Hi,
It is never a good idea to have an odd number of birds in a cage. You need to remove her, or remove one of the males. But if the males were already bonded with each other, it is better to remove her. It is unlikely the egg is fertile and she shouldn’t be allowed to incubate it anyway. It’s too much work for her. She would need a mate and he would sit on the eggs half the time. Did her mate die, or why was she separated from him? Once bonded, a pair should not be separated. It’s actually cruel because they do mate for life. If a mate dies, the surviving mate may or may not accept another. But pairs should not be split up once bonded. Unless you plan to let her try to bond with a male, you need to discourage egg laying. It is very hard on her and female cockatiels can become chronic egg layers, laying eggs over and over until they die from laying too many eggs. You should try some changes to discourage more egg laying, and until she has a mate, discard any eggs she lays.
Keep in mind that to lay eggs, she needs longer daylight, warmer weather, abundant food, and a quiet, private environment. The goal is to reverse these conditions.
Limit her light to 8-10 hours by covering the cage early each evening
Do not give her anything to use as a nest – no bird huts or tents, no box, bowl, etc. If she decides to sit in a food bowl, remove it and replace with smaller cups.
Do not give her anything to shred such as paper or cardboard.
Rearrange the toys in the cage frequently.
Move the cage to a different place in the room. Move the cage about once a week, or whenever she shows signs of nesting – settling on the cage floor for example. This disrupts her idea of having a stable place to lay eggs and raise chicks.
If you feed a lot of fresh foods, stop offering any for a couple of weeks, and then only offer them in small amounts about 2 or 3 times a week. You can resume normal feeding later when the birds aren’t being hormonal.
If she is let out of the cage, do not let her get in any dark cozy places and don’t give her free roam.
When you handle her, limit any petting to only the head and neck – do not pet a bird on the body. Only a bonded mate is allowed to groom the body. We can’t be a mate, so touching the body is off limits.
If there is no metal floor grate, then do not use any bedding or paper in the cage tray – leave it bare and clean it daily.
If the hen doesn’t stop laying, and continues to lay clutch after clutch, then a hormone implant or shots should be considered. The implant is proving to be very effective with most chronic egg layers.
Thank you for asking Lafeber,
Brenda