Mortlake is a district of the modern borough of Richmond upon Thames  (London, England).

In London Labour and the London Poor edition: 

Phase 1

Of the Street Sellers of Live Birds. (Volume 2): "The localities where these men "catch," are the neighbourhoods of the places I have mentioned as their residences, and at Holloway, Hampstead, Highgate, Finchley, Battersea, Blackheath, Putney, Mortlake, Chiswick, Richmond, Hampton, Kingston, Eltham, Carshalton, Streatham, the Tootings, Woodford, Epping, Snaresbrook, Walthamstow, Tottenham, Edmonton—wherever, in fine, are open fields, plains, or commons around the metropolis."