Cogswell 1948 Sterna hirundo 1 Oct. 10. Princeton, San Mateo Co., Calif. observed an immature (either this sp. or Sterna paradisea) at close range as it flew up and down and dove just beyond lines extending from fishing poles along the pier. Blackish nape and side of head, dusky primaries from above, dark brown leading edge of wing to beyond bend, and even the dark outer web of outer rectrices were all noted; the bill was reddish at base and seemed too heavy for paradisea; rump & most of tail pure white.