Why would imbalance hormone levels cause a male to be unable to reproduce

Many Reasons

Explanation:

For starters, low T - or low Testosterone can lead to low libido, which may physically cause him not to want to reproduce. Low T can also have detrimental effects to the fidelity or health of sperm cells, as testosterone is necessary for the proper maturation of sperm. That means then, that at the cellular level if you have unhealthy sperm then they may not be able to fertilize an egg.

if the type of the food available changes, then the frequency of beak types will change, because birds with beaks more suited to the available food will be more successful over time.