Only if the egg is fertilized would this be a fair comparison; when fertilized the egg contains an embryonic chicken, or a "chick". Basically a baby chicken. A human zygote, being a fertilized egg, is a unique human life.
This isn't hard to understand and is part of almost any 6th Grader's Life Science textbook.
Where the pro-abortionist seems to diverge from facts is when they start getting into measuring the value of that life. The argument of whether it is a unique human life is already answered. One may argue that it is valueless until it is somehow magically imparted with whatever measure they call "personhood"... or one can believe that it has value regardless, or because we cannot be sure of, the magical moment of "person" or "soul infusion"... some measure this by "viability" which is a silly measure, that human life will have many years of dependence even after they are born, hence the idea of "viability" is simply a different level of medical necessity. Some babies born will need medical assistance, should they not be considered human? It's actually quite a foolish measure.
Some religions measure it by sentience, others believe that the "soul" is infused at the moment of conception...
Either way it is just another divergent way of defining the value of that life, not arguing that the life doesn't exist at all or isn't human.