Robins will eat a mixture of bugs and other things not just one food. Worms are not a sufficient diet. Cat food is a much better choice. Feeding can also be tricky. Do a search on google for how to feed altricial chicks. The information for hand raising parrots and pet birds mostly applies except they require a different diet and the amount will vary by bird size. It's easy for them to aspirate the food by placing it wrong or giving too much. You also want the food to be the proper temp. Both too cold or too hot and it will cause crop problems. Over feeding is actually a major cause of death in wild orphan animals. People try to get as much food as possible down them and end up causing digestive problems. You want to control the amount they are fed preferably by weighing the animal several times daily and feeding a percentage of their weight. The proper amount for each animal takes some searching to find. That's why wildlife rehabbers get training and information on these things. Aside from feeding altricial chicks will not regulate their temp like precocial chicks (chickens, quail, etc...) and move in and out of a heat lamp. You will have to maintain very specific temperatures where the babies are.
I had some very good links from when I hatched a robin egg after the nest got destroyed in a very bad storm. I don't remember them though and my computer has crashed since then losing all bookmarks. The information is out there and there was a very good blog by someone who really watched a robin nest and recorded everything. That's what helped me hatch the egg since they even put temp probes in the nest.
