2:00 minutes (1.61 MB)
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Black-headed Grosbeaks are one of very few birds that regularly eat Monarch butterflies. Most birds and other animals find the butterflies unpalatable, if not downright toxic. The caterpillars of Monarchs consume milkweeds that contain toxic substances known as cardenolides. The poison is stored in the adult butterfly's abdomen, giving it a powerful form of defense.