The Causes of Avian Extinction and Rarity by Christopher James Lennard Town Cape of University Thesis submitted in the Faculty of Science (Department of Ornithology); University of Cape Town for the degree of Master of Science. June 1997 The University of Cape Town has been given the rllf'lt to reproduce this ~la In whole or In pil't. Copytlght is held by the autl>p'lr . ' 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 Declaration: I I certify that this thesis results from my original investigation, except where acknowledged, and has not been submitted for a degree at any other university. Christopher J. Lennard Table of contents Page Table of contents ................................................................................................................ iii List oftigures ................................................................................................................... viii List of tables ....... :............................................................................................................... ix Acknowledgments ..................... , .................................... :.· ................................................. xii Abstract ............................................................................................................................... 1 Chapter One: Introduction and Methods ............................................................................. 2 Introduction ......................................................................................................................... 2 The next mass extinction ............................................................................. 3 Birds and extinction .................................................................................... 5 Thesis structure ........................................................................................... 6 Methods ............................................................................................................................... 7 Extinction literature ..................................................................................... 7 Threat literature ............................................. :............................................. 8 Data analyses ............................................................................................... 9 Extinction data ...................................................................................... 9 Distinguishing species and subspecies .................................... 10 Data compilation ..................................................................... 10 Chronology of extinction ........................................................ 11 Causes of extinction ............. ·................................................... 11 Geography of extinction .......................: .................................. 12 Phylogeny of extinction .......................................................... 13 Body size ................................................................................. 13 Threat data ........................................................................................... 14 Data compilation ..................................................................... 14 Causes of threat ....................................................................... 16 iii Geography of threat. ................................................................ 17 Taxonomy of threatened species ............................................. 18 Habitats of threatened species ................................................. 18 Body size, endemicity, threat and extinction on ten selected islands ................................................................................... 18 Prehistoric extinctions, historical extinctions and current threat ........ 18 Phylogenetic analysis .......................................................................... 19 Chapter Two: The extinctions of avifauna since 1600 ...................................................... 20 Part One - Results .............................................................................................................. 20 Chronology of extinction .......................................................................... 20 Chronology of mainland extinctions ................................................... 20 Chronology of island extinctions ........................................................ 21 Causes of extinction .................................................................................. 24 Cause and chronology ......................................................................... 25 Geography of extinction ............................................................................ 27 Island location ................................................................................... :;· 27 Island sizes .......................................................................................... 2 8 Endemicity ................................................................................................ 35 Migratory birds and extinction .................................................................. 36 Phylogeny of extinction ............................................................................ 36 Orders ................................................................................................... 36 Families ............................................................................................... 39 Body size and extinction ........................................................................... 43 Body size, island size and extinction ........................................................ 45 Part Two - Discussion ....................................................................................................... 46 Prehistoric extinctions ................................................................................ 46 Historical extinction rates:: ....................................................................... 47 Causes of historical extinction .................................................................. 50 lV Introduced predators ............................................................................ 50 Exploitation ............................................. .-........................................... 51 Habitat destruction .............................................................................. 51 Unknown ............................................................................................. 52 Combinations of factors ....................................................................... 53 Geography of historical extinctions·~························································ 54 Island extinctions ................................................................................ 54 Island size ................................................................................ 54 Oceanic regions ....................................................................... 54 Islands most severely affected ................................................. 55 Islands experiencing between two and four extinctions .......... 64 Islands experiencing one extinction ........................................ 64 Some conclusions .................................................................... 66 Mainland extinctions ........................................................................... 67 Taxonomy of extinct species ..................................................................... 68 Orders .............................................· ...................................................... 68 Families ............................................................................................... 69 Prehistoric extinctions ............................................................................... 70 Extinction filters ........................................................................................ 71 ) Extinction debt .......................................................................................... 73 Avian extinctions over the last 46 years ................................................... 74 Body size ................................................................................................... 75 Chapter Three: Threatened avifauna................................................................................. 77 Part One - Results .............................................................................................................. 77 Causes of threat ......................................................................................... 77 All threatened species ......................................................................... 77 Endangered species ............................................................................. 79 Critical species .................................................................................... 80 Geography of threat. .................................................................................. 81 v All threatened species ........................................................................