Page 555 - Atlas Sea Birds Ver1

3.16 Numbers, trends, status, and conservation of Damara Tern
(Sternula balaenarum) in Namibia and Angola

Authors: RJ Braby, RJM Crawford, S Braby, RE Simmons, and J Braby

Abstract:
Damara Terns (Sternula balaenarum), endemic to the Benguela ecosystem, are known to have bred at 57 localities in Namibia and one
in south Angola. They also bred in South Africa. The most up-to-date estimates at colonies suggested that in 2021/22 minima of 715 pairs
bred in Namibia and six pairs in Angola, or c. 92% and c. 1% of the species’ population, derived from colony counts, respectively. This
number was 23% lower than minima of 930 pairs in Namibia and six pairs in Angola derived from colony counts 11 years earlier in 2010.
Generation length (G) for Damara Terns was 12.33 years, so the 23% decrease equates to 77% in 3G. A comparison of the minimum
numbers of adults estimated to occur in Namibia in1991 and 2021/22 (a period of 30 years) suggested that it decreased by 52%, equivalent
to 64% in 3G. Both results support a re-classification of Damara Terns in Namibia and Angola as Endangered (EN) in terms of International
Union for Conservation of Nature Red List criteria. In the 1990s, it was estimated from stratified, random sampling along 95% of the ~1,570
km coast that about 14,000 Damara Terns occurred in the region, of which 63% bred. Hence, colony counts may only cover c. 60% of the
population. However, since no repeat random sampling has been conducted, nest counts at colonies and estimates of minimum numbers
of adults breeding are the best gauges of population trends. The most recent estimates of numbers at colonies suggested that 31 breeding
localities in Namibia and one in Angola held ≥ 5 pairs and so met that criterion for an Important Bird Area for an EN species.The largest
colony was at Caution Reef, Namibia, which had 147 pairs or c. 19% of the colony-derived population. Damara Terns have a relatively late
age at maturity, so factors influencing survival, such as anthropogenic threats, may cause population decreases. Reproductive success
decreased between 1991 and 2010, when it was thought to be insufficient to maintain the population. This parameter is influenced by loss
of habitat to development, disturbance at colonies, attraction of predators to colonies, and tidal flooding of breeding areas.

Introduction:
Damara Terns (Sternula balaenarum) are a breeding endemic to southern Africa, where they breed around the coast from the Baia dos
Tigres, in southern Angola to the Alexandria Dunefields, in South Africa’s Eastern Cape Province (Figure 1). About 98% of the population
nests in Namibia (Crawford and Simmons 1997, Braby 2011). After breeding, the majority leave the area for their non-breeding grounds
farther north in Africa, mostly in West Africa (Simmons 2005).
This chapter collates information on numbers of Damara Terns at different localities in Angola and Namibia to examine trends in
species abundance. It re-assesses the Red List status of, identifies Important Bird and Biodiversity Areas (IBAs) for, and summarises
threats to this species in the northern Benguela ecosystem.
Numbers of birds and breeders

The overall population of Damara Terns is difficult to
estimate on account of its widely dispersed breeding
colonies in largely inaccessible habitat, especially in
Namibia (Braby et al. 1992). Estimates of numbers have
been derived from counts of individuals (Braby et al. 1992,
Simmons 2010), counts of pairs or nests at all known
colonies (Braby 2011), and from stratified, random sampling
(Simmons 1993, Simmons et al. 1998). A flock of at least
5,068 Damara Terns was counted on photographs taken
about 178 km south of the Cunene River in March 1991
(Braby et al. 1992). After accounting for birds observed in
two separate flocks farther south, the proportion of birds
in immature plumage in flocks (c. 20%, distinguished from
dark-headed adults by their white foreheads and browner
appearance), and birds migrating north from South Africa, Damara Terns banded in Namibia on a polluted beach in Nigeria
it was considered that the Namibian population numbered (photo J Braby)
at least 5,515 individuals, of which c. 4,412 were in adult population of northern Namibia. Results suggested that
plumage (Braby et al. 1992). As birds also bred in Angola, 13,024 Damara Terns occurred in the region, of which
it was thought the species’ population might be as high as 908 were chicks and 12,116 were flying birds (Simmons
7,000 individuals (Braby et al. 1992). 1993). Similar random surveys undertaken in December
In February 1992, during the Damara Tern breeding 1994 and from January–February 1996, also during the
season, a stratified, random-sampling survey was breeding season, covered the 690 km southern portion of
conducted along a 780 km stretch of coast from the Cunene Namibia’s coastline from Sandwich Harbour to the Orange
River Mouth on the Namibia-Angola border to Sandwich River Mouth. It was estimated that 1,627 Damara Terns
Harbour. The coast was surveyed from the shoreline to occurred in this region, of which 174 were chicks and 1,453
3 km inland. It was estimated that 93% of nests occurred were flying birds (Simmons et al. 1998). Combination of
within this distance from the shore (Simmons and Braine the surveys suggested that Namibia’s overall population
1994) and values were scaled up to estimate the whole of Damara Terns comprised 14,651 individuals, of which

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