Why aren't Gouldians as prolific as Zebras?

[Lucille]

Looking at my Zebras this morning, thinking that they are juicy morsels for predators. Compared to a hummingbird they fly fairly slowly, and flight seems to be their only protection.
Perhaps that is why they are so prolific, they are such an easy target that producing a lot of them is the only way for the species to survive.
If anything, Gouldians would seem to be even a more enticing target, with their vivid adult colors. Why are they not as prolific?

[debbie276]

The numbers of gouldians have risen over the years 10 fold. The cost was so expensive years ago that very few dared to try. All the rumors about how hard they were to breed kept interested breeders at bay.
Costs now are a quarter of what they used to be and more and more people are adding them to their flocks. I have no doubt in time they will be as prolific as zebras.

[cindy]

I agree with Debbie, I remember the prices of gouldians being ridiculously high and everyone thought of them as so delicate. I find them just as hardy as zebras.... zebras though are like little mice with wings and produce anytime anywhere!

[paul-inAZ]

Seems to me we have two different things going on here. The original post was about 'prolific'. That would have to do with reproductive rate which is generally species specific. Mosquitos vs elephants [a few days vs. close to two years]. Would that mosquitos were as un-prolific as elephants.
Why the differences in pet birds? Some molecular biologist may have figured it out but I don't know.

The other thing mentioned is population numbers which is largely externally determined. Habitat, diet, epidemics etc. in the wild. Commercial desirability [think cows], or in the case of Gouldians appeal to and propagation by hobbyists account for the growing numbers.