|Cold, barren, bird-less...|
Before we take pity on the birds, we must remember that millions of years of adaptation have morphed these creatures into a form wherein they are highly able to eek out a living in the winter. But what does this mean? In nature, any adaptation is always a compromise, a balance, between the new and the old, as the new develops from the old. For most songbirds, the old behavior is to cover larger areas in search of every morsel of food in every nook and cranny to reap the greatest benefits from their territory. For example, Baltimore Oriole pairs maintain a territory around the size of a football field during the breeding season. While doing this, they must defend their territory from intruders and themselves from predators. But this old way of behavior must change entirely for the winter, and especially during a snowstorm.
Our first factor in winter survival is that food is far less evenly distributed, with some areas being supplied with super-abundant food, while others have no available food at all. With food sources fewer and farther in between, songbirds have to find these isolated food sources to supply their daily energy needs. This breaks down the breeding season concept of territory. Now that resident songbirds no longer have to defend territory containing nests, they can roam more freely in search of reliable food sources. Once they find them, the bird is more likely to stay there because constantly searching for food requires much more energy in the cold, which is the second factor in adapting to survival in the winter. With more energy used to stay warm, it makes more sense to stop wandering and stay put in areas that will reliably provide food for a sustained period of time, e.g. feeders or large areas packed fruiting plants. That's where the initial adaptation is.
|European winter feeding flock|
The breeding season could be said to tear birds apart, and then the challenge of surviving winter, especially snowstorms, brings them back together. It would be accurate to summarize this process by saying that once the territorial boundaries of breeding songbirds break down, and food sources become more difficult to find, songbirds adapt their behavior to cluster together in social feeding flocks, and remain tight around food rich areas. That's all it is: an adaptation of behavior to survive in the winter.
With more birds clustered tightly in specific areas, this leaves greater areas of perfectly desirable habitat, well, bird-less because they lack reliable food sources. And voila!! The perfect recipe for making it seem like resident songbirds "disappear" in a snowstorm, and the winter overall.
Winter is a perfect time to see this strategy in survival--how staying alive requires an exact formula that results from millions of years of adaptation in similar conditions. That's not to say that songbirds are never found alone in the winter, because they are. That's not to that songbirds don't die in the winter, because they do, but the majority survive in an average winter, and there's a reason for that.
|Stunning winter Cardinal by Daniel Behm|