There is no better time to view wild birds than winter. The bare trees and snow-covered surroundings provide very little camouflage, which makes bird activities more visible. Winter is a very fragile time for wild birds, however, and not all birds survive it. Birds that winter over have acquired some adaptive behaviors that help them survive, and they also rely upon humans for survival during these crucial months.
How birds stay warm
Wild birds have many different ways to stay warm and conserve energy in winter. First, some species can grow additional feathers as the temperatures drop, which thickens their insulation. Some birds use the practice of feather fluffing, a process that puffs out the down feathers to create air pockets, which gives a bird better insulation and traps body heat.
Some birds can lower their metabolic rate to an almost torpor-like state. Their heart rate slows down and their body temperature declines. They burn fewer calories in this state, which helps them survive the coldest nights.
Other birds, especially the more social species like chickadees, stay warm at night by roosting with other birds in tree cavities or man-made nest boxes. We can help by cleaning nests and other debris out of our birdhouses at the end of the breeding season, so birds can use them for roosting in winter.
What birds eat in winter
Cold weather increases a bird's caloric requirements at a time when food is most scarce. There are no insects flying around. Seeds, weeds, fruits, and nuts are often used up or covered in snow.
Some birds that winter over prepare for the food-scarce months of winter by collecting food in the summer and fall months and hiding it away for later use in winter, a process called caching. Birds return to this stash when natural food sources run scarce. The caveat is that sometimes other birds or animals find the food, too.
Some birds eat dormant insects they find in the crevices of tree bark. Some birds will also eat the berries of winter-hardy species, such as bayberry and juniper.
Other birds flock together to find reliable feeders. The ironic part is that though they work together to find these food sources, they are often very competitive with each other once they find it. We can help by providing feeders with Suet, Nyjer thistle seed, and black oil sunflower seed. The important thing to remember, if you're not a year-round feeder, is that birds begin to look for reliable backyard feeders in late summer to early fall. If you are not feeding during this time, you may miss the opportunity to attract them for the winter months. Be sure to hang feeders in August or September for winter feeding. Also, remember that if you start feeding birds for the winter, they count on you to keep them stocked all winter long.
Water is crucial, and scarce, in winter
Though food is scarce in winter, dehydration can be a bigger threat to birds than starvation. Fewer non-frozen sources of water exist. Though birds can eat snow, it takes much more precious energy for a bird to eat snow and warm it to body temperature than it does for them to drink unfrozen water.
Water is not only important for hydration, but it also helps birds preen their feathers. Without proper preening, birds' feathers won't stay positioned and aligned. Feathers out of alignment in winter create gaps in insulation, which makes birds lose body heat faster.
Birds may have to fly great distances in winter to find unfrozen water sources. Some birds take advantage of unfrozen sections in rivers or swift streams, but these are rare in some areas. Some birds take advantage of open water in lakes or ponds due to human aerating.
We can give birds access to unfrozen water right in our backyards by providing a heated birdbath. Or, we can use an existing birdbath and add a heating element. Most of these units turn on and off automatically when temperatures dip below freezing.
Wintering birds have done quite well in order to survive the coldest months. They've also learned to rely heavily upon humans for food, water, and roosting spots. The more we chip in and help, the better their chances of survival.