Visibility, Sound Propagation and Exposure to Predators: Effect of Height on Birds’ Perch Use in a Meadow Habitat

Elevated perches allow songbirds to better transmit their songs and increase the visibility of territorial displays, but there is a cost: increased predation risk. To investigate how grassland birds evaluate these tradeoffs, we placed artificial perches in one of four meadows kept open by mowing in Williamstown, Massachusetts. We tracked meadow and perch usage by passerine birds using both a weekly census and monthly counts of fecal boli as a proxy for occupancy of the artificial perches. The same species were observed in the meadow with artificial perches and the meadows without such perches. Nevertheless, all of the artificial perches were used, some extensively. Much of the variation in perch use could be explained by perch height. Birds preferred taller perches, which are the most visible to predators, but also provide the largest advantages in terms of song propagation and visibility for better territory advertisement. Other advantages include increased visibility for foragers hunting insects, as well as possible earlier detection of predators. The increased predation risk of perching in the open on higher perches appears to be offset by the advantages gained by being seen, being heard, and having a better view of the surrounding area.