The effects of prey availability on the endangered bank cormorant Phalacroxorax neglectus

 

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dc.contributor.advisor Underhill, Les en_ZA
dc.contributor.advisor Ryan, Peter G en_ZA
dc.contributor.advisor Sherley, Richard en_ZA
dc.contributor.advisor Cook, Timothée en_ZA
dc.contributor.author Botha, Philna en_ZA
dc.date.accessioned 2015-05-18T14:24:23Z
dc.date.available 2015-05-18T14:24:23Z
dc.date.issued 2014 en_ZA
dc.identifier.citation Botha, P. 2014. The effects of prey availability on the endangered bank cormorant Phalacroxorax neglectus. University of Cape Town. en_ZA
dc.identifier.uri http://hdl.handle.net/11427/12823
dc.description Includes bibliographical references. en_ZA
dc.description.abstract The bank cormorant Phalacrocorax neglectus is a seabird endemic to the south-western coast of southern Africa and the Benguela Upwelling System and has suffered a decline of more than 50% over three generations. Main threats include displacement by Cape fur seals Arctocephalus pusillus, direct human disturbance, pollution, climate change and food shortage. This thesis focuses on the bank cormorant’s response to food shortage, both directly and indirectly. Four colonies (Jutten Island, Dassen Island, Robben Island and Stony Point) were studied in terms of responses on population level in relation to the spatial distribution of prey surrounding the various colonies, foraging behaviour and breeding success. First, I tested the response of the bank cormorant ’ s population dynamics in relation to the availability of West Coast rock lobster Jasus lalandii in different spatial scales around three colonies (Jutten Island, Dassen Island and Stony Point) over a subset of years. I found that birds at Dassen Island showed the strongest response to the availability of rock lobster. Birds also showed strongest response to the availability of rock lobster in an accumulative distance around colonies, and their largest response was to rock lobster within 30 km distance from the colony. Various aspects including the life - history traits and moulting stages of this particular rock lobster species may be the reason to this response. Second, I present foraging effort data of bank cormorants in localities known to be situated in areas with different prey availability. I found that at Jutten Island, situated in an area where West Coast rock lobster have dramatically decreased, bank cormorants spent significantly longer time at sea than at Robben Island and Stony Point, which were situated in areas where rock lobster were known to be abundant at the time of the study. Third, I tested the effect of food availability on the breeding success of bank cormorants at Jutten Island, Robben Island and Stony Point. There was no significant relationship between food availability and the survival probability of the birds. The number of chicks fledged per successful nest, however was significantly related to the availability of rock lobster during the relevant breeding season, as well as during the relevant month of hatching. en_ZA
dc.language.iso eng en_ZA
dc.subject.other Zoology en_ZA
dc.title The effects of prey availability on the endangered bank cormorant Phalacroxorax neglectus en_ZA
dc.type Master Thesis
uct.type.publication Research en_ZA
uct.type.resource Thesis en_ZA
dc.publisher.institution University of Cape Town
dc.publisher.faculty Faculty of Science en_ZA
dc.publisher.department Department of Biological Sciences en_ZA
dc.type.qualificationlevel Masters
dc.type.qualificationname MSc en_ZA
uct.type.filetype Text
uct.type.filetype Image
dc.identifier.apacitation Botha, P. (2014). <i>The effects of prey availability on the endangered bank cormorant Phalacroxorax neglectus</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Biological Sciences. Retrieved from http://hdl.handle.net/11427/12823 en_ZA
dc.identifier.chicagocitation Botha, Philna. <i>"The effects of prey availability on the endangered bank cormorant Phalacroxorax neglectus."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 2014. http://hdl.handle.net/11427/12823 en_ZA
dc.identifier.vancouvercitation Botha P. The effects of prey availability on the endangered bank cormorant Phalacroxorax neglectus. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 2014 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/12823 en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Botha, Philna AB - The bank cormorant Phalacrocorax neglectus is a seabird endemic to the south-western coast of southern Africa and the Benguela Upwelling System and has suffered a decline of more than 50% over three generations. Main threats include displacement by Cape fur seals Arctocephalus pusillus, direct human disturbance, pollution, climate change and food shortage. This thesis focuses on the bank cormorant’s response to food shortage, both directly and indirectly. Four colonies (Jutten Island, Dassen Island, Robben Island and Stony Point) were studied in terms of responses on population level in relation to the spatial distribution of prey surrounding the various colonies, foraging behaviour and breeding success. First, I tested the response of the bank cormorant ’ s population dynamics in relation to the availability of West Coast rock lobster Jasus lalandii in different spatial scales around three colonies (Jutten Island, Dassen Island and Stony Point) over a subset of years. I found that birds at Dassen Island showed the strongest response to the availability of rock lobster. Birds also showed strongest response to the availability of rock lobster in an accumulative distance around colonies, and their largest response was to rock lobster within 30 km distance from the colony. Various aspects including the life - history traits and moulting stages of this particular rock lobster species may be the reason to this response. Second, I present foraging effort data of bank cormorants in localities known to be situated in areas with different prey availability. I found that at Jutten Island, situated in an area where West Coast rock lobster have dramatically decreased, bank cormorants spent significantly longer time at sea than at Robben Island and Stony Point, which were situated in areas where rock lobster were known to be abundant at the time of the study. Third, I tested the effect of food availability on the breeding success of bank cormorants at Jutten Island, Robben Island and Stony Point. There was no significant relationship between food availability and the survival probability of the birds. The number of chicks fledged per successful nest, however was significantly related to the availability of rock lobster during the relevant breeding season, as well as during the relevant month of hatching. DA - 2014 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2014 T1 - The effects of prey availability on the endangered bank cormorant Phalacroxorax neglectus TI - The effects of prey availability on the endangered bank cormorant Phalacroxorax neglectus UR - http://hdl.handle.net/11427/12823 ER - en_ZA


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