![]() In fact, just around half of the members of an acorn woodpecker group contribute directly to reproduction at any given time, while the rest help care for nestlings. That, in an acorn shell, is kin selection, and it explains why helping family members can be such a powerful evolutionary force in the animal kingdom. Helping my parents raise an additional kid actually gives the same genetic benefit as having a kid myself. ![]() If I’m old enough to help but too young to get a mate of my own, helping my parents care for new children would also be a great way to ensure the continuation of our genetic lineage. If life continues by passing along genes, it therefore benefits me to help my siblings care for their children. Even if I do not end up having children, if my sister has children, or even my cousin, a lot of my genes will still get passed along. You and your close relatives will carry many of the same genes, and at the end of the day, that is what counts. Chances are, some of your relatives have siblings or children of their own. But think about it: where did your genes come from? Your parents. One integral part of evolutionary biology is the idea of fitness, which is an individual’s ability to pass on their genes to the next generation. The important factor at play for the woodpecker’s communal nesting is kin selection. This behavior makes sense given what we know about evolutionary biology. After all, it’s far faster to grab a granary that’s already been installed than to make a new one from scratch. Researchers have observed long, brutal conflicts in which groups of acorn woodpeckers jab at each other relentlessly with their spear-like beaks over control of a tree. Turf wars are common, with neighboring groups frequently jostling for granary trees. Each member of the nest contributes to finding food, caring for the young, and defending their shared territory. They are highly communal, usually nesting in groups of up to twelve individuals, almost always composed of close relatives. Acorn woodpeckers are unusual in this way. Most birds nest in pairs with one male and one female. Out of all the bird species we know, acorn woodpeckers are the only ones that make granaries in this way.Īn acorn woodpecker at a granary As such, the pockmarked trees these woodpeckers live and work in are called granaries. While acorn woodpeckers eat insects, flowers, and berries when the weather is warm, they rely heavily on their acorn stockpiles to make it through the winter. The trees in their territory are peppered with holes, indentations made by generations of careful bark drilling to provide storage space for - what else? - acorns. Calls emerge from somewhere in the treetops, ascending in pitch and volume:Įven if you can’t spot an acorn woodpecker ( Melanerpes formicivorus) - wide-eyed and black and white with a brilliant red cap - signs of its activity abound. In the early spring mists of the California coast, deep within hilly oak and evergreen forests, their voices cut through the morning air. This article is a modified excerpt from the author’s upcoming book, “Are You There God? It’s Me, Darwin.”
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