Birds as Indicators of Ecosystem Health

birds as indicator

Since the Stone Age, humans have been fascinated with birds. Their variety in colors and sizes, a wide repertoire of songs and calls, their ability to fly and migrate across the globe, and their ubiquitous presence have been a source of inspiration for stories about human interactions with the natural world.

Birds as Components of Ecosystems

Birds are an integral part of food chains and food webs. Birds get their food mainly from plants. Others eat mammals, insects, and other invertebrates. At the same time, birds and bird eggs are also food for other animals. The feeding relationships among all the animals in an ecosystem help prevent any one species from becoming too numerous.

birds as indicator species
A Green and Black Fruiteater (Pipriola riffieri) about to swallow a whole berry. The seed will be regurgitated far from where it was eaten.

Birds provide many direct and indirect contributions to the ecosystems they occupy
These are often called “Ecosystem Services” and include serving as:

  • Pollinators: Nectar-feeding birds are important pollinators, meaning they move the pollen from flower to flower to help fertilize the seeds that will become new plants. Hummingbirds, orioles, honeycreepers, tanagers and flower piercers are common pollinators.
  • Seed dispersers: Many plants produce fleshy fruit with seeds that Fruit-eating birds help disperse. After eating fruit, they carry the seeds and deposit them in new places enabling the tree to potentially colonize a new area. Some plants need their seeds to pass through the digestive tract of a bird to soften the coats of a seed to help the seed germinate. Fruit-eating birds include mockingbirds, orioles, cotingas, tanagers, manakins, and thrushes.
  • Agents of Biological control: Birds occupy most levels of trophic webs and help maintain sustainable population levels of their prey and predator species. A bird eats hundreds of insects each day. Insect-eating birds include Flycatchers, warblers, bluebirds, and woodpeckers.
  • Birds as Keystone species: Some birds are considered keystone species as their presence in (or disappearance from) an ecosystem affects other species indirectly. For example, woodpeckers create cavities that are then used by small owls, cavity-nesting ducks, swifts, bluebirds, swallows, wrens, and other birds, as well as many small mammals.
  • Birds as a source of joy and inspiration: On a less quantitative level, birds provide humans with pleasure, joy, and spiritual inspiration merely by their presence. In addition, bird watching and related eco-tourism is a major economic force in many parts of the world.

birds as indicator
Woodpeckers make cavities that are also used by other birds and small mammals for sheltering and nesting.

Why is studying birds important?

To live sustainably and have a healthy planet, we must understand how the natural systems on which we depend on function. Birds are a critical element to nearly every ecosystem on earth, and their fate is intertwined with ours. Studying birds and bird populations is a way to further our understanding of the ecosystems that support all life on earth, including humans. Changes in bird populations can tell us a great deal about the impacts of climate change, drought, weather, and habitat change.

birds as indicator
Bird-banding studies are among the more popular techniques to learn about bird population dynamics.

What is an indicator bird species?

An indicator species is one whose status provides information on the overall condition of the ecosystem and of other species in that ecosystem. They reflect the quality and changes in environmental conditions as well as aspects of community composition.

The cliché “the canary in the coal mine” is used to imply an early indicator of potential danger or failure. Coal miners really did take canaries with them to provide early detection against carbon monoxide and other gases. As in the coal mines, birds provide an accessible window into the health of ecosystems where clues to otherwise difficult to detect changes in ecosystem processes can be detected through changes in bird populations. Declines in Peregrine Falcons and Bald Eagles provided important information about the dangers and spread of DDT and heavy metals.

What Makes a good bird indicator species

Good indicator species need to meet a few criteria:

  • It should be sensitive to changes in the environment in order to serve as an early warning. A resilient species not sensitive to environmental changes would offer little information about what is happening in the environment.
  • The species needs to respond to changes in a predictable manner. If it responds erratically to change, this would make it hard to interpret the underlying environmental causes of the changes that are observed.
  • It should be easy to compile and interpret data on the species to inform policy decisions. Species that are very rare would make poor indicator species because it would be hard to find and study enough of them to draw any meaningful conclusions. Similarly, it would be difficult to gather data on species that have very cryptic life histories or that are in general poorly understood.

With these criteria established, we can explore the different kinds of ecosystem changes that birds can tell us about.

indicator species
Guanay Cormorants (Phalacrocorax bougainvillii) is a good indicator species. They are highly visible, abundant, and use the same roost and nesting sites where they can be easily monitored.

What specific characteristics make birds such good indicators of environmental changes?

  • Birds are Colorful, conspicuous, relatively abundant, they vocalize and are easily observed or detected in their habitats.
  • They are Mostly diurnal and richly variable in size, structure, and behavior, which make them easily identifiable.
  • Birds have a rapid metabolism and occupy a high position on the food chain, which makes some species in each ecosystem sensitive to minor habitat changes.
  • Birds can fly and migrate at global scales and in great numbers. Their migratory movements linked with the seasons have the potential to shed light on issues at a global scale.
Conclusions

Birds are incredibly useful as environmental indicators. The intimate linkages between some bird species and their habitats make them useful for identifying ecosystem health. As such, they can be indicators of deteriorating habitat quality and environmental pollution, as well as metrics to determine the success of restoration efforts. Combined with their ability to signal the imminent outbreak of disease birds is great indicators of ecosystem health.


Sources:

  • Bioindicators. Science Learning Hub. The University of Waikato, New Zealand. 2015-02-10.
  • “Biological Stream Monitoring”. Izaak Walton League of America. Archived from the original on 2015-04-21.
  • Center for Global Environmental Education. What are the frogs trying to tell us? OR Malformed Amphibians. Retrieved from http://cgee.hamline.edu/frogs/archives/corner3.html