THE BREEDING STATUS OF THE CAPE VULTURE IN THE TRANSVAAL DURING 1980—1985

Benson, P. C., Tarboton, W. R., Allan, D. G. & Dobbs, J. C. 1990. The breeding status of the Cape Vulture in the Transvaal during 1980–1985. Ostrich 61: 134–142.

Ten of the 11 extant Cape Vulture Gyps coprotheres colonies in the Transvaal were censused using aerial and/or ground census techniques in the 1980–1985 breeding seasons. Minimum counts were obtained and best estimates of total numbers of “active nests” were determined using correction factors to compensate for incomplete photocoverage in the aerial technique and nest failures prior to the census dates. In 1985, the year when the most complete data were available, a minimum of 2741 and a best estimate of 2987 active nests were determined to be present in the Transvaal. At the large colonies, which were intensively monitored, breeding numbers did not fluctuate greatly from year to year, and it is thus estimated that about 3000 pairs of birds bred yearly in the Transvaal during the study period. Although the data indicate that the total numbers are greater than previously thought this is due to improved census techniques, rather than an increase in the population. Ninety-eight percent of breeding occurred at six colonies and 82% at three (Kransberg, Blouberg and Manutsa). The large colonies are associated with communal grazing (homelands) Private cattle and game farming and nature conservation areas, where the use of poison for predator control is minimal. The vulnerable status afforded the Cape Vulture in the South African Red Data Book—Birds (Brooke 1984) is justified because of the bird's disappearance from some breeding colonies, reduction in numbers at others and its vulnerability to poisoning.     

Cape Vulture Gyps coprotheres breeding status in southern Africa: monitoring results from 2010–2014

Monitoring of eight Cape Vulture Gyps coprotheres breeding colonies in South Africa and Botswana took place between 2010 and 2014 using standardised counting methods. Counts of breeding pairs, nestlings and fledglings were used to calculate breeding success and general population trends. While our data suggests multiple colonies are stable or increasing, the extinction of peripheral colonies and contraction of the species’ range is alarming and gives evidence for unsustainable population declines. Monitoring efforts chronicled the extinction of the previously large core colony at Roberts’ Farm, which was abandoned as a breeding site in 2013. Standardised monitoring is urgently needed across the entire species range to better understand current population dynamics.     

High occurrence of extra-pair partnerships and homosexuality in a captive Cape Vulture Gyps coprotheres colony§

The Cape Vulture Gyps coprotheres is an Endangered colonial cliff-nesting species that is typically cited as monogamous. Observations of wild Cape Vulture colonies note extra-pair breeding activities but homosexual activity has never been confirmed. Observations of breeding behaviours within a captive colony were conducted at VulPro’s breeding facilities in South Africa The captive breeding programme included 10 breeding pairs and a total of 41 non-releasable, individually recognisable, and genetically sexed subadults or adults. Observations were conducted over the 2014 breeding season as part of a study investigating the social and rearing conditions of chicks intended for release in a population supplementation programme. A high percentage of total colony copulation attempts (22%) were extra-pair copulations but only 23 interactions resulted in cloacal contact or possible sperm transfer. Four paired males formed extra-pair relationships, two of which were homosexual.     

SOME OBSERVATIONS ON BEHAVIOUR AND CALL IN THE PALM THRUSH CICHLADUSA ARQUATA

Boshoff, A. F. &; Vernon, C. J. 1980. The past and present distribution and status of the Cape Vulture in the Cape Province. Ostrich 51:230-250.

Because of the apparent decline in range and numbers of the Cape Vulture Gyps coprotheres in the Cape Province, the distribution and status of this species were reviewed according to four time periods from before 1905 to the present day. All available information was assembled, assessed and interpreted. It is apparent that, although the present decline is real, the population has undergone previous fluctuations. The magnitude, nature and possible causes of the fluctuations are discussed. It is postulated that the drastic decline in the game herds, particularly during the 19th century, together with the recent changes in stock farming, are the most important factors determining the numbers and distribution of Cape Vultures. Direct and indirect persecution also have a detrimental effect on vulture populations. Farmers' attitudes towards vultures are mentioned and conservation priorities and problems are listed.     

Cliff characteristics,neighbour requirements and breeding success of the colonial Cape Vulture Gyps coprotheres

The breeding success of endangered colonial nesting species is important for their conservation. Many species of Gyps vultures form large breeding colonies that are the foci of conservation efforts. The Cape Vulture is a globally threatened species that is endemic to southern Africa and has seen a major reduction in its population size (≥ 50% over 48 years). There is evidence that breeding colonies are prone to desertion as a result of human disturbance. Factors that influence the occupancy and breeding success of individual nest‐sites is not fully understood for any African vulture species. We investigated cliff characteristics and neighbour requirements of the Msikaba Cape Vulture colony, a major breeding colony in the southern node of the population in the Eastern Cape, South Africa, together with their nest‐site occupation and breeding success over 13 years. In total, 1767 breeding attempts were recorded. Nest‐sites that had a higher elevation, smaller ledge depth, greater total productivity and were surrounded by conspecifics were more likely to be occupied, although the amount of overhang above the nest was not an important predictor of occupancy. In accordance with occupation, nest‐sites with a smaller ledge depth had higher breeding success; however, nests with a greater overhang were also more successful and height of the nest‐site was not an important predictor of breeding success. The breeding success of a nest‐site in a given year was positively influenced by the number of direct nest neighbours, and nests in the middle of high‐density areas had greater breeding success. This suggests that maintaining a high nest density may be an important consideration if declines of reproducing adults continue. Breeding success declined over the study period, highlighting the effects of a temporal variation or observer bias. Our results identified optimal nest‐site locations (ledge depths of 1 m, at a height of 180 m) and their effects on breeding success. This information can be used for planning reintroduction efforts of the endangered Cape Vulture and for their ongoing conservation.     

The Cape Vulture at Colleywobbles: 1977–1997

Vernon, C.J. 1998. The Cape Vulture at Colleywobbles: 1977–1997. Ostrich 70 (3&4): 200–202.

In the late 1970s there were about 180 breeding pairs of Cape Vulture Gyps coprotheres at Colleywobbles colony. In the 1980s the colony increased to over 300 pairs, presumably as a result of birds immigrating to the Transkei. In the 1990s the colony declined to about 60 pairs, either through emigration or mortality. The decrease from the 1980s to the 1990s was probably related to a reduction in food supply (carcasses of domestic livestock) as a result of changes in human social activities.     

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.     

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.     

Genetic diversity is retained in a bottlenecked Cinereous Vulture population in Turkey

Vulture populations worldwide have suffered precipitous declines in recent decades. The Cinereous Vulture Aegypius monachus, a highly philopatric scavenger distributed across southern Europe and the central Asian plateau, is threatened in many parts of its range. Turkey holds the second largest population of this species in the Western Palaearctic, but there has been no research on its genetic structure and the possible implications of this structure for the future of the species. Here we report nuclear diversity and relatedness determined by short tandem repeat genotyping of 81 individuals from the four largest colonies. Our results demonstrated no significant genetic structuring, suggesting a single panmictic metapopulation connected by frequent dispersal. Furthermore, we show that the study population has retained moderate levels of genetic diversity, despite passing through a recent demographic bottleneck. We estimated the effective population size to be 112 individuals (95% confidence interval 74–201). Our results imply that the observed lack of increase in population size since the 1990s has not been caused by lowered fitness due to genetic inbreeding but rather by increased mortality via demographic processes. In the short term, we suggest that conservation efforts should treat the Turkish subpopulations as a single management unit and aim to increase population size through effective protection, especially during the breeding season.     

A STUDY OF THE CINNAMON-BREASTED ROCK BUNTING Fringillaria tahapisi tehepisi

Brown, C. J. &; Piper, S. E. 1988. Status of Cape Vultures in the Natal Drakensberg and their cliff site selection. Ostrich 59:126-136.

Ground, aerial and questionnaire surveys on the status of the Cape Vulture Gyps coprotheres in the Little and High Drakensberg mountain ranges of Natal were carried out from 1981–1983. The area supported at least 1325 Cape Vultures, 60% on the High Drakensberg in 17 nesting colonies (mean of 31 birds per colony) and 38 roosts (mean of 7 birds). In the Little Drakensberg 17 sites were found, six of which were confirmed nesting colonies (mean of 53 birds) and seven were roosts (mean of 16 birds). A minimum of 215 nests was recorded while the actual number of breeding pairs was probably about 325. In the Natal Drakensberg 84% of nests and 77% of roosting birds occupied ledges that faced between east and south, on the lee side of the generally westerly and northwesterly “Bergwind”. Nesting ledges in the High Drakensberg were on average about 100 m lower than roosting ledges. The northern Drakensberg supported the largest numbers of Cape Vultures (19 birds per 10 km of cliffs), while the smallest numbers were recorded in the south (8 birds per 10 km of cliffs). In the south smallstock farming predominates and the availability of carrion is higher than in the north where mainly largestock are farmed. The use of poisons (mainly strychnine) for killing mammalian predators on farms is considered to be the main reason for fewer birds occurring in the south, and is the main threat to Cape Vultures in the Natal Drakensberg.     

High mortality and sex ratio imbalance in a critically declining Oriental White-backed Vulture population (Gyps bengalensis) in Pakistan

Populations of Oriental White-backed Vulture (Gyps bengalensis) and Long-billed Vulture (Gyps indicus) declined dramatically by 95–100% on the Indian subcontinent in during the mid-1990s. The study reported here was conducted in Pakistan to compare the population size, breeding success, patterns of mortality and sex ratios among dead vultures and newly hatched nestlings of G. bengalensis and G. indicus at Toawala (TW) and Nagar Parkar (NP), respectively, during the breeding seasons 2005/2006 and 2006/2007. At TW, diclofenac poisoning was most likely responsible for the high mortality and sex ratio imbalance among dead G. bengalensis, where vulture counts and breeding success declined quickly during the study period. However, at NP no significant difference in population size, breeding success and annual mortality of G. indicus was recorded during the study period. A sex ratio imbalance was detected among nestlings of G. bengalensis, with 68% males and 32% females. In contrast, the sex ratio did not differ significantly in G. indicus.     

The population dynamics of Notothenia rossii from South Georgia (Antarctica)

Summary The population dynamics of nearshore juvenile Notothenia rossii were studied at South Georgia during 1978 and 1979. Mortality of the population was calculated from length-class abundance of fish sampled by trammel nets, and the population size estimated using a mark and recapture technique. Instantaneous natural mortality in the nearshore population was high (M=0.78) although other author's estimate for the mortality in the offshore population was only 0.35. Therefore it is likely that no single estimate of mortality will apply to fish of all ages. The population density of juvenile N. rossii was about 11 g m^-2 nearshore. The size of the offshore population was estimated by calculating survival from the nearshore age classes. The data suggest that the population around South Georgia has been reduced by overfishing to about one tenth of its previous unexploited level. Yield could have been increased by fishing less intensively, and the population maintained at or near its initial level if recruitment remained constant.     

Sexing Cape Vulture Gyps coprotheres based on head morphometrics

The Cape Vulture Gyps coprotheres is considered sexually monomorphic in the literature, but visual differences in head shape between the sexes have been observed. Furthermore, head morphometrics of other Gyps species show statistically significant variation between the sexes. We show that head morphometrics can be used to determine the sex of Cape Vultures. Males generally have wider and shorter heads, and larger bill depths than females. Discriminant function analysis with data from 63 individuals identified the three most predictive variables in sex determination to be head width, head length and bill depth. We also provide an equation that can be used in conjunction with head measurements as a method to determine the sex of Cape Vultures in the field with an overall accuracy of 84% (92% accuracy for females and 72% for males).     

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.     

Mortality of the terrestrial adult and aquatic nymphal life stages of Baetis vernus and Baetis rhodani in the Breitenbach, Germany (Insecta: Ephemeroptera)

1. The mortality of Baetis vernus Curtis and Baetis rhodani Pictet during the terrestrial-aerial and aquatic life stages was studied at the Breitenbach near Schlitz, Hesse, Germany. The number of females emerging from the stream was recorded with emergence traps. To estimate mortality of females of both species during terrestrial life, numbers of emerging females were compared with numbers of females returning to the stream for oviposition, as shown by numbers of egg masses found in the stream. 2. Mortality of female B. vernus during their terrestrial life stage was 98.8%. It was 91.2 and 96.6%, respectively, during the first and second generations of B. rhodani. 3. To estimate the mortality of both sexes of B. rhodani during the aquatic life stage, the number of eggs laid by the first generation was compared with the number of adults emerging during the second generation. 4. Mortality during the aquatic phase (both sexes combined) of B. rhodani was 91.1%. 5. Mortality during the terrestrial life stages was at least as high, if not higher than during the aquatic stages. Evidently, there is a considerable export of organic material into the terrestrial environment around the stream. Mortality during terrestrial life may be an important regulator of population size.     

Chronic and catastrophic natural mortality of three common Caribbean reef corals

Compared to catastrophic impacts from storms, disease epidemics and bleaching events, little is known about the effects of more routine chronic mortality in reef corals. To monitor this ongoing mortality, monthly visual assessments of the cause of tissue damage were related to mortality rates (changes in planar surface area) of tagged colonies of three common reef corals: Montastrea annularis, Porites astreoides and Diploria strigosa at Buck Island Reef National Monument, St. Croix, US Virgin Islands. During the study Hurricane Hugo, the most powerful cyclone to affect the area in at least 60 y, made a direct impact on the site. Effects of the hurricane were extremely localized, with certain exposed sites being almost completely razed while others showed no detectable changes in community structure. Mortality caused both by the hurricane and by other factors during the 26 month study varied between species and also between site locations around the island. Differences in susceptibility were not dependent solely on gross morphology, because two robust, massive species showed opposite responses to hurricane damage and chronic mortality. Diploria strigosa was virtually unaffected by chronic factors, but was heavily damaged at exposed sites during the hurricane. In contrast, mortality from predation and tissue necrosis was high in Montastrea annularis, but it largely escaped damage from the hurricane because it was absent from the most severely scoured locations. Porites astreoides, with populations dominated by much smaller colonies, was affected by both chronic and hurricanerelated mortality. Differences in susceptibility to the various types of natural disturbance among species, coupled with high spatial and temporal variability in the effects of such disturbances, may be critical to the maintenance of species diversity on the reef.     

Density effects in a colonial monoculture: experimental studies with a marine bryozoan (Membranipora membranacea L.)

Summary Naturally occurring monocultures of plants and animals are not common, despite recent emphasis on the analysis of density effects in artificial plant monocultures. In natural populations, Membranipora membranacea, an encrusting marine bryozoan, usually forms monospecific, nearly even-aged stands on kelp blades. We experimentally manipulated the density of M. membranacea colonies and monitored the responses of individual colonies on settling panels. Colonies undergo a sub-annual cycle of growth, stasis and reproduction, shrinkage, and death. However, crowding by conspecifics accelerates the transition to stasis, triggers early onset of reproduction, and results in increased stage-specific mortality. Unlike many interactions involving colonial invertebrates, overgrowth rarely occurs at boundaries of M. membranacea colonies. Instead, colonies stop growing when they contact conspecifics; therefore more dense assemblages are populated with smaller individual colonies. At the peak in colony size during August, the mean size among colonies grown at high population densities was 300 mm² less than colonies grown at low densities or approximately 62% smaller. Mortality was concentrated in small size classes; at the end of the season colonies gradually shrank to the smallest size classes and then died. We summarized the demography of M. membranacea colonies on low- and high-density panels using size-classified transition matrices and used loglinear analysis to examine the effects of density and time on the transition patterns. As the amount of free space on panels declined, so did the frequency of upward size-class transitions. Our analysis revealed that free space declined more rapidly on panels in the high density treatment and that the transitional probabilities were sensitive to density of conspecifics and seasonal change, but only for some size classes and during some time periods.     

Juvenile summer flounder,Paralichthys dentatus,mortalities in the western Atlantic Ocean caused by the hemoflagellateTrypanoplasma bullocki: evidence from field and experimental studies

Juvenile summer flounder (140–200 mm) inoculated withT. bullocki by leech vector or syringe in November 1980, and held in flowing seawater tanks all died within 11 weeks. Water temperature during the period of highest mortality ranged from 0.5 to 1.5 °C and may have been a contributing factor in mortality. No uninoculated control fish died even though held in the same tank. Symptoms of disease were anemia, splenomegaly and obvious ascites. Mortality of feral juvenile summer flunder in the lower York River during January 1981 was also attributable toT. bullocki because of identical symptoms to moribund fish in the experiment. Results suggest that the presence of ascites can be used as an estimate of mortality in fishes north of Cape Hatteras.     

A long-term study of Pinus banksiana population dynamics

Abstract. The long-term population dynamics of a pure, naturally-established stand of Pinus banksiana (jack pine) in southeastern Manitoba, Canada is described. The study was initiated at stand age 15, when all 468 trees in a plot were mapped and their trunk diameter at breast height (DBH) measured. The plot was remeasured eight times — every five years (six years in one case) — and mortality and DBH changes recorded. Total mortality over the 41-yr study period was ca. 84 %. Mortality was initially very low, increased once the stand entered the self-thinning stage from ages 25–46, and declined at ages 46–56. Mortality was restricted to the smallest size classes throughout. The stand reached the self-thinning line at ca. age 30. The self-thinning slope was significantly less steep than the theoretically expected value of ?0.5. The distribution of DBH values was initially symmetric, showed increasing positive skewness during the period of highest mortality, and became symmetric again at later stages. Size (DBH) inequality was highest just prior to the onset of density-dependent mortality, and subsequently declined. Tree DBH values were positively autocorrelated both initially and at later stages of stand development, but were spatially independent during the period of highest density-dependent mortality. The stand initially had a strongly clumped pattern at all spatial scales. Patterns of mortality were non-random during stand development, however, resulting in increased spatial regularity over time. Mortality was initially restricted to high density patches of the stand, but occurred throughout the plot once the self-thinning line was reached. Mortality during the self-thinning stage deviated from random expectation at local spatial scales (1–2m radius), suggesting that individuals were competing with their immediate neighbours. It is argued that an integrated approach, incorporating both population size and spatial structures, is essential in improving our understanding of long-term plant population dynamics.     

High microsatellite genetic diversity fails to predict greater population resistance to extreme drought

There is intense debate whether genetic diversity measured via neutral molecular markers can be used as a surrogate for fitness and as an indirect estimate of the amount of genetic variation for fitness-related traits in a population. Here, we measured microsatellite DNA genetic diversity (before the onset of drought) and mortality after prolonged drought in 15 populations of Banksia hookeriana in the species-rich southwestern Australian flora, to test the relationship between population genetic diversity and resistance to extreme climate fluctuations. Number of alleles per locus varied from 5.2 to 8.2 at eleven microsatellite loci among 30 individuals in each population. Mortality varied from 25 to 50% in individual populations after prolonged drought. Lower mortality was not observed in populations with higher genetic diversity, but in populations with lower genetic diversity. Thus, higher microsatellite genetic diversity fails to predict lower population mortality during extreme drought in B. hookeriana. Our results imply that it may be misleading to use studies of neutral genetic variation exclusively as the basis for inferring population and species capacity for resisting extreme climate events and for species conservation and management decisions.