Structure and diversity of cloud forest bird communities in Alta Verapaz, Guatemala, and implications for conservation Published online: http://www.sub.uni-goettingen.de Dissertation zur Erlangung des Doktorgrades der Mathematisch-Naturwissenschaftlichen Fakultäten der Georg-August-Universität zu Göttingen vorgelegt von Diplom-Biologe Swen Christoph Renner aus Wuppertal Göttingen, 2003 D 7 Referent: Prof. Dr. M. Mühlenberg Korreferent: Prof. Dr. M. Schaefer Tag der mündlichen Prüfung: 05. November 2003 Table of contents Structure and diversity of cloud forest bird communities in Alta Verapaz Abbreviations iv 1 Introduction 1 2 Background 4 3 Objectives and hypotheses 6 4 Methods, material, and study area 9 4.1 Study area 9 4.1.1 Topology and geology 9 4.1.2 Climate 10 4.1.3 Natural vegetation 11 4.1.4 Habitat types of the Sierra Yalijux 11 4.1.5 Fauna 13 4.2 Study plot 13 4.2.1 Diameter at breast height (DBH) 14 4.2.2 Tree height 15 4.2.3 Tree stem cover 16 4.3 Vegetation structure 16 4.4 Ornithological fieldwork 17 4.4.1 Mist netting 18 4.4.2 Transect census 19 4.4.3 Further recording of birds and behavior 20 4.5 Statistics and calculation methods 20 4.5.1 Analysis of vegetation structure 21 4.5.2 Diversity and population indices and estimators 21 4.5.3 Comparison of habitats, similarity 23 4.5.4 Evenness 24 4.5.5 Further population parameters 24 4.5.5.1 Dominance 24 4.5.5.2 Density 25 4.5.5.3 Recapture rate 25 4.5.6 Estimation of population size 25 4.5.7 Guild composition 26 4.5.8 Understory birds 26 4.5.9 Body mass 27 4.5.10 Morphometrics 27 4.6 Geographic Information System 27 5 Results 29 5.1 Vegetation structure and birds 29 5.2 Avifauna 31 5.2.1 Observed and expected species 31 5.2.2 Bird community structure 32 5.2.2.1 Abundance, dominance, habitat preferences 32 5.2.2.2 Guild composition 34 5.2.2.3 Species-abundance models 36 5.2.3 Similarity 37 5.2.4 Species richness and diversity 38 5.2.5 Species-area dependence 41 5.2.6 Evenness 42 5.2.7 Edge effect 42 5.2.8 Estimation of population size 43 5.2.9 Recapture rate 44 i Table of contents Structure and diversity of cloud forest bird communities in Alta Verapaz 5.2.10 Transect census 45 5.2.11 Density of species 45 5.2.12 Geographic Information System-based analyses 47 5.2.12.1 Highland Guan – Penelopina nigra 48 5.2.12.2 Mountain Trogon – Trogon mexicanus 48 5.2.12.3 Resplendent Quetzal – Pharomachrus mocinno 48 5.2.12.4 Bushy-crested Jay – Cyanocorax melanocyaneus 54 5.2.12.5 Black-throated Jay – Cyanolyca pumilo 54 5.2.12.6 Individual density 54 5.2.13 Understory birds 55 5.3 Body mass 58 5.4 Morphometrics 61 5.5 Syntheses 61 6 Discussion 63 6.1 Methods 63 6.1.1 Nets and transects 63 6.1.2 Diversity indices and species-abundance models 64 6.1.3 Neotropical and Nearctic migrants 64 6.2 Diversity 65 6.2.1 Species richness, diversity and evenness 65 6.2.2 Vegetation structure and birds 66 6.2.3 Understory birds 66 6.2.4 Edge effect 68 6.2.5 Recaptures and recapture rate 69 6.2.6 Population dynamics, influence of meta-populations and patchy distribution 72 6.3 Comparison 73 6.3.1 Neotropical bird communities 74 6.3.2 Further studies involved in tropical bird communities 76 6.3.3 Bird communities in non-tropical regions 77 6.3.4 Differences between natural forest and young secondary forest 77 6.3.4.1 Guild composition 78 6.3.4.2 Is body mass a measure of habitat quality? 78 6.4 Biogeographic affinities 79 6.5 Human impact 82 6.6 Conservation of natural montane cloud forest in the Sierra Yalijux 83 6.6.1 Predicting extinctions 83 6.6.2 Endemics 85 6.6.3 Keystone and target species 86 6.6.3.1 Resplendent Quetzal – Pharomachrus mocinno 86 6.6.3.2 Yucatán Black-Howler Monkey – Alouatta pigra 88 6.6.4 Red Lists and extinction risk 88 6.6.5 Conservation strategy 89 6.6.5.1 Factors threatening species and habitat 90 6.6.5.2 Possibilities to preserve the natural forest remnants 90 6.6.5.3 Priority areas and corridors: existing strategies 91 6.6.5.4 Suggestions for a new strategy/extension of the existing strategy 92 6.6.5.5 Conservation of diversity within secondary habitats 92 6.7 Conclusion 93 7 Summary 95 8 Zusammenfassung 97 9 Resumen 99 ii Table of contents Structure and diversity of cloud forest bird communities in Alta Verapaz 10 Acknowledgments 101 11 References 102 Appendix A 113 Appendix B 121 Appendix C 122 iii Abbreviations Structure and diversity of cloud forest bird communities in Alta Verapaz Abbreviations BM body mass [g] S species numbers N individuals numbers c mist-net captures (marked individuals) r recaptures Rt recapture rate DBH diameter at breast height UTD understory tree density [m] UTH understory tree height [m] UTS understory tree size [m] OTD overstory tree density [m] OTH overstory tree height [m] OTS overstory tree size [m] ha hectare (1 ha = 10,000 m² = 0.1 km²) NF natural forest YSF young secondary forest Guatemala belongs to the Mexican Time Zone (UTC/WTC – 6:00 h) and has no time shift during summer. iv Introduction Structure and diversity of cloud forest bird communities in Alta Verapaz 1 Introduction Biological diversity, at least in terms of species richness, is distributed unequally around the Earth (e.g., Mittermeier et al. 1998, Myers et al. 2000, Barthlott & Winger 2001). The majority of species is located in tropical regions, many in special habitats like mountain cloud forest or coral reefs (Primack 1993). More than 50 % of species occur within 7 % of land cover (Whitmore 1990, Conservation International 1990). Higher vertebrates and vascular plants show a higher frequency of species in the 25 terrestrial Biodiversity Hotspots, which are located mainly within the tropics, some reaching subtropical areas (Myers et al. 2000). Parallel to the high level of biodiversity, there is a high degree of habitat loss in the same hotspot regions (Stattersfield et al. 1998, Myers et al. 2000). Deforestation is one of the major factors (Tanner et al. 1996, FAO 2001). ‘Contemporary human activities is the latest chapter in a long saga of disturbances […]’ and the most threatening (Whitemore & Burslem 1996). Fragmentation, degradation, and complete habitat loss are diminishing the natural forests. Species specialized to natural forests will vanish after a relaxation time when area is too small (e.g., Brooks et al. 1999). The extinction of species as a consequence of habitat loss is leading to biodiversity loss, in temperate landscapes as well as in the tropics (e.g., Myers et al. 2000). Conservation and preservation of natural habitats is essential to preserve a high degree of biological diversity (e.g., Hughes et al. 2002). The exact order of magnitude of species numbers is not known to the scientific community (Primack 1993, and others). There are several estimations of species numbers (e.g., Cox & Moore 2000). Taxonomists estimate that the majority of invertebrate species are yet undiscovered. For instance, insects are believed to be known to scientists with less than 10 % of all species (e.g., Cox & Moore 2000, Primack 1993). For other arthropods or invertebrates, the situation might be even worse (Wilson 1992). Numbers for higher vertebrates like birds are relatively constant and annual descriptions of new species are comparatively low (e.g., del Hoyo et al. 1992). Deforestation and loss of natural habitats are the result of human activities. Rural human populations are reduced to basic and subsistence agricultures to obtain sufficient food for survival (Terborgh 1999, World Bank 2001). Traditional knowledge and increasing human populations force contemporary and future generations to continue or even increase deforestation to provide sufficient area for agriculture and land use. Inappropriate use and overexploitation of land makes it necessary to move on and exploit new areas, leaving vast unproductive areas (Markussen 2003). While most species are still unknown, deforestation rates and human impacts are still increasing (e.g., FAO 2001, World Bank 2001). Hence biologists with their long-term studies are documenting the status quo of the remaining natural environments (Terborgh 1999). 1 Introduction Structure and diversity of cloud forest bird communities in Alta Verapaz Habitat loss and degradation often interact with scientific investigations and prevent surveys or falsify results. In contrast to increasing biodiversity research (mainly the socio-economic part), patterns and processes of biodiversity loss are still poorly known (Loreau et al. 2002). Community ecology focuses on “factors of biodiversity”, while ecosystem ecology focuses on rates, dynamics, stability of energy and nutrition cycles (Naeem et al. 2002). Here, the focus is on the first part, i.e. community and diversity. Different ecosystem processes respond differently to biodiversity loss (Naeem et al. 1994, Naeem et al. 2002). Studies involving standardized and comparable bird community measures in the tropics are rare (Terborgh et al. 1990). Studies estimating the impact of human activities on nature and its functioning are even more rare (Terborgh 1999). Worldwide there are less then 10 study plots with a more or less completely censused bird species inventory for an approximate area of 100 ha (Brosset & Erard 1986, Thiollay 1994a, Robinson et al.