Document Type

Dissertation

Degree

Doctor of Philosophy

Major

Biology

Date of Defense

7-8-2026

Graduate Advisor

Michael Tobler

Co-Advisor

Haldre Rogers

Committee

Nathan Muchhala

Bethany Zolman

Lisa Kelley

Abstract

Island birds are among the world’s most imperiled vertebrates, and conservation translocations are increasingly used to combat threats, but their success depends on understanding the mechanics of whether and how to conduct translocations effectively. In the Commonwealth of the Northern Mariana Islands, native forest birds persist across a chain of islands where habitat degradation and loss, invasive species, and extreme weather create persistent conservation challenges. For my dissertation, I investigated how avian conservation programs and translocations can be planned, implemented, and improved under biological, logistical, and social uncertainty. For Chapter 1 I analyzed 15 years of avian translocations across seven species and four stages: capture, holding, transport, and release. Most individuals moved successfully through the translocation pipeline with the holding stage being the greatest place for stage-specific risk. Chapter 2 paired fecal glucocorticoid metabolite data with daily body mass measurements in 5 Mariana bird species to test whether early physiological responses predicted later body mass loss during temporary holding. Early physiological responses did not predict subsequent maximum body mass loss, showing that measuring physiological stress and body mass provide different information about how birds respond to holding. Chapter 3 evaluated short-term holding and post-removal territory occupancy for the critically endangered ga'ga karisu (Malul Ghariisu, Acrocephalus hiwae, Saipan reed warbler). Birds tolerated short-term holding without mortality, although some individuals lost body mass or required early release, and live insects were the most consistently consumed diet item. Revisit surveys detected additional ga'ga karisu at all territories after removals, indicating that limited removals may create territory openings for remaining birds. Finally, Chapter 4 used a structured, community-engaged assessment to evaluate potential causes of decline for the critically endangered and endemic nosa' Luta (Litchoghil Luuta, Zosterops rotensis, Rota white-eye). The assessment did not identify a single cause of decline, but highlighted interacting threats, and the process helped to show that recovery planning should be collaborative, locally informed, and designed around interacting pressures and histories rather than a single threat. This dissertation provides a framework for evidence-based avian conservation in tropical island systems, from translocation planning and implementation to community-integrated assessment of future recovery actions.

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