BREEDING NOMADISM IN SOUTHERN AFRICAN SEABIRDS-CONSTRAINTS,CAUSES AND CONSERVATION

Crawford, R.J.M., Dyer, B.M. & Brooke, R.K. 1994. Breeding nomadism in southern African seabirds-constraints, causes and conservation. Ostrich 65:231-246.

Fourteen species of seabirds representing three orders and five families breed in southern Africa. Nomadism in the breeding populations of 13 of these seabirds is examined. African Penguins Spheniscus demersus, Cape Gannets Morus capensis. Bank Cormorants Phalacrocorax neglectus, Whitebreasted Cormorants P. carbo and White Pelicans Pelecanus onocrotalus show strong fidelity to specific localities. Caspian Terns Sterna caspia change breeding localities at a low frequency; Cape Cormorants P. capensis, Hartlaub's Gulls Larus hartlaubii and Swift S. bergii and Roseate S. dougallii Terns at a higher frequency. At some localities, Bank Cormorants remain at the same breeding sites for extended periods, whereas Crowned Cormorants P. coronatus, Whitebreasted Cormorants, Kelp Gulls L. dominicanus, Hartlaub's Gulls, Damara Terns S. balaenarum, Swift Terns and Roseate Terns all alter breeding sites. Where space is not limiting, African Penguins may also change sites. Constraints on nomadism include strong attachment to traditional breeding localities, unwillingness to roost at non-breeding localities, and lack of suitable alternative nesting localities. Amongst causes of nomadism are excessive disturbance by humans and South African Fur Seals Arctocephalus pusillus and competition for breeding space, which have resulted in even the least nomadic of the species changing their breeding locations. Regularly nomadic species are likely to respond to environmental cues that enable them either to reduce cost of breeding or to increase reproductive output. Therefore, they are potentially useful indicators of ecological health. Nomadic breeders additionally have the ability to establish new breeding colonies. Some species have used artificial structures to expand their breeding range, and probably also to increase their overall populations. However, nomadic tendencies complicate the conservation of breeding activities. By contrast, breeding species with strong fidelity to traditional localities are more easily protected.     

COMPARISON OF THE DIET OF BREEDING AND NONBREEDING CAPE GANNETS MORUS CAPENSIS

Berruti, A. 1991. Comparison of the diet of breeding and nonbreeding Cape Gannets Morus capensis. Ostrich 62:8-12.

The effects of breeding status on the diet composition of Cape Gannets Morus capensis were tested at two colonies in the western Cape, South Africa. At both colonies, there were no significant differences in the species composition of the diet, but the mean energy content of regurgitations of breeders was significantly greater. Although the regurgitations of breeders were heavier and contained more fish at both colonies, only the number of fish per regurgitation from breeders at one colony was significantly greater. Birds feeding chicks at Malgas Island took significantly shorter fish than nonbreeders. The small effect of breeding status on prey species composition shows that temporal and geographical variation in prey availability is more important than breeding status in affecting diet cornposition of the Cape Gannet.     

DISTRIBUTION,POPULATION SIZE AND CONSERVATION OF HARTLAUB'S GULL LARUS HARTLAUBIL

Williams, A. J., Steele, W. K., Cooper, J. & Crawford, R. J. M. 1990. Distribution, population size and conservation of Hartlaub's Gull Lorus hurtlaubii. Ostrich 61: 66–76.

Hartlaub's Gull Larus hartlaubii is endemic to southern Africa, where it breeds between Swakopmund, Namibia and Dyer Island, southwestern Cape Province, South Africa. The species has been re breeding at 48 localities within this range. Between 1984 and 1989 an estimated 12000 pain brered at 31 localities. Twenty-eet percent of the population breeds at Robben Island off the Cape Peninsula, sQuth Africa. Hartlaub's Gull frequently has low breeding success and is considered endangered in Narmbia, where 12% of the poulation occurs. However, the population is increaslng around the urbanmd Cape Peninsula where HartLub's Gull has the potential to become a pest species.     

Lanternfish (Myctophidae) in the diet of the Cape petrel Daption capense at the South Shetland and South Orkney Islands, Antarctica

All of the fish identified in stomach contents and regurgitations of breeding and chick Cape petrels collected during January and February 1996 at Fildes Peninsula and Harmony Point, both in the South Shetland Islands and at Laurie Island, South Orkney Islands, were myctophids, a family never previously reported in the diet of breeding Cape petrels. Electrona antarctica was the most important fish prey, followed by Electrona carlsbergi at Fildes Peninsula, Krefftichthys anderssoni at Harmony Point and Gymnoscopelus braueri at Laurie Island. The absence of Pleuragramma antarcticum in the diet of this petrel, which is considered a P. antarcticum-feeder, is discussed. Received: 22 December 1997 / Accepted: 6 June 1998     

The status and conservation of the Cape Gannet Morus capensis

The Cape Gannet Morus capensis is one of several seabird species endemic to the Benguela upwelling ecosystem (BUS) but whose population has recently decreased, leading to an unfavourable IUCN Red List assessment. Application of ‘JARA’ (‘Just Another Red-List Assessment,’ a Bayesian state-space tool used for IUCN Red List assessments) to updated information on the areas occupied by Cape Gannets and the nest densities of breeding birds at their six colonies, suggested that the species should be classified as Vulnerable. However, the rate of decrease of Cape Gannets in their most-recent generation exceeded that of the previous generation, primarily as a result of large decreases at Bird Island, Lambert’s Bay, and Malgas Island, off South Africa’s west coast (the western part of their range). Since the 1960s, there has been an ongoing redistribution of the species from northwest to southeast around southern Africa, and ～70% of the population now occurs on the south coast of South Africa, at Bird Island in Algoa Bay, on the eastern border of the BUS. Recruitment rather than adult survival may be limiting the present population; however, information on the seabird’s demographic parameters and mortality in fisheries is lacking for colonies in the northern part of the BUS. Presently, major threats to Cape Gannet include: substantially decreased availability of their preferred prey in the west; heavy mortalities of eggs, chicks and fledglings at and around colonies, inflicted by Cape Fur Seals Arctocephalus pusillus and other seabirds; substantial disturbance at colonies caused by Cape Fur Seals attacking adult gannets ashore; oiling; and disease.     

THE POPULATION,ECOLOGY AND CONSERVATION OF THE BLACK OYSTERCATCHER HAEMATOPUS MOQUINI

Summers, R. W. & Cooper, J. 1977. The population, ecology and conservation of the Black Oystercatcher Haematopus moquini. Ostrich 48:28-40.

The population of Black Oystercatchers Haematopus moquini in the southwestern Cape, South Africa, was estimated to be 2 942 birds. Birds occurred most abundantly on coastal islands and were also abundant on mixed (sandy and rocky) shores of the mainland. Sandy shores and coastal wetlands supported few birds. Black Oystercatchers bred mainly from December to February with the number of clutches present reaching a peak in the first half of January. The most frequent clutch size was two eggs, the mean clutch size was 1,81. No significant differences were found in either linear dimensions or mass between the first and second eggs. The mean proportion of juveniles in groups of birds in July was 3,6 % suggesting a low recruitment to the adult population. The breeding population at Marcus Island is apparently sedentary throughout the year. The primary moult season for adults extends from March to October (eight months). Introduced mammalian predators should be controlled on islands and important mainland breeding sites should be protected by the creation of nature reserves and restricting human access during the breeding season.     

Timing of breeding and primary moult of the Masked Weaver Ploceus velatus in the summer and winter rainfall regions of South Africa

Oschadleus, H.D., Underhill, G.D. & Underhill, L.G. 2000. Timing of breeding and primary moult of the Masked Weaver Ploceus velatus in the summer and winter rainfall regions of South Africa. Ostrich 71 (1 & 2): 91–94.

Timing of breeding and moult is analysed in the Masked Weaver Ploceus velatus. It is common throughout southern Africa, which is largely a summer rainfall area. This species expanded its range into the Western Cape, a winter rainfall region, in the twentieth century. The peak breeding period is one month earlier in the winter rainfall area (September to November) than in the summer rainfall area (October to December). The mean starting date of primary moult is one month earlier in the winter rainfall area (9 January) than in the summer rainfall area (15 February). The duration of primary moult is similar in both regions (74 days in the winter rainfall area and 80 days in the summer rainfall area).     

ON THE BREEDING OF THE WHITE-RUMPED SWIFT (APUS CAFFER CAFFER) IN GATOOMA

Crawford, R. J. M., Cooper, J. &; Shelton, P. A. 1982. Distribution, population size, breeding and conservation of the Kelp Gull in southern Africa. Ostrich 53:164:177.

The Kelp Gull Lams dominicanus in Africa occurs coastally between Luanda, Angola and Delagoa Bay, Moçmbique. It breeds between Cape Cross Lagoon, South West Africa/Namibia and Riet River, eastern Cape, South Africa. Censuses of nests and breeding birds at all known southern African breeding localities in the period 1976–1981 indicated that 11 199 pairs bred at 52 localities; 79.5% of this population occurred in South Africa, 57,1% in the Saldanha Bay to Dassen Island region, southwestern Cape. Of the breeding pairs 83% occurred on offshore islands and rocks. Colony size at islands is related to their surface area andMayalso be influenced by food availability and the level of human disturbance. The species breeds in a wide variety of habitats ranging from cliffs and rock stacks to wooden platforms, lowlying vegetation among sand dunes and estuarine sandbars. Any available material is used in the construction of nests, whichMaybe as dense as 4/m² Clutch size is 2–3 eggs. In 1978 breeding took place earlier in South Africa than in South West Africa/Namibia. 92% of the population breeds m sites which are legally protected. Kelp Gulls have decreased or increased in numbers at some breeding localities but there is no clear overall trend. Any increases in colony size near urban areasMayresult in added airstrike hazards.     

DISTRIBUTION,POPULATION SIZE AND CONSERVATION OF THE SWIFT TERN STERNA BERGII IN SOUTHERN AFRICA

Cooper, J., Crawford, R. J. M., Suter, W. & Williams, A. J. 1990. Distribution, population size and conservation of the Swift Tern Sterna bergü in southern Africa. Ostrich 61: 56–65.

The Swift Tern Srerna bergü occurs commonly in coastal southern Africa, with a nonbreeding distribution extending the length of the southern African coast and into southern Angola. The known nonbreeding distribubon of the nominate subspecies S. b. bergü extends from Swakomund, Namibia to Kosi Bay, Natal, South Africa. In Natal its nonbreeding distribution overlaps with that of the subspecies S. b. enigma. The species very rarely occurs inland or far out to sea. The geedin distribution of tre nominate subspecies extends from Swakopmund to Algoa Bay, eastern Cape, South Afcnca.

Twenty-two breeding localities are known in southern Africa, but usually only six to seven are occupied. in any one year. Most breeding localities are marine islands where Swift Terns often breed in muted colonies with Hartlaub's Gulls Lorus hartloubii. In 1984 a complete breeding ansus estimated a breeding population of 4835 pairs. However, 6088 pairs were counted at only three localities in 1988. The size of the annual breeding population varies by a factor of as much as 1,6; although the overall size of the adult population is thought to be reasonably stable with no temporal trends evident. Thirteen breeding localities which are legally proclaimed nature reserves supported 72% of the 1984 breeding population. Existing and perceived threats to the Swift Tern are discussed in detail. To improve further tRe conservation status of the Swift Tern in southern Africa, it is recommended that: unprotected breeding localities be proclaimed reserves, also protecting those not on islands with adequate fences; feral cats be removed from breeding islands where they are present; and fisherman be educated to release entangled terns and not to discard lines and nets.     

Responses by four seabird species to a fluctuating availability of Cape Anchovy Engraulis capensis off South Africa

In recent years, Cape Anchovy Engraulis capensis has been the most important food for four seabirds breeding in South Africa–African Penguin Spheniscus demersus, Cape Gannet Morus capensis, Cape Cormorant Phalacrocorax capensis and Swift Tern Sterna bergii. Between 1984 and 1992, biomass of spawning anchovy fluctuated between about 0.5 and 1.75 million tons. Abundance of anchovy was significantly related to numbers of chicks fledged by African Penguins, occurrence of anchovy in the diet of Cape Gannets and numbers of Cape Cormorants and Swift Terns that attempted to breed. Numbers of African Penguins and Cape Gannets that attempted breeding probably also were influenced by abundance of anchovy. African Penguins and Cape Cormorants abandoned nests when anchovy were scarce and deferred breeding until anchovy became more plentiful. Survival of immature African Penguins in a period of anchovy scarcity was enhanced by availability of South African Sardine Sardinops sagax as an alternative food. When anchovy abundance was low, Cape Gannets fed on sardine.     

Lumbering the gauntlet: Cape Gannet fledglings killed by African Penguins

This account presents the first known observations of Cape Gannet Morus capensis fledgling mortalities as a result of aggressive nest defence behaviour by African Penguins Spheniscus demersus. Observations were conducted in 2013 on Bird Island, Algoa Bay, South Africa – the world's largest breeding colony of Cape Gannets. Twentyeight attacks were witnessed between 21 March and 18 May 2013 of which 16 resulted in mortality. The absence of previous observations of this phenomenon may be due to an unusually high proportion of African Penguin chicks being present relatively early on in the breeding season, associated with a potential for increased nest defence at this stage, and a larger number of gannet fledglings that year compared to previous years over the same period.     

RELATIVE ABUNDANCE OF CRANES (GRUIDAE) IN THE CAPE PROVINCE

Siegfried, W. R. 1985. Relative abundance of cranes (Gruidae) in the Cape Province. Ostrich 56:101-103.

The results of monthly roadside counts of Crowned Cranes Balearica regulorum, Wattled Cranes Grus carunculatas and Blue Cranes Anthropoides paradisea show that Blue and Crowned cranes occurred most abundantly and densely in the eastern part of the Cape Province in 1965–1966. The Blue Crane's average relative abundance was approximately four times that of the Crowned Crane whose population occupied tend to breed in summer, the Blue Crane slightly earlier than the Crowned Crane. The population of the Wattled Crane was a small relict, occurrin in East Griqualand. Based on a rough estimate, there were about 1000–1500 Crowned Cranes and about 7000–10000 Blue Cranes in the Cape Province in the mid-1960s.     

ECTOPARASITE LOAD IN A LAUGHING DOVE WITH A DEFORMED MANDIBLE

At Dyer Island, South Africa, observations of predation of seabirds by Cape Fur Seals Arctocephalus pusillus pusillus were made during 2004 and 2006/07. It was estimated that seals killed about 7% of adult African Penguins Spheniscus demersus annually. This may have contributed to the penguin colony not increasing in spite of food becoming more available in its vicinity during an eastward shift of epipelagic fish resources off South Africa at the start of the twenty-first century. Adult penguins were most susceptible to mortality in the breeding season as they returned to feed chicks in the evening. Seals also killed substantial numbers (3–9%) of Cape Cormorant Phalacrocorax capensis fledglings as they left the island, mostly in the morning. The losses of Cape Cormorant fledglings accounted for about 95% of the overall mortality of seabirds attributable to seals. Mortality inflicted by seals on adults of four species of cormorant was negligible and no predation by seals on gulls and terns was observed.     

POPULATION SIZE,DISTRIBUTION AND DISPERSAL OF KELP GULLS IN THE SOUTHWESTERN CAPE,SOUTH AFRICA

Steele, W.K. & Hockey, P.A.R. 1990. Population size, distribution and dispersal of Kelp Gulls in the southwestern Cape, South Africa. Ostrich 61:97-106.

There are indications that the Kelp Gull Larus dominicanus population of the southwestern Cape Province, South Africa, is increasing. It is proposed that decreased post-fledging mortality due to supplementary food from man's activities, at sites such as fishing harbours and refuse dumps, is likely to be the main cause of this population increase. Kelp Gulls aggregate, and juveniles (first-year birds) are disproportionately abundant, at sites where supplementary food is available. Juvenile dispersal from the two largest breeding colonies, 38 km apart, is in opposite directions.     

THE BREEDING BIOLOGY OF AN URBAN POPULATION OF ROCK PIGEONS COLUMBA GUINEA

Elliott, C. C. H. & Cooper, J. 1980. The breeding biology of an urban population of Rock Pigeons Columba guinea. Ostrich 51:198-203.

The breeding biology of the Rock Pigeon Columba guinea was studied for three seasons from 1972 to 1975 at the University of Cape Town, southwestern Cape, South Africa. Nests were visited at approximately weekly intervals. The breeding season (September to February) coincided with the end of the winter rainy season and the presence of cereal crops. Clutch size was two eggs in 99% of cases. Mean incubation period was 14,8 days. Incubation was shared as two continuous shifts per day. Growth rate was similar to that in other studies. The mean nestling period was 23,6 days. Second broods after the successful departure of chicks were frequent, the interval between nest departure and re-laying being as little as five days. Hatching success was 66%, chick rearing success 83% and overall breeding success 49%, similar to other Columba pigeons. It is suggested that the production of pigeon's milk is the limiting factor controlling the invariable clutch size.     

Primary moult,mass and movements of the Rock Pigeon Columba guinea in the Western Cape,South Africa

Underhill, L.G. & Underhill, G.D. 1997. Primary moult, mass and movements of the Rock Pigeon Columba guinea in the Western Cape, South Africa. Ostrich 68 (24): 86–89.

Rock Pigeons Columba guinea in the Western Cape, South Africa, take an estimated 7.2 months to complete primary moult. The mean starting and completion dates are 26 December and 2 August, with 95% of birds starting and completing within two months of these dates. The overall mean mass was 344 g, but birds were heaviest in winter (356 g) and lightest in spring and summer (334 g). Twenty-four of 48 recoveries of Rock Pigeons ringed in the Western Cape were more than 2 km from the ringing site. These recoveries demonstrate movements of Rock Pigeons between the mountains of the Cape Peninsula and the wheat-growing areas to the northeast.     

BIOLOGY OF THE BANK CORMORANT,PART 1: DISTRIBUTION,POPULATION SIZE,MOVEMENTS AND CONSERVATION

Cooper, J. 1981. Biology of the Bank Cormorant, Part 1: Distribution, population size, movements and conservation. Ostrich 52: 208–215.

The Bank Cormorant Phalacrocorax neglectus is a marine species, endemic to southern Africa. Its non-breeding range extends from Walvis Bay to Cape Agulhas. Breeding range extends from Hollamsbird Island to Quoin Rock. Its distribution is broadly similar to that of kelp beds Ecklonia maxima. A total of 44 breeding localities supports approximately 18 000 adult birds; 12 800 (71%) occur on two islands (Ichaboe and Mercury) north of large kelp beds. Adult Bank Cormorants are resident but juveniles may disperse several hundred kilometres. The species is not considered to be seriously at risk to disturbance at most breeding localities. However, modern expansion of fishing activities may affect the very large populations of Ichaboe and Mercury Islands.     

Raptor conservation in the Northern Cape Province,South Africa

Anderson, M.D. 2000. Raptor conservation in the Northern Cape Province, South Africa. Ostrich 71 (1 & 2): 25–32.

The semi-arid Northern Cape is the largest and most sparsely populated province in South Africa. One of the main economic activities is sheep farming, and the properties are generally very large (>5 000 ha). A heterogeneous environment results in many habitats for a wide diversity of raptors. Fifty-one different species have been recorded, of which 37 are resident, 21 are common, and eight species are listed in the South African Red Data Book—Birds. As habitat degradation is limited, besides the areas immediately adjacent to the perennial rivers, raptors are still commonly encountered in many areas. Conflict with small-stock farming, however, results in some birds being inadvertently or directly persecuted each year. Two farmer questionnaire postal surveys (1976 and 1992) indicated a decrease in range and abundance of certain scavenging species, such as the Tawny Eagle. The more recent survey also indicated that most stock mortalities occurred in the mountainous areas, with the Black Eagle being the apparent culprit. In the Northern Cape there are both positive and negative anthropogenic effects on raptors. For example, 14 species have been recorded breeding on man-made structures, while 18 species have been documented to drown in farm reservoirs. Through the activities of the Raptor Conservation Group, the Northern Cape Nature Conservation Service and the Northern Cape Raptor Conservation Forum various threats are being addressed. Raptor conservation activities include: monitoring of raptor breeding populations, road censuses, farmer extension, establishment of raptor conservancies, rehabilitation of injured raptors, issuing of certificates to land-owners who have breeding raptors on their properties, presentation of the annual Gariep Raptor Conservationist Award, production and distribution of raptor pamphlets and booklets, modification of farm reservoirs to prevent raptor drownings, modification of powerlines to prevent electrocutions, and establishment of “vulture restaurants”. Through these efforts, the status of many raptor species is improving and species such as the Bateleur and Lappet-faced Vulture are becoming increasingly common.