Pigeons occasionally suffer from a condition in which the egg, which takes 24 hours to fully develop, gets caught within the bird's vent and backs up the pigeon's reproductive system. It's not always clear why this happens, but typically the condition is caused by an oversized egg. The egg in question could have two yolks, making it much larger than normal.
Loss of Appetite
One of the earliest signs of egg binding is a lack of normal appetite. The hen suddenly stops eating, or eats much less than normal. This is due to the egg taking up too much space in her body, creating an uncomfortable feeling which causes the pigeon to refuse food. In a large flock this symptom could go unnoticed, unless the bird has already isolated herself from the others, as they are prone to do when sick.
Signs of Depression
The egg-bound pigeon does not act normal. She will just sit by herself in a corner somewhere and look listless and sick. Her feathers may be fluffed slightly, making her look rounder than normal. (This feather fluffing is something birds will naturally do in low temperatures; the egg-bound pigeon may have a feeling of being very cold.) The bird will look droopy and have dull eyes and feathers. An egg-bound pigeon will not usually attempt flight.
Check the bird's droppings if possible. If the pigeon's vent or bedding is dry and clean, the hen is probably not passing her stool at all. Some egg-bound birds do exactly the opposite and have large, wet droppings that create a mess on the bird's feathers and where she is lying or sitting. Checking for abnormal stool is a good idea at any time, as this symptom can signal a variety of diseases.
Straining to Lay
An egg-bound pigeon will try to lay her egg no matter how long it takes, and this results in a bird who strains for days. Her vent will open and close and her body will tense up. The bird can feel the egg inside her and will try repeatedly to push it out. Sometimes this constant straining results in prolapse of the oviduct outside of the vent, which is a serious problem requiring veterinary care.
Inability to Walk
A stuck egg that presses on the nerves in the pigeon's legs can cause her to have difficulty standing and walking. If she has any ambition to walk at all she might do it with an odd gait, or she might stumble a lot. This stumbling can result in a fall, which can cause the bound eggshell to break inside the bird. A serious infection can result from this breakage, so the bird should be kept caged.
Abdominal Distention and Labored Breathing
An egg-bound pigeon usually displays a hard region of distention around her vent area. Gentle probing of the area will reveal the hard swelling commonly associated with a trapped egg. This also causes trouble with her breathing as the overly large blockage fills her small body, making it difficult for the air sacs in her lungs to inflate properly. The bird will gasp and pant while straining to lay the egg.
Sometimes an egg-bound pigeon displays no symptoms at all, or very mild ones, resulting in a bird that appears to be perfectly healthy one day and is suddenly and mysteriously found dead the next. This is uncommon with egg binding but can happen even when the pigeon owner is keeping a close eye on the bird's health and behavior. The correct diagnosis is usually found after a veterinarian's necropsy of the dead bird.