1.So the researchers set up an experiment.
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2.They set up a bunch of nest boxes for warblers,boxes that were constructed so that they be safe from non avian predators like snakes or raccoons,then after a cow bird laid an egg alongside the warbler eggs,the researchers removed the cowbird egg from each nest box.
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3.After removing the eggs. For some of the nests,they restricted access.
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4.They made sure that the small host bird could enter the nest, but the larger cowbird couldn't.
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5.So for some of the nests, cow birds could reenter, and for others, they couldn't.
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6.And sure enough, the nests with smaller openings remained undisturbed.
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7.While most of the others were destroyed, all the warbler eggs were destroyed.
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8.So the researchers were right.
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9.The cow birds were coming back to check on their eggs, and if one had disappeared, they noticed and retaliated.
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