Nesting Season is Coming

 As we anticipate Spring's arrival it's time to make sure our nest boxes are ready. Soon the chickadees and wrens will begin to search for and establish territories, then begin nesting. Before they start it's best to have your nest box clean and ready for new tenants. 

Not all birds use nest boxes. The Anna's Hummingbird, for example, builds tiny cup-shaped nests in shrubs and trees. Unlike other birds, the Anna's nest earlier, in mid-February, and their young should be out and flying around before the end of March.

Anna's Hummingbird in Nest - K. MacDonald

Common cavity nesters in backyards are the Bewick's Wren, Chestnut-backed Chickadee, Red-breasted Nuthatch, Tree and Violet-green Swallows, and all species of woodpeckers. Equally common but less welcome are the European Starling and House Sparrow. These birds naturally build their nests in cavities that have been excavated by woodpeckers or through other means, but will also use nest boxes that we provide, especially if natural cavities are scarce or have been removed. 

Northern Flicker in Cavity Nest - S. Petersen

Nest boxes have a few requirements that should be considered in order to make sure it's beneficial for the birds. The entrance hole size determines who can get in and making it too big can allow predators or unwelcome birds inside. If you are wanting to attract smaller birds like chickadees and wrens, having the entrance hole be 1" keeps other birds out while still allowing them inside. Enlarging the hole from 1" to 1 1/8" lets nuthatches use it as well. Entrance holes of 1 3/8" are useful for these smaller birds as well as swallows and House Sparrows. To keep the sparrows and starlings out, swallow boxes can be made with an oval hole. The oval should be 7/8" high and 3 1/2" wide. Swallows can rotate their shoulders and make themselves flat while the starlings and sparrows cannot. The smallest woodpecker in our area, the Downy Woodpecker, uses an entrance hole of 1 1/4", while the larger Hairy Woodpecker can use a 1 1/2" hole. Northern Flickers need a hole size of 2 1/2" in their nest boxes. Once difference between woodpecker nest boxes and other nest boxes is that woodpeckers excavate cavities and we need to emulate this in their boxes. Filling woodpecker nest boxes with wood chips allows them to imitate the excavation and makes them more likely to use your box.

Oval Hole Swallow Box

The size of the floor determines how much energy the birds will have to use and how much work they do to build their nests, so bigger isn't always better. The height of the box is also important, as well as the distance from the bottom of the box to the entrance hole. Having a deeper box helps keep the eggs and young out of the hands of predators, and the birds will build their nests inside to the height they want from the hole. Nest boxes for chickadees, wrens, and Downy Woodpeckers are best made with a floor of 4"x4", or 5x5" max with the hole around 6" above. Adding something to the back of the door such as grooves or strips of wood can help act as a ladder and help young birds climb out when they are ready. Swallow or Downy Woodpecker boxes should also have the entrance hole around 6" above the floor, though the ideal floor for these boxes is 5"x5". The box for a Northern Flicker should have a floor size of 8"x8" with the entrance hole 10-12" up. 

Ladder on nest box door

Ventilation is a must, whether it's holes drilled in the sides or other ways to allow airflow. Birds have difficulty cooling down so making sure there's decent airflow to keep heat down is vital. Placing the box somewhere shadier or where it gets limited sunlight during the day can help keep it cool as well. If you decide to paint your box, go with light colours to reflect some heat. 

You also need to consider cleaning. Being able to clean out the nest box when nesting season is over is an important part of having a nest box you want to use more than once. Make sure whatever box you have has an easy way to get inside to clean it out. Cleaning your box can help keep small bugs and parasites from infesting the box. Remove the nest each year and give the box a quick brush out. If you notice mold or rotting, it may be time to replace the box. A solution of 9 parts water to 1 part bleach can be used to kill mold, just make sure the box is given time to completely airdry to avoid encouraging more mold or bugs. Sometimes bees may attempt to build their hives in your box. Use a bar of soap and rub the inside walls of your box to leave a thin layer that the bees nest will be unable to adhere to. Check your nest boxes even if you don't think they were nested in, as some birds will leave debris in boxes to keep other birds from using them. 

Often we see nest boxes with little perches, but we do not recommend adding one. Perches allow predators to sit and attack the adults and young in the nest box. The birds in the box can easily get in and out without the use of a perch. 

When placing your nest box, try and put it somewhere where wind and rain do not blow directly into the box. Also consider the type of bird you are wanting to use the box and make sure you place it in a location that appeals to them. For example, chickadee boxes should be near trees or shrubs they can dart in and out of, while swallow boxes should have open space around them to allow the birds to swoop in and out. The boxes don't need to be mounted very high, 6-12ft. off the ground works just fine for anything except a bat box. Try and keep nest boxes at least 20ft. from bird feeders with the entrance hole turned away to avoid interference between the two. 

The most important thing when placing a nest box is to make sure you put it somewhere you can see it. Adding a nest box to your backyard can be very entertaining, and watching the young fledge cannot be missed.

Good birding!