Anyone who has a small, female bird, especially a cockatiel is probably experiencing hostile behavior and an abundance of eggs. Females  can lay eggs without the presence of a male just like chickens. These usually sweet little girls turn into hostile, aggressive defenders of these eggs and usually their cages (aka nests).   TO REMOVE OR NOT TO REMOVE   In a female bird's head, there is a pre-set number of eggs which make up a clutch....for example, if your bird has determined 5 eggs is her clutch of which she has laid 2 eggs, she has 3 more to go. If you remove the first 2 before she has finished laying, she will replace those 2 and continue on to her goal of 5 eggs. It is best to allow her to lay her entire clutch....this should be completed in 10 to 14 days. At this time, you should take her from the cage and into another room, clean her cage, move a few things around and maybe even gift a new toy or so. * don't let her see you remove the eggs.   A FEW TIPS TO HELP DURING THIS HORMONAL STORM   * because seasonal hormones are triggered by external stimuli, removing some that you have control over might ease this stressful time....   * reducing the amount of light from 12 to 14 hours per day to 9 to 10 hours per day can significantly affect your bird's hormones. Sometimes having a night time cage can really  help with the light issue.   * diet is another aid in taming the hormones....calcium is imperative when laying eggs...this can be provided through cuttle bones as well as calcium supplements.These items can be found in most reputable pet supply shoppes.   * as for biting and aggression, learn to read your birds biting body language and keep your fingers out of the line of fire until your sweetie is off the 'war path'.   * to help with the bird's possessiveness, try and give her time away from her cage daily. This might help with her territorial behavior.   * when cleaning and rearraging her cage, remove all mirrors, huts, and toys that she might like a tad bit too much......(follow me here)...this can help a lot in this hormonal storm.   I hope this helps....we are having the same problem here.....sometimes our lights dim due  to our Hormonal Tsunami.   Come in and visit sometime soon.....make sure you say hello   Have a peaceful April anne