The recent drouth of the late 1950’s and early 1960’s produced some dramatic effects on the quality and quantity of emergent vegetation in glacial marshes of the central United States and Canada. These vegetative changes have had great impact on the distribution and size of marsh bird populations. Similar plant responses must have resulted from the dry years of the late 1800’s and the 1930’s, and intervening wet years produced opposite extremes on many marshes. Such habitat changes undoubtedly have occurred throughout the racial history of many marsh animals, and the maintenance of a species depended upon its adaptability.