This video from North America is called How Birds Survive The Winter Season – Mini Documentary.
From the Cornell Lab of Ornithology in the USA:
Winter-Proofing Your Birdhouse
by Karen Patricio, BirdSleuth student intern
Some birds don’t mind using last spring’s nesting box as this winter’s roost box to keep warm during windy, cold nights. Roost boxes and birdhouses both provide shelter for birds, but roost boxes are not intended for building nests or raising young. They are meant to give cavity-dwelling birds protection from cold temperatures, precipitation, and predators. In his book Birds Asleep, Alexander Skutch describes how birds (particularly those given to nesting in cavities) may crowd together inside a nest box or other hole when temperatures are harsh and food is scarce.
With some modifications, you can repurpose your spring birdhouses by turning them into winter shelters for your backyard birds! Here’s how:
1. Before you get started, clean the birdhouse and repair any damage from the nesting season.
2. Start winter-proofing your birdhouse by sealing the ventilation and drainage holes to keep warm air trapped inside. You can seal holes with rags, hay, foam weatherstripping, duct tape (on the outside), or any material that will prevent wind from entering.
3. Some birdhouses are designed with a movable front panel with an entrance hole at the top. If possible, flip this front panel upside down so that the entrance is on the bottom to reduce heat loss (since hot air rises). If you can’t do that, don’t worry! Remember that any type of shelter, no matter how imperfect, is helpful on a freezing cold night.
4. Lastly, place the shelter in a warm and safe location. Choose a spot that has long light exposure–the more sunlight the box sees in the afternoon, the longer it will stay warm in the evening.
Position the house so that the entrance is facing away from prevailing winds to prevent gusts from blowing into the shelter. Also, be sure the placement is safe from predators by placing it high off the ground, or on a baffled pole. Now you have a winter roost box that can help your backyard birds stay warm during those long winter nights!
What about birds that don’t use cavities? They will seek shelter in an evergreen tree, often huddling together on severe nights. Maintain evergreen trees on your property, and consider placing an old Christmas tree outside through the winter (until the needles drop).
Liquid water is essential for all winter birds, but it takes more than just plugging in a heater to keep a bird bath fresh, clean and full. By understanding the importance of water and taking a few simple steps, every backyard birder can be sure their neighborhood flock has a safe place to drink all winter long: here.
North American Winter Backyard Birds: here.