Values indicate estimated seabird abundance using a relative breeding index
Description of time series:
Between 2015 and 2019 the seabird breeding index showed no significant trend.
Description of gauge:
The gauge value of 12 indicates that between 2015 and 2019 the seabird breeding index in Alaska (Eastern Bering Sea) was much lower than the median of all breeding index values between 1996 and 2019.
Overall Scores means the following:
- 0 - 10: The five-year seabirds average is very low compared to the median value.
- 10 - 25: The five-year seabirds average is much lower than the median value.
- 25 - 50: The five-year seabirds average is lower than the median value.
- 50: The five-year seabirds average equals the median value.
- 50 - 75: The five-year seabirds average is higher than the median value.
- 75 - 90: The five-year seabirds average is much higher than the median value.
- 90 - 100: The five-year seabirds average is very high compared to the median value.
Indicator and Source Information:
This data was compiled by the Alaska Integrated Ecosystem Assessment Program’s East Bering Sea Sub-region. The Alaska Maritime National Wildlife Refuge has monitored seabirds at colonies around Alaska in most years since the early- to mid-1970’s. Time series of annual breeding success and phenology (among other parameters) are available from over a dozen species at eight Refuge sites in the Gulf of Alaska, Aleutian Islands, and Bering and Chukchi Seas. Monitored colonies in the eastern Bering Sea include St. Paul and St. George Islands. Here, we focus on cliff-nesting, primarily fish-eating species: black-legged kittiwake (Rissa tridactyla), red-legged kittwake (R. brevirostris), common murre (Uria aalge), thick-billed murre (U. lomvia), and redfaced cormorants (Phalacrocorax urile). Reproductive success is defined as the proportion of nest sites with eggs (or just eggs for murres that do not build nests) that fledged a chick.
Data Background and Caveats:
Data only include the species listed above in the East Bering Sea Sub Region of Alaska. Reproductive activity of central-place foraging seabirds can reflect ecosystem conditions at multiple spatial and temporal scales. For piscivorous species that feed at higher trophic levels, continued reduced reproductive success may indicate that the ecosystem has not yet shifted back from warm conditions and/or there is a lagged response of the prey. Despite environmental changes returning back to more neutral conditions, seabird foraging conditions do not appear to have recovered in the eastern Bering Sea. In contrast, the improvement in attendance and minimal reproductive activity among murres in the Gulf of Alaska during 2017 indicates some improvement in foraging conditions for those species.