Browsing by Author "Underhill, Leslie"

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    A contribution to understanding the primary moult of birds
    (2023) Scott, Tanya; Underhill, Leslie; Erni Birgit
    Moult is an essential component of the annual cycle of birds, along with breeding, and, if migratory, migration. The leading statistical model for the analysis of primary moult is the Underhill-Zucchini moult model. It estimates moult parameters (duration, the mean start date and its standard deviation). An objective of this thesis was to assemble all published results which had used the UnderhillZucchini moult and to examine the resulting database for patterns in the timing, duration and synchronisation of moult. A total of 242 analyses of 136 species were found. The initial analysis of the database generated two observations: firstly, that latitude played an important role in determining patterns of primary moult, and, secondly, that the available data were latitudinally, spatially across continents, and taxonomically not representative. These gaps in knowledge were too large to rectify within the confines of a single PhD thesis. The preliminary chapters of the thesis added 18 analyses, for 11 species, and have made a contribution towards representativity. Two of the preliminary chapters make substantive contributions to the methods of undertaking statistical studies of moult. A new moult index, the Relative Duration Index, is introduced. Moult studies are frequently undertaken by combining datasets collected in different years (or different places). This thesis contains the first practical application of a proposed method to identify which of the individual datasets have a large influence of the estimates of the moult parameters. Nine analyses extended the latitudinal range of studies southwards and were based on datasets assembled in New Zealand. These are the first analyses of primary moult using the UnderhillZucchini moult model from this country. For seven species, this thesis undertakes moult studies of a species in both its original country, the United Kingdom, and the country into which it had been introduced, New Zealand. These are the first analyses of primary moult of this kind. Preliminary patterns of moult strategies are discussed. Critical gaps in our understanding of primary moult are identified. Priorities for fieldwork and analysis are described in order that key gaps are filled and a global review of primary moult can be undertaken.
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    Monkey beetles on the beat: urban monkey beetles reveal opportunities for pollinator habitat management in a South African city
    (2022) Brom, Peta; Underhill, Leslie; Winter, Kevin; Colville, Jonathan
    Against a backdrop of global declines in pollinators, evidence suggests that some guilds thrive in urban landscapes and relatively small interventions can provide habitat support in otherwise inhospitable urban landscapes. Despite this knowledge, there is a paucity of research on urban pollinators in Africa. This gap is noteworthy because Africa is a megadiverse region and southern Africa has three global biodiversity hotspots. This thesis is a first step towards filling the Africa gap. Its ought to do so by investigating urban monkey beetles (Coleoptera: Scarabaeidae: Hopliini) in two ways. Firstly, it relates Hopliini community structure to urban environmental gradients and local habitat composition. This was achieved by using pan traps to sample pollinators at 145 sites during two austral spring seasons in greater Cape Town in 2018 and 2019. The findings are that there were three divergent responses to urban landscape dynamics. 1) Those which exploited the urban environment. 2) Those which did not respond to an urban intensity gradient, but did respond to flower‐richness, 3) Those which preferred larger, less disturbed sites at the edge of the city. Secondly, ways that the management of Public Open Space (POS) and road verges can better support the connectivity of habitats containing endemic geophytes and spring annuals were considered. These flower populations provide breeding and foraging resources to Hopliini and other pollinators. They are an especially important resource to the group who are unable to move through or exploit the urban environment without them (Group 2 above). A mowing suspension was investigated to determine how long the indigenous spring show would take to complete the reproductive cycle and reach seed set. The study took a phenological approach to estimating the duration of the suspension. The findings indicate that mowing should be suspended for spring geophyte patches from the first week of August until after the first week of November. The charismatic Baeometra uniflora can be used as an indicator species for when the season has concluded. Methods of strategic landscaping and interplanting are discussed, noting that the peak flowering season in spring is followed by a lesser abundant summer show.
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    Moult strategies of oystercatchers (Haematopidae) in New Zealand, Australia and South Africa
    (2023) Bate, Taylyn; Underhill, Leslie; Ryan Peter
    While there are a number of studies that have examined the moult strategies of migrant waders (Charadrii), only a few have focused on non-migrant waders. As part of a collection of papers that have analysed moult using the Underhill-Zucchini moult model, we used this method to observe the moult strategies of species within the family Haematopidae. Our data includes a combination of previously acquired ringing data and that which we collected, along with contributions by citizen scientists, in the form of photographic records. The first chapter provides an introduction to the study, placing it within the context of comparable research, and placing moult within the context of the birds' important life stages. Our second chapter focuses on the Australian Pied Oystercatcher Haematopus longirostris, of which we completed a detailed analysis of the wing and feather moult. Within chapters 3-6 we examine the wing moult strategies of the Sooty Oystercatcher H. fuliginosus of Australia, the South Island Pied Oystercatcher H. finschi and Variable Oystercatcher H. unicolor of New Zealand, and the African Oystercatcher H. moquini of South Africa. With no long-distance movements, these oystercatchers are free to devote more time and energy towards other stages in their life cycle: breeding and moult. We identified the moult parameters of start date, standard deviation in start date, duration and end date for each of the five species. We acquired the relative feather masses and used these in the conversion of the moult scores to proportion feather mass grown (PFMG). The final chapter synthesizes the work, consisting of a comparison and identification of the similarities and differences between the species' moult strategies, and possible reasons for these. We approach the conclusion that further research is needed on the strategies of moult for resident waders, and this may be achieved successfully through the use of digital photography. With an expanding knowledge of the parameters of moult, there is opportunity for even more discoveries into these birds' lives, which will have benefits for their conservation.
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    Surviving off junk: low-energy prey dominates the diet of African penguins Spheniscus demersus at Mercury Island Namibia between 1996 and 2009
    (2010) Ludynia, Katrin; Roux, J-P; Jones, R; Kemper, J; Underhill, Leslie
    The diet of African penguins Spheniscus demersus in Namibia consisted mainly of sardine Sardinops sagax in the 1950s. Since the collapse of pelagic fish stocks in the 1970s, birds fed mainly on bearded (pelagic) goby Sufflogobius bibarbatus, a low-energy prey species. We present diet data for African penguins breeding at Mercury Island, the largest colony for this species in Namibia, between 1996 and 2009. Bearded goby was the main prey item throughout the study period, both in terms of frequency of occurrence (67.8%; SD 31.2) and in terms of mass (59.2%; SD 31.5). Diet composition varied throughout the year as well as between years; birds occasionally fed on a variety of fish species other than bearded goby. In Namibia, poor prey abundance is considered as a major factor contributing to the decline of penguin numbers after the collapse of the sardine stocks. However, bearded goby appears to be relatively abundant along Namibia's southern coast and low prey quality rather than low abundance appears to be a key factor influencing population dynamics of African penguins and other marine top predators in southern Namibia.
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    The breeding ecology and behavioural adaptations of African black oystercatchers in light of climate change
    (2021) Azaki, Bukola Debola Aderewa; Underhill, Leslie; Cunningham, Susan
    This thesis examined how weather conditions and other environmental factors influence the vulnerability of nesting African Black Oystercatchers Haematopus moquini (oystercatchers) to climate and habitat change. I explore, for the first time, the behavioural adaptations used by the species to cope with breeding in a limited strip of beach, between high tides and terrestrial predators, and with little nesting shelter, and their breeding decisions to maximise breeding outcomes. Behavioural and breeding data were collected over three breeding seasons (2016—2018) on Robben Island, South Africa (a site with about 5% of the global population of the species) using time-lapse digital cameras and direct observations. Climate and environmental variables were obtained either through on-site iButton data loggers or from the relevant South African meteorological agencies. The results show that oystercatchers are vulnerable to increasing heat loads as temperature increases. However, oystercatchers used a suite of thermoregulatory behaviours to cope with a wide range of environmental temperatures and decreased the length of their incubation bouts as temperature increased. The proximity of the oystercatchers' breeding site to the ocean appears to contribute significantly to their capacity to cope with increasing heat loads. But such sites potentially expose the oystercatchers to the risk of nest losses to storm surges. Oystercatchers reduced this risk by using habitat selection to optimise the placement of their nests close to the midpoint of the beach, but some were constrained by the narrowness of their territories. Oystercatchers also used the biweekly semilunar spring tide cycle to synchronise the incubation start date of their clutches probably to minimise the number of spring tides that they experience during incubation. Predation was the main cause of oystercatcher nest failure. Surprisingly, Mole Snakes Pseudaspis cana were responsible in all cases where the predator identity was known rather than Kelp Gulls which have historically been suggested to be the main agent. Nest predation probability was influenced by temperature and distance to predator-concealing vegetation and increased as more nests became available, causing a seasonal decline of nest survival. Hence, oystercatcher pairs laying large clutches early in the season were more likely to produce one juvenile in a season. The average number of fledgelings per pair per season was 0.38 and close to that (0.35) required to maintain a stable population. These findings improve our understanding of the breeding ecology and behavioural adaptations of the oystercatchers which might help them to cope with climate change as well as provide new insights on which management decisions and further studies can be based.