Cliff Swallows gather in spring, in nesting colonies of up to 3,700 nests. Look for swarms of them under bridges, under the eaves of barns, or even the side of your house. The swallows use mud to make gourd-shaped nests - side by side and jumbled together. Watch the video! And Cliff Swallows consume hordes of flying pests. For more about this bird, visit Cornell's All About Birds. You can learn about bugs that aren't pests at Audubon.org.More info and transcript at BirdNote.org. Want more BirdNote? Subscribe to our weekly newsletter. Sign up for BirdNote+ to get ad-free listening and other perks. BirdNote is a nonprofit. Your tax-deductible gift makes these shows possible.