FIGURE 3.

(a) Forage fish availability indices (frequency of occurrence) in seabird diets by feeding guild (color) at Middleton Island. Mean values across all years are shown as horizontal lines, and dotted vertical lines demarcate the timing of the Pacific Marine Heatwave. (b) Portfolio effects as a measure of the degree of synchrony among capelin, herring, and sand lance indices by seabird feeding guild. Portfolio effects were computed from variance ratios across 3‐year centered rolling windows, with lower values indicating greater synchrony and lower buffering capacity by the forage fish community