How To Protect Nesting Birds During Construction, Tree Pruning, Tree Removal, and Other Activities That Can Disturb Bird Habitat

Photo of a round bird's nest covered with soft green plant material and four tiny baby birds in center, three with beaks open.
About 135 species of birds breed around Portland. The majority of these birds are federally protected under the Migratory Bird Treaty Act, which protects the birds, their nests, eggs, and feathers. Learn about best management practices to protect birds and their nests when working on City projects.
On this page

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 DateEnd DateSeasonApproach
August 1January 31Non-breedingBest time for disturbance
February 1April 14Early nesting
April 15July 31Primary nesting
  • Avoid disturbance.
  • Survey, if avoidance is not an option.

How should you proceed?


  • 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.

  1. Plan disturbance during non-breeding season. No risk of impact on birds or project delay.
  2. Remove vegetation in early nesting season. Survey for and avoid nests. Less risk of impact on birds or project delay
  3. 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.


Birds and Bird Nesting Best Management Practices

Jade U. Ashcroft, Environmental Services