The correct options are
B Wildfires in a forest
D Landslides
Increased population density has many effects in a population. In case of the flamingoes, more population density will reduce the size of the feeding grounds, increasing struggle for food. Birds compete with each other and fight for nesting sites. If their population increases, it will in turn increase competition for limited nesting areas. Natural disasters like forest fire or landslides also affect population density but are not dependent on population density.