Birds as Indicators of Ecosystem Health
Birds are excellent indicators of ecosystem condition because they are responsive to environmental change, have important ecological functions – such as seed dispersal and insect consumption, and are easy to observe.
Monitoring birds, even from a limited number of locations, can provide researchers with information on the condition of forests spanning hundreds of acres. The significant cultural and economic importance of birds and their popularity with the public can also help raise awareness and promote public investment in stewardship of natural areas. Researchers at the Forest and Rangeland Ecosystem Science Center are involved in studies using birds as indicators of the health of different types of ecosystems:
Willamette River Floodplain
Since 2008, large-scale restoration programs are in progress along the Willamette River in Oregon to address habitat loss due to dam construction, large wood removal, conversion of woodland to agriculture, and other land uses. Restoration projects include modifying human-made barriers to water flow, increasing floodplain forest vegetation, and removing aquatic invasive plant species. Several agencies are contributing to a strategic monitoring framework for Willamette River restoration. The framework covers strategies for monitoring the responses of hydrology and water temperature, fish, forest vegetation, aquatic invasive species, and birds to restoration actions.
Increasing the diversity of floodplain plant communities enhances the habitat available to fish, birds, and other wildlife. Many of the same features of healthy floodplain vegetation that are key for birds also benefit fish. For example, tree cover used by birds for nesting and foraging also provides shade that can maintain cool water temperatures that are essential for the health of salmon and trout.
The USGS is a member of Partners in Flight (PIF), a network of organizations in the western hemisphere working on bird conservation. PIF promotes the use of focal species to inform conservation projects. Focal species are native species selected by land managers to represent desired environmental conditions through their association with particular habitat features. These native species are highly responsive to environmental factors and can be cost-effective to monitor. For example, the presence and abundance of focal species that represent habitats near rivers and streams in western Oregon reflect the condition of riparian and floodplain areas and can be used as indicators of expected additional ecosystem benefits.
| Riparian Focal Species for Western Oregon | Associated Habitat Feature | Ecosystem Benefit |
|---|---|---|
|
Yellow-breasted chat (Icteria virens) 
Sources/Usage: Public Domain. View Media Details
|
Dense shrubs | Runoff and erosion control |
|
Yellow warbler (Setophaga petechia) 
Sources/Usage: Public Domain. View Media Details
|
Tall shrubs in woodland subcanopy and understory | River bank stabilization, shading, nutrients for aquatic food webs |
|
Bullock's oriole (Icterus bullockii) 
Sources/Usage: Public Domain. View Media Details
|
Large canopy trees | River bank stabilization, shading |
|
Red-shouldered hawk (Buteo lineatus) 
Sources/Usage: Some content may have restrictions. View Media Details
|
Large patches of structurally diverse woodland | Overall maintenance of floodplain processes |
Recovery of Forests after Disturbance
Birds can be used to monitor the condition and development of early-seral forest communities. Early-seral communities are the first stage of recovery after a disturbance such as wildfire or timber harvest, before conifers - pine, fir, or spruce trees - dominate the site. They are characterized by a high diversity of plants, especially broadleaf shrubs, that in turn support a high diversity of insects and wildlife. Western purple martins require open, early-seral habit with abundant insects and retained snags (or dead trees), which are used for nesting. A decrease during recent decades in the amount of diverse early-seral forest available for purple martin breeding may be partially a result of a reduction in timber harvest on Federal lands and intensive management to promote conifer dominance on private industrial timber lands. This decline is most evident in the Cascades and Coast Range of western Oregon, including the Siuslaw National Forest. Fire suppression, post-fire salvage logging, and removal of snags during timber harvest have all contributed to decreased nesting-site availability.
Recent surveys throughout western Oregon monitored purple martin distribution and nesting. Researchers identified sites in the Siuslaw National Forest that were suitable for purple martin nesting and visited three times during the summer to watch and listen for purple martins. The probability of successful purple martin nesting was positively correlated with a productive early-seral habitat with large, open spaces and scattered large snags. These observations suggest that timber harvest practices that retain large snags can benefit species that utilize features of disturbed habitats.
How do Wildlife Biologists Study Birds?
Point-Count Surveys
An observer visits a designated station and records all birds seen or heard. One station per 4-8 hectares - or about 1-20 acres - is the goal, with multiple surveys per season over multiple years to get a good estimate of bird abundance and species richness. Point-count surveys are most effective during the breeding season when birds are vocalizing to attract mates and defend their territory.
Mist-Netting
After breeding season and during migration season, when birds are more dispersed and not vocalizing, point count surveys are not as effective. Mist nets are used to safely capture birds without harming them. Mist-netting provides researchers with an opportunity to collect information about bird health, age, and sex, that is only possible when birds are in the hand. Birds are banded on one leg with a tiny metal "bracelet" bearing a unique identification code before they are released so individuals can be monitored over time. Mist net surveys are usually conducted on 2-3 consecutive days at least once per month.
Productivity and Survival
The number of young birds captured in mist nets is a measure of productivity, or reproductive success of the population. Banded birds that are recaptured over multiple seasons or years are an indication of survival. Captured birds can also be assessed for body condition, for example, signs of disease, injury, or malnutrition to give clues as to why survival may fluctuate.
Learn more about bird banding at the USGS Bird Banding Laboratory website.
Birds are excellent indicators of ecosystem condition because they are responsive to environmental change, have important ecological functions – such as seed dispersal and insect consumption, and are easy to observe.
Monitoring birds, even from a limited number of locations, can provide researchers with information on the condition of forests spanning hundreds of acres. The significant cultural and economic importance of birds and their popularity with the public can also help raise awareness and promote public investment in stewardship of natural areas. Researchers at the Forest and Rangeland Ecosystem Science Center are involved in studies using birds as indicators of the health of different types of ecosystems:
Willamette River Floodplain
Since 2008, large-scale restoration programs are in progress along the Willamette River in Oregon to address habitat loss due to dam construction, large wood removal, conversion of woodland to agriculture, and other land uses. Restoration projects include modifying human-made barriers to water flow, increasing floodplain forest vegetation, and removing aquatic invasive plant species. Several agencies are contributing to a strategic monitoring framework for Willamette River restoration. The framework covers strategies for monitoring the responses of hydrology and water temperature, fish, forest vegetation, aquatic invasive species, and birds to restoration actions.
Increasing the diversity of floodplain plant communities enhances the habitat available to fish, birds, and other wildlife. Many of the same features of healthy floodplain vegetation that are key for birds also benefit fish. For example, tree cover used by birds for nesting and foraging also provides shade that can maintain cool water temperatures that are essential for the health of salmon and trout.
The USGS is a member of Partners in Flight (PIF), a network of organizations in the western hemisphere working on bird conservation. PIF promotes the use of focal species to inform conservation projects. Focal species are native species selected by land managers to represent desired environmental conditions through their association with particular habitat features. These native species are highly responsive to environmental factors and can be cost-effective to monitor. For example, the presence and abundance of focal species that represent habitats near rivers and streams in western Oregon reflect the condition of riparian and floodplain areas and can be used as indicators of expected additional ecosystem benefits.
| Riparian Focal Species for Western Oregon | Associated Habitat Feature | Ecosystem Benefit |
|---|---|---|
|
Yellow-breasted chat (Icteria virens)
Sources/Usage: Public Domain. View Media Details
|
Dense shrubs | Runoff and erosion control |
|
Yellow warbler (Setophaga petechia)
Sources/Usage: Public Domain. View Media Details
|
Tall shrubs in woodland subcanopy and understory | River bank stabilization, shading, nutrients for aquatic food webs |
|
Bullock's oriole (Icterus bullockii)
Sources/Usage: Public Domain. View Media Details
|
Large canopy trees | River bank stabilization, shading |
|
Red-shouldered hawk (Buteo lineatus)
Sources/Usage: Some content may have restrictions. View Media Details
|
Large patches of structurally diverse woodland | Overall maintenance of floodplain processes |
Recovery of Forests after Disturbance
Birds can be used to monitor the condition and development of early-seral forest communities. Early-seral communities are the first stage of recovery after a disturbance such as wildfire or timber harvest, before conifers - pine, fir, or spruce trees - dominate the site. They are characterized by a high diversity of plants, especially broadleaf shrubs, that in turn support a high diversity of insects and wildlife. Western purple martins require open, early-seral habit with abundant insects and retained snags (or dead trees), which are used for nesting. A decrease during recent decades in the amount of diverse early-seral forest available for purple martin breeding may be partially a result of a reduction in timber harvest on Federal lands and intensive management to promote conifer dominance on private industrial timber lands. This decline is most evident in the Cascades and Coast Range of western Oregon, including the Siuslaw National Forest. Fire suppression, post-fire salvage logging, and removal of snags during timber harvest have all contributed to decreased nesting-site availability.
Recent surveys throughout western Oregon monitored purple martin distribution and nesting. Researchers identified sites in the Siuslaw National Forest that were suitable for purple martin nesting and visited three times during the summer to watch and listen for purple martins. The probability of successful purple martin nesting was positively correlated with a productive early-seral habitat with large, open spaces and scattered large snags. These observations suggest that timber harvest practices that retain large snags can benefit species that utilize features of disturbed habitats.
How do Wildlife Biologists Study Birds?
Point-Count Surveys
An observer visits a designated station and records all birds seen or heard. One station per 4-8 hectares - or about 1-20 acres - is the goal, with multiple surveys per season over multiple years to get a good estimate of bird abundance and species richness. Point-count surveys are most effective during the breeding season when birds are vocalizing to attract mates and defend their territory.
Mist-Netting
After breeding season and during migration season, when birds are more dispersed and not vocalizing, point count surveys are not as effective. Mist nets are used to safely capture birds without harming them. Mist-netting provides researchers with an opportunity to collect information about bird health, age, and sex, that is only possible when birds are in the hand. Birds are banded on one leg with a tiny metal "bracelet" bearing a unique identification code before they are released so individuals can be monitored over time. Mist net surveys are usually conducted on 2-3 consecutive days at least once per month.
Productivity and Survival
The number of young birds captured in mist nets is a measure of productivity, or reproductive success of the population. Banded birds that are recaptured over multiple seasons or years are an indication of survival. Captured birds can also be assessed for body condition, for example, signs of disease, injury, or malnutrition to give clues as to why survival may fluctuate.
Learn more about bird banding at the USGS Bird Banding Laboratory website.