Bird whistlers... any good?

["Robert Read" <>]

I have found mine effective with Variegatied and Splendid Fairywrens, and
very effective with Dusky Grasswrens.  A whole flock of the latter came out
of the spinifex and hopped toward me after only one squeak.  I have not used
it much since as I am not sure whether there are any negative impacts on the
birds.

Eyrean Grasswrens just ignored it, as did other species I have tried.

Robert Read
Alice Springs