That happens sometimes, but in my experience, it isn't permanent (depending on your reactions etc). My bird is obsessed with my dad and sometimes does that stuff around him--more so when other people are holding her and he enters the room, but she is definitely more nippy with me here than when we are at home (she has drawn blood). At home, she never bites, so even a bite every few days is a MAJOR shift for her.
That having been said, the shine *cough OBSESSION* is starting to wear off and after weeks of daily interaction with everyone (dad, mom, sister etc), she is liking the rest of my family more (and adjusting to the transition of a long stay at a non-home place). She has visited before, but this may be our most successful long-term visit (although looking at my hands, you might not know it). She is getting way better about letting everyone handle her (even when dad is around) and she is following directions like she did at home w/ out major issues---but this took a long time. This is our longest visit and it is not our first, and for the past 2 weeks, it was kind of rocky and unpredictable (as anticipated). It always is weird when new dynamics, environments, and people are introduced. This can be punctuated when there is a perceived slight by you (e.g, "abandoning her")---I know you didn't but cockatoos can hold a grudge like a middle school girl. I know you think your bird picked your mom, but just because your bird is infatuated with her (following your absence) does not mean this will last. She was probably like a raft in a raging river ---the closest thing to grab onto in your absence (a rebound person lol). Now, I'm sure your bird will always like your mom, and maybe even prefer her (hard to say) but cockatoos CAN bond closely to more than one human as long as their hormones/sleep/petting etc are all kept in-check and behavioral issues are not reinforced.
How long had you had Cooper before leaving him with your mom?
