This presentation was given at the 8th Pan-African Ornitholigcal Congress in September 2008. The abstract reads as follows: The Damara Tern (Sterna balaenarum) is a near-endemic, near-threatened seabird that breeds along the Namibian coastline. Its breeding range extends into the Sperrgebiet, a diamond mining area along the southern coast of Namibia about to be proclaimed as a National Park. A study is being conducted to investigate the potential impact of diamond mining on the breeding productivity of the Damara Tern at one mined locality, Elizabeth Bay, and three other nesting sites along the southern Namibian coastline. Diamond mining may impact the breeding productivity in several ways: habitat destruction, disturbance, and foraging efficiency due to sediment discharge. Parameters monitored are colony size, breeding success, chick growth and condition, and adult foraging success. Out of the four breeding sites monitored, Elizabeth Bay has the smallest number of nests. The number of nests has also decreased from 30 in 1979 (before mining), to 13 (during mining) in 2008. Nests were previously found in areas which have since been mined and are now unsuitable nesting habitats. The other non-mined sites were Marmora Pan (55 nests), Grossebucht (21 nests) and Hottentot’s Bay (80 nests). Breeding success and chick predation rates differ between sites. So far no differences in chick growth rates and adult foraging success could be established between mined and non-mined sites. Chick growth and condition, however seem to be dependent on the distance between colony and feeding sites.

1. The breeding success of the Damara Tern Sterna
balaenarum in the restricted diamond mining area
of southern Namibia
Justine Braby, Les Underhill, Rob Simmons and Jean Paul Roux

2. Damara Tern Sterna balaenarum
• Small seabird (52g) that breeds in
small, isolated colonies
(predominantly) along the desert
coastlines of Namibia and South Africa
• Classified as Near-threatened under
the IUCN red-data list (world
population - 13,500)
• Migrates to West African countries like
Gabon, Cameroon, Nigeria and Benin
during the non-breeding season
• The Damara Tern is a near-endemic
breeder to the region
• It has held special conservation status
among Namibian conservation
authorities for 25 years and has in
recent years become a flagship
species of the Namibian coastline
• Will be classified as a Specially
Protected species under the draft
Parks and Wildlife Management Bill of
the Ministry of Environment and
Tourism

3. BREEDING AREAS STUDIED
• Elizabeth
Bay – the
main study
site
• Grosse
Bucht –
outside
restricted
area and
used as a
control for
foraging
• Marmora Pan
(Pocket
Beaches)
• Anigab Pan
(Hottentot’s
Bay)

4. Elizabeth Bay

5. FEEDING:
• Simmons (2005) suggested
that the introduction of
sediment into the bay has
been detrimental to breeding
Damara Terns
• Control area is Grosse Bucht
(22km north)
• Preliminary analysis (Elizabeth
Bay, n=91; Grosse Bucht,
n=70) showed no significant
difference in foraging success
between Grosse Bucht and
Elizabeth Bay (χ21 = 1.158,
P=0.2819)
• Further analysis will be
completed once sediment
discharge data has been
received from Elizabeth Bay
mine (and a greater sample
size at both areas is collected)

6. Adult populations and breeding
success
• During the height of breeding
season (mid-December 2007)
a minimum of 405 Damara
Terns were found in the
Sperrgebiet: Hottentot’s Bay
(n=287), Marmora Pan (n=68),
Elizabeth Bay and surrounds
(n=32), Grossebucht (n=18)
• Elizabeth Bay had the smallest
nest number (13), Hottentot’s
Bay (Anigab Pan) had by far
the greatest number of nests
(80)
Nest Totals for Season 2007/08
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
Hottentot's Bay Elizabeth Bay Grosse Bucht Marmora Pan
Breeding locality
Numberofnests

7. Breeding success
• Nests were deemed successful when chicks fledged
• Only nests with known fates are shown
0%
20%
40%
60%
80%
100%
Hottentot's
Bay
Elizabeth
Bay
Grosse
Bucht
Marmora
Pan
Other
Failures
Other
Predations
Jackal
Predation
Fledging

8. Egg measurements
• The mean length and breadth (mm) at Hottentot’s Bay were l=32.58,
b=24.16, n=37, Grossebucht l=33.51, b=24.07, n=26, Elizabeth Bay
l=33.09, b=24.34, n=10, and Marmora Pan l=33.24, b=23.85, n=50
• There was no significant difference in egg volume between the
different colonies (F3,128
=0.63, P>0.05)
• Mean volume (ml) was 9.214, SD=0.572 (range 7.590 – 10.812)
Egg length versus breadth (mm)
30
31
32
33
34
35
36
37
38
22 22.5 23 23.5 24 24.5 25 25.5 26
Egg breadth (mm)
Egglength(mm)

9. Chick condition
• Chick condition is determined by weight related to structural size
(length of head+bill) (Jan Veen’s unpublished method)
• No significant difference between colonies (F3,52
=2.1935, P>0.05),
this may be due to small sample sizes
• Hottentots Bay colony lowest mean standardized condition
(-0.502) and Grosse Bucht highest (0.376) indicating possible
relationship between condition and distance to sea
0
10
20
30
40
50
60
25 30 35 40 45 50
Chick Head Length (mm)
ChickMass(g)
Other colonies
Hottentot Bay (Anigab Pan)
Linear (Other colonies )
Linear (Hottentot Bay (Anigab
Pan))

10. Key findings
• Nest number has decreased at Elizabeth Bay, but increased at all
other colonies
• Chick condition was not lowest at Elizabeth Bay
• There seems to be a trade-off between predation rates and distance
to the sea, where in breeding areas closer to foraging sites chicks
can be fed more frequently but predation levels are higher, whereas
in breeding areas further from foraging sites chicks may not be fed
as frequently (and adults may work harder to feed chicks as flying
distances between colonies and feeding areas are much greater),
but predation rates are much lower and chicks have a greater
chance at survival to fledging
• More data needs to be collected to analyse breeding success, chick
growth rates, foraging success as well as adult condition at different
colonies. Thus far there have been no significant differences, apart
from the smaller colony size, between the mined area, Elizabeth
Bay, and the non-mined sites

11. Acknowledgements
• Megan Murgatroyd for her help in the collection of data
during the past field season
• Namdeb for their continued support on the project
• MET, especially Trygve Cooper and MFMR, especially
Jean-Paul Roux and Jessica Kemper
• Animal Demography Unit, Les Underhill and Sue Kuyper
(UCT)
• Percy FitzPatrick Institute, Rob Simmons (UCT)
• Elizabeth Bay Mine, and especially Urban Burger, Senior
Geologist at Namdeb for his support on the project
• Environmental Unit at Namdeb (Ronel van der Merwe,
Ursula Witbooi)