I wrote last week about our cold temperatures and thought it good to consider how many birds make it through the cold winter months here in the Adirondacks. The answer for the most of them is to migrate south to warmer climes. Most breeding birds here in the North Country must head south in order to find enough warm temperatures and food to survive. Many of these birds fly all the way to Latin America or the Caribbean, while others head south to places like New Jersey, the Carolinas, or Florida. And while migration is dangerous and energetically expensive, it is advantageous for them to do so.
The few birds that remain are a hardy bunch and while they skip the perils of migration and its energetic costs, they must face the harsh Adirondack winter. Birds don't hibernate like many mammals do, so these species are forced to feed enough to maintain their internal body temperatures in order to survive. As a result, bird feeders are often a center of activity as birds stock up on food to make it through the day and often bitterly cold nights. Many birds also do not waste energy, resting often throughout the day with their feathers fluffed to trap heat.
Birds which remain during the winter must eat available food, and seed is the easiest thing to find. Despite the presence of such high energy their insulating feathers, many birds do succumb to the elements. In fact, adult mortality is generally higher in year-round resident species in temperate regions than it is in those species which migrate.
Just today I was hiking near Lake Placid and found a dead mourning dove which sat looking as if it was asleep. The bird sat with its eyes closed and feathers fluffed symmetrically as if trying to stay warm. There were no signs of trauma or that anything had killed it, but its tail feathers were missing – perhaps the work of a scavenger after a meal. I suppose it could have lost the tail in a narrow escape and then died later as a result. But there was no damage to the flesh, no body eaten, and its body was a bit gaunt on further inspection. It did not look as if something had killed it, but rather that it had simply died. It had, after all, been an extremely cold week, and a bird that was perhaps sick would have struggled to survive. I picked it up and it felt like a cold stone – then sat it down to its peaceful pose and walked on.
In order to have enough energy to survive the winter, birds must stock up on fat reserves during the fall (hence they eat voraciously at that time of plenty, and some, like gray jays and blue jays, cache food for future eating, using their remarkable spatial memory to find it in the cold months. Predatory birds, like owls and hawks, are a different matter altogether and they must scrap together their meager means by hunting rodents, birds, and scavenging carcasses.
Besides eating and bolstering their energetic reserves, birds also attempt to minimize their energy lost through harsh conditions. For one, they hunker down in dense foliage such as conifers – your old Christmas tree can prove a great asset to birds at your bird feeder as a result. Many birds also roost at night in cavities to protect themselves from the elements and may do so communally to conserve heat through huddling. This is even done by birds of different species (to which my ornithology students always exclaim, "ah, isn't that cute?!). Survival is, after all, a need for all.
Other birds use the insulating properties of snow and will bury themselves in it. I knew a man who was cross country skiing and noticed a place where a ruffed grouse had burrowed into the snow. He skied over to look at its tracks and unbeknown to him, the bird had tunneled under the snow and was sitting directly beneath him. Frightened by his presence it burst through the snow right between his legs, scaring him witless!
Some songbirds use snow in a similar way. Common redpolls – a finch which is so prevalent in our area this winter – will dive into snow banks regularly for shelter, a useful behavior for a bird that inhabits such cold arctic regions for so much of their lives.
It is this set of adaptations what allow birds to make it in such harsh conditions in the Adirondacks and even farther north. It is nothing short of miraculous when you consider that the -30 degree temperatures we witnessed this past week are survived by birds weighing just a few ounces. So keep your feeders full, and enjoy the birds which add life to our cold landscape during this time of year.
