While it is impossible for us to know the cause of each local increase and decline, there are several common causes for bird population fluctuations.

  • Habitat changes affect bird populations. If there has been a change in your neighborhood, such as trees being cut down or new houses being built, that could be the reason you are seeing a decrease in birds.
  • Natural food supplies – such as cones, berries, seeds, and insects – fluctuate from year to year, causing birds to shift ranges to take advantage of food surpluses or to compensate for food shortages.
  • Weather patterns often cause birds to shift ranges, especially in winter.
  • Birds of prey sometimes move into an area causing the local birds to feed elsewhere until the predator moves on.

Bird populations normally fluctuate from one season to the next and from one year to the next. Sometimes, however, there are significant, long-term changes in the numbers of particular birds in certain areas.

Project FeederWatch