Probably:

Civil Registration Indexes (Births)

Gertrude Fanny T. Whicker, reg. 1st quarter of 1879, Camberwell, London, England.
Rosa Gertrude Whicker, reg. 4th quarter of 1881, Edmonton, Middlesex, England.
Gertrude Louisa Whicker, reg. 3rd quarter of 1890, Wandsworth, London, England.

Probably:

Collection Channel Islands, select births and baptisms
Gertrude Whicker was born in St. Pierre Port, Guernsey, Channel Islands on 11 February 1872. Her parents were Samuel George Whicker and Rebecca Whicker.