Using Fishing Line to Deter House Sparrows

By Joan Watroba

Many people have been experimenting with this method using the diagram below with very good results. I have been using it with much success on my bluebird trails for the past 6 years. It was originally used on a 12 nest box trail that had many house sparrows attempting to use the nest boxes. After I installed the line, the house sparrows stopped using the nest boxes, yet the native songbird species like the bluebirds, tree swallows, tufted titmice, black-capped chickadees and house wrens adapted to it with ease and successfully fledged their young.

Why this method may work — Bluebirds and many other cavity-nesting birds are insect eaters and they have keen eyesight. House sparrows are mostly seed eaters and their eyesight may not be able to see the line; they may be spooked if they hit the line which may cause them to avoid the box. The few times that house sparrows have built a nest in a nest box with the line installed, they did not try to re-nest after the initial removal of their nests and eggs. This method may be effective to reduce repeated nesting attempts of house sparrows.

Installation tips:

  • Use 6 lb. test, clear or lightly-tinted monofilament fishing line
  • Best to install the line before the house sparrows start using the nest box
    and become bonded to it
  • Replace the line when it becomes brittle and discard the old line
  • The line should protude in front of the nest box at an angle, so that from the
    side view, there is a space of a least 2 inches between the line and the front
    of the nest box


  1. Place 2 screws on the front of the nest box roof and 2 screws on the bottom
    front of the nest box spaced about 1 3/4″ inches apart. (The goal is to have
    the line run as close to the sides of the entrance hole without covering it.
  2. Tie the line to the top left screw or screw eye, then bring it down and wind
    around the lower left screw, then wind around the lower right screw, then
    bring it up to the top right screw and leave about 1″ of line that can then
    be wound around and fastened tightly to the top right screw.
  3. To monitor top or front-opening boxes, reverse the installation instructions
    and then “re-install” the line after checking the box. For side-opening nest
    boxes, there is no need to remove the line to monitor the box.
  4. Check the line during each trail visit to make sure that it is secured tightly
    and properly.