Habitat specialization explains avian persistence in tidal marshes

Abstract

Abstract Habitat specialists are declining at alarming rates worldwide, driving biodiversity loss of the earth's next mass extinction. Specialist organisms maintain smaller functional niches than their generalist counterparts, and tradeoffs exist between these contrasting life history strategies, creating conservation challenges for specialist taxa. There is little work, however, explicitly quantifying “specialization”; such information is necessary for the development of focused conservation strategies in light of the rapidly changing landscapes of the modern world. In this study, we tested whether habitat specialism explains the persistence of breeding bird populations in tidal marshes of the northeastern United States. We used the North American Breeding Bird Survey (BBS) together with contemporary marsh bird surveys to develop a Marsh Specialization Index (MSI) for 106 bird species that regularly use tidal marshes during the breeding season. We produced four metrics of species persistence (occupancy, abundance, total biomass supported, and 14‐yr population trends) and compared them to MSI values in one of the first community‐scale demonstrations of specialist loss in disturbed landscapes. Our results confirm that tidal marsh specialism has short‐term benefits but long‐term consequences for bird persistence in coastal marsh systems, results that are generalizable across many changing landscapes. We then use this robust support of niche theory to recommend MSI as a tool for quantitatively identifying species of conservation concern in disturbed and rapidly changing landscapes such as tidal marsh.

Keywords

• climate change
• niche
• specialism
• species conservation
• tidal marsh