Bird List Anomalies

There are a few anomalies in my birding list.  I'm referring to families or groups of birds where I have seen a member that is rare (or difficult to find) yet I am missing "straightforward" members.  Here are a few:

• Terns:  I have seen an Arctic Tern (a rare vagrant to Perth) yet I am yet to see a Bridled Tern or a Roseate Tern (both semi-regular along the coast near Perth);
• Emu-wrens: I have seen a Rufous-crowned Emu-wren (apparently a potentially difficult bird to find) but not a Southern Emu-wren (relatively common along the south coast of WA);
• Ducks: I have seen a Northern Pintail (the third record for WA - BARC accepted) but not a Freckled Duck (probably the hardest resident/regular duck to find in Perth but still... Northern Pintail?!?).

I am fortunate to have a group of very talented birding friends: these people are the source of most of my rarities and are fantastic companions when I do get out and about birding.  One way or another they are all involved in the "rare" or difficult to find birds in the list above.  I've just got to search out all the common birds missing on my list now...