How might scarcity of food affect the size of a finch population?

Scarcity will affect the finch population because if there is less food for their population they might die or migrate into the place that food is abundant, food is the main source of life in every animal or even humans so this affects the population of the finch. The finch is a population of fifteen species of a passerine bird. 

do you have a picture?

a tetrad is the foursome during meiosis made by two homologous chromosomes that have each already replicated into a pair of sister chromatids.