You are Not Cute.
It was true that the phoenix did not sleep much. Tom did not bother attempting to provide it with a nest. It had managed to feed itself just fine without his assistance at dinner. It could sort out its own stupid bedding arrangements. He put it down on his desk and ignored it while he studied, and then he went to bed.
The rustling started about five minutes after he dispelled the light.
“Do not mess up my runes homework,” Tom growled irritably. There was a sweetly agreeable chirp. He scowled into the darkness. He did not want a pet.
He did not want what Dumbledore had said the phoenix was, either - an angel of justice sent to lead him to the path of righteousness. Did Dumbledore even understand the religious connotations of that kind of language? But from the rest of what he’d said, maybe he did. It will rise up and cleanse you from the face of the earth.
The stupid thing cheeped again. Then there was a thump. It had just either fallen or jumped off his desk onto the floor. Dumb bird.
He considered, briefly, whether he ought to take Warren’s advice and put it back on the desk with an open book. Just in case it could actually read and would actually stay put if he did that. Then he discarded the idea sheerly because of its source.
It took the phoenix chick fifteen minutes and about ten tries to climb up the blankets onto his bed. Tom picked it up and took it back to the desk.
It took ten minutes and seven tries the next time.
“This is my bed,” he informed it, then returned it to his desk. It replied with an affirmative sort of chortling sound. “You are not cute.”
It chirped. He hissed irritably and dropped it on top of his arithmancy book.
The third time it climbed up on his bed, it had waited until he was almost asleep.
“Why,” he mumbled. It was not a question. The bird did not answer. It just clambered on top of his chest and sat down on its ugly awkward feet like it meant to stay there all night.
It was warm.
“Fine,” he mumbled. “But it doesn’t mean I like you.”
At least Slytherins had single rooms. If he’d had roommates there was no way he would be caught dead letting a bird sit on his chest.