Migratory connectivity and the conservation of migratory animals.

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Migratory connectivity and the conservation of migratory animals.

I. INTRODUCTION II. THE IMPORTANCE OF MIGRATORY CONNECTIVITY III. APPROACHES FOR MEASURING MIGRATORY CONNECTIVITY A. Marked Animal Approaches B. Molecular Genetic Approaches C. Stable Isotope Approaches IV. LEGAL IMPLICATIONS OF MIGRATORY CONNECTIVITY STUDIES A. Improving Conservation Decision Making with Migratory Connectivity. 1. Acquiring Habitat Through Eminent Domain 2. Conserving Critical Habitat of Endangered Species 3. Assessing Impacts to Migratory Species 4. Expanding Judicial and Administrative Standing B. Implications for Regime Design in International Wildlife Conservation Treaties 1. General Conservation Agreements 2. Threat-Specific Conventions 3. Site-Specific Conventions 4. Conventions Aimed at Migratory Species C. Customary Law: Shifting Migration from Common Concern to Shared Resource V. Strengthening Social Connectivity A. Enhancing Conservation Connectivity B. Educational Connectivity VI. CONCLUSION I. INTRODUCTION

Migration is the repeated seasonal movement to and from a breeding area. (1) The linking of individuals or populations within a species range is known as migratory connectivity. This includes not only the geographic linking of breeding, migratory, and wintering areas of given populations, but also an understanding of how demographic components, such as sex and age, relate to the annual distribution of these populations in geographically linked areas. Currently, we know the overall year-round ranges for most species, but we have a poor understanding of their migratory connectivity. (2) Not known is where individuals or populations, including different age and sex classes, go subsequent to breeding or whether these populations mix or remain independent of one another. (3) What is known is that events during one period of the annual cycle, such as reproductive success and survival, can be driven by events in previous periods--often thousands of miles away and often across international boundaries--where legal protection can be different, if not absent.

In this Article, we review and discuss why understanding migratory connectivity is essential for the conservation of migratory animals and consider legal and other approaches in response to this understanding. Both the individuals and the habitats upon which they depend for their various life history stages (e.g., reproduction, molt, growth, and migration) throughout the year need protection. We argue that existing conservation efforts, including domestic laws and international treaties, can be made more effective by considering information on migratory connectivity. Advances in our understanding of the migratory connectivity of different species populations between regions and countries could also help to build "social connectivity"--the cultural, educational, economic, and institutional linkages between these same regions and countries. Increased social connectivity between distant locations that share biological resources will build a more reliable foundation for effective and sustainable conservation efforts to protect migratory species.

II. THE IMPORTANCE OF MIGRATORY CONNECTIVITY

Migration varies across species and can include seasonal migrations across latitudes, altitudinal migrations up and down mountains, and migrations that can span multiple generations over space and time. (4) It is found in all major groups of animals, both invertebrates and vertebrates, including insects (e.g., dragonflies and butterflies), (5) fish (e.g., eels and salmon), (6) amphibians (e.g., salamanders and toads), (7) reptiles (e.g., snakes and sea turtles), (8) birds (e.g., terns and warblers), (9) and mammals (e.g., wildebeest and whales). (10)

The Gray Catbird (Dumatella carolinensis) is an example of a longdistance migratory songbird that migrates across latitudes and is also a common backyard breeder in the eastern United States. (11) Post-breeding in the autumn, catbirds leave on a long-distance migration for their wintering grounds where they spend the majority of their annual cycle and then return north the following spring to breed. (12) The birds often return to the same exact location (within meters) where they bred the previous year. (13) Although the general nature of this remarkable boomerang journey has been known for years and continues to inspire and befuddle us, only recently--due to technological advances in our ability to track birds--did we come to learn where specific breeding individuals and populations spent the winter. During the 2009 breeding season, scientists from the Smithsonian's Migratory Bird Center attached miniature daylight level data loggers to the backs of 20 breeding catbirds in the Washington, D.C. suburb of Takoma Park, Maryland. (14) Diiring the subsequent breeding season, six of these catbirds were recaptured, the data loggers recovered and the mysteries of their migratory journey revealed. (15) Scientists learned the exact day of departure from Takoma Park and the exact day of arrival at th...

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