The copyright of this thesis vests in the author. No quotation from it or information derived from it is to be published without full acknowledgementTown of the source. The thesis is to be used for private study or non- commercial research purposes only. Cape Published by the University ofof Cape Town (UCT) in terms of the non-exclusive license granted to UCT by the author. University The Biology and Conservation of the Damara Tern in Namibia by Justine Braby Town Cape of University Supervised by: Prof LG Underhill Thesis presented for the Animal Demography Unit Degree of Department of Zoology University of Cape Town Rondebosch 7701 Doctor of Philosophy South Africa In the Department of Dr RE Simmons Percy-Fitz Patrick Institute Zoology Department of Zoology University of Cape Town University of Cape Town Rondebosch 7701 South Africa February 2011 Dr J-P Roux Ministry of Fisheries and Marine Resources Lüderitz Marine Research PO Box 394, Lüderitz Namibia For my parents, Town Rod and Sigi Braby, who have devoted so much to the Damara Tern Cape of University Table of Contents Abstract...................................................................................................................................................i Layout and contributions………………………………………………………………………........iii Acknowledgements………………………………………………………………………………………v Chapter 1 Introduction………………………………………………………………………………1 Chapter 2 Clutch size and breeding success of Damara Terns Sterna balaenarum in Namibia……………………………………………………………………………….Town 29 Chapter 3 Growth patterns, fledging period and feeding rate of Damara Tern Sterna balaenarum chicks in Namibia………………………………..….......54 Cape Chapter 4 Immature survival and ageof at first breeding of Damara Terns Sterna balaenarum: conservation from a non-breeding perspective……..73 Chapter 5 Annual dispersal and survival of a seabird adapted to a stable environment: implications for conservation……………………………...86 Chapter 6 PreyUniversity capture success and chick diet of Damara Terns Sterna balaenarum in southern Namibia………………………………………………98 Chapter 7 The impacts of diamond mining activities on breeding Damara Terns Sterna balaenarum in southern Namibia………………………………….117 Chapter 8 Protecting Damara Terns Sterna balaenarum from recreational disturbance in the Namib Desert increases breeding density and overall success……………………………………………………………………….135 Chapter 9 Population estimates, distribution and conservation of the Damara Tern Sterna balaenarum…………………………………………………………146 Chapter 10 Synthesis and recommendations…………………………………………….188 Reference List……………………………………………………………………………………………194 Appendix 1………………………………………………………………………………………………...220 Town Annex 1……………………………………………………………………………………………………...221 Annex 2………………………………………………………………………Cape... ……………………………223 of Plates…………………………………………………………………………………………...………..…...227 University Abstract Author: Justine Braby Title: The Biology and Conservation of the Damara Tern in Namibia Date: February 2011 The globally Near-threatened Damara Tern Sterna balaenarum is little known and faces several conservation issues. The aim of this study was to provide a description of the ecology and numbers of the species and discuss conservation management plans that will effectively ensure its survival. Because 98% of the population breeds in Namibia, all dataTown for the study pertaining to the species’ breeding biology were collected here. Overall breeding success (probability of fledgingCape one chick per pair per season) in Namibia was 0.36, althoughof breeding success fluctuated between seasons and colonies. Predation of eggs and chicks was found to be the main factor impacting the breeding success of Damara Terns. Chick growth rate was slower than that of chicks of similar species. Resources allocated to growth favoured initial development of legs, then wings, and lastly, bill. Immature survivalUniversity from fledging to breeding was estimated using mark- capture-recapture techniques and found to be 0.59 (95% confidence interval=0.48–0.68). This estimate includes an element of chick mortality. The survival estimate for chicks older than 23 days (fledging age) was 0.84. Age at first breeding was found to be three to four years. Annual adult survival was found to be 0.88 (95% CI=0.73–0.96). Annual dispersal between two adjacent breeding colonies was 0.06 (95% CI=0.03–0.12); these low i dispersal probabilities indicate that protection of breeding sites is an important management approach for the species. Prey capture success of Damara Terns in relation to six environmental variables was investigated at two colonies in southern Namibia. Prey capture success was greatest at high tide, strong winds and in least turbid water. Overall prey capture success was 30.5%. (SD=3.1%). Mining activities, in the form of discharging sediment into the sea where breeding Damara Terns fed, were not found to overall significantly impact the breeding success of Damara Terns at one colony in southern Namibia. The effectiveness of conservation measures on breedingTown Damara Terns was assessed at a colony vulnerable to extensive recreational off-road vehicle disturbances in central Namibia. The study found that Damara Terns benefited from reduced disturbance becauseCape the access restrictions prevented entry to the colony by off-road vehicles. of A review of all accessible information of breeding populations in Angola, Namibia and South Africa found that 70 breeding colonies exist globally. The breeding population of Damara Terns was estimated to range up to 5370 breeding individuals. The continued survival of the species requires an urgent updated Universitysurvey of the breeding population to reassess the species’ conservation status. Conservation measures should focus on the protection of important breeding colony sites in Namibia, and also at the extremities of the range in South Africa and Angola. On migration along the west coast of Africa, and during the non-breeding season in West Africa, legal and enforced protection of Damara Terns from human disturbance (such as off-road driving trampling nests, trapping and killing birds, indirect disturbances affecting breeding and feeding habitat) is required. ii Layout and contributions This thesis consists of eight main chapters, most of which are written as papers for submission to a journal. Tables and figures follow the text of each chapter; references for all chapters are combined at the end of the thesis. I collected all field data in southern Namibia from January 2007 to March 2009, and at various colonies in central Namibia from December 2009 to February 2010, and have contributed to field data collection at most other Damara Tern colonies since 1995. I collated, computerized and validated monitoring data for Damara Terns collected by staff of the Ministry of Environment and Tourism for various breeding areas fromTown 1982–1993 and by Rod and Sigi Braby who monitored the breeding sites called Caution Reef and Horses Graves from 1995–2010. Without their fieldwork various aspects of this thesis would not have been possible; theirCape vital roles will be acknowledged in co-authorships of the forthcoming series of papers. I was responsible for the analysis and writingof of each chapter. I discussed some of the fundamental ideas with my supervisors, Les Underhill, Rob Simmons and Jean-Paul Roux. Les Underhill (and to some extent, Jean-Paul Roux and Rob Simmons) advised on methods of data analysis. All three supervisors assisted with the wording of some methods sections and commented on chapter drafts. Jessica Kemper,University Rod and Sigi Braby , Res Altwegg, David Wiggins, Teresa Catry, Nicole Braby, Rene Navarro, Mariette Wheeler and Katrin Ludynia commented on some of my chapter drafts. Res Altwegg assisted with the analysis and drafting of Chapter 4 and 5 and will be acknowledged in co- authorship for those papers. Katrin Ludynia conducted the bomb calirometry work for Chapter 6. Maps for all chapters except one were constructed by Holger Kolberg. The maps in Chapter 8 were constructed by Chris Bartholomeau. Photographs not taken by me were credited accordingly. iii The planned co-authorships for the papers are outlined below. Chapter 2: Braby J, Braby RJ, Braby SJ, Simmons RE, Underhill LG, Roux JP and Kolberg H. Clutch size and breeding success of Damara Terns in Namibia. Chapter 3: Braby J and Underhill LG. Growth patterns, fledging period and feeding rate of Damara Tern chicks in Namibia. Chapter 4: Braby J, Braby SJ, Braby RJ and Altwegg R. Immature survival and age at first breeding of Damara Terns: conservation from a non-breeding perspective. Town Chapter 5: Braby J, Braby SJ, Braby RJ and Altwegg R. Annual survival and dispersal of a seabird adapted to a stable environment: implications for conservation. Submitted to Journal of Ornithology.Cape of Chapter 6: Braby J, Underhill LG and Simmons RE. Prey capture success and chick diet of Damara Terns in southern Namibia.. Chapter 7: Braby J, Underhill LG, Simmons RE and Roux JP. The impacts of diamond mining activities on breeding Damara Terns in southern Namibia. University Chapter 8: Braby J, Braby RJ, Braby N and Simmons RE. 2009. Protecting Damara Terns from recreational disturbance in the Namib Desert increases breeding density and overall success. Ostrich 80: 71–75. Chapter 9: Braby J, Braby RJ, Braby SJ, Simmons RE, Kolberg H, Braine S, Loutit R, Whittington P, Tree T, Underhill LG, Cooper J, Boorman M, Lonser J, Bartlett P, Kemper J and Roux JP. Population estimates, distribution and conservation