There is no single definition for marine birds, but it includes species that live in saltwater or interact closely with the marine environment on a regular basis. For our purposes, this includes seabird, shorebird, and coastal bird species. Marine birds are found across the globe, from the poles to the tropics, where they live at the interface between air, land, and sea (or ice). The harsh conditions found in these environments have caused unique adaptations in their physiology and morphology and require enormous flexibility in life history strategies.
Some of the evolutionary traits that make marine birds well suited to their environment, however, also make them vulnerable to extinction. Many marine bird species are considered threatened or endangered at both global and continental scales. Around the world, marine birds face multiple ecological and environmental stressors, including habitat loss and alteration, disturbance, hunting, interactions with commercial fisheries, oil spills, persistent pollutants, ocean acidification, and other issues associated with climate change.
As such, marine birds are considered useful indicators of the general health of the marine ecosystem, and they play an increasingly important role in assessments of marine health and in conservation and marine spatial planning exercises.
Marine birds are regularly exposed to chemical pollutants, where exposure may be acute or chronic. The impacts of pollutants, such as heavy metals, organochlorines, hydrocarbons, and plastics, may occur at the individual or the population level. In the 1960s and '70s, many coastal and marine fish-eating species were subject to eggshell thinning as a direct result of exposure to the insecticide DDT. Since then, marine birds have been shown to be useful “bioindicators” of coastal and marine ecosystem health because they are generally conspicuous, easily observed, long-lived, and wide-ranging. They are often at the top of their food chain where pollutants are accumulated over time. Studying contaminants in conjunction with tracking marine bird movements and migrations can highlight problem geographical areas or indicate contaminant exposure at particularly critical life stages.
Much of what we know about marine birds has been gleaned from studies of birds during breeding, when they are tied to land. Banding, including color-banding, has traditionally been used to gain information about marine bird movements. Recent and continuing innovations in technology, however, have opened up increasing opportunities to track marine birds across the world’s oceans in space and time. In the last decade, the development of smaller tracking devices has profoundly changed our understanding of the ecology of marine birds, many of which spend the bulk of their lives well out at sea.
At BRI, we use an array of tracking methods (nanotags, geolocators, satellite transmitters) to track the movements of a variety of marine bird species. Birds fitted with nanotags can be remotely tracked regionally, while birds carrying satellite transmitters are remotely tracked on a global scale. Off the mid-Atlantic region of the U.S., we are currently involved in the capture and tagging of vulnerable marine bird species to track their annual movements in relation to federally-designated Wind Energy Areas (WEAs). Tracking data of this kind will assist in identifying hotspot areas consistently used by seabirds in this region of the Atlantic continental shelf where the nation’s first offshore wind development is most likely to occur.
Evaluating the conservation status of bird populations is difficult at the best of times, but gathering reliable data on the abundance and distribution of marine birds at sea is an enormously challenging exercise. We employ a series of traditional and innovative techniques to achieve this, including the first broad-scale use of high-definition videography in aerial surveys across the mid-Atlantic region of the continental shelf. This remote-sensing technique uses an array of high-definition cameras mounted to the belly of a small aircraft to capture video footage of the area, in a well-defined strip transect. Experienced biologists later examine all wildlife species present on screen during review of the footage and identify them to species or closest taxonomic grouping. This technique has a number of distinct advantages over traditional observational aerial surveys. The aircraft is able to fly at a much greater altitude, for example, completely removing the issue of disturbance often caused by low-flying aircraft. Furthermore, the digital data is archivable, should it require further review at a later date, and an estimate of the height of each flying animal can be calculated, which is particularly important in assessments related to offshore wind development.