Despite where Seafoam Island would be in comparative Japan, I thought that there was a hint that the climate of the Islands is oddly cold. Imagery of the island seems to always point that it is cold, and it is where one can find a lot of ice Pokémon like Dewgong, Jynx (in HG/SS), and Shelldar that turns into an ice type.
My take on the locations of the Legendary Bird Pokémon locations, that perhaps there are some geothermal areas in the Victory Road cave, something opposing in Seafoam, perhaps like the Ice Rocks we have seen in other regions, and a somewhat obvious connection for Zapdos and a power plant, but maybe a bit of guesses for why. A lot of electric Pokémon seem drawn to the powerplant, maybe there is still power running, or some are drawn to the natural conduciveness of the place, and others are drawn to the electrical charge.
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Through dream I travel, at lantern's call
To consume the flames of a kingdom's fall