Publications

apparent absorption efficiencies of nectar sugars in the cape sugarbird, with a comparison of methods.	nectarivore sugar preferences and nectar composition in the cape floristic kingdom (southern africa) differ from trends reported for analogous systems in america and europe in that sugarbirds and sunbirds show no aversion to sucrose, which is the dominant nectar sugar in many of their food plants. to elucidate the physiological bases (if any) of nectarivore sugar preferences, we determined apparent sugar absorption efficiencies in a passerine endemic to this region, the cape sugarbird promerops ...	2013	9472818
female cape sugarbirds (promerops cafer) modify egg investment both for extra-pair mates and for male tail length.	the differential allocation hypothesis predicts that females should invest more in reproduction when paired with attractive males. we measured egg volume in cape sugarbirds (promerops cafer), a sexually dimorphic passerine, in relation to paternity of the offspring and in response to an experimental tail length treatment. we manipulated tail length, after pair formation, but before egg laying: males had their tails either shortened or left unmanipulated. our manipulation was designed to affect f ...	2010	20695964
a bird pollinator shows positive frequency dependence and constancy of species choice in natural plant communities.	animal pollinators mediate reproduction of many plant species. foraging theory suggests that animal pollinators exhibit preferences for common plant species in natural communities (positive frequency-dependent foraging) and temporary single-species specialization (flower constancy) during foraging bouts. positive frequency dependence may favor common plant species; flower constancy may enhance conspecific pollen transfer particularly in rare plant species. previous experimental studies suggest t ...	2016	27870050
mutualism between co-occurring plant species in south africa's mediterranean climate heathland is mediated by birds.	interactions among plant species via pollinators vary from competitive to mutualistic and can influence the probability of stable coexistence of plant species. we aimed to determine the nature of the interaction via flower visitors between leucospermum conocarpodendron and mimetes fimbriifolius, two shrubs in the proteaceae that share many ecological traits and coexist on the cape peninsula, south africa. to assess the extent of pollinator sharing we analysed nectar properties and recorded the p ...	2018	28960844
birds mediate a fungus-mite mutualism.	mutualisms between ophiostomatoid fungi and arthropods have been well documented. these fungi commonly aid arthropod nutrition and, in turn, are transported to new niches by these arthropods. the inflorescences of protea trees provide a niche for a unique assemblage of ophiostomatoid fungi. here, mites feed on sporothrix fungi and vector the spores to new niches. protea-pollinating beetles transport the spore-carrying mites between protea trees. however, many protea species are primarily pollina ...	2017	29071368
acute, fatal, presumptive xylitol toxicosis in cape sugarbirds ( promerops cafer).	twenty-nine wild cape sugarbirds ( promerops cafer) died acutely after ingestion of a homemade xylitol nectar solution from a bird feeder. the most aggressive feeders were first affected. most birds showed clinical signs within 15 minutes of nectar ingestion, including incoordination, weakness, falling from perches, collapse, and death. a few birds showing clinical signs seemed to spontaneously recover and fly away. full necropsy examinations done on 27 birds were hampered by freezing artifact a ...	2017	29327962
population diversity and relatedness in sugarbirds (promeropidae: promerops spp.).	sugarbirds are a family of two socially-monogamous passerine species endemic to southern africa. cape and gurney's sugarbird (promerops cafer and p. gurneyi) differ in abundance, dispersion across their range and in the degree of sexual dimorphism in tail length, factors that affect breeding systems and potentially genetic diversity. according to recent data, p. gurneyi are in decline and revision of the species' iucn conservation status to a threatened category may be warranted. it is therefore ...	2018	29915704