birds was in 1987 and the lowest
annual maximum of 37 birds was in 2006. The largest
400 800 1 200 number of Grey-headed Gulls recorded breeding at
Caspian Tern Lake St Lucia was c. 1,500 pairs in 1992 (Bowker and
400 Downs 2012). Maxima between 400 and 750 pairs were
recorded in the 1970s, 1980s, 1990s and 2010s (Table 2).
300 Colonies are easily overlooked and difficult to count so low
values should be interpreted with caution.
200 Counts of Caspian Terns were made in 44 of the years
between 1976 and 2021 (Table 1). Annual maxima showed
100 no obvious trend. They fluctuated around a mean of
373 birds (sd ± 246). The highest count of 965 birds in
2015 was followed by the lowest annual maximum of
250 500 750 1 000 one bird in 2016. About 750 pairs of Caspian Tern bred at
Maximum count of individuals Lake St Lucia in 1972 (500–1,000, Berruti 1980). A further
23 annual estimates were between 100 and 400 pairs
Figure 2. Best-fitting relationships between counts of numbers
of pairs breeding and maximum counts of individuals at Lake St (Table 2). It is likely that some Caspian Terns move between
Lucia for Great White Pelican, White-breasted Cormorant, Grey- breeding localities (Cooper et al. 1992).
headed Gull and Caspian Tern, 1975–2021 Three other seabirds considered by the atlas were re-
corded in counts of waterbirds at Lake St Lucia conducted
There was substantial variation in annual maxima, which by Ezemvelo KZN Wildlife but have not bred there: 7–155
peaked at 7,240 birds in 2012 and had a minimum of seven Cape Cormorants in 1978, 1994, 1995, 1997 and 2015;
birds in 1976. The average of annual maxima was 1,723 1–5 Kelp Gulls in 11 years between 1986 and 2001
birds (standard deviation ± 1813). Maxima tended to be and again in 2011; and 2–296 (mean 62, sd 64) Greater
lower before the recent turn of the century than afterwards, Crested Terns in 31 of the years from 1978–2018
perhaps because counts were from boats until 2003 and (Figure 3).
subsequently from the air. Numbers breeding were thought
to be ≥ c. 2,000 pairs in 1978, 1997, 1998, 2002, 2011, Breeding sites
2012 and 2015, with a peak estimate of 3,700 pairs in
2012. Great White Pelicans did not breed at Lake St Lu- Narrows, Oxbow
cia in 1960, 1967, 1980 and 1995 (Table 2). Bowker and Coordinates: 28.33 S; 32.41 E
Downs (2008b) noted that no Great White Pelicans were Description: Channel lined with Phragmites reeds and
present at Lake St Lucia when water levels were very low mangroves.

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