I have rescued a nestling raven. He seems to be eating okay but has not put on weight over past few days. Should I be concerned? Also, I wondered what the best thing for a nest would be, as he is at present in a small washing up bowl with a couple of pillowcases?
Weight gain is not the only criteria for the well being of nestlings. Also, weight gain is not a continuous or linear process either. To begin with, weight gain per day is huge, which will then slow down dramatically. However, literature is scarce when it comes to find weight figures for comparison purposes. There is also a lot of variation with regards to individuals, including gender. Assuming the bird is getting a well balanced diet, and ideally has company of its own kind, or at least enough mental stimulation, then it is more important to rely on features like behaviour and interaction. Assuming that the bird’s droppings are okay, and that there are no signs of dehydration (e.g. standing skin folds), and that the bird is getting more and more active, meaning he or she is not sleeping excessively or is lethargic, then things should be okay. Close monitoring of the situation is essential, as the situation may change quickly. Regarding the nest, it is important that the bird can stand properly and can find areas in the nest to perch and exercise. If the nest is too soft or wobbly, perhaps even slippery, then birds are prone to get feet deformities. You could use a thick towel instead of a pillow case to provide more grip and put a natural branch or perch onto the nest floor, so that there is enough space left for the bird to lay down and rest.