Several subspecies are recognized across its range and some of them may be treated as full species.

However, it has been considered a full species in recent literature.

Four subspecies are usually recognized, one of which has recently been given full species status (see below).

It has at least three distinctive subspecies which are considered by some authorities to be full species.

Therefore its status has not changed after its elevation to a full species.

It is sometimes considered to be a full species.

However recent studies of differences in call and distribution have led to it being treated as a full species.

Four full species were originally named, and are clearly recognisable in the field.

It was not given full species status until 1988.

Jill Cowley raised it to a full species in 1982.