This autumn, I saw my first Cape May warbler in the state where I live. Unfortunately, the sighting occurred when a colleague walked into my lab and handed me the corpse. Every year during migration, the ground around our building is littered with the bodies of birds that crashed into it and died during the night. This phenomenon, of course, is not restricted to my campus. Radio towers, skyscrapers, and wind farms tend to receive most media attention, but birds are flying into all sorts of residential and commercial structures all the time, and the cumulative numbers add up to the hundreds of millions in the US alone (Loss et al. 2014).
In addition to direct mortality, there is of course habitat loss associated with the building of human structures. Even when little habitat is built upon, there is often an area that extends beyond the structure’s footprint from which species are displaced. Quantifying these effects is key to environmental impact assessment, and especially important when determining whether mitigation is warranted. Because we lack the resources to study every species, syntheses – especially quantitative meta-analyses – are essential if we are to make informed judgments about the many situations where detailed data collection is not possible.
Recently in Journal of Applied Ecology, Torre Hovick of Oklahoma State University and colleagues compile information from multiple studies of the effects of human structures (Horvick et al. 2014). They focus on one well-studied group of birds – the Tetraoninae, or grouse – many of which are considered to be of high conservation concern. Hovick et al. also focus their attention on human structures associated with energy production, although they took a broad view of what those structures are, including fences, roads, and buildings as well as wind turbines, oil and gas structures, and power lines in their review. To increase their ability to generalize, they also compiled data from throughout the annual cycle and examined the effects on both grouse survival and behaviour.
They found a consistent pattern of displacement, with bigger effects for oil and gas structures and roads, and during breeding periods. Additionally, they found evidence that both annual survival and attendance at leks – communal breeding display grounds – were adversely affected. Despite the considerable research attention that is paid to this group of gamebirds, they also found that there were insufficient studies to evaluate certain types of effects and that more than half of the available studies had to be excluded from the analysis because they lacked necessary comparisons (controls or before-after data). Two clear messages emerge: First, structures associated with energy production are generally bad for grouse. One recent study (Winder et al. 2014) found little effect of wind turbines on greater prairie-chickens, however, suggesting that not all structures are bad, and that careful planning might allow grouse to coexist with energy production. Second, much research is failing to contribute knowledge in a way that allows for the quantitative syntheses that are so essential to drawing broad conclusions. Despite the move towards the better production and compilation of a strong evidence base for conservation decision making (Sutherland et al. 2004; see also http://www.conservationevidence.com/), applied ecologists clearly have much to do still to maximize the impact of our science.
Hovick, T.J., Elmore, R.D., Dahlgren, D.K., Fuhlendorf, S.D., Engle, D.M. (2014) Evidence of negative effects of anthropogenic structures on wildlife: a review of grouse survival and behavior. Journal of Applied Ecology DOI: 10.1111/1365-2664.12331
Loss, S.R., Will, T., Loss, S.S. & Marra, P.P. (2014) Bird–building collisions in the United States: Estimates of annual mortality and species vulnerability. Condor: Ornithological Applications 116, 8-23.
Sutherland, W.J., Pullin, A.S., Dolman, P.M. & Knight, T.M. (2004). The need for evidence-based conservation. Trends in Ecology & Evolution 19, 305-308.
Winder, V.L., McNew, L.B., Gregory, A.J., Hunt, L.M., Wisely, S.M. & Sandercock, B.K. (2014) Effects of wind energy development on the survival of Greater Prairie-Chickens. Journal of Applied Ecology 51, 395-405.