The City's Role
The Migratory Bird Treaty Act prohibits the intentional or accidental killing of native birds and the destruction of their nests. Bird nests are only protected when the nests contain eggs or young birds. In Portland, this is in spring and summer. Environmental Services has developed best management practices to follow to protect birds and bird nests while working on City of Portland projects.
If you find a bird nest in your treatment area with eggs or young, please stop work immediately and notify an Environmental Services wildlife biologist.
What types of activities disturb bird nests?
Many activities pose a significant threat to birds and their nests. These activities should be avoided during the nesting season:
- Mowing and clearing
- Invasive or native vegetation removal
- Herbicide application
- Tree and snag removal
- Tree trimming and pruning
- Grading of project sites
- Removal/modification of built structures
- Water level management
Where are bird nests found?
Nests are not just found in trees! Many birds nest in shrubs, ground vegetation, gravel, stream banks, and a variety of human-made structures.
When is the nesting season?
The bird nesting season is divided into three windows. We recommend that potentially disruptive activities be performed during the non-breeding season (August 1 to January 31).
| Start Date | End Date | Season | Approach |
|---|---|---|---|
| August 1 | January 31 | Non-breeding | Best time for disturbance |
| February 1 | April 14 | Early nesting |
|
| April 15 | July 31 | Primary nesting |
|
How should you proceed?
Recommendations
- Avoidance! Avoiding disturbance to nests is the preferred approach.
- Plan disruptive activities during the non-nesting season (August 1 – January 31)
- If this is not possible, plan to survey for bird nests and phase work around active nests.
Plan projects around the bird nesting season when possible to avoid disturbance and violation of the Migratory Bird Treaty Act. There are three potential scenarios, in order of preference.
- Plan disturbance during non-breeding season. No risk of impact on birds or project delay.
- Remove vegetation in early nesting season. Survey for and avoid nests. Less risk of impact on birds or project delay
- Remove vegetation in primary nesting season. Survey for and avoid nests (assume you will miss some). Highest risk of impact on birds and project delay.
What to do when you find a nest during a City project
Consult Protecting Nesting Birds: Best Management Practices for Vegetation and Construction Projects for guidance on establishing a protection buffer and phasing work around the nest.