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Photo by Tom Grey

Bird-friendly Tree Maintenance Guide

Bird-friendly Tree Maintenance Guide

Each spring and summer, city workers and residents trim, prune, and clear brush that has accumulated over the year. Unfortunately, this is the same time that many birds nest. Trimming, cutting, removing trees and other vegetation can destroy active nests and kill birds. It also removes valuable nesting sites.

Simply put, the best time for tree maintenance is September to February, to ensure the least disturbance of birds and nests and to lessen the stress on your plants.

About Bird Nests

More than 170 species of birds breed in Santa Clara County. Most birds build nests to raise their young in hidden sites on the ground and in bushes, trees, cavities, and even man-made structures. Parent birds chose a particular nest location due to its preferred habitat, proximity food or water source, and for protection against predators and weather. Birds are extremely creative when it comes to choosing nesting material, using natural substances such as mud, twigs, spider webs, feathers, leaves, grasses, and other plant fibers. The nests are meant to be strong and warm, protecting eggs from predators and weather.

In our area, most species of birds nest in spring and summer, between March and August. The largest and smallest may nest at other times (egrets, herons, raptors, and hummingbirds), some nest colonially (swallows, egrets and herons), and some often re-use nests (hawks, owls, crows, and ravens).

If an occupied nest is moved or disturbed, the parents will most likely abandon the nest. Permission to move a nest can only be given by qualified authorities and done by qualified persons.

Why protect nests?

Birds and their songs enhance our lives and play a role in our culture and heritage. They are often the only connection that people have to natural ecosystems in our urban landscape. Indeed, bird watching is a hobby to millions and a growing sport among nature enthusiasts.

Nesting birds play a beneficial role in our local ecosystems by eating insect pests (helping to avoid the use of toxic pesticides), pollinating plants, and distributing seeds to encourage native plant diversity and re-growth.

Many bird populations are declining due to habitat modification, disruption of migration routes, domestic and feral cats, and many other human activities.

What to know before performing tree maintenance

• The best timing for tree maintenance is September to February, to ensure the least disturbance of birds and nests.

• Certain birds such as hawks, owls, herons, egrets, crows, and ravens often re-use nests and nest outside of the traditional spring and summer season. If a large nest made of twigs is encountered, even if unoccupied, assume that it belongs to one of these birds and do not disturb it.

• Inspect the area carefully for birds and nests. If dealing with large areas or sensitive habitats containing native plants, dense brush, stream sides, or stands of trees, consult with a trained biologist beforehand to conduct a survey.

• An independent qualified biologist should conduct a nest survey. Contact California's Department of Fish and Wildlife or search online for a qualified biologist. Don't be tempted to do your own survey since special training is needed to do an effective survey. Additionally, nesting birds and their young that reside in an area with abandoned buildings, heavy brush, or high in trees require special care.

• All persons should be aware of laws (see inset at right) pertaining to the protection of birds and their nests and procedures to follow if a nest is encountered.

• Learn what to do if you find an injured bird or other wildlife.

• Be sure to hire a licensed landscaper, a certified arborist, or qualified tree trimmer that is concerned with tree health. Handymen and other unqualified trimmers may do more harm than good.

• The majority of trees are excessively and inappropriately trimmed. Not only does this diminish locations for nests and disturb birds, it is bad for tree health. Unnecessary tree trimming includes: thinning out pine trees and conifers until you can see through them, pruning sycamore trees without reason as they do not drop limbs, and removing valuable dead palm fronds from palm trees as these are perfect nest locations for orioles and kingbirds.

• Be sure to choose tree varieties wisely before you plant and base their location on future growth and maintenance. For example, do not plant a large tree near a sidewalk that may buckle the walkway and cause a future expense and public safety nuisance.

• For guidance on safe maintenance around bird rookeries (such as for herons and egrets), contact California's Department of Fish and Wildlife or search online for a qualified biologist.

• To determine if a nest is present: Look for concentrations of white colored droppings then check the vegetation above. When walking nearby, be aware of birds erupting from vegetation or if they scold you as you approach. Observe quietly and note any birds carrying nesting material or food to one place repeatedly.

If an active nest is found or disturbed

Stop work immediately within a range of 50 ft of songbird and 500 ft of raptor nests. Do not move or touch the nest, eggs or young.

The nest should be left alone until the young have fledged on their own. If the species is identifiable, California Department of Fish and Wildlife or Santa Clara Valley Audubon Society may be able to approximate the time until the birds will leave the nest (fledge) when you can start work again. Often this is only 4 to 8 weeks.

If city workers or others are doing the work, ask them to stop immediately and inform them of the laws (see inset at right) pertaining to protection of nesting birds. Give them the contact information for California Department of Fish and Wildlife or Santa Clara Valley Audubon Society. You should also contact these groups yourself. Record the nest location in the tree or brush, bird species if known, address and cross streets, the maintenance company contact information, and type of maintenance activity.