Unfortunately, this contest also seems like a "rights grab" to me. Unless I'm reading this wrong, if you enter the next "Mad Bluebird" photo, Smithsonian can make a bundle selling mugs, posters, t-shirts, etc. without you getting a dime, even if the photo doesn't win anything in the contest. But at least you will get a photo credit.
What rights to my photograph do I retain?
You retain your rights to your photograph; however, by entering the contest, you grant the Smithsonian Institution a royalty-free, world-wide, perpetual, non-exclusive license to display, distribute, reproduce, and create derivative works of the entries, in whole or in part, in any media now existing or subsequently developed, for any Smithsonian Institution purpose, including, but not limited to, advertising and promotion of the magazine and its website, exhibition, and commercial products, including but not limited to Smithsonian Institution publications. Photographs may appear on the Smithsonian Journeys Web site as well as in Journeys publications. Any photograph reproduced will include a photographer credit. The Smithsonian Institution will not be required to pay any additional consideration or seek any additional approval in connection with such uses.