Well not really or it depends on your interest and experience level. Mimicry is
a fascinating thing for study of its own, in terms of song learning and for
possible adaptiveness. With all the work done on lyrebirds these people don't
think it is the other birds calling.
The aspect of identifying birds is its own skill and something quite separate
from the issues of mimicry and such advice is fair enough. Actually in most
cases, even though the copying quality may be good, the difference is obvious.
Most bird mimics copy a whole range of sounds in a long string, most do so at
low volume in "subsong" (Silvereyes and Starlings are good examples) and some
are very loud (such as lyrebirds). Usually it is obvious that the whole long
string is at the same volume or from an unexpected part of the habitat, so one
can tell it is likely to be is a mimicking bird, rather than a whole collection
of other things calling from one spot. Having said that, sure sometimes it is
possible to get it wrong on a heard only identification. In situations where
lyrebirds, bowerbirds, orioles and several other good mimic species are
present, it is best not to identify other species on call alone, if only heard
once or in a situation where you haven't discounted the possibility of mimicry
by something else. As for the Regent Honeyeater, they are different in that
they only mimic one species at a time and their mimicry of wattlebirds is
virtually identical to the model except not as loud or rough.