7 research outputs found
Comparing imaging, acoustics, and radar to monitor Leach’s storm-petrel colonies
Seabirds are integral components of marine ecosystems and, with many populations globally threatened, there is a critical need for effective and scalable seabird monitoring strategies. Many seabird species nest in burrows, which can make traditional monitoring methods costly, infeasible, or damaging to nesting habitats. Traditional burrow occupancy surveys, where possible, can occur infrequently and therefore lead to an incomplete understanding of population trends. For example, in Oregon, during the last three decades there have been large changes in the abundance of Leach’s storm-petrels (Hydrobates leucorhoa), which included drastic declines at some colonies. Unfortunately, traditional monitoring failed to capture the timing and magnitude of change, limiting managers’ ability to determine causes of the decline and curtailing management options. New, easily repeatable methods of quantifying relative abundance are needed. For this study, we tested three methods of remote monitoring: passive acoustic monitoring, time-lapse cameras, and radar. Abundance indices derived from acoustics and imagery: call rates, acoustic energy, and counts were significantly related to traditional estimates of burrow occupancy of Leach’s storm-petrels. Due to sampling limitations, we were unable to compare radar to burrow occupancy. Image counts were significantly correlated with all other indices, including radar, while indices derived from acoustics and radar were not correlated. Acoustic data likely reflect different aspects of the population and hold the potential for the further development of indices to disentangle phenology, attendance of breeding birds, and reproductive success. We found that image counts are comparable with standard methods (e.g., radar) in producing annual abundance indices. We recommend that managers consider a sampling scheme that incorporates both acoustics and imaging, but for sites inaccessible to humans, radar remains the sole option. Implementation of acoustic and camera based monitoring programs will provide much needed information for a vulnerable group of seabirds
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Marine bird colony and at-sea distributions along the Oregon coast: Implications for marine spatial planning and information gap analysis
Increasingly diverse interests in commercial and recreational use of marine resources are creating new challenges for coastal ocean management. One concern of increased offshore use and development off the Oregon coast is the potential impact on marine bird populations. We summarized the primary surveys of seabird breeding colonies and at-sea distribution along the Oregon coast to describe spatial patterns in species distribution and identify gaps where additional data are needed. The abundance of breeding birds during the summer (over 1 million in total, primarily Common Murre Uria aalge and Leach’s Storm-Petrel Oceanodroma leucorhoa) is greatest in northern and southern Oregon due to the availability of breeding habitat on large offshore rocks and islands. While there are fewer breeding colonies along sandy shorelines, the adjacent coastal waters are still frequented by breeding birds and nonbreeding migrants, but generally in lower densities during summer. Seabird density, and likely potential interaction with offshore structures, is greatest nearshore and steadily declines to lowest levels beyond the outer continental shelf. Dynamic soaring species, however, which have a greater potential to interact with taller structures such as wind turbines, tend to be more common on the middle to outer shelf. Species composition also changes dramatically among seasons. Low flying (< 30 m above sea level) diving species dominate in most seasons, however, which has potential conservation implications for interactions with structures above and below the water’s surface. Given the abundance of storm-petrels, increased light pollution is also a concern for these and other nocturnal, phototactic species. Dramatic declines or redistributions have occurred at some breeding colonies, indicating long-term planning should consider changing habitat requirements. The greatest data needs currently include fall/winter/spring at-sea distribution, summer distribution off southern Oregon, and more accurate estimates and monitoring of burrow-nesting seabirds. Oregon’s coastal waters provide habitat for a large portion of breeding and nonbreeding marine birds along the U.S. west coast and a thorough knowledge of their spatial distribution, seasonal abundance, and migration corridors is critical for well-informed marine spatial planning