Avian Demography Unit
Department of Statistical Sciences
University of Cape Town
|BIRD NUMBERS||Volume 10 Number 1, July 2001|
16. Notes on the birds and other animals recorded at the Cunene River mouth from 6-8 January 2001
M.D. Anderson*, R.A. Anderson, S.L. Anderson, T.A. Anderson,
The Cunene River is the third-largest Namibian river, emerging in the Atlantic Ocean approximately 1000 km from its source. The banks of the river do not have extensive riparian vegetation and the lagoon and vegetated islands at the mouth are probably the most biologically productive areas on the lower Cunene River. The mouth and lagoon have been described in detail by Simmons et al. (1993) and Simmons et al. (1998).
The Cunene River mouth never supports large numbers of waterbirds, but it is nevertheless an important staging and feeding area for waders, probably as a result of its isolated location along the Atlantic coast. The nearest permanent wetland is Walvis Bay, some 700 km away. The low number of waterbirds can be attributed partly to the relatively small area of the mouth and suitable waterbird habitats. For example, the area of exposed sand and mudflats when the river flow is low is only 125 ha and there are only thin strips of riparian vegetation along the banks and on several small islands (Simmons et al. 1998).
Despite the low numerical abundance of waterbirds, the Cunene River mouth regularly supports the second-largest wetland species total in Namibia and 72 species have been recorded. This wetland is recognized as an Important Bird Area because of significant populations of Damara Tern, White Pelican, Chestnutbanded Plover and a few other species (Simmons et al. 1998).
Although waterbird surveys have been conducted at the Cunene River mouth during the period 1982–2000 (Ryan et al. 1984; Braine 1990; Simmons et al. 1993), it is less frequently counted than other important Namibian wetlands. The aim of this January 2001 study was to count the waterbirds and terrestrial birds at the Cunene River mouth.
The waterbird survey was conducted from 08h15–13h00 on 7 January 2001. We divided into three groups (each comprising three people; two observers and a scribe) and simultaneously counted three separate areas. These areas were (1) the northern and southern beach areas adjacent to the mouth opening, (2) the 1.9 km section of the river from our campsite (17°15'316''S, 11°45'544''E) to the river mouth (17°14'434''S, 11°45'133''E), which included the islands, sandbars, and large lagoon on the southern bank, and (3) the river section from the campsite upstream to opposite the Foz do Cunene (17°16'065''S, 11°47'020''E), a length of 2.3 km. The total straight-line distance of the river that was surveyed was approximately 4.2 km. Simmons et al. (1998) considered the section of the Cunene River up to 4 km from the coast to constitute the river mouth.
The waterbird survey was conducted with the aid of binoculars and spotting scopes. Although we did not have a boat and thus were not able to access the islands and the Angolan bank, an attempt was made to survey these areas from the southern bank. Nevertheless, it is likely that many birds present on the northern bank, islands and reedbeds were not counted and the results of the survey therefore represent a minimum species and population estimate.
All terrestrial birds were also counted during the waterbird survey and additional species recorded during the duration of our three-day stay were also noted. For some waterbirds, such as White Pelican, we conducted additional counts in order to obtain maximum numbers for these species. Notes were also kept of all mammals and reptiles observed.
Dirk Heinrich set up seven mistnets on the mudflats, reedbeds and a small accessible reedbed island throughout the three-day period. On some occasions, strong southwesterly winds prevented continuous netting operations and the nets were then closed. All captured birds were weighed, measured, ringed and released.
During the survey a total of 2452 birds of 61 species were recorded (Table 1). Waterbirds significantly outnumbered terrestrial birds, with only 155 individuals of 20 different terrestrial bird species being recorded – an indication of the extremely arid nature of the surrounding terrestrial habitats (Table 1).
Seven waterbird species were observed which have not been recorded during four previous comprehensive surveys (Ryan et al. 1984; Braine 1990; Simmons et al. 1993), namely Yellowbilled Egret, Dwarf Bittern, Cape Shoveller, African Crake, Wood Sandpiper, Baird’s Sandpiper and Yellow Wagtail. Some species, such as Yellowbilled Egret and African Crake, have been recorded at other localities in the Skeleton Coast Park (Braine 1988). Forty-three species of waterbirds recorded during the previous surveys were not observed during our January 2001 visit.
Unusual birds recording during the survey included Baird’s Sandpiper, Royal Tern, Whitebrowed Coucal, Dwarf Bittern and African Crake. During the waterbird survey, two Baird’s Sandpipers were observed along the camp-Foz do Cunene river section and, later that day, one of these individuals was located again and studied in detail which enabled confirmation of the identity of the species. We observed one (possibly two) Royal Terns on two occasions (6 and 7 January), roosting on sandbars in the mouth area. Although no Swift Terns were present, the presence of many Caspian Terns allowed for a comparison between these two similar species. Royal Terns have previously been recorded at the Cunene River mouth (e.g. Ryan et al. 1984; Komen & Paterson 1999). A coucal, possibly Whitebrowed, first recorded at the mouth during November 2000 by R.E. Simmons (in litt.), was heard calling on two occasions during this survey. Forty-nine individuals of 13 species were caught in the mistnets (Table 2), also providing two species (Dwarf Bittern and African Crake) that were not recorded during the waterbird survey.
The number of waterbirds recorded was lower than several previous counts (Simmons et al. 1993); this may be due to the time of the survey, especially if the Cunene River mouth is more important as a staging area during early and late summer for Palearctic migrants moving north or south along the south-west African coastline. The number of water and terrestrial birds was nevertheless significantly more than the 1412 individuals of 33 species recorded by Simmons (in litt.) on 10/11 November 2000. A comparison with the numbers of waterbirds reported by Ryan et al. (1984), Braine (1990) and Simmons et al. (1993) reveals higher numbers for several species during our survey, namely Whitebreasted Cormorant, Caspian Tern, White Pelican, Egyptian Goose and Redbilled Teal.
Although no effort was made to systematically search for and count mammals and reptiles, Tables 3–4 provides a list of these animals that were incidentally observed during our stay.
The Namibian Ministry of Environment & Tourism is thanked for access to the Skeleton Coast National Park. Dr Rob Simmons provided information on the birds of the Cunene River mouth and commented on this manuscript.
Braine S. 1988. Vagrants and range extensions found in and adjacent to the Skeleton Coast Park. Lanioturdus 24: 4–12.
Office Avian Demography Unit
Enquiries/More Information: firstname.lastname@example.org
Document posted: 24-Aug-2001
Office Avian Demography Unit