Robin M. Little

Waterbird assemblages and associated habitat characteristics of farm ponds in the Western Cape, South Africa

Natural freshwater wetlands are among the most threatened habitats on Earth. Effective wetland biodiversity conservation can not, however, be evaluated without fully understanding the roles of artificial waterbodies as refuges for water-dependent plants and animals. Waterbird assemblages were examined on 59 farm ponds in the Elgin and Caledon districts of the Western Cape, South Africa. This study examines the relationship between waterbird use and habitat characteristics of farm ponds. Patterns of temporal and spatial variation of waterbird species richness and abundance were quantified in relation to the habitat characteristics of each pond. Cluster analysis and multiple regression analyses identified surface area of the farm ponds as an important variable determining the presence and abundance of many waterbird species. Structural diversity in terms of vegetation in and around the ponds was especially important in determining their usage by waterbirds. These variables were evaluated in terms of creating a mosaic of habitat types (by varying vegetation structure and pond topography), which may be a useful way to enhance waterbird diversity at farm ponds. This study concludes that the high number of farm ponds in the transformed habitat matrix of the Western Cape plays an important role in conserving waterbirds.

Sandgrouse (pterocleidae) and sociable weavers Philetarius socius lack avian haematozoa in semi-arid regions of South Africa

Blood smears from 97 sandgrouse (64 Namaqua Sandgrouse Pterocles namaqua , 28 Burchells Sandgrouse P. burchelli and five Doublebanded Sandgrouse P. bicinctus ) and from 20 Sociable Weavers Philetarius socius collected in the semi-arid Northern Cape Province, South Africa were examined. No blood parasites were observed in any of the smears examined. Because of the scarcity of breeding habitats for the vectors of avian Haematozoa in arid and semi-arid regions of southern Africa, it is suggested that these environments are generally free of avian Haematozoa.

INVESTIGATOR EFFECTS ON THE NESTING SUCCESS OF ARID-ZONE BIRDS

Abstract We examined whether regular researcher visits affected egg hatchability or nest predation for three ground-nesting bird species that incur high levels of nest predation, primarily by small mammals. Frequently visited finch-lark (Eremopterix verticalis and E. australis) nests suffered similar predation to nests visited infrequently, suggesting that regular visits had no additive effects on nest survival. A comparison of finch-lark nests visited for the second time either one or two days after the first visit found that predation during the first 24 h (7.4%) was lower than predation during the second 24-h period (9.9%), suggesting that the act of visiting a nest did not increase the risk of predation. Daily predation rates on Namaqua Sandgrouse (Pterocles namaqua) and finch-lark nests showed no observable trend with an increasing number of visits over time, indicating that frequent visits had no cumulative effect on predation probabilities. Nests of both Grey-backed Finch-lark (E. verticalis) and Black-eared Finch-lark (E. australis) discovered at the egg stage did not fledge significantly fewer young than nests discovered at the nestling stage, suggesting that investigator disturbance had no effect on egg hatchability. These results from the southern hemisphere subtropics support the findings of limited north-temperate studies that largely mammalian nest predation does not increase after researcher disturbance.

The breeding biology of the Namaqua Sandgrouse, Pterocles namaqua

The breeding biology of the Namaqua Sandgrouse, Pterocles namaqua, was studied and its nesting success determined through the observation of 278 nests over four consecutive breeding seasons at Droëgrond, Northern Cape Province, South Africa. The normal clutch of three eggs is laid over five days (±48-hour laying interval). The incomplete clutch is left unattended overnight, but is attended during the heat of the day by the female on days when an egg is laid and by the male on alternate days. After clutch completion, the pair share incubation, with the female relieving the male 151 min (±21 S.D.) after sunrise and the male relieving the female 105 min (±21 S.D.) before sunset. The incubation period is 21 days from clutch completion, and the three chicks normally hatch within 18 hours of one another. Nesting success ranged from 5.7% to 13.5% between seasons and averaged 8.2%. Predation, primarily by small mammals, was responsible for 96% of nest losses. Estimates of annual recruitment at Droëgrond ranged from minima of 3–10% to maxima of 6–20%, and are believed to be representative of a core area of the distribution of the Namaqua Sandgrouse in South Africa. These low estimates suggest that annual juvenile recruitment may be too low to maintain Namaqua Sandgrouse populations locally. Possible reasons for the sustained low level of breeding success are discussed.

The effectiveness of helmeted guineafowl Numida meleagris (Linnaeus 1766) in controlling the banded fruit weevil Phlyctinus callosus (Schönherr 1826), and their impact on other invertebrates in apple orchards in the Western Cape Province, South Africa

Abstract The role of indigenous vertebrate predators, especially birds, in controlling pest insects is poorly known. This study quantifies the effectiveness of helmeted guineafowl Numida meleagris (Linnaeus 1766; Aves: Numididae) in controlling the banded fruit weevil Phlyctinus callosus (Schonherr 1826; Coleoptera: Curculionidae), a pest in apple and nectarine orchards in the Western Cape Province, South Africa. The impact of guineafowl on other invertebrates and on apple crops is also assessed. Periodic counts of weevils under trunk bands showed that guineafowl did not reduce weevil numbers significantly, but suction samples indicated that weevils were more abundant in plots without guineafowl. On average only 1.07 weevils were found in 30 guineafowl crops (range 0–14 weevils). The results suggest that although guineafowl consume weevils, they have a negligible impact on large weevil populations. Other invertebrates, especially molluscs and elaterid larvae (Coleoptera) were often eaten. Guineafowl reduced insect diversity in apple orchards either directly through predation or indirectly by altering the structure of the cover plants. The damage that guineafowl allegedly cause to apples was not confirmed.

THE DISTRIBUTION AND ABUNDANCE OF GREYWING FRANCOLIN FRANCOLINUS AFRICANUS ON THE STORMBERG PLATEAU, EASTERN CAPE PROVINCE, SOUTH AFRICA, IN RELATION TO DIET AND SUBSTRATA

Summary Little, R.M., Gous, R.M. & Crowe, T.M. 1993. The distribution and abundance of Greywing Francolin Francolinus africonus on the Stormberg Plateau, eastern Cape Province, South Africa, in relation to diet and substrata. Ostrich 64:105-114. Previous research indicates that Greywing Francolin Francolinus africanus in conserved grasslands are isolated on areas over igneous substrata and are highly qualitatively selective in their diet, but are more widespread in grazed grasslands. This study examines whether this variation in dispersion and ecology is a result of quantity and/or quality of diet, or because of veld management policies. We studied quantitative and qualitative aspects of the diet of Greywing Francolin populations, and the distribution and abundance of these populations over various land-form types and substrata on the Stormberg Plateau, eastern Cape Province, south Africa. Within the montane grassland areas of the range of the Greywing Francolin, veld management and the resultant structur...

Rainfall and food availability as factors influencing the migration and breeding activity of Namaqua Sandgrouse, Pterocles namaqua

This study examines whether rainfall and its effects on food availability control the timing of migratory movements and breeding activity in the Namaqua Sandgrouse, Pterocles namaqua. Namaqua Sandgrouse exhibit a pattern of partial migration between two late-summer-rainfall regions, birds spending the summer months in the Nama Karoo and the winter months in the Kalahari. Across southern Africa, the breeding season for this species is unexpectedly variable, and not consistently correlated with periods of peak food availability. The main egg-laying periods in the late-summer-rainfall regions are: (a) in northwestern Namibia from January–May with a peak in May, (b) in southwestern Namibia in any month with a peak in July, (c) in the Kalahari from June to December, and (d) in the Nama Karoo from September to December. Breeding in the Nama Karoo often starts five months after food becomes abundant, and extends into the start of the rainy season, when food availability can reach the lowest levels in the annual cycle. This suggests that some factor(s) other than proximate food availability is/are involved in determining the timing of movements and breeding in this species, at least in some regions. The possible complicating influences of biannual breeding, moulting, adult nutritional reserves and seasonal variation in nest predation pressure are discussed. We conclude that further long-term monitoring throughout the range of the Namaqua Sandgrouse is required to unravel the potential contribution of three factors (food availability, pottern of migratory movement and risk of nest predation) to the timing of migratory movements and breeding seasons in this species.

Conservation implications of long-term population trends, environmental correlates and predictive models for Namaqua sandgrouse Pterocles namaqua

Abstract Hunting bag data for Namaqua sandgrouse Pterocles namaqua from an estate near Kimberley, South Africa, for the period 1907–1992 were analysed to investigate population trends, environmental correlates and to develop predictive models for population fluctuations. An apparent population decline between 1950 and 1992 may be an artifact of increased sandgrouse dispersion in response to an increased number of artificial watering points on the estate, and in the surrounding area, during this latter period. Peaks in sandgrouse abundance are significantly negatively correlated with December rainfall and significantly positively correlated with March rainfall. Furthermore, annual sandgrouse abundance and March rainfall showed similar peaks at four-year cycles during 1909–1939. Therefore, a rainfall ‘score’ which takes cognizance of both December and March rainfall is useful for predicting annual sandgrouse abundance before the forthcoming hunting season. However, correct predictions of low sandgrouse abundance were more common than correct predictions of high sandgrouse abundance. These environmental correlates and predictive models are useful for forecasting the annual viability of commercial hunting of these populations.

How sedentary are greywing francolins (Francolinus africanus)

Phasianids are considered to be sedentary birds with limited dispersal so that populations may be expected to show genetic isolation by distance. To test this, we examined genetic variability in 618 greywing francolins (Francolinus africanus) at 24 localities over a 1,500 km2 area. We subdivided the samples to measure genetic population structure among localities separated by 6–60 km, and among coveys separated by 0.1–6 km. Thirteen of 30 (43%) allozyme loci were polymorphic, and heterozygosity ranged from 5.3 to 8.5% over 24 localities and averaged 7.0%, a value much larger than that found for other phasianids. Significant allele‐frequency heterogeneity was detected among localities and among coveys at several localities for several loci. Mantels test, however, showed that there was no correlation between geographical distance and the allele‐frequency difference between localities for all but one allele. Although spatial autocorrelation was detected with Morans I and Gearys c for two alleles, the geographical patterns of I in correlograms of 18 independent alleles showed a “crazy‐quilt” pattern of allele‐frequency patches. This shows that the isolation‐by‐distance model of subpopulation structure is inappropriate for these birds. Individuals, therefore, appear to disperse far beyond neighboring populations. “Private‐allele” and FST estimates of migration under the island model were 8–9 individuals between localities of each generation. Allele‐frequency heterogeneity, large amounts of gene flow, and the general lack of spatial autocorrelation imply that the small, socially‐structured populations of greywing are subject to high rates of turnover, founder effects, and random drift.

Does hunting affect the demography and genetic structure of the greywing francolin Francolinus africanus

Hunted and unhunted populations of greywing francolin Francolinus africanus have been studied in the eastern Cape Province of South Africa in order to understand the effects of hunting on the demography and genetic structure of these populations. Greywing population density cycled annually for both hunted and unhunted populations. However, there was an apparent ‘pulse’ of immigration of sub-dominant birds, and earlier reproduction, in the hunted populations immediately after the winter hunting season. Average levels of allozyme heterozygosity (H) for hunted and unhunted populations were both 0.076, and although the proportion of polymorphic loci per sample and the mean number of alleles per locus for each sample were lower for the hunted populations than for the unhunted populations, these differences were not significant. However, the hunted populations displayed higher levels of outbreeding (lower FIS and FIT values) than those for unhunted populations. Therefore, it is concluded that although greywing francolin populations contain relatively high levels of genetic heterogeneity, it is probably the increased levels of local immigration following hunting which reduces the effects of any reduction in genetic variation due to a decrease in local population size from hunting.