I happened to be looking through an old CBN (March 1990, p18) where there was a note on Sacred Kingfishers referring to the ‘considerable amount of rufous that young birds have on their breasts’. It went on ‘this rufous colouration is not well shown in the field guides and can easily result in identification of juvenile Sacred Kingfishers as Azure Kingfishers’. The 1989 rev of Slater (text and illustration) gives the MALE with pale buff underparts and the FEMALE as ‘less buff below, some almost white’. Since vol 4 of HANZAB (1999) it is more widely accepted that the ‘buff’ (to call it that for convenience rather than accuracy) is not particularly a juv or female character but related to moult – ‘when plumage fresh, birds can look very buff below’. ‘Individual variation’ is also a consideration. The below old photo shows a recently fledged juv –
Don’t bring up Restless Flycatchers. There is a respectable view (for the present) that the rusty colour is usually but not always a female characteristic.