An exception. What are other exceptions of this kind?

you could also use מצייצות = tweeting (pronounced metzaytzot)

Tuki (תוכי) is a Tamil word (Tokai) that was imported into the Hebrew lexicon a long time ago, so only for the sake of of being consistent with birds which have a modern convention (that a Tzipor/Tsipor (Ṣipor more correctly) (ציפור) is feminine) of having a noun that has an irregular pluralisation (think for example Shaneem Rabot VeNe`eemot שנים רבות ונעימות), that tuki/tukeem takes this on

תודה