In brief answer to Teresa's inquiry on why one would wish to see to see a
Black-throated Blue Warbler on Mercer Is. or a BTCU at Ocean Shores --
well, simply because it is a joy to observe the birds themselves, vagrant
or on track, and to wonder at what natural forces brought those birds to be
in that unlikely location. The Vermillion Flycatcher in rural Redmond a few
years back was such a case, too. In the scheme of things, I'd say it's
pretty harmless to chase "rarities". Besides, "vagrancy" is certainly part
of a species' history, as they stochastically explore new regions, and,
perhaps, begin a colonization. The ancestors of Darwin's Finches were,
after all, originally vagrants...