The Eastern Bluebird (Sialia sialis) is a beloved species, and providing a safe nesting site is a rewarding conservation effort. Successfully helping a pair raise a brood hinges on selecting the correct mounting system, which must prioritize the safety of the nestlings. A free-standing pole mount, as opposed to a tree or fence post, is the most effective method for deterring climbing predators and is associated with a high rate of nesting success.
Essential Habitat Criteria and Placement Height
The location of the birdhouse directly influences whether bluebirds will choose to nest there. Bluebirds are insectivores that prefer open, sparsely treed environments, such as pastures, large lawns, and golf courses, where they can easily spot prey from a low perch. The ideal setting is a grassy area with low vegetation, which allows them to hunt efficiently while maintaining a clear flight path to and from the box.
The house should be set back from thick woods or dense shrubbery, ideally at least 50 to 100 feet away, since this cover is favored by competing species like House Wrens. Placing the box within 25 to 100 feet of a small tree or shrub offers a safe staging area for fledglings taking their first flight. The optimal height for the bottom of the birdhouse is between five and six feet off the ground, which is low enough for easy monitoring and cleaning, while still being high enough to accommodate an effective predator baffle.
Necessary Hardware and Pole Selection
The choice of mounting pole is a critical factor in predator defense. Round, smooth metal poles are highly recommended because they are difficult for climbing mammals to grip, unlike traditional wooden posts, which offer easy purchase for raccoons and squirrels. A common and effective choice is 1/2-inch or 3/4-inch Electrical Metallic Tubing (EMT) conduit or galvanized pipe, which is rust-resistant and durable.
The pole system often requires a piece of rebar or a heavy-duty ground socket to serve as an anchor in the soil. Attachment hardware, such as specialized flange mounts, U-bolts, or a metal conduit coupler, is needed to connect the house to the pole. Essential tools for installation include a post driver for sinking the anchor, a drill, and a level to ensure the nest box sits upright.
Step-by-Step Pole Installation and House Attachment
A robust method for securing the pole involves using the EMT conduit and rebar system. Begin by driving a piece of 4-foot rebar approximately 18 to 24 inches deep into the ground using a post driver, leaving the top half exposed to act as a stable stake. Drive the rebar as straight as possible to prevent the final pole from leaning.
Next, slide a 5-foot section of 1/2-inch EMT conduit over the exposed rebar stake; the rebar anchors the smooth conduit and prevents twisting. If using a specialized mounting bracket or flange, secure it to the back or bottom of the birdhouse with weather-resistant screws before placing it on the pole. Many bluebird houses are designed to slip directly over the conduit and are then secured with a self-tapping screw or bolt through the wood and into the metal.
The final placement requires adjusting the house so it is perfectly level and oriented correctly. The entrance hole should generally face away from prevailing winds, often toward the east or southeast, to protect the interior from rain and harsh afternoon sun. Tighten all screws or clamps to ensure the house is anchored firmly and does not wobble, which could discourage nesting birds.
Securing the Nest: Installing Predator Baffles
The installation of a predator baffle is a non-negotiable step to protect the nest from threats like raccoons, snakes, and domestic cats. Even a smooth metal pole can be climbed by persistent predators, making a physical barrier necessary for nesting success. The most effective design is the stovepipe baffle, which is a metal cylinder, typically 8 inches in diameter and 24 inches long.
The baffle is installed below the birdhouse and must be mounted so it can wobble freely on the pole. This instability prevents climbing animals from gaining a foothold and scaling the slick surface. The bottom of the baffle should be positioned at least four feet off the ground, which is higher than most predators can reach when jumping.
To install a stovepipe baffle, a support mechanism, such as a hose clamp or angled strips of hanger iron, is secured to the pole to hold the baffle in place. The baffle is then slipped over the pole to rest on this support, ensuring a gap remains between the top of the baffle and the bottom of the birdhouse. This design creates a barrier that is too wide and unstable for predators to navigate.