Movement and Space Use by the Green Hermit (Phaethornis Guy) in a Fragmented Landscape in Costa Rica
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AN ABSTRACT OF THE THESIS OF Noelia L. Volpe for the degree of Master of Science in Wildlife Science presented on March 19, 2014. Title: Movement and Space Use by the Green Hermit (Phaethornis guy) in a Fragmented Landscape in Costa Rica Abstract approved: _______________________________________________________________________ W. Douglas Robinson Matthew G. Betts Human activities have altered Earth’s ecosystems. Most biomes have experienced a 20-50% conversion to human use. Loss of habitat has obvious effects on the persistence of species. Fragmentation, however, may also negatively affect biodiversity for those species that exhibit behavioral responses to changes in habitat configuration. Such behavioral changes include movement, which is influenced by subdividing and isolating habitats through which animals prefer to travel. Ecosystem services that depend on the ability of animals to move through the landscape could be affected by changes in habitat configuration. Pollination is one such process because access of pollinators to flowers is often the key determinant of plant reproductive success. Yet, relatively little is known about how forest fragmentation may influence the flow of pollen carried by forest- dwelling pollinators, such as hummingbirds. I evaluate how changes in the distribution of pollinators produced by habitat fragmentation in southern Costa Rica affects a pollination web occupied by a generalist tropical pollinator, the green hermit hummingbird (Phaethornis guy). I used radio- telemetry to measure patterns of space use by green hermits living in forested areas with different levels of fragmentation. I first characterize patterns of space use by green hermits at three scales: point, path and home range. I found that green hermits have marked preference for locations in forested areas with high density of Heliconia plants and canopy cover; prefer paths close to streams that minimize crossing large stretches of non-forested matrix; and establish their home ranges in areas with high forest amount. In addition, home range area was negatively related to the amount of forest within it and positively related to fragmentation per se. Average resource density within the home range appeared to be unrelated to the area covered by the green hermits. My observations indicate that while the presence of green hermits in an area is mainly determined by the amount of forest available, the way they move through a landscape will be strongly affected by habitat configuration. In this context, pollen transfer by green hermits will be limited by the presence of open, non-forested areas owing to matrix avoidance. In landscapes with small discontinuous patches, the total area covered by an individual green hermit is likely to be small so I hypothesize that the genetic variability of pollen it transports may be diminished. I also assess the effectiveness of a tool commonly used to study the effect of habitat fragmentation on animal movement: translocation experiments. Such experiments are purported to have important advantages of being time efficient and standardizing across individuals the ‘motivation’ to move. Yet, we lack tests of whether movement behavior of translocated birds reflects natural behavior of unmanipulated birds. I compared the routine movement behavior of green hermits to that of experimentally translocated individuals. Behaviors documented during translocation experiments reflected those observed during routine movements. Both translocated and non- translocated birds showed similar levels of preference for mature tropical forest at the point level and avoided moving across non-forested matrix while selecting streams as movement corridors at the path level. Movement rates (distance covered per unit time) were generally higher during translocation experiments. However, the negative influence of forest cover on movement rates was proportionately similar in translocation and routine movement treatments. My results show that movement behavior of birds during translocation experiments is similar to natural movement behavior of birds. Therefore, translocation experiments may be reliable tools to address effects of landscape structure on animal movement. ©Copyright by Noelia L. Volpe March 19, 2014 All Rights Reserved Movement and Space Use by the Green Hermit (Phaethornis guy) in a Fragmented Landscape in Costa Rica by Noelia L. Volpe A THESIS submitted to Oregon State University in partial fulfillment of the requirements for the degree of Master of Science Presented March 19, 2014 Commencement June 2014 Master of Science thesis of Noelia L. Volpe presented on March 19, 2014 APPROVED: Co-major Professor, representing Wildlife Science Co-major Professor, representing Wildlife Science Head of the Department of Fisheries and Wildlife Dean of the Graduate School I understand that my thesis will become part of the permanent collection of Oregon State University libraries. My signature below authorizes release of my thesis to any reader upon request. Noelia L. Volpe, Author ACKNOWLEDGEMENTS My studies were possible thanks to funding provided by the Fulbright Commission, the P.E.O. Sisterhood, David B. & Georgia Leupold Marshall and The Wildlife Society. My field work was funded by a grant from the National Science Foundation, awarded to Matthew Betts and Douglas Robinson. I would like to thank my advisors Matt and Doug for their guidance and patience when coming up with new and intricate ways to analyze my data, as well as Adam Hadley for being my un-official “third advisor” and helping me stay on track when I found myself with too much in my plate. I would also like to thank Sarah Frey, Evan Jackson, Urs Kormann, Veronica Pereira and Mauricio Paniagua for their great help in the field as well as Ariel Muldoon and Dan Bigelow for helping me understand stats. My family and friends back in Argentina provided long-distance support, despite how bad I was at keeping in touch with them. There is a number of awesome people I met living in wonderful Corvallis who I would like to thank for helping me stay sane during these years of hard word: the gals in Forestry for the girl- talks and teaching me how to knit, my friends from ALAS for helping me re-discover my “Latinhood”, the graduate students from Fisheries and Wildlife for all the “from the movies” experiences, my Applied Economics crew for letting me be an “honorary economist” and crash at Ballard basement, the Betts lab for the great discussions, the Robinson lab for their support and friendship even when I was a hermit who they hardly saw, and of course Bill: thanks for all your patience and cooking. Finally, I would like to thank two fine local establishments, Harrison and The Peacock, for opening my eyes to the greatness of karaoke. CONTRIBUTION OF AUTHORS Dr. W. Douglas Robinson and Dr. Matthew G. Betts contributed to study design, interpretation of data, and writing of chapters 2-3. Dr. Adam Hadley provided data on translocation experiments and contributed in writing of chapter 2. TABLE OF CONTENTS Page Chapter 1: Introduction............................................................................................... 1 Chapter 2: Effects of forest fragmentation and habitat loss on space use of a tropical pollinator........................................................................................................ 5 Abstract.............................................................................................................. 5 Introduction........................................................................................................ 6 Materials and methods....................................................................................... 12 Study site..................................................................................................... 12 Data collection............................................................................................. 12 Data analysis................................................................................................ 16 Results............................................................................................................... 26 Point-scale habitat selection....................................................................... 26 Path-scale habitat selection....................................................................... 27 Home range scale habitat selection........................................................... 29 Discussion.......................................................................................................... 33 Tables................................................................................................................. 40 Figures............................................................................................................... 43 Chapter 3: Functional connectivity experiments reflect routine movement behavior of a tropical hummingbird species.............................................................................. 48 Abstract............................................................................................................ 48 Introduction...................................................................................................... 49 Materials and methods...................................................................................... 53 Study site.................................................................................................. 53 TABLE OF CONTENTS (Continued) Page Focal species............................................................................................