Your saying that a reptile layed an egg and it hatched into a bird ?
Also the olive egger is still a chicken, breeds and a species are different things .
This is a DEEPLY oversimplified and inaccurate description... But perhaps if I was trying to explain evolution to a toddler I might say that? In reality the change is gradual over hundreds or even thousands of years.
Breeds and species are just a list of defined traits. Can you define a species to me? Biologists can't.
A species can't be defined by phenotype, since many animals with VERY different phenotypes (Chihuahuas and wolves for example) are the same species.
It can't be defined by chomosome count since many animals with different chomosome counts can have viable offspring like servals crossed with domestic shorthairs.
It can't be defined be reproductive populations since reproductively distinct populations may exist in other areas and still be able to breed back. And it doesn't even touch on the subject of animals like sharks and reptiles that can reproduce without any other animals.
It can't be defined by ecological niche. Flying squirrels and sugar gliders are totally different despite having nearly identical roles and appearance...
Wikipedia says;
https://en.wikipedia.org/wiki/Species
"While the definitions given above may seem adequate, when looked at more closely they represent problematic species concepts. For example, the boundaries between closely related species become unclear with hybridisation, in a species complex of hundreds of similar microspecies, and in a ring species. Also, among organisms that reproduce only asexually, the concept of a reproductive species breaks down, and each clone is potentially a microspecies. Though none of these are entirely satisfactory definitions, scientists and conservationists need a species definition which allows them to work, regardless of the theoretical difficulties. If species were fixed and clearly distinct from one another, there would be no problem, but evolutionary processes cause species to change continually, and to grade into one another. "
There's no real difference between "breed" and "species" except how tightly we're defining an animals traits. When it comes to the questions like this the answer is identical just on a different scale. Is it a Cream Legbar if I cross it to a barred rock, then back to CL again three times? Or is it mixed? It's all semantics.