Willow Warbler - 1949 status

Phylloscopus trochilus trochilus

Common summer visitor, and abundant passage migrant, arrives last week in March.

He also mentions, under the section of the book on Land-Birds:

The first Willow-Warblers are trapped at Skokholm during the last week of March.  This is one of the largest small bird migrations in Pembrokeshire, and for the whole month between mid-April and mid-May there are days when the county swarms with these charming singers.

R.M.Lockley, G.C.S.Ingram, H.M.Salmon, 1949, The Birds of Pembrokeshire, The West Wales Field Society