The following blog article created by Brad Guhr, of the Dyck Arboretum, in Hesston, KS, and the wing collection assembled by Karen and Dick Fulk, describe an instance of intense predation by 5 immature Mississippi kites on migratory monarchs that had taken temporary shelter within the grounds of the arboretum. Still, the stories that reach us have always been fragmentary. Unlike blue jays, that stopped eating monarchs after one experience, the scissor-tails and Mississippi kites appear to be undeterred by the cardiac glycosides in the monarchs. Yet, now and then, we hear of instances in which observers have reported seeing scissor-tailed flycatchers and Mississippi kites feeding on monarchs during the migration. Indeed, observations of birds feeding on monarchs, other than the black-backed orioles and black-headed grosbeaks that prey on monarchs clustered in the oyamel fir trees in Mexico, are rare. This learning by experience, though some monarchs are consumed in the process, is said to provide monarchs, as a population, with a degree of protection from bird predation since birds, being highly visual, recognize the contrasting colors and, after a feeding experience, subsequently avoid feeding on monarchs or perhaps all species displaying these colors. The jays thereafter refused to eat monarchs when presented among food items. A picture of this reaction is iconic (see “ The Case of the Barfing Blue Jay“), having graced the pages of Scientific American and many a biology textbook. Within a short interval, the jays would vomit up the monarch due to the emetic properties of the cardiac glycosides. Young jays, that had never seen a monarch, would unhesitatingly eat one when it was first presented as a food item. Among these tests were feeding experiments with caged naïve blue jays. This interpretation is strongly supported by the experiments and numerous analyses conducted by Lincoln Brower and his colleagues. This contrasting orange and black color combination is thought to be a feature that effectively advertises the toxic cardiac glycosides (also called cardenolides) sequestered in the tissues of adult butterflies from the milkweeds consumed during the larval stage. Predation by birds has been offered as the explanation for monarchs’ aposematic coloration. This text is both a preamble and addendum to the “Monarch Fallout and A Predator Story” blog article posted recently by Brad Guhr of the Dyck Arboretum (republished below, with permission). Monarch coloration, milkweed toxins, and predation by birds Thursday, November 5th, 2020 at 2:08 pm by Chip Taylorįiled under Monarch Biology | Comments Off on Monarch coloration, milkweed toxins, and predation by birds
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