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What Biotic Factors Affect Birds?

Biotic factors are the consequences all living things exert on their environments. How plants and animals affect one another is what forms ecosystems around the world. The biotic factors that affect birds relate to other organisms in their environments. What birds eat, the animals that eat birds, where birds live and their relationships with humans are major biotic factors that affect birds.

Diet
- Because there are many species of birds that live in any one environment -- a forest or swamp, for example -- evolution dictates they must compete for different resources. If all birds ate the same things, there wouldn't be enough food to support many birds. Over time, birds have evolved to eat insects, seeds, other birds and animals. The availability of a particular seed, insect or animal can be an important biotic factor on the number of given birds in an environment.
Predators
- Predatory animals are a major biotic factor for any species of bird, due to a predatory species' ability to impact bird populations. For example, scientists on the island of Hispaniola began investigating why populations of Bicknell's thrush, a songbird, were decreasing at a higher than normal rate during the wintertime. A 2009 study released in "The Condor" revealed that rats had begun climbing into trees to eat the thrush's eggs and newly hatched chicks. Scientists knew rats preyed on ground nesting birds, but underestimated their aggressiveness in pursuing birds that nested in the trees.
Habitat
- The types of trees birds use for nesting present a variety of biotic factors that can affect a population. Some birds, such as the red-cockaded woodpecker, thrive in forests with larger trees and little understory. Birds of prey, such as the osprey, nest in tall trees with open space around them. The way a tree grows, and where it can grow, affects the types of birds in its environment. Many birds are migratory and require specific types of trees in two separate locations in order to survive.
Human Impact
- Human beings are often significant biotic factors in the lives of birds, and are not always aware of it. While actions such as hunting or lumber harvesting affect a bird's environment, it is pollution that can have the largest impact. On April 20, 2010, the Deepwater Horizon oil rig malfunctioned in the Gulf of Mexico and leaked millions of gallons of oil into the sea. The biological effects on thousands of birds, from the toxicity of the oil harming their bodies to the death and contamination of large portions of their food chain, will take decades to measure.

Animals & Science