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DAMARA TERN
Sterna balaenarum
Near Threatened, Near-endemic
Range: Endemic breeder to southern Africa,
Area of Occupancy: **** km2
Population estimate: 6000-13500 birds
Population trend: Declining
Habitat: coastal salt pans and gravel plains and marine
Threats: 4WD tourism, diamond mining,
Distribution and abundance
This species is confined to the Namibian and South African coasts during breeding (Crawford &
Simmons 1997, Braby 2011), but with about 600 birds recently found breeding south of the Baia
dos Tigres in southern Angola (Simmons 2010). All but about 100 post-breeding birds migrate to
West Africa (Braby et al.1992, Underhill et al.1999, Oschadleus 2001) from between April and
June where they spend about four months before returning in October (Braby 2010). In Namibia,
where 98% of the population is estimated to occur (Simmons et al.1998), the Damara Tern is
found from the Orange River Mouth through the Sperrgebiet, where about between 780 and 900
birds occur in seven known colonies (Simmons et al.1998, Braby 2011). Populations decrease
slightly through Meob and Conception Bays to Sandwich Harbour where between 370 and 410
birds occur and breed in three known colonoies (Simmons et al. 1998, Braby 2011). Density
increases through the central coast where the densest population, up to 571 pairs occur south of
Swakopmund and on Pelican Point (Braby et al.2002, Braby & Braby 2003, Braby 2011).
Populations remain high through to the Ugab (248 birds) and decrease thereafter up to the
Cunene River Mouth (density of 0.3 birds per km2) giving a total population estimate for
Namibia of 13 500 birds based on random sampling (Simmons et al.1998). A recent (2010) reassessment of breeding birds in known colonies puts the population at a minimum of 5370
breeding adults (Braby 2010) in 57 colonies in Namibia (Braby 2011) (Table 1.
The Damara Tern is thinly distributed in South Africa with 12 small breeding colonies from
Alexander Bay and Port Nolloth (just south of Oranjemund), to, De Hoop Nature Reserve, Port
Elizabeth,
to
the
Alexandria Dune fields
(Crawford & Simmons
1997, Braby 2011). The
South African population is
estimated between 65 and
148 pairs (Underhill 2000,
Braby 2011) a decline from
the 150 pairs estimated in
the late 1970s (Cooper et
al. 1984).
The increasing numbers
estimated from various
surveys from below 3000
birds in 1978 (Johnson &
Frost 1978) and 7000 birds
Damara Tern
Distribution of birds in
Namibia derived from
SABAP records, tern
surveys, wetland counts
and nest records
in 1992 (Braby et al.1992), to the 13 500 birds in 1998 (Simmons et al.1998) followed by a
decrease to 5370 birds arises partly from a greater appreciation of the range of breeding habitat
and length of breeding season, and partly due to different census methods. It is unlikely to
represent any intrinsic increase or decrease. There is some evidence, however, of a local declines
in Namibia. particularly in residential areas that have expanded into breeding habitat (e.g. north
of Swakopmund: R Braby pers. obs.), in a previously pristine gravel plain (Dolphin Beach)
between Swakopmund and Walvis Bay where a colony of 32 pairs has declined to zero after
development in 2005/2006 (Braby 2011) and in the diamond area of south Namibia where a
colony at Elizabeth Bay has declined from about 20 pairs in the 1970s (Frost & Johnson 1977,
Johnson 1979) to an average of seven to 13 pairs between 2002 and 2009 (Simmons 2005, Braby
2011). It is also likely that tern populations have decreased in the high intensity diamond area
(Mining Area 1) closest to Oranjemund where coastal substrates have been resorted. Only one
breeding pair was found in about 100 kilometres of suitable gravel plains within the mining area,
while a colony of about 15 pairs occurred immediately outside on Chameis salt pan (Simmons et
al.1998). Where diamondiferous layers have been removed in Alexander Bay, terns resort to
breeding on the exposed bedrock (Underhill 2000).
Ecology
In Namibia, the Damara Tern occurs entirely along the arid Namib Desert coastline, on high
energy coasts during the non-breeding season and in sheltered bays and shallow reefs during the
breeding season. Salt pans and gravel plains within three to five kilometres of the ocean are
preferred nesting areas. In southern Namibia salt pans are preferred as nesting areas, but in
northern Namibia gravel plains are preferred (Simmons et al. 1998), possibly because
temperatures get too high on some salt pans in the northern desert. It also breeds in dune slacks in
vegetated areas on the south coast of South Africa (Watson & Kerley 1995), and between
barchan dunes on exposed gravels in central and south Namibia. It rarely nests on dunes, as the
eggs are covered by moving sand (Johnson 1979, N Hess unpubl. data, Braby 2011).
It forages mainly over shallow water, often in bays, over reefs, or in salt works, probably because
surf zone fish are concentrated here and less common in open water (B Clark pers. comm.). It
catches fish by plunge diving fast into the water. It also occasionally feeds behind breakers in
open ocean and may do so at night (Braby et al.1992). Foraging birds tend to avoid murky,
sediment-filled water in preference for clear water (Simmons & Braine 1994, Braby et al. 2011),
and their dive success can reach 30% in clear water (Braby et al. 2011) Damara Terns feed on
small fish rarely longer than a bill length (3 cm), and in samples of 42 and 50 identified fish
from northern and south-central regions of Namibia respectively, the diet was dominated by
Needle Fish (Tylosaurus species - 43% of 42) and larval blennies (Blennidae, 36% of 42), in the
northern sample (Clinning 1978, Simmons & Braine 1994) and Cape Silverside (Atherina
breviceps – 20% of 50), and Cape Anchovy (Engraulis encrasicolus – 12% of 50) in the southcentral sample (Braby et al. 2011).
Courting birds may, however, carry larger fish (and possibly eels) in their bills while looking for
a mate. It breeds mainly from November through to March with variation according to location.
The peak of the egg-laying season occurs in November and December in central regions
(Swakopmund 22.5o S), in December farther north (22 o S), and in January to February at Mowe
Bay (19.5 o S, Simmons and Braine 1994, Braby 1995, Braby et al. 2002). Clutch size is typically
a single egg (99.9% of 2528 records: Braby 2011), which is unusual for terns. The egg is laid on
the ground in exposed locations in a small depression which is sometimes lined by shell
fragments or small stones. Nest location is strongly influenced by jackal activity: nests are
located farther inland where density of jackal tracks at the coast is high (RE Simmons, R. Heber-
Percy and J Braby unpubl. data), and well studied colonies have moved away from their core to
peripheral areas as jackals move in (R Braby pers. obs.). Moreover, the presence of jackals and
humans influences success of nests - reducing disturbance can double the production of chicks in
protected colonies (Braby et al. 2002, Williams et al. 2004, Braby et al. 2009).
Pre-migratory flocks typically contain tens to hundreds of birds. On five occasions flocks of 1
000 to 2 400 birds have been observed in the vicinity of Cunene River mouth and there is one
record of over 5000 post-breeding birds north of Möwe Bay (Braby et al.1992). It is rarely found
roosting with other terns on desert coasts, and where they do occur Damara Terns appear to roost
independently of other tern species (Braby 2010, Simmons 2010).
Recent studies indicate that immature survival from fledging to adult hood is high at 0.59 and
start to breed at 3-4 years of age (Braby 2011). Annual adult survival is high at 0.88 and the
probability of a breeding bird moving to another colony is very low at 0.06 (Braby 2011). These
indicate that adults birds live for long periods and they are faithful to their breeding colonies.
Threats
The most obvious threat to breeding colonies is disturbance caused by off-road vehicles and
direct fatalities due to crushed eggs and chicks (Braby 1995, Braby et al. 2002, Braby et al.
2009). It is probable that this form of disturbance will increase in Namibia due to three factors.
Firstly, the banning of off-road vehicles on South African beaches means that many more quadbikes and four-wheel drive vehicles now come to Namibia and abuse beach habitats(R Braby
pers. obs.). Secondly, as coastal tourist density increases, so more remote areas where terns breed
will be impacted. Thirdly, jackal and gull densities are artificially high because of the increasing
numbers of seal colonies on mainland Namibia and the large number of line-fishermen along the
shorelines. The intensity of predation on tern colonies from jackals is likely to increase in future,
as jackal populations increase.
A further threat is the development of housing in coastal areas for the burgeoning tourist industry
and for vacationing residents. Planned developments at Dolphin Beach (in 2005) by the Walvis
Bay Municipality turned a tern breeding site and an IBA (Simmons et al. 2001) into a highincome housing development. The colony of 32 pairs has not returned to the area (J Braby pers
comm.). It is likely that without strong representation from the Ministry of Environment and
other conservation bodies the entire 30km coastline between Walvis Bay and Swakopmund is
likely to be developed with little regard for Namibia’s densest tern colony (Braby et al. 2002), or
the highest linear density of shorebirds on the southern African coast (Simmons & Cordes 2000).
This area now lies within the Dorob National Park and this may afford the terns greater
protection.
A natural threat to this species and all fish-eating species comes from the possible consequences
of global warming which may reduce the winds driving the Benguela upwellings (IPCC 2001).
This in turn will affect primary productivity and fish populations available to all marine species
(Roux 2003). The level of the threat is, however, hard to gauge and may indeed bring increased
El Niño oscillations and higher productivity to the Benguela system (Timmerman et al.1999).
Conservation status
This species is classified as a Near Threatened Near-endemic because, while there is little
evidence for declines except for three populations (above), the continuing demand on Namibia’s
beaches by off-road vehicles and tourists will probably impact all but the most remote colonies in
the future. Its population is reasonably healthy at an estimated 2700 to 6000 pairs. This does not
mean however, that some populations are not threatened. For example, the largest population at
Caution Reef was disturbed to such an extent that off-road drivers have now been banned from
traversing the colony (Braby et al. 2002). This has improved breeding success significantly
(Braby et al. 2009). It is also classified as globally Near Threatened (Stattersfield & Capper
2000) but is Endangered in South Africa (Underhill 2000) because of its small, fragmented and
declining population there. As a previously poorly known near-endemic species it has held
special status among Namibian conservation authorities for almost 25 years (e.g. Clinning 1978)
and it is classified as a Specially Protected species under the draft Parks and Wildlife
Management Bill of the Ministry of Environment and Tourism (2002). We now know the bird’s
life history, the threats to it and the conservation actions required, thanks to long term work by
the Braby family (summarised in Braby 2011). Thus the species future is well mapped out and it
remains for conservation authorities to implement these plans to secure the birds’ future.
Actions
Either the complete banning of off-road vehicles from Namibian beaches or strict regulations of
these vehicles is required to control the rise in abuse of beaches and pristine gravel plains.
Studies on the Caution Reef Colony have confirmed that banning vehicles (and thus people) from
breeding tern colonies is a successful protection measure, in conjunction with education
campaigns (Braby et al. 2009). Both breeding density and hatching success increased after the
colony was protected from off-road vehicles, which had previously put thousands of vehicle
tracks per month across the colony, using a one-strand cable fence (Braby et al. 2002). The result
in the first year was a doubling of the number of chicks hatched from the colony (Braby et al.
2002, Braby et al. 2009). This may become necessary for other colonies as beach traffic increases
in future.
Further coastal development must come under the critical eye of environmental impact
assessments not only because they may impact terns, but because of their likely impact on
thousands of migratory shorebirds from elsewhere and the over-use of fresh water that is already
affecting coastal towns such as Lüderitz.
In coastal diamond mining areas where tern colonies have been reduced by direct exploitation of
their breeding habitat and the pollution of waters in which they feed (Simmons 2005, Braby
2011), simple rehabilitation measures are needed. These include depositing mining silts onto
nearby salt pans rather than the bays in which terns feed and returning gravel plains to their
former levels and topography.
Ultimately parts of the 30 kilometre beach Important Bird Area between Swakopmund and
Walvis Bay and other large tern colonies (e.g. Durissa Bay salt pan) are protected by law under
the proclamation of the Dorob National Park and this should give them formal protection from
the pressure of developments and off road vehicles.
Barnes KN (ed) 2000.The Eskom Red data book of birds of South Africa, Lesotho and Swaziland
Braby RJ 1995 Effects of human disturbance on Damara Tern breeding success in the central Namib. Unpublished
report. Ministry of Environment and Tourism, Swakopmund
Braby, Rod Ornithologist, coastal zone manager. Personal observations ([email protected])
Braby J, Braby N 2003. Report on daily observations at the breeding colony of Damara Terns Sterna balaenarum
south of Swakopmund in the gravel plains surrounding the “horses grave yards”, during the 2001/2002 season.
unpublished report on file, MET Swakopmund.
Braby R, Braby SJ, Simmons RE 1992 5000 Damara Terns in the northern Namib Desert: a reassessment of world
population numbers. Ostrich 63:133-135
Braby R, Shapira A, Simmons RE 2001 Successful conservation measures and new breeding records for Damara
Terns Sterna balaenarum in Namibia. Mar. Ornithol. 28:81-84
Braby J, Braby RJ, Braby N & Simmons RE 2009. Protecting Damara Terns Sterna balaenarum from
recreational disturbance in the Namib Desert increases breeding density and overall success. Ostrich 80: 7175.
Braby J. 2010. New migration records for the Damara Tern Sterna baleanarum. Ornithological Observations
1: 38-41.
Braby, J. 2011. The biology and conservation of the Damara Tern in Namibia. PhD thesis University of Cape
Town.
Clinning CF 1978 The biology and conservation of the Damara Tern in South West Africa. Madoqua 11: 31-39
Cooper J, Williams AJ, Britton PL 1984 Distribution, population sizes and conservation of breeding seabirds in
the Afrotropical region. In: Croxall JP, Evans PGH, Schreiber RW (eds). Status and Conservation of the World's
Seabirds: ICBP Techn. Publ. 2:403-419. International Council for Bird Preservation, Cambridge
Crawford RJM, Simmons RE 1997 Damara Tern. In: Harrison JA, Allan DG, Underhill LG, Herremans M, Tree
AJ, Parker V, Brown CJ (eds). The Atlas of Southern African Birds. Vol. 1: 480-481. BirdLife South Africa,
Johannesburg
de Villiers D, Simmons R 1997 The high incidence and origin of two-egg clutches in a Damara Tern colony in
southwestern Namibia. Madoqua 19:111-113.
Frost PGH & Johnson P. 1977. Seabirds on the Diamond Coast, South West Africa. December 1976.
Cormorant 3:13
Hess N 2002 Damara Tern breeding report of the western beach stretch, [deMond], October ‘01 - January ‘02.
Unpublished report Western Cape Conservation Service.
IPCC 2001.
Johnson P 1979 Third census of the Damara Tern at Elizabeth Bay, South West Africa, December 1978. Cormorant
7:32
Oschadleus D 2001 Safring news - Damara Tern migration. Africa - Birds & Birding 6:19
Roux JP 2003. Risks. In: Molloy F & Reinikainen (eds). Namibia's Marine Environment. Directorate of
Environmental Affairs. Ministry of Environment & Tourism, Windhoek.
Simmons R, Braine S 1994 Breeding, foraging, trapping and sexing of Damara Terns in the Skeleton Coast Park,
Namibia. Ostrich 65:264-273
Simmons RE, Cordes I, Braby R 1998 Latitudinal trends, population size and habitat preferences of the Damara
Tern Sterna balaenarum on Namibia's desert coast. Ibis 140:439-445
Simmons RE, Heber-Percy R, Braby R 1995 Geographical variation in the breeding of Damara Terns in the
Namib Desert: effects of predators and upwellings. Unpublished report. Ministry of Environment and Tourism,
Windhoek
Simmons RE, Boix-Hinzen C, Barnes KN, Jarvis AM, Robertson A. 2001. Namibia. In: Fishpool LDC, Evans
MI (eds) Important Bird Areas of Africa and its islands. Pp 339 - 360. Birdlife International , Cambridge UK
Simmons RE, Cordes, I. 2000. Why is shorebird density so high in Walvis Bay? Delayed blooming and Benguela
upwellings. (Abstract). Afr. J. Aquat. Sci. 25: 229.
Simmons RE 2005 Declining coastal avifauna at a diamond-mining site in Namibia: comparisons and causes.
Ostrich 76: 97-103.
Simmons RE 2010. First breeding records for Damara Terns and density of other shorebirds along
Angola’s Namib Desert coast. Ostrich 81: 19-23.
Stattersfield AJ, Capper DR (eds) 2000 Threatened Birds of the World. Birdlife International, Cambridge.
Timmerman A, Oberhuber J, Bachet A, Esch M, Latif M, Roeckner E 1999. Increased El Nino frequency in a
climate model forced by future greenhouse warming Nature 398: 694-696.
Underhill LG, Tree AJ, Oschadleus HD, Parker V 1999 Review of ring recoveries of waterbirds in southern
Africa. Avian Demography Unit, University of Cape Town.
Underhill LG 2000 Damara Tern Sterna balaenarum In: Barnes KN (ed) 2000.The Eskom Red data book of birds
of South Africa, Lesotho and Swaziland
Watson JJ, Kerley GIH 1995. A survey of dune-breeding birds in the Eastern Cape, South Africa. Ostrich 66: 1520.
Williams AJ, Ward VL, Underhill LG 2004 Waders respond quickly and positively to the banning of off-road
vehicles from beaches in South Africa. Wader Study Group Bulletin 104: 79-81
Table 1: The location and estimated size of all presently known or extinct colonies of Damara
Terns in Namibia from the period 1992-2002 (after Braby 2011)
Colony location
Chameis Pan
Latitude
27.9 oS
Number
Trends
of pairs
(ORV= off-road vehicles)
1-7
Stable
Marmora Pan
27.7 oS
13 - 55
Increasing
Elizabeth Bay
26.9 oS
4 – 13
Declined since 1970s from 20 pairs
2–2
Possession Island
Grosse Bucht
26.7 oS
11 - 15
Stable
Hottentot Bay pan
26.2 S
11 – 15
Stable (some clutches of two eggs)
Easter Point
25.3 oS
10+
Unknown
o
o
Meob Bay
24.5 S
20 - 28
Probably stable
Conception Bay
23.9 oS
15 - 18
Probably stable
Sandwich Harbour
23.4 S
0 - 10
Fluctuates – occasionally no breeding
Sandwich N Saltpans
23.2 oS
10-15
Stable
o
o
Walvis Bay
23.0 S
10-15
Currently disturbed by development
Dolphin Park
22.8 oS
18-30
declined, disturbance/development
o
Caution Reef
22.7 S
60-130
Fluctuates inversely with next colony
Horses Graveyard
22.7 oS
50-120
stable, threatened by ORV, protected 2000
Mile 4
22.6 oS
10-20
extinct, since 1980 development
Mile 8
22.5 oS
18-30
fluctuates, ORV disturbance
Mile 14
22.4 oS
30-40
fluctuates, ORV disturbance
Wlotzkas Baken
22.3 oS
15-20
fluctuates, ORV disturbance
Mile 30
22.3 oS
15-25
fluctuates, ORV disturbance
o
Jakkalsputz
22.2 S
25-30
fluctuates, ORV disturbance
Henties Bay
22.1 oS
20-30
Extinct
o
Omaruru Delta
22.0 S
28-40
fluctuates, ORV disturbance
Mile 72
21.8 oS
50-80
fluctuates, ORV disturbance
o
Mile 100
21.5 S
10-30
fluctuates, ORV disturbance
Horing Bay
21.6 oS
10-15
fluctuates, ORV disturbance
o
Mile 108
21.4 S
20-30
abandoned, area flooded
Durissa Bay
21.4 oS
80-100
fluctuates, ORV disturbance
21.1 oS
30-50
stable - diamond prospecting
SKELETON COAST
Odgen Rocks
o
Huab Oil Rig
20.9 S
20-30
Stable
Toscannini
20.7 oS
40-80
Fluctuates –diamond mining
Torra Bay
20.3 oS
50-80
Fluctuates prospecting/tourism
North of Terrace Bay
19.9 oS
40-80
Stable
South of Hoanib
19.7 oS
50-60
Stable
Möwe Bay Airstrip
19.4 oS
30-50
Stable
Möwe Bay Gravel Plain
19.3 oS
30-50
Stable
o
Westies Mine
19.2 S
25-45
Stable
Sarusas
18.7 oS
50-60
Stable
Angra Fria
18.2 oS
20-30
Stable
Cunene
17.4 oS
10-15
Stable
RE Simmons, RJ Braby, SJ Braby