Join BirdNote tomorrow, November 30th!
Illustrator David Sibley and actor H. Jon Benjamin will face off in the bird illustration battle of the century during BirdNote's Year-end Celebration and Auction!
© Dan Streiffert
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.
Support for BirdNote comes from the Cornell Lab of Ornithology, presenting its new “Bird Photography” online course, featuring Melissa Groo. Learn more at academy.allaboutbirds.org.
BirdNote®
Grosbeaks and Monarchs - Black-headed Grosbeaks Dine on Poisonous Butterflies
Written by Bob Sundstrom
This is BirdNote!
[Black-headed Grosbeak song]
The Black-headed Grosbeak’s rollicking refrain may be the most joyous bird song of the western summer. Beginning in early May and continuing right through July, the Black-headed Grosbeak sings and sings: from the treetops, from deep in the leaves, and even while sitting on its nest. [Black-headed Grosbeak song]
Black-headed Grosbeaks are one of very few birds that regularly eat Monarch butterflies, which most birds and other animals find unpalatable, if not downright toxic.
The caterpillars of Monarch butterflies consume milkweeds containing toxic substances known as cardenolides (pronounced kar-DEN-oh-lydz). The poison is stored in the adult butterfly’s abdomen, giving it a powerful form of defense.
Many Black-headed Grosbeaks winter in the same areas of central Mexico as millions of Monarchs. The birds consume a great number of Monarchs through the winter, including their toxin-laden abdomens. One other bird in the area, the Black-backed Oriole, also preys on the butterflies, but studiously avoids the tainted abdomen.
So perhaps what other birds find toxic is just the tonic the grosbeak needs to put that jazzy feel in its song.
[Black-headed Grosbeak song]
For BirdNote, I’m Mary McCann.
Support for BirdNote comes from the Cornell Lab of Ornithology, presenting its new “Bird Photography” online course, featuring Melissa Groo. Learn more at academy.allaboutbirds.org.
###
Song of the Black-headed Grosbeak 126546 provided by The Macaulay Library at the Cornell Lab of Ornithology, Ithaca, New York. Recorded by T.G. Sander.
BirdNote's theme music was composed and played by Nancy Rumbel and John Kessler.
Producer: John Kessler
Executive Producer: Chris Peterson
© 2013 Tune In to Nature.org July 2017/2020 Narrator: Mary McCann
ID#062507BHGR2KPLU BHGR-02b
Key source: Journey North website, 2004 article contributed by Bill Calvert.
Sights & Sounds
