Raptors play an integral role in Wisconsin’s diverse ecosystems and can alert us when conservation investigation and action is needed. An ecosystem is a community of living beings and non-living factors that interact with each other in their environment. Living things include animals, plants, fungi and microbes, while non-living factors include things like air, water, soil, and sunlight.
The nature of these interactions is summed up well by this core principle of ecology: everything is connected to everything else. Perhaps the most familiar example of this concept is the food web. A food web is made up of many overlapping and interconnected food chains. Each food chain is one possible path of nutrients and energy through an ecosystem, with each non-living and living thing in the chain being essential to the path.
The role of predators, often depicted at the top of a food web, is important for monitoring the interactions in an ecosystem. When the interactions within a food web are balanced, it creates a healthy ecosystem that provides natural diversity of plants and animals, clean air and water, and healthy soil. If something changes, it will affect the living and non-living things that interact with it through a chain reaction.
If a predator’s population declines, such as that of the Red-shouldered Hawk, it can lead to cascading impacts across the food web. Red-shouldered Hawks are a Wisconsin State Threatened species who prefer mature hardwood forests, ideally with a water source nearby. Human development is causing many of these habitats to fragment or vanish altogether. If the hawk population continues to decline, it could lead to the populations of rodents, amphibians, and fish they prey upon to increase. As a result, these animals would consume more invertebrates. During their aquatic larval stage, invertebrates help maintain water quality. If they disappear, it could lead to lower water quality, which impacts many other living things in the overall ecosystem.
Indicator species are organisms whose presence, or absence, can signal overall ecosystem health. When their populations are stable or increasing, it can mean that the ecosystem is thriving. In contrast, population decline raises the alarm on a potentially bigger picture issue.
In the 1960s, changes in raptor populations alerted us to the negative ecosystem impacts of synthetic insecticide DDT. Peregrine Falcon populations suddenly plummeted because their eggshells were too thin, causing the eggs to break apart during incubation. By investigating the relationships in the ecosystem, scientists discovered that DDT was the cause. It was creeping through the food web because the birds that Peregrine Falcons were hunting were eating insects poisoned by DDT. This discovery resulted in a ban on DDT and, with strong efforts from the conservation community, the recovery of Peregrine Falcon populations.
Raptors today still indicate when there is a problem in their ecosystem. American Kestrel populations have been declining, particularly in the Northeastern and Southern US. Though more information is needed to be sure, scientists hypothesize that pesticides, changes in farming practices, or increased urbanization are potential causes. Continuing to study the relationships of these raptors to their ecosystems will help scientists better pinpoint causes and determine how to help nature recover.
