Date of death does not coincide with death of copyright in the US. Although English, I am sure Weatherby had US copyrights as well.
This makes no nevermind, however, since the date is far enough back that even with the additional allowed in the revisions of copyright statutes for 1998-2000, I would guess that his © entitlements are all dead.

Michaelr, I put Danny Boy into that site, and got 16 listings. Dates, renewals, details, etc. are not given.