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This work by Matthew Wills is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License.
Backyard and Beyond
Starting out from Brooklyn, an amateur naturalist explores our world. "The place to observe nature is where you are."—John Burroughs
This work by Matthew Wills is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License.
Backyard and Beyond 
Presumaby, in the nest the size advantage the cowbird has over the Chipping Sparrow nestlings guarantees a relatively easy victory when the cowbird chick reaches a size to need all the room and all the food. Female cowbirds raised by Chipping Sparrows might deposit eggs in Chippie nests preferentually, so the scales are tipped.