By David Wojick
In my last Wyoming wind power article I noted a National Audubon Society warning that the growing masses of wind farms could be “population sinks” for golden eagles. This means that many eagles will be attracted to them, to then be killed by them. See my article here.
Digging into the scientific literature I found that this is a well recognized wildlife management issue. It usually goes by the name “ecological trap.” Since being trapped means being killed I think ecological death trap is more appropriate.
In fact Wyoming wind power is a double death trap for golden eagles. First, as Audubon says, when the local eagles are killed this creates a sparsely populated area which other eagles will then come into. Eagles like most birds try to spread out, probably to maintain the local food supply for their hatchlings. These new eagles are then also killed and the cycle is repeated in a true death spiral.
In addition wind farms kill a lot of other birds as well as a huge number of bats. Golden eagles are scavengers so they are attracted by this abundant food supply. In fact being struck by cars while eating road kill is a major cause of golden eagle death.
Ecological death traps are not new science so the Federal and State Wyoming wildlife managers must know about them. To give you the flavor of the science, below are two quotes from a 2002 literature review article entitled “Ecological and evolutionary traps” available here.
“Deterministic models have shown that, as one might expect, when there are major differences in quality between habitats and population sizes are small, behavioral preferences for the habitats that yield no net reproduction (habitat ‘sinks’) can lead to population extinction. More surprisingly, this result appears to hold true even when patches of poor habitat represent a relatively small proportion of the entire landscape. Thus, alteration of only a fraction of the habitat in such a way that the decision-making rules of an organism no longer yield adaptive outcomes can result in the demise of the whole population if the preferences of individuals are strong enough.”
“Organisms often rely on environmental cues to make behavioral and life-history decisions. However, in environments that have been altered suddenly by humans, formerly reliable cues might no longer be associated with adaptive outcomes. In such cases, organisms can become ‘trapped’ by their evolutionary responses to the cues and experience reduced survival or reproduction. Ecological traps occur when organisms make poor habitat choices based on cues that correlated formerly with habitat quality. Ecological traps are part of a broader phenomenon, evolutionary traps, involving a dissociation between cues that organisms use to make any behavioral or life-history decision and outcomes normally associated with that decision. A trap can lead to extinction if a population falls below a critical size threshold before adaptation to the novel environment occurs. Conservation and management protocols must be designed in light of, rather than in spite of, the behavioral mechanisms and evolutionary history of populations and species to avoid ‘trapping’ them.”
Spacing out their nesting and scavenging for food are two deeply rooted survival instincts in golden eagles. Wind farms turn these survival skills into a death trap. Federal and State Wyoming wildlife and energy managers need to recognize this potentially catastrophic fact.
Wind power does more than kill the eagles that happen by; it repeatedly draws them in then kills them.
