Now keep in mind, pigeons dont give birth, they lay eggs, nd the eggs hatch.
Now, how old is the squab? Is it a month and a half old. As in it hatched over a month ago, or the egg was laid over a month ago?
Once a squab reaches the age of 5 weeks, it should be eating on its own, at times the cock is usually the one to feed them when they are around 3-4 weeks because the hen is usually sitting on freshly laid eggs once the babies are a few weeks old.
If its on baby, im sure the male can handle it.
Also as to what you hen died from sounds like sour crop. Usually when birds arnt feed grit, they start to have in build up in the crop and it gets infected, and causes lots of mucus to come out of the beak. The only way of curing sour crop is by sucking out all the mucus and giving antibiotics.
A way to always prevent it from happening again is to make sure you give your pigeons 'chick grit' its nice and small for them to eat.
Hope all goes well!