Applesauce (plain - un-spiced and un-flavored) is great to add to a baby pigeon's food. Small amounts of plain Greek yoghurt and a drop or two of ACV (apple cider vinegar) are also great in giving the chick extra protein, nutrition and for making the crop just a little more acid to help deter crop fungal issues or other digestive problems. I have had good results with mixing plain Greek Zoi yoghurt in with baby pigeon food (10% - 15% yoghurt in the food).
Does the smaller chick by any chance feel warmer than the larger chick or warmer than usual, like he/she is overheated? Place your fingers on the pinkish odd-colored areas of the skin and compare the temperature to the normal-colored skin or the skin of the other baby pigeon. Also, what is the size difference between the two nestlings - is there any way that you could post a picture of the two on here?
What you mentioned about the chick not gaining weight and having odd-colored areas of skin concerns me a little. About 5 months ago I encountered a problem with a baby pigeon which somehow contracted PMV and did not make it through. The loft, nest etc. were clean and the parents were perfectly healthy, but the younger sibling still became terminally ill. Here is everything that happened if it might help as reference to you:
At one week after the parents hatched out both of their eggs, the smaller chick was only 1/3 the size of the larger chick, despite being fed adequately and being carefully cared for by both of the doting parents. Both male and female then became very hesitant to sit on the chicks in early morning between 4:00 and 7:00. I would wake and check on the birds to find that the babies were trying to huddle next to each other, and the parents were standing two feet away from the nest or in the sunning cage. This was too early for the parents to stop sitting on the chicks, but trying to place the parents in the nest and over the chicks did nothing because they would get off again 10 minutes later. Thinking that this might be because the larger chick was growing so fast and it was uncomfortable for the adults to sit on both, I placed the larger chick with the only available foster parents at that time hoping the smaller one would then get the care it needed. It worked for about three days and everything seemed to be normal again except for the chick's stunted growth, but upon the fourth morning the mother had again left the nest and the baby almost died from getting too cold. I would have switched the young pigeon to fosters, but there were no available pigeon parents at that time. Every morning at four I woke up and brought the baby inside to a heated nest until about 8:00, then returned it to the parents.
The parents began to feed it less and less, so I began hand-feeding to ensure the baby pigeon got enough food. At a week and a half old and still hardly any body growth or feather quill growth and with oddly skinny-looking legs, the young baby began swallowing air along with the hand-fed food I was giving it and I had to place gentle pressure on the crop to cause the pigeon to burp it out. Two days later, the skin began to heat up and show discolored pinkish-reddish blotches. I double and triple-checked the pigeon daily for any signs of canker, crop yeast infection, cocciddiosis, anything I could think of, but found nothing relating to any sickness I knew the symptoms of. At two weeks at this time I removed the baby from the parents altogether, as there was something going on and I did not want the parents to somehow contract it if they didn't already. The parents were quarantined, medicated and then boosted with probiotics and vitamins for two weeks, but thankfully no signs of sickness ever showed up on them, the older nest mate to the sick baby or any other youngsters from that pair so far.
Two and a half weeks, the droppings became unnaturally watery and the pigeon began twisting it's head and neck sideways, looking like it was gazing at the ceiling any time it was not being fed. I scoured the internet looking for any help as to what this might be and found that the pigeon had somehow contracted PMV (Paramyxovirus). I had never heard of baby pigeons in clean environments contracting this and it is very rare, but I did what was recommended and administered small amounts of Baytril and liquid vitamins containing Vitamin C and D - supposedly vitamins which were depleted by the presence of the virus and the chick would die without them. I had heard the complete recovery time for PMV (if there was a recovery) would be 6 to 8 months total, and the bird would have to be quarantined and cared for during that time. Needless to say, despite keeping the chick warm and giving it the best care I knew how, it still did not survive past 3 1/2 weeks.
The parents, although seemingly changing from doting, caring parents to uncaring snobs within a week, actually knew what was going on more than I did and stopped caring for the young bird because of it's affliction.
I hope that the baby pigeon you are caring for does not have this
Please keep an eye on him/her in the next couple of days and watch for any signs of torticollis (star-gazing, neck twisting). If you suspect the chick might have a sickness or virus, please please use separate feeding utensils for each of the baby birds - placing each in seperate heated areas or nests would greatly help too but I don't know if you would be able to do this.
Good luck and keep us updated!
Faith
