E604 is a female Caspian tern originally banded a chick at Goose Island in 2009. After being banded as a young bird, she was first recorded back at her natal colony three years later in 2012. She was observed nesting the following two years; first at Goose Island in 2013 and then at Crescent Island in 2014. On 02 April, 2015, she was captured and fitted with a satellite tag at Crescent Island. After that, she relocated to the Blalock Islands (in the Columbia River near Boardman, OR) to successfully raise a chick during the 2015 breeding season. She had moved down to the Salton Sea area in southern California by the end of July, and was well established at a wintering location in Mexico by the beginning of January 2016. By the end of March 2016, she had started her move north and was staged back at the Salton Sea.
During the 2016 breeding season, E604 spent considerable time at Potholes Reservoir but not at Goose Island. Instead, she was tracked to a newly initiated colony in the northern portion of the reservoir, and visually observed there three times in late May and early June. She may have initiated a nesting attempt there. The colony failed on 04 June, however, due to predator disturbance, likely a mink. Since failure of the colony, E604 wandered the Columbia Plateau region and did not associate with any other colony for any prolonged period.