You're most welcome Monica
Cockatiels can be a little flighty at first, and building that bond may be a slow process. One of my previous cockatiels, a beautiful lutino girl called Twinkle, was an escapee I found on the street one Christmas Day. She had probably escaped from an aviary and was of an unknown age when I found her, and it took probably 8 YEARS before one day that little switch flicked on in her head and she decided she could trust me. She still gave me some sass every now and then but she was always up for a cuddle and stepped up every single time. I don't think it will take that long for Collins to come around by any means but Twinkle's example shows that it's never too late!
My lorikeet Lilly came to me a bit wild, having spent the first few months of her life at the breeders' in an outdoor aviary with no human interaction, and she was TERRIFIED of me! Each day I would just bring my chair just a bit closer to her cage, I would read to her in a calm voice, play YouTube videos on my phone of her species so she could hear them, and she would come just a bit closer every day. Finally after about 3 weeks she jumped on my shoulder and nibbled at the bottlebrush flowers I had for her and she has been my little velcro bird ever since.
Just find whatever Collins favourite foods are, those millet sprays you can get from the pet shops are usually pretty good. Move slowly around the bird and allow him to come to you. Make the trust building and bonding sessions fun and always try to end on a positive note, never forcing Collins to do anything he doesn't want to.
Above all, patience. My boy Fang is still a bit flighty even after 9 years, that's just the way he is, he's a bit of a doofus. He prefers my husband over me, which in my opinion makes him a great judge of character. But he sure as heck knows to come to his mum when he wants some love and a big scratch