Note 20 — Part I.—April.

Kittiwakes and Black-headed Gulls in swarms during March and early April, whitening acres of water. The latter remained till perfect summer-plumage is attained (by March 21st). Little Gulls frequent: on two occasions (in February and March) observed in scores. Larus fuscus and L. argentatus were common in March, and on April 5th we obtained an adult of L. marinus in the marisma. Of British Terns, S. cantiaca and S. fluviatilis, were noticed in early spring.