What is a Seahawk?
Mike at 10000 birds offered his opinion that a Seahawk is another name for an Osprey, a fish-eating hawk that can be found along sheltered coastal waters. True enough, in The Audubon Society encyclopedia of North American birds, author John K. Terres lists “sea hawk” as one of the colloquial names of the Osprey. But Terres also lists "sea hawk" as a colloquial name for the Skua, an ill-tempered seabird that employees piracy to filch food from other birds.
The Seahawks team logo features a stylized profile depicting the head of a rather fierce-looking raptorial bird of some kind. But does it really represent an Osprey? To me, the profile is much more characteristic of an eagle than an Osprey. One of the colloquial names for the Bald Eagle is "sea eagle." That said, I have to admit that the alternate logo used from 2002 to present is very representative of an Osprey. But, on the other, Blitz, the Seahawks mascot, doesn’t come close to representing an Osprey, a Bald Eagle, or any other kind of hawk.
According to sportsecyclopedia, the Seahawks nickname "was the result of a fan contest that drew 20,365 entries and suggested 1,742 different names. Seahawks was suggested by 151 entrants and judged by the team ownership as the best choice." The logo is described as "a Native American totem-style hawk with a fierce look."
Professional sports teams are fond of naming themselves after large birds with reputations for having fierce dispositions. See, for example, Atlanta Falcons, Atlanta Hawks, Toronto Raptors, and Philadelphia Eagles. In conclusion, I believe it is more than likely that the Seahawks name and logo was never meant to represent a real bird, but was merely a marketing gimmick to get fans to relate to the newest (and first?) professional sports team in town.