Pigeons and doves have different sized crops, so the best guide to feeding them is to let them eat until the crop is soft and squidgy like a balloon 3/4 filled with water. The crop hangs like a bag down the inside of a pigeon's chest.
There are small bubbles that appear on a hatchling's shoulders when it had received enough food. Once these bubbles start to inflate stop feeding, it means that the crop is full enough. The pigeon on the left of the photo has an overfilled crop. The arrows show the "warning bubbles", the yellow swelling on the side of the crop shows it has been overfilled. The pigeon on the right is OK, it has food in its crop but has not been over filled.
This is a photo of a baby wood pigeon with a slightly overfilled crop! I panicked the first time I overfed a baby (it happens), but was told that unless they are showing signs of distress it is best to just leave them to be quiet and digest their food in peace and to not do it again!. Duddly was OK, but if the crop is overfilled too often it will stretch and form a pocket that traps food which can become sour and harmful.
When the crop has flattened and the baby squeaks to be fed you can feed again. But allow the crop to empty completely every 24 hours.
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