Browsing by Author "Baigrie, Bruce"

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    Exploring the breeding diet of the Black Sparrowhawk (Accipiter Melanoleucus) on the Cape Peninsula
    (2013) Baigrie, Bruce; Amar, Arjun
    This study investigates the diet of breeding Black Sparrowhawks (Accipiter melanoleucus) on the Cape Peninsula of South Africa. Macro-remains of prey were collected from below and around the vicinity of nests throughout the breeding seasons of 2012 and 2013. These prey items were then identified down to species where possible through the use of a museum reference collection. In both years 85.9% of the individual remains were those of Columbidae, which corresponds with the only other diet study on Black Sparrowhawks. Redeyed Doves were the most common prey species, accounting for around 35% of the diet’s biomass and 45% of the prey items. Helmeted Guineafowl were also an important component of the diet for certain nests, making up on average 26.4% biomass of the diet. I found very little difference in diet between the different stages of breeding (pre-lay, incubation and nestling), despite the fact that females only contribute significantly during the nestling state and are considerably larger than the males. I also found little difference in the diet composition between pairs which bred either earlier or later in the year, despite productivity being significantly higher for earlier breeding pairs. However, a crude analysis of the overall diet per month revealed increased diet breadth in the early lay months as opposed to the later months. This was a result of fluctuations in the presence of Laughing Doves, Feral Pigeons and Helmeted Guineafowl, probably driven by those species breeding behaviour. Lastly, I also found no difference in the diet composition between pairs with either pure or mixed plumage morph compositions in this polymorphic species. This study provides further evidence to the claim that Black Sparrowhawks on the Cape Peninsula are benefiting from man-altered environments that provide perfect habitat for suitable prey.
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    Fun and fear in False Bay Nature Reserve: green space affordances in the post-apartheid city
    (2015) Baigrie, Bruce; Anderson, Pippin; Daya, Shari; Wright, Dale
    The phenomenon and increasing rate of urbanisation is causing many researchers to look deeper at life in cities. Increasingly recognised are the benefits of urban green space and their associated recreational parks and nature reserves. While there is a growing literature on the environmental services provided by these areas; so too is there a growing literature on the numerous social benefits that recreational green spaces in particular afford their users. Although imagined and generally designed as salubrious public spaces, many parks often fall short of this. In fact research has shown that a park's design, its surroundings, and its management can all combine to exclude certain types of people. In this study I conducted ethnographic research to participate in and observe the activities of visitors to False Bay Nature Reserve in Cape Town. False Bay Nature Reserve includes a series of nature reserves and the Cape Flats Waste Water Treatment Works, and is situated in the area of Cape Town known as the Cape Flats. Much of the Cape Flats is beset by poverty, unemployment, and violent drug - related crime carried out by notorious gangs. Despite the challenges of the surrounding areas, my study reveals that False Bay Nature Reserve provides relative safety to its users as well a range of enjoyable re creational activities. Some of the key recreational activities are separated distinctively between two key sites in the reserve. Furthermore the visitors of these sites differ markedly in race, ethnicity and income. The legacy of apartheid almost certainly accounts for much of this separation; however, the study indicates that the barriers of this legacy are eroding and can potentially be further dismantled with engaged and informed management strategies. Due to its surroundings, the reserve is vulnerable and recently experienced a period where crime was prevalent, vegetation was overgrown, and it was feared by many of its users, particularly women. The reserve had in many ways become what researchers call a landscape of fear, a not so uncommon description of parks around the world. However, management and the majority of visitors feel the reserve has recovered from this period. This is in large part due to upgrades that improved recreational facilities and security in the reserve. Accounts from visitors high light how important a sense of safety is for people frequenting this reserve, most of who live in nearby neighbourhoods. The reserve still faces some challenges today, but is a significant asset to the City of Cape Town and many of its more marginalised residents. This study challenges much of the literature on the benefits of urban green space and associated parks. It shows that particularly in cities of the Global South such as Cape Town, parks require specific management strategies that prioritise safety and in doing so promote and ensure inclusivity for all.
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    Mutualism benefits and the evolution of an interspecific sentry call in associations between Sociable Weavers and Fork-tailed Drongos
    (2013) Baigrie, Bruce; Ryan, Peter G; Flower, Thomas
    Mutualisms, where organisms benefit from cooperation, are common in nature, but payoffs are dynamic and mutualists can incur costs as well as benefits from their association. Nevertheless, selection can favour the coevolution of behaviour that increases benefits. Such coevolution can potentially result in new mutualistic behaviours. Our study considered associations between Fork-tailed Drongos (Dicrurus adsimilis), birds which use both false alarms and aggression to steal food from other species (kleptoparasitism), and their most frequent host, the Sociable Weaver (Philetairus socius). While drongos apparently gain and weavers lose from this association, we investigated whether weavers derive foraging and predator protection benefits, and whether drongos increase foraging opportunities through sentry call behaviour. When with drongos, weavers increased their foraging time and reduced vigilance. Experimental playbacks further demonstrated that drongo sentry calls attract sociable weavers, as well as increasing their foraging time and decreasing their vigilance. Weavers also resumed foraging after an alarm more quickly when sentry calls were made, but sentry calls do not appear to improve drongo false alarm success since sentry calls did not increase the likelihood weavers fled to subsequent drongo false alarms. Consequently sentry calls benefit weavers via foraging payoffs and drongos via weaver attraction and potentially by increasing opportunities for kleptoparasitism. Results demonstrate that despite costly deception between mutualists, individuals nevertheless derive benefits which may be enhanced by the coevolution of a mutually beneficial vocal signal, specific to interspecific communication.