Crowtail was born as a house cat but was given away to a Normad Clan named ShardClan when she was still a kit. 

Her father was the deputy of the said clan and had an affair with a female house cat. She didn't want to join him to live in the wilderness, but she was willing to give one of her kittens away so he would be able to remember her. Crowtail never missed her. 

She grew up under the care of a nice queen together with her own son Lizardkit.

When they both became apprentices, the Clan was attacked by a pack of wild dogs and the cats were scattered apart. Crowtail and Lizardpaw, the latter being gravely injured, got lost in the riot and found shelter in an abandoned house.
Crowtail didn't know a thing about herbs or medicine and without the necessary care, Lizardpaw died the following day. Crowtail was devastated. 

After losing her beloved brother and with no home to return to - after all, she still didn't know where she was and where to find her Clan - she decided to just live on her own.

She was alone for a long time until one day when she was wandering around daydreaming. She got caught by a hawk and because she is a rather small cat, she was easily lifted up in the air. But as soon as the bird realized, that this prey was willing to defend itself with claws, it let go of her very quickly. 

She was able to catch a branch and hold onto it, but, as if she wasn't already unlucky enough, the branch was too small for her and was on the verge of breaking. Now, Crowtail never climbed a tree in her whole life, so there was nothing left she could do but to call for help in hopes that somebody would come along. 

It appears she wasn't that unlucky after all, because Shellstar heard her call and helped her. Crowtail, being thankful towards her lifesaver and also thrilled to live together with other cats again, then decided to join ShoreClan.