Spring means birds singing. But at 2 AM?
We've been serenaded by a mockingbird for the last week, at all hours, at top volume, mixing samples collected from all over the western hemisphere to create a crazy-wild DJ scene on the premises. The bird is awe-inspiring to say the least, giving pitch-perfect renditions of titmice, crows, blue jays, and frogs, as well as a few call-and-response numbers, among many other turntable classics.
Why? What is the origin of this bird and its behaviors? A recent article in science laid out the DNA-based phylogeny of birds, of which there are over 10,000 species. It upset quite a few previous classifications, and definitively, since sequence-based phylogenies have greater resolution than character-based ones. Mockingbirds reside in the largest group, the passeriformes, along with other songbirds. I had assumed, from its shape, size, flight style, wing bars, and aggressive behavior that they are closely related to jays, which are related to corvids/crows. But not true! Mockingbirds are cousins of starlings, showing that vocal facility, which starlings share in spades, is also a crucial diagnostic trait. Indeed, an incredibly charming book, now out of print, relates how one starling was taught to speak (and sing) passable English.
The study of birds continues to fascinate the evolutionary community, with new specimens of Archaeopteryx being lovingly studied as it becomes common knowledge that birds are our only living connection to the dinosaur lineage. The fossil record in this case, as is true for whales and other organisms, is filling out to give us an ever-fuller account of complexity and gradualism in the history of life. Additionally, studies of bird memory were the first to demonstrate the birth of new neurons in adult brains, concomitant with the memorization of new songs. Subsequent work found the same phenomenon in humans- an important focus of contemporary neurobiology and even stem cell-associated hopes.
Archaeopteryx from the Jurassic (~150 to 200 million years ago).
Note the claws at the end of the wing/fingers.
Mockingbirds have upwards of 150 song samples at their command, and change their repertoires between spring and fall. The function of their singing, other than attracting mates, is not clear. But one could speculate that the high volume and enormous fund of mimicked songs functions to keep other species at bay, creating better-quality territories for the omnivorous mockingbird. The utility of this trait would in turn create a sexual selection rationale for females (who also sing, just not a 2 AM) to select mates with larger repertoires, more accurate reproduction, and higher volume.
As our culture gradually transitions away from the Christian fetishes of false hope, blood, and death at this time of year to the much more ancient themes of life, fertility, and birth, it is wonderous to participate (if unwillingly!) in the rituals of birds who are so diligently and flamboyantly engaged in the tasks of life.
- Subscription site at Cornell is the leading resource for general bird knowledge.
