The answer should be from the article attached:
At hatching, the upper and lower beaks of the skimmer are equal in length, but by fledging at 4 weeks, the lower beak is approximately 1 cm longer than the upper beak. Under the assumption that the bone formation rates of the upper and lower jaws are equal from hatching to fledging, explain what would be the reason that causes the lower beak to become longer than the upper beak at fledging. What assay would you use to support your conclusion?
If the chicks are fed with bisphosphonates (a strong inhibitor of osteoclasts) after hatching, how would their beaks turn out compared to untreated chicks in terms of beak length and why?