In drinking water, the more turbid it appears, the higher the chance that those using it could end up with gastrointestinal diseases. The water may be having contaminants such as viruses and pathogenic bacteria which are found attached to suspended solids. These solids may interfere with disinfection of the water.
Erosion and effluent from highly urbanized areas contribute to the turbidity of water in those areas. In open bodies of water, organisms such as phytoplankton can contribute to turbidity in the water.
You can infer that the birds once had a common ancestor but became separated. Mutations in copying their genes stacked and caused changes in the beaks so the birds could be more well off or better adapted in their new environment.
