Density – Independent factors: - These factors are described as density independent because they exert their effect irrespective of the size of the population. E.g.: Drought, freezes, hurricane, floods, forest fires.
1) Weather – unfavorable weather can limit breeding success or cause mortality during the non-breeding season. (Example: Winter mortality).
2) Food supply – Abundance of food is often dependent on climatic factors, and in poor years food supply may limit population size.
3) Habitat limitation – Seasonal, annual or anthropogenic changes can affect resource levels such as nesting sites or availability of nesting materials.