Study the Science: Seabirds
The seabird ecology component collects data on the distribution and abundance of seabirds in the northeastern Chukchi Sea in the vicinity of several oil and gas lease areas and the region including Hanna Shoal. We conduct surveys for seabirds from the bridge of the research vessel during daylight hours. By observing birds July–October, we can describe spatial, seasonal, and interannual characteristics of the seabird community. We also provide detailed information on species that are of conservation concern (e.g., endangered, threatened, candidate species). Seabirds have to be good at finding food at sea because of their high metabolisms. Their ability to move over large areas easily and sense their environment helps them forage efficiently—they are excellent oceanographers. The advantage of being a component of a multi-disciplinary study is that we integrate the information about seabirds in this area with the data from other components such as physical oceanography, zooplankton ecology, benthic ecology, fisheries oceanography, and marine mammals to investigate the relationships between seabirds and their marine environment.
Short-tailed Shearwaters make a round trip of 30,000 km each year from breeding grounds in Australia to feed in Arctic waters, a feat managed in only 6 weeks.
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The abundance of seabirds in the offshore part of the northeastern Chukchi varies dramatically (by a factor of up to 100) among years, presumably reflecting variation in the abundance, species-composition, and availability of preferred prey. There also is seasonal variation in the seabird community. For example, approximately 100 times as many birds were recorded in the study area in 2009, a year of warm water with lots of zooplankton that seabirds like to eat, than were recorded in 2008, a year of cold water and very few large zooplankton. In most years, seabirds were more abundant in September than August, but, in 2012, we saw more seabirds in August than we did in September, possibly because the region cooled rapidly when arctic ice moved south and then melted in the study area.
The seabird community in the Chukchi Sea appears to have undergone a major change in structure over the past 40 years. In the 1970s and early 1980s, the Chukchi’s seabird community consisted primarily of fish-eating seabirds; now, it consists primarily of zooplankton-feeding seabirds. This change in the structure of the seabird community appears to result from long-term environmental change in the Chukchi Sea: the area generally was ice-covered much of the year in historical times but now is ice-free much of the year, and consequently the abundance of large zooplankton appears to have increased over time.
In addition to changes in the structure of the seabird community, new seabird species are being recorded in the Chukchi as the environment changes—we have recorded 3 new species since 2006, and a fourth species that had been rare in the Chukchi now is much more abundant than it was before 2006. Three of these four new seabird species (Short-tailed Albatross, Ancient Murrelet, Rhinoceros Auklet) are from farther south in the North Pacific, whereas the fourth new species (Northern Gannet) actually came from the North Atlantic via the Northwest Passage, which has had no ice in several of the past 10 years.
The distribution of seabirds, particularly the plankton-eating species, may be influenced by the currents that transport large zooplankton from the Bering Sea to the Chukchi Sea. This transport apparently differed between years and resulted in a broader northeastward intrusion of Bering Sea Water, higher abundance of large oceanic copepods and euphausiids, and wider distribution of plankton-eating seabirds in both study areas, in 2009 than in 2008.
The seabird community of the northeastern Chukchi Sea consists of approximately 40 species, with approximately 8–10 species being common to abundant and the other species being uncommon to rare or accidental. The overall seabird community is composed primarily of zooplankton-feeding seabird species; in particular, Crested Auklets and Short-tailed Shearwaters are the most abundant species every year. Fish-feeding seabirds are second in abundance, omnivorous species are third in abundance, and benthic-feeding seaducks are least abundant in this offshore area (although they are much more abundant closer to shore).