DO THE WORK
Nesting Bird Surveys
While vegetation management is an important component of fire safety and land management, it’s critical that this work be done with care and patience to avoid disturbing birds and other wildlife. This informal guide explains why it is critical to observe for nesting birds before undertaking vegetation removal of any kind, and provides guidelines on how and when to undertake a survey.
According to the California Department of Fish and Wildlife, “Nesting birds are particularly sensitive to human disturbance and may abandon their nest, eggs and/or young due to human presence and noise.”
Benefits
A nesting bird survey increases your understanding of how birds use the land and improves your overall land stewardship. Observing for nests before altering the landscape helps birds survive and reproduce at a time when bird populations are globally declining due to multiple stressors, including habitat loss and climate change.
For example, Dark-eyed Juncos and California Quail are both ground nesting species found in Sonoma County. For both these species, any disturbance of vegetation around their nest can cause them to abandon that nest site, greatly reducing their ability to reproduce. Additionally, pruning or removing vegetation can inadvertently crush, destroy, or remove active bird nests.
The Migratory Bird Treaty Act protects migratory birds from being “taken” or killed.
When And Where to Survey For Nesting Birds
Protecting birds from the impacts of stewardship activities is important on any site that has any vegetation. Birds’ entire existence revolves around plants: They eat plants and the insects that eat plants, nest in plants, roost in and hunt from plants, and hide and sleep in plants. Removing plants harms birds in the short term.
Bird nesting surveys are done during bird nesting season, generally from March through August in Sonoma County. This timeframe covers the majority of songbirds and raptors (birds of prey). Surveying over a longer period can protect more types of birds. For example, the Northern Spotted Owl can begin nesting as early as January in Sonoma County.
Key Points Before Proceeding
You can avoid harming or killing birds if you survey for nesting birds before altering vegetation during bird nesting season. The how-to guidance below is designed for use by any land steward. For a larger project, a project done on public land, or a project that is publicly funded, it’s best to hire a professional to assure there is no violation of CEQA or the Migratory Bird Treaty Act.
As you plan for a project, you can do an informal or formal nesting bird survey during the previous breeding season to learn well ahead of time which species are likely nesting on the site. It’s important to learn how to identify nesting behavior. See the Resources [Anchor link to section at bottom of page] for helpful links, or consider hiring a consulting biologist to conduct a nesting bird survey before doing any work.
Keep in mind that different ecosystems will have different nesting bird species, each of which will be affected differently by your activities.
If nesting birds are present, a biologist can recommend an appropriate buffer area where you can refrain from doing vegetation management. A general rule would be to leave a 150’ buffer around the nesting area.
How to Perform a Nesting Bird Survey
- Survey for bird nests between sunrise and 11:00am, when birds are most active.
- Before beginning work on any project, walk through the project footprint to detect birds.
- If you suspect an individual bird is nesting in the area, observe it until you can confirm whether it is building a nest, tending a nest, or just passing through.
Finding nesting birds
You can find birds visually and by ear. Songbirds are most vocal during breeding season, when they are attracting mates and defending territories.
Nesting birds exhibit these nesting behaviors, but any bird exhibiting unusual behavior is worth watching to determine if they are nesting.
- Alarm Calls: Almost every species has its own quick and harsh calls, repeated incessantly until the threat to the nest is gone.
- Carrying Nesting Material: Carrying any non-food item is a strong indicator that a bird is in the construction phase of nesting. Watch where the bird is traveling to.
- Repeated Location Perching: If a bird flies from and to the same spots at intervals lasting 30 seconds to a few minutes, usually it is constructing a nest or bringing food to its young. Very young nestlings are fed regurgitated food; therefore you may not see the adult carrying anything, unless you notice that the adult has a bulging crop.
- Carrying Food: If a bird carries food without eating it, this often indicates that the nestlings are nearing their fledgling stage.
- Guarding: consists of a bird remaining within a small area, and not fleeing even in the presence of humans. Typically, guarding is combined with alarm calls.
In grassy areas, walk through the grass you plan to mow in order to locate any nesting birds by scanning for the behaviors listed above.
If you find a nest
- Watch the nest from a distance (check out how to be a responsible observer) to see if it is still active. If possible, identify the bird species. The nest is considered “active” if it’s under construction, has eggs, or has young birds still using it. If you can’t identify the species, it is best to give it space and decide whether it is a songbird or raptor species (they need different buffer sizes).
- Record the location and date you found the nest.
- Flag a buffer around the nest:
- 150 ft radius for songbirds
- 250 ft radius for raptors
- Observe the nest regularly.
- Avoid disturbance within the buffer area until the young have fledged and the nest is no longer active (e.g. birds flying in and out). Disturbance means: removing any vegetation; the presence of dogs, vehicles, or people; or power tools or anything else that makes noise. This could take up to 6 weeks–from construction through fledging–for songbirds, or 12 weeks for raptors. Overriding safety needs, naturally, supersede this guideline.
Variations on this Practice
Surveys for other types of wildlife, including amphibians, reptiles, mammals, and invertebrates, can be found at this CDFW resource.
Timing Considerations
- Bird nesting surveys are done during bird nesting season, generally from March through August in Sonoma County. This covers the majority of songbirds and raptors (birds of prey). Surveying over a longer period can protect more types of birds–for example, the Northern Spotted Owl can begin nesting as early as January in Sonoma County.
- Survey between sunrise and 11:00am, when birds are most active.
- Bird nesting surveys should be done within a week of starting physical work. Another survey the morning that work is set to begin will ensure no birds have started nesting since the original survey.
Equipment
Personal Protective Equipment (PPE)
- Long pants and a long sleeve shirt if needed to avoid poison oak
- sturdy boots for steep uneven ground
Tools
- Bird ID resources (see below)
- Binoculars
- Range finder, tape measure, or Google Maps to measure distance
- Flagging or ribbon to mark buffers around nest
Learn more about bird nesting cycles
Maintenance
Repeat surveys prior to any and all work being initiated during the nesting season.
Related Practices
Retaining & Creating Habitat Features
Please note: this is a general guide. The specifics of how and when to do this practice will depend on many factors, including the site’s particular vegetation, climate and topography, history, and land management goals. Always consult with a professional if you’re unsure.
Do you have your principles in mind? Remember to regularly check in with your land management goals, to assure your practices and actions will actually achieve them.
Additional Resources
- Sonoma County birding books
- Field guides (such as Peterson’s or Sibley’s)
- Smartphone applications allow you to use a device to record bird sounds and identify their species
- A fun quiz app
- More information on nesting habits and duration of individual species
- Wildlife survey protocols from California Department of Fish & Wildlife
- Madrone Audubon Society sometimes has skilled volunteers who will conduct nesting bird surveys
- CDFW short description of bird nesting surveys and their use
- Tree care and bird safety from Golden Gate Bird Alliance
- Ecologically sound practices for vegetation management from Fire Safe Marin
Thanks to Marin County Parks Natural Resources Division for helpful information on this practice, which was adapted from their internal employee training workshops.