There are many ways that windows can be treated to become “bird-friendly”. Bird-friendly windows essentially give context clues to the birds that a window is in front of them rather than open air. One of the simplest, most cost-effective solution for windows that are already installed is to add tape. The tape is typically set onto the window in lines or dots around the entirety of windows to give the bird hints that the window is there. Translucent tape can be placed on the window’s exterior and allows birds to notice the glass while still allowing light to pass through to the inside of the building.
Another mitigation technique used currently is multiple varieties of curtains, some being cords that drape down in front of the window’s exterior, others being more of a lightweight netting that can be placed over the windows. Either way, these curtains must be placed a few inches away from the window itself, so that if a bird does hit the net or cords, then they will decrease their speed enough so the collision with the window is not deadly, or they stop their momentum before they hit the window entirely.
There are also techniques that treat the glass itself. Especially using UV technology. One way is using a UV Liquid that can be applied to the exterior of the window that dries clear, which leaves marks that birds can see while remaining translucent to humans. Another technique using UV technology is to temper and laminate the glass in a specific way to make the window UV-reflective, doing the same job as the UV paint.
Another important note relating to mitigation techniques does not have to do with the window itself, but rather the lighting outside the building. Upward-facing lighting at night confuses the birds and may increase the number of bird strikes on specific buildings. If lighting at night is necessary, using techniques like using shielded light fixtures, having downlighting instead of uplighting, or using lights that have been approved by the International Dark Sky Association, will all help mitigate bird strikes at night, specifically during migration periods.