The graph below shows a population of pigeons living in a neighborhood over a ten-year period. ​Which of the following statements could account for the change in population seen between years 7 and 8?

A
The birth rate of the pigeons increased.
B
The emigration rate of the pigeons decreased.
C
The death rate of the pigeons exceeded the birth rate.
D
The neighborhood reached its carrying capacity for the pigeon population.