Expert: Julia Booth - 9/21/2008

Question
Having watched sandhills migrating south through Central Washington state for many years, I'm wondering what prompts their migration. I've conjectured temperature, amount of daylight, position of sun in the sky but have no science to base my opinion on. They were nowhere to be seen this year for the first time on my annual fishing trip (same time and place for 20 years). Thus the curiosity and the question.

Answer
Whenever there is a change in migration, there are usually one of two reasons: a change in environment or weather -meaning the temperature, rainfall, amount of available vegetation, available breeding room OR a change in food supply, which is usually directly related to the populations of other animals in their eco system. Cranes eat fish. So do bears, eagles, osprey, harriers and well...fisherman. Less fish means less cranes. Cranes don't have many natural enemies, because of their combined size and ability to fly, so that rules out the possibility of them staying away due to an overpopulation of predators. It's probably a food source or environmental issue. To really be sure, I would contact the department of fish and game for your state. They keep monthly records of patterns and changes in animal population.

Here is an excellent source on the migratory studies of the sandhill crane:

http://www.npwrc.usgs.gov/resource/birds/comroost/index.htm#contents