Institute for Integrative Conservation, William & Mary, Williamsburg, VA, United States of America.
PeerJ. 2023 Feb 2;11:e14676. doi: 10.7717/peerj.14676. eCollection 2023.
Window collisions are one of the largest human-caused causes of avian mortality in built environments and, therefore, cause population declines that can be a significant conservation issue. Applications of visibly noticeable films, patterns, and decals on the external surfaces of windows have been associated with reductions in both window collisions and avian mortality. It is often logistically difficult and economically prohibitive to apply these films and decals to external surfaces, especially if the windows are above the first floor of a building. Therefore, there is interest and incentive to apply the products to internal surfaces that are much easier to reach and maintain. However, there is debate as to whether application to the internal surface of windows renders any collision-reduction benefit, as the patterns on the films and decals may not be sufficiently visible to birds. To address this knowledge gap, we performed the first experimental study to compare the effectiveness of two distinct window films when applied to either the internal or external surface of double-glazed windows. Specifically, we assessed whether Haverkamp and BirdShades window film products were effective in promoting the avoidance of window collisions (and by inference, a reduction of collisions) by zebra finches through controlled aviary flight trials employing a repeated-measures design that allowed us to isolate the effect of the window treatments on avoidance flight behaviors. We chose these two products because they engage with different wavelengths of light (and by inference, colors) visible to many songbirds: the BirdShades film is visible in the ultraviolet (shorter wavelength) range, while the Haverkamp film includes signals in the orange (longer wavelength) range. We found consistent evidence that, when applied to the external surface of windows, the BirdShades product resulted in reduced likelihood of collision and there was marginal evidence of this effect with the Haverkamp film. Specifically, in our collision avoidance trials, BirdShades increased window avoidance by 47% and the Haverkamp increased avoidance by 39%. However, neither product was effective when the films were applied to the internal surface of windows. Hence, it is imperative that installers apply these products to exterior surfaces of windows to render their protective benefits and reduce the risk of daytime window collision.
窗户碰撞是人为导致建成环境中鸟类死亡的最大原因之一，因此导致了种群数量下降，这可能成为一个重大的保护问题。在窗户的外部表面应用可见的薄膜、图案和贴纸已被证明可以减少窗户碰撞和鸟类死亡。在外部表面应用这些薄膜和贴纸在操作上往往很困难，在经济上也很昂贵，尤其是如果窗户在建筑物的第一层以上。因此，人们有兴趣也有动力将这些产品应用于内部表面，因为内部表面更容易到达和维护。然而，对于将产品应用于窗户的内部表面是否会产生任何减少碰撞的好处存在争议，因为薄膜和贴纸的图案可能对鸟类不够明显。为了解决这一知识空白，我们进行了第一项实验研究，比较了两种不同的窗户薄膜应用于双层玻璃窗的内部或外部表面时的效果。具体来说，我们评估了 Haverkamp 和 BirdShades 窗户薄膜产品是否通过控制鸟类飞行试验有效促进了斑马雀避免窗户碰撞（并推断减少了碰撞），该试验采用了重复测量设计，使我们能够隔离窗户处理对回避飞行行为的影响。我们选择这两种产品是因为它们涉及到许多鸣禽可见的不同波长的光（并推断是颜色）：BirdShades 薄膜在紫外线（较短波长）范围内可见，而 Haverkamp 薄膜则包括橙色（较长波长）范围内的信号。我们发现一致的证据表明，当应用于窗户的外部表面时，BirdShades 产品降低了碰撞的可能性，而 Haverkamp 产品则有轻微的效果。具体来说，在我们的回避碰撞试验中，BirdShades 增加了 47%的窗户回避率，而 Haverkamp 增加了 39%的回避率。然而，当薄膜应用于窗户的内部表面时，这两种产品都没有效果。因此，安装人员必须将这些产品应用于窗户的外部表面，以发挥其保护作用，降低白天窗户碰撞的风险。
