This tuft of feathers, preserved in all its details in yellowish amber, belonged to a chick 99 million years ago.
The researchers, who examined the unusual find of amber more closely, assume that the small primeval bird was moulting at the time, i.e. it exchanged its baby feathers for adult ones. Similar to a human child losing its milk teeth. After one of these tufts of feathers had come loose from the fluff of the young bird, it ended up in sticky tree sap. This solidified and turned into amber, which has preserved the primeval feather to this day.
The bird comes from the group of Enantiornithes – toothed primordial birds that became extinct along with the dinosaurs at the end of the Cretaceous period. The feathers of the Enantiornithes chick, preserved in amber, are now telling paleontologists why this group may not have made it into modern times. One reason lies in the way in which these primeval birds once moulted. “All of the chick’s body feathers are essentially at the same stage of development, which means that all of the feathers started growing at or near the same time,” reports Jingmai O’Connor of the Field Museum in Chicago.
From the point of view of paleontologists, this type of feather change is problematic because the chicks of Enantiornithes were probably left to their own devices early on. If they changed their plumage in one go, they had to do without its warmth, at least temporarily. Because there were no parents around who could have warmed the chick.
During the mass extinction at the end of the Cretaceous, these moulting tactics probably worked against the Enantiornithes. “When the asteroid hit, global temperatures plummeted and resources became scarce, leaving these birds not only with even greater energy needs to keep warm, but also without the resources to meet those needs,” explain the scientists. As a result, these ancient birds probably died out, while the ancestors of modern birds survived with more efficient moulting techniques.