Download and print our Healthy Trees, Healthy Birds brochure in English or in Spanish! Or read this page to learn how to protect birds while trimming and caring for trees and other vegetation.
We also have a brochure on how to create a bird-friendly garden: Inviting Wildlife Into Your Backyard. It includes a list of nurseries that specialize in native plants. Download a copy for San Francisco, the East Bay, or in Spanish.
Birds build homes in which to raise their young just as humans do, although their site selections are more varied and often in obscure, hidden places. It is common to think of nests being in tree branches. But some birds build nests on the ground, in bushes and cavities; some build on the sides and eaves of houses, as well as on other man-made structures. Birds use natural substances and materials to construct: mud, saliva, spider webs, caterpillar silk, leaf mold, twigs, grasses, and certain other plant fibers. The nest protects the bird’s eggs from windy and wet weather and predators, and keeps eggs and nestlings warm. Click here for information on different kinds of nests.
Over 180 Species Nest in the Bay Area
What comes to mind when most people think about city birds are pigeons, crows, sparrows, and gulls. Yet these birds are only a small portion of the more than 120 species that reside in Alameda, Contra Costa and San Francisco Counties year round.
Annual migration brings in additional species to the area, including more than 60 other breeding species (such as orioles and kingbirds). In total, over 350 species live, nest, or pass through the San Francisco Bay Area during the year. Most birds rely on trees, shrubs, and brush for food, cover, nesting, and rest.
Many birds nest during the spring and summer. Unfortunately this is also the time of year that people tend to trim trees, prune shrubs, and clear brush. Severely cutting, trimming, and topping trees, bushes, reeds, and other greenery in the spring and summer can destroy nests and eliminate valuable nest sites.
There are laws that protect birds, their nests, eggs, and young from being removed, destroyed or harassed. Click here for a list of those laws. Violating any of these laws may result in fines and imprisonment.
When Birds Typically Nest
Many species nest between March 1 and August 31. The California Department of Fish and Wildlife often requires surveys for raptor (bird of prey) nests from January 15 to September 15.
Several species court and nest outside this time frame, such as some herons and egrets, many raptors, and most hummingbirds. Click here for guidance on safe times for trimming near heron, egret, and cormorant nests. Depending on the species, nesting birds may be found at any time of year.
Consult an independent qualified biologist for safe trimming times upon discovering any large nest.
NOTE: Certain species such as hawks, owls, herons, egrets, crows, and ravens often re-use nests. If you find a large nest made of twigs — even if it’s unoccupied — assume that it belongs to one of these birds and do not disturb it.
Planning Your Tree Project
Plan your project for the months outside of nesting season — generally September through January. Hire an arborist who is ISA (International Society of Arborists) certified, a licensed landscaper, or a qualified tree trimmer who knows and cares about a tree’s health. Avoid hiring “bargain‟ tree trimmers or handymen, as they are generally inexperienced and may cause more harm than good to the trees. Click here for more tips on planning your tree project.
What To Do Before Trimming
It is best to avoid nesting season altogether and do your tree trimming from September through January. At any time of year, inspect the area carefully before you begin your operation. Click here for descriptions of the different kinds of nests you may find.
For larger areas and sensitive habitats such as areas of native plants, dense brush, stream sides and stands of trees, it is best to hire a trained biologist to conduct the survey.
Laypersons may attempt to conduct their own nest survey; however in most cases this is not possible or practical. Most birds conceal their nests carefully and will not be visible to the average observer.
Here are some clues that nests may be hidden nearby:
- Look on the ground for concentrations of white-colored droppings, then check the vegetation above.
- As you walk through an area, look for birds flying out of vegetation close to you and intensely scolding you; they may have a nest nearby.
- Sit quietly and watch for birds that may be bringing nest material or food repeatedly to one place. Birds tend to place their nests just on the undersides of the tree canopy and where branches join together.
When an Active Nest is Found – Reschedule!
All work that has the potential to disturb or destroy the nest should cease in the immediate vicinity. Fifty feet is a good rule of thumb for songbirds, and 500 feet for raptors. The nest should not be touched or moved.
A qualified biologist or the California Department of Fish and Wildlife can assist in making determinations on how far away to remain from the nest and other measures to avoid disturbing or destroying it. Ideally the nest should remain undisturbed until the young have fleft the nest on their own or the nest is abandoned.
Professional Nest Surveys
If you are not comfortable or able to perform a nest survey prior to your project, seek help from a qualified biological consultant or the California Department of Fish and Wildlife. Either one can perform a nest survey of the trees, shrubs, brush, or other vegetation in question. Many nests are not easy to spot. Special care needs to be taken to survey the project area if it includes trees, abandoned buildings, brush, vacant lots, and deadfall.
How Finding Nests May Affect a Project
If the nest contains unhatched eggs or young, you may need to delay work within 50 feet or more of the nest. Once the species is identified, the California Department of Fish and Wildlife or Golden Gate Bird Alliance may be able to provide the amount of time until the eggs hatch and nestlings fledge. If the nest is voluntarily abandoned or depredated, work probably can be continued. However, a precise determination can only be made by an expert such as a consulting biologist or the California Department of Fish and Wildlife.
Why Nests Can’t be Disturbed or Moved to Another Location
Parents choose a nest location for specific reasons: proximity to food and water sources, and protection from predators and the elements. Birds may abandon their nest and offspring if it is disturbed or if the parents are harassed. Moving a nest requires special permission from the U.S. Fish and Wildlife Service and is usually only granted for human health and safety reasons.
What to Do If You See Someone Disturbing or Destroying Nests
Ask them to stop, and make them aware it is against the law. Then call the California Department of Fish and Wildlife at (888) 334-2258.
Be prepared to provide the exact location of the activity. Specifically note address and cross streets, as well as a vehicle license plate number or name of the company doing the trimming.
Why Protect Birds’ Nests?
First and foremost, birds are protected under the law. Second, birds provide numerous beneficial activities, such as eating many thousands of insect pests, which may eliminate some of the need for toxic pesticides. They also disperse seeds over wide areas, ensuring plant health and biodiversity. Finally, many bird populations nationwide are plummeting primarily due to the impact of human activities. Birds are creatures of the earth, a family of animals with which we share this planet and its limited resources. Our positive, cumulative actions can make the difference in ensuring their long-term survival.
Important Phone Numbers
To report bird harassment, killing, and/or destruction of bird nests: California Department of Fish and Wildlife: (888) 334-2258 U.S. Fish and Wildlife Service Northern California: (916) 414-6464 For advice on nesting birds or referrals for professional nest surveys: Golden Gate Bird Alliance: (510) 843-2222 Monday, Wednesday and Thursday, 9 am to 12 noon To report destruction or harassments of birds or nests in San Francisco parks, or to report inappropriate trimming and nest disturbance in the city of San Francisco: San Francisco Urban Forestry Division: Emergency Line 311 To report nest disturbance or inappropriate trimming in the coastal zone: California Coastal Commission Enforcement Officer: (562) 590-5223