Monday, April 30, 2012

Great-tailed Grackle

Great-tailed Grackles spread from Mexico into the United States and Canada during the 1900s. Urbanization and agricultural irrigation seem to have contributed to the species' spread. Until the 1960s, Great-tailed and Boat-tailed grackles were thought to be the same species. Now they are considered to be distinct. For one thing, Boat-tailed Grackles in Florida and the Gulf Coast, like the one in the lower photo, have dark eyes. Great-tailed Grackles, like the one above from Rockport, Texas, have yellow eyes. (Boat-tailed Grackles outside the areas of overlap, like along the Atlantic Coast, also have yellow eyes.) Great-tailed Grackles are found in prairies, agricultural areas, and towns; Boat-tailed Grackles prefer marshy areas (Johnson and Peer 2001).

Great-tailed Grackles are polygynous. Social bonds are "ephemeral;" females (and males) may switch mates within or between breeding seasons. Males defend small territories containing trees in which females nest. One reason for this pattern may be that males suffer relatively hight mortality rates, resulting in more females in the population (Johnson and Peer 2001).

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