FEEDING ECOLOGY AND COMPETITION FOR FOOD IN TWO PHILIPPINE HORNBILL SPECIES (BUCEROTIDAE; Aceros waldeni, Penelopides panini) IN THE BREEDING SEASON Dissertation to obtain the degree Doctor of Philosophy (PhD) At the Faculty of Biology and Biotechnology International Graduate School of Biosciences Ruhr-University Bochum Conservation Biology Unit Submitted by Basharat Ahmad From Muzaffarabad, Pakistan Bochum (January 2013) NAHRUNGSÖKOLOGIE UND NAHRUNGSKONKURRENZ ZWEIER PHILIPPINISCHER NASHORNVOGELARTEN (Bucerotidae; Aceros waldeni, Penelopides panini) IN DER BRUTZEIT Dissertation zur Erlangung des Grades eines Doktors der Philosophie (PhD) an der Fakultät für Biologie und Biotechnologie Internationalen Graduiertenschule für Biowissenschaften der Ruhr-Universität Bochum Conservation Biology Unit Vorgelegt von Basharat Ahmad aus Muzaffarabad, Pakistan Bochum (Januar 2013) Supervisor: Prof. Dr. Eberhard Curio Conservation Biology Unit Faculty of Biology and Biotechnology Co-Supervisor: Prof. Dr. Ralph Tollrian Department of Animal Ecology, Evolution and Biodiversity Faculty of Biology and Biotechnology Table of contents Table of Contents Abstract ............................................................................................................................ i Kurzfassung ................................................................................................................... iv Chapter 1 INTRODUCTION ............................................................................................1 1.1 General distribution .............................................................................................2 1.2 Feeding behaviour ...............................................................................................3 1.3 Reproduction and sexual behaviour .....................................................................5 1.4 Nesting Habit ......................................................................................................8 1.5 Scope of the present study ................................................................................. 10 Chapter 2 MATERIALS AND METHODS ............................................................... 13 2.1 Study area ......................................................................................................... 13 2.2 Methods ............................................................................................................ 15 2.2.1 Field survey and species identification ......................................................... 15 2.2.2 Nest site selection and nest tree characteristics ............................................. 16 2.2.3 Nest orientation ........................................................................................... 17 2.2.4 Estimation of population size and breeding pair density ............................... 17 2.2.5 Dispersion pattern ........................................................................................ 18 2.2.6 Feeding ecology........................................................................................... 20 2.3.7 Statistical analysis........................................................................................ 21 Chapter 3 RESULTS ................................................................................................. 22 3.1 Status and characteristics of nest hole trees ........................................................ 22 3.1.1 Status of nest hole trees................................................................................ 24 3.1.1.1 Status of nest hole trees of the Dulungan .......................................................... 26 3.1.1.2 Status of nest hole trees of the Tarictic .............................................................. 26 3.1.2 Characteristics of nest hole trees .................................................................. 27 3.1.2.1 Measurements of nest trees of Dulungan .......................................................... 30 3.1.2.2 Measurements of nest trees of Tarictic.............................................................. 31 3.1.3 Orientation of the entrance of the nest hole .................................................. 32 3.1.3.1 Orientation of the entrance of the Dulungan nest holes .................................... 32 3.1.3.2 Orientation of the entrance of the Tarictic nest holes ........................................ 33 3.2 Dispersion pattern ............................................................................................. 34 3.2.1 Dispersion pattern of the Dulungan .............................................................. 34 3.2.2 Dispersion pattern of the Tarictic ................................................................. 35 3.3 Population density ............................................................................................. 37 3.3.1 Population dependence on elevation ............................................................ 38 Table of contents 3.3.1.1 Population dependence of the Dulungan ........................................................... 38 3.3.1.2 Population dependence of the Tarictic .............................................................. 40 3.4 Food and feeding ecology .................................................................................. 45 3.4.1 Fruit species consumed during the breeding seasons 2009-10 ...................... 45 3.4.2 Feeding ecology of the Dulungan ................................................................. 49 3.4.2.1 Food type and food diversity ............................................................................. 49 3.4.2.2 Intraspecific nearest neighbour food overlap..................................................... 54 3.4.3 Feeding ecology of the Tarictic .................................................................... 56 3.4.3.1 Food type and food diversity ............................................................................. 56 3.4.3.2 Intraspecific nearest neighbour food overlap..................................................... 57 3.4.4 Interspecific nearest neighbour food overlap ................................................ 58 3.5 Breeding biology ............................................................................................... 60 3.5.1 Breeding biology of the Dulungan ............................................................... 60 3.5.2 Breeding biology of the Tarictic................................................................... 62 3.5.3 Moulting of feathers of the breeding female ................................................. 63 3.5.4 Behavioural observations during the breeding season ................................... 64 3.5.4.1 Vigilance and nest concealment behaviour of hornbills ..................................... 64 3.5.4.2 Acclimation of hornbills to change of habitat ..................................................... 65 3.5.4.3 Food withholding and fledging .......................................................................... 67 3.6 Habitat disturbance and threats to hornbill species ............................................. 69 Chapter 4 DISCUSSION ................................................................................................ 73 4.1 Status and characteristics of nest hole trees ........................................................ 73 4.1.1 Status of nest hole trees................................................................................ 73 4.1.2 Nest site characters ...................................................................................... 74 4.1.2.1 Nest height and GBH ......................................................................................... 75 4.1.2.2 Nest orientation ................................................................................................ 76 4.1.3 Nest competition .......................................................................................... 77 4.2 Dispersion pattern ............................................................................................. 78 4.3 Population density ............................................................................................. 78 4.4 Food and feeding ecology .................................................................................. 80 4.4.1 Fruit species consumed ................................................................................ 80 4.4.2 Interspecific competition.............................................................................. 81 4.4.3 Nearest neighbour food overlap ................................................................... 83 4.4.3.1 Intraspecific nearest neighbour food overlap..................................................... 83 4.4.3.2 Interspecific nearest neighbour food overlap .................................................... 84 4.5 Breeding biology of the Dulungan and the Tarictic ............................................ 85 Table of contents 4.5.1 Timing of breeding ...................................................................................... 85 4.5.2 Clutch size, brood size and fledging ............................................................. 87 4.5.3 Moulting of feathers of the breeding female ................................................. 88 4.5.4 Behavioural observations during the breeding season ................................... 88 Chapter 5 CONCLUSIONS AND RECOMMENDATIONS ..................................... 90 Chapter 6 REFERENCES ........................................................................................