The smallest bird is the bee hummingbird (Mellisuga helenae) of Cuba and the Isle of Youth. Males measure 57 mm (2.24 in) in total length, half of which is taken up by the bill and tail, and weigh 1.6 g (0.056 oz) Females are slightly larger.

One option is to have an Announcement:

Please wait while we try to connect your call, etc.

Also, you can change the hold music after the Announcement so it's more clear that your trying to connect them.

(IE: Hold Music vs. Ringing)