Birds that sound like fighting cats?

Last night I stepped out onto my porch around midnight to the sound of what I thought was a really nasty cat fight at the end of the street. But the sound started to get closer, as if the cats were fighting each other while quickly approaching my house. That's when I looked up to see the actual source of the noise, which was a row of about 7 or 8 bright white, significantly sized birds (looked the size of canadian geese with the body of a seagull or crow) flying south over my house. Now, I have heard many cat fights, and many birds, but I have never heard this sort of sound come from either creature. I was thinking maybe one of the birds had picked up a particularly vocal mouse or rabbit, but that seems highly unlikely considering how loud the sound was. Anyone have any ideas on what sort of bird this way? I live in Washington state if that helps at all.