Browsing by Author "Barnard, P"

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    Experimental evidence for bird pollination and corolla damage by ants in the short-tubed flowers of Erica halicacaba (Ericaceae)
    (Elsevier, 2012) Turner, R C; Midgley, J J; Barnard, P; Simmons, R E; Johnson, S D
    Unrelated plants pollinated by similar animals tend to show convergent evolution of floral traits. Floral syndromes have been used successfully to develop hypotheses about pollination systems but can be misleading when plants have unusual floral morphology or mechanisms of pollen transfer. A case in point is Erica halicacaba, a local endemic shrub on the Cape Peninsula of South Africa. Its short-tubed greenish-yellowish flowers with a narrow aperture have been considered to be insect pollinated. However, field observations, selective exclusion experiments and analysis of pollen loads all indicate that its primary pollinator is the Orange-breasted Sunbird (Anthobaphes violacea). These sunbirds were common visitors and netted individuals carried large numbers of E. halicacaba pollen tetrads on their culmens, rather than on their head plumage as is typical for Cape Erica species with longer tubular flowers. Plants of E. halicacaba from which vertebrates were excluded had a lower incidence of anther tripping and set significantly fewer seeds than those exposed to both birds and insect visitors. Nectar in E. halicacaba is present in small concentrated amounts and, typical of sunbird-pollinated plants, is dominated by sucrose. Flowers often had holes in their corollas and we identified ants, specifically Myrmicaria nigra, as the likely agents. This was supported by reduced rates of corolla damage on branches from which crawling insects such as ants were experimentally excluded. These findings indicate that considerable caution should be applied when attempting to predict pollinators from floral syndromes, and highlight the role that crawling insects can play in damaging flowers.
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    Impacts of environmental change on large terrestrial bird species in South Africa: insights from citizen science data
    (2012) Hofmeyr, Sally D; Underhill, Leslie G; Barnard, P
    Large terrestrial bird species, especially cranes and bustards, have adapted to low intensity agriculture to varying degrees, but large-scale industrial agriculture is in general inimical to these species. Cranes are charismatic and well studied, but bustards are retiring and in general cryptically coloured, and little is known of most species. Of South Africa's 10 bustard species, two are endemic and three subspecies are endemic or near-endemic. Six species are threatened or near-threatened. Three crane species occur in South Africa, one of which is near-endemic; all are threatened. This thesis used data from two long-term public participation bird monitoring projects to improve our understanding of six of these 13 species. The first and second Southern African Bird Atlas Projects (SABAP1, 1987-1992, and SABAP2, 2007-) provide two sets of presence/absence data which can be compared. The Coordinated Avifaunal Roadcounts (CAR; 1993-) project provides roadcount data spanning a similar period.
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    The seminal legacy of the Southern African Bird Atlas Project
    (2008) Harrison, J A; Underhill, L G; Barnard, P
    The first Southern African Bird Atlas Project was launched in 1986 and gathered bird distribution data from six countries of southern Africa. The project culminated with the publication of The Atlas of Southern African Birds in 1997. The database generated by the project, seven million bird distribution records, has been widely used by four groups: environmental consultants (for example, to locate electricity transmission lines), conservationists (planning conservation strategies), research scientists (especially macro-ecologists and biogeographers) and birders (ecotourism materials). By 2007, the database had spawned 50 research publications and eight Ph.D.s and master's degrees. These products are a tribute to the more than 5000 'citizen scientists', who gathered the bulk of the data. The atlas concept has been extended to frogs, reptiles, spiders and butterflies; a second bird atlas started in 2007 and will, for example, facilitate knowledge of the impact of environmental change on birds. The South African National Biodiversity Institute is playing a lead role in initiating these new projects.
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    When to stay, when to go: trade-offs for southern African arid-zone birds in times of drought
    (2009) Dean, W R J; Barnard, P; Anderson, M D
    Arid environments remind one of the punctuated equilibrium theory of evolution : they experience long periods of stasis and low productivity, interrupted with episodic rainfall which spurs reproduction and movement. Birds, as highly dispersive organisms, are among the most dramatic indicators of these fluctuations. Here we review birds' two main strategies, residency and nomadism, and the trade-offs faced by individuals in uncertain times. In general, wet years stimulate higher densities of nests (i.e. smaller territories), larger clutch sizes, unseasonal breeding, and at some times of year, higher breeding success. Rainfall above a certain threshold triggers breeding in resident species and an influx of nomadic species which breed and then move on. The environmental cues which trigger nomadism are sometimes poorly understood, but include distant thunderstorms for aquatic species, and perhaps for insectivores. Environmental cues that draw nomadic granivores to areas that have had recent rain are not known.