<span>BROCA'S AREA
Broca's area or the Broca area is a region in the left frontal lobe of the dominant hemisphere of the hominid brain with functions linked to speech production.
Broca area, also called convolution of Broca, region of the brain that contains neurons involved in speech function. This was discovered in 1861 by French surgeon Paul Broca, who found that it serves a vital role in the generation of articulate speech.</span>
<span>Russell's case (two illnesses: bipolar disorder and substance use disorder) illustrates </span>comorbidity. The term comorbity is used in medicine to denote a presence of two diseases or disorders, one primary and one additional, both occurring at the same person.
In this question, there are no options given to choose from. So i would answer this question based on my knowledge. The most likely cause of the observed variation is adaptation and evolution. The birds of that island adapted to the food source and then they evolved as per the requirement of the place and food source.