There are five million bird eggs stowed away in museums across the world — and the study of eggs, called oology, can give us great insight into birds. The link between DDT and the decline of Peregrine Falcon populations was identified in part using museum and personal egg collections, and this evidence helped lead to a ban on DDT. And today, Peregrines can still be seen zipping across the sky.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.