Spring is not the time to trim or cut down trees. Five newly orphaned Barn owl nestlings were received by Wildlife Rescue, Inc. on March 21st after the palm tree they called home was cut down with them still in it. If you must trim, prune, or cut down trees during the nesting season, please check them out completely for other creatures before you cut. Read on for a few guidelines on tree trimming.

by Karen Hoyt

“Trees, Trees, Beautiful Trees!” This could be the human translation of the Brown Creeper’s call as it moves through our lovely Redwood trees. Most of our local birds need trees to live. They nest and raise their young in trees; they shelter and find food in trees. We even have ducks that nest in trees.

photo (C) Karen Hoyt

Many of our local cities, such as Los Altos and Los Altos Hills, are known for their large, old tree lined streets. We take pride in our native and non-native trees alike. We not only want to protect our trees and keep them healthy, but we want to continue having the diversity of life around us that live in our trees.

Most arborists will tell you that a tree is healthiest not being pruned or trimmed at all. Pruning can actually harm the tree by causing trauma which requires a great deal of energy to heal, and makes the tree more susceptible to diseases. Arborists recommend only cutting dead or diseased branches from trees and to keep the tree limbs balanced on each side of the tree.

Many of the plants in the Bay area aren’t native and can grow much larger and faster than they normally would due to the ample water, rich soil, and extended levels of sunlight we have in California. This presents a higher risk of damage unless the plants are properly trimmed and maintained. Proper pruning will not only improve the plants health and appearance, but will help homeowners protect their investment in their landscaping and protect against damage caused by broken limbs.

If you must prune, have a plan. Late Fall or early Winter are the ideal times for the major pruning of trees as they are dormant. Winters in Los Altos are mild and many trees do not go into a true dormant phase, but a good rule of thumb is to watch in the fall for our deciduous trees to loose their leaves to determine if they are dormant or not. The trees themselves store up energy and go into a hibernation to survive the winter cold. Most of the bird life that uses our trees to nest and glean insects also leave the area at this time of year.

Don’t prune unless there is a reason to and if you do decide to trim or prune a tree, it is important to be mindful of the other creatures that use them as well as for the health of the tree itself.

Spring is not the time to trim or prune trees! Not only are the trees coming fully alive with new growth, it is also the beginning of the nesting season for many of our migrant and local bird and mammal species.

The Anna’s hummingbird is one of our earliest nesting birds and it is not unknown for them to nest and have young in late December and early January. It is very easy to overlook a hummingbirds nest in our shrubs or attached to the end of a branch as it is about the size of a walnut, 2”-3”, and well camouflaged.

Great Horned owls are also early nesters. They will take over the old abandoned nests of hawks and crows. They start laying eggs in late December and early January and the young don’t leave the nest until May or early June.

Western grey squirrels also nest in trees; they form elaborate constructions of leaves and have young in April and August of each year.

Don’t forget our cavity nesters. Hidden nests inside the trees are important to be aware of. Barn owls, Western Screech owl, woodpeckers, Western bluebirds, Chickadees and wrens make their nests in tree cavities. Check your trees out thoroughly before trimming or pruning, not matter what time of year. Palm trees are common in a lot of neighborhoods. Many birds and mammals find their high fronds the perfect place to nest.

The Migratory Treaty Act protects all native bird species and it is a federal offense to disturb a nest once the bird has started to build. Be mindful of disturbing nesting birds and causing orphans of their young. Most nests are only occupied for a few short weeks and necessary trimming or pruning should wait until the young have left the nest.

Enjoy the life renewed each spring and listen for the Brown Creeper’s call “Trees, trees, beautiful trees”!

Plans for increasing American kestrel numbers in Santa Clara and San Mateo Counties with nest boxes.

Sky Hunters is planning to start a project to build and place kestrel next boxes in our local open spaces and preserves in Santa Clara and San Mateo Counties. American kestrel numbers have been low in our communities due to nest sites disappearing as we take down old trees that provide nesting sites. If you are interested in helping, please contact Karen at accipiter@sky-hunters.org.

Update on Avian Influenza

With widespread interest in avian influenza or “bird flu”, Audubon California is providing the following information and links as a resource for those who may be concerned about avian influenza, as well as about how birds are involved. Also included are some general precautions for protecting both human and bird health.

Background on Avian Flu

There are over 144 different strains of avian influenza virus. Most strains circulate in low levels within wild bird populations. Though they usually cause only mild illness in wild birds, some strains may cause lethal outbreaks in domestic poultry. A few avian influenza strains are more virulent, and can cause high mortality in both wild birds and poultry stocks.

Most avian influenza strains do not normally infect species other than birds, though a few subtypes can be transmitted from birds to humans. Avian influenza viruses become much more dangerous if they mutate to allow easy transmission from one human to another, not just from birds to humans. The most devastating avian influenza epidemic occurred in 1918 when a highly pathogenic strain of avian influenza mutated allowing people to infect other people. An estimated 40 to 50 million people died worldwide as a result.

The Current Strain of Avian Influenza: H5N1

Since 1997, a highly pathogenic strain of H5N1 strain of avian influenza has infected over 100 people and caused at least 65 deaths in East and Southeast Asia. While any human infection is cause for concern and action, this current avian flu outbreak has affected a relatively small number of people, and has very limited ability to be transmitted from person to person. Rather, the virus appears to be transmitted to humans through direct contact with infected poultry or contaminated surfaces. .Over 150 million domestic birds have been culled to contain outbreaks. There is no evidence that the virus has mutated to spread widely from person to person.

Do Wild Birds Transmit H5N1 to People?

In the summer of 2005, the virus spread to Central Asia and China where it was detected in both domestic birds and wild birds. By October 2005, the virus was detected in domestic ducks and poultry in Turkey and Romania, and a wild Mute Swan in Croatia. In November it was detected in a flamingo in Kuwait. While there is no evidence of wild birds being able to transmit H5N1 directly to people, laboratory studies indicate that domestic ducks, as well as mallards and perhaps other wild species, may be able to carry and transmit the virus to other birds without showing signs of illness. While there is strong circumstantial evidence that wild birds may be able to spread the disease along their migratory paths, more testing of healthy waterfowl and other birds is needed before we can be certain that migratory birds are the source of the H5N1 virus infections reported in Eastern Europe. Global testing of both domestic waterfowl and wild birds is urgently needed in order to monitor the extent and spread of the virus in domestic flocks and wild bird populations.

Leading experts including the World Health Organization, Food and Agricultural Organization of the United Nations, and World Organization for Animal Health all emphasize that culling wild bird populations is highly unlikely to stop the spread of the disease, and would only divert resources away from more important disease control measures. (See statements by UN Food and Agricultural Organization http://www.fao.org/newsroom/en/news/2004/48287/index.html)

Has H5N1 Been Found in North America?

The H5N1 avian influenza virus has not been found in wild birds in North America. There is a remote chance that infected wild birds from Asia could bring the virus with them during fall migration to North America. The US Fish and Wildlife Service, US Geological Survey (USGS), Alaska Department of Fish & Game, and public health agencies are working together to test thousands of waterfowl and shorebirds for the virus in Alaska, and field sampling is being integrated with surveillance programs throughout the United States and Canada.

What You Can Do?

1) While the possibility of contracting the H5N1 virus from wild birds is very unlikely, people who have close personal contact with wild birds should take measures to protect themselves by practicing animal handling and sanitary practices recommended by the USGS National Wildlife Health Center Wildlife Health Bulletin #05-03.

2) People who feed birds are not at high risk of contracting avian influenza from birds in their yards or at their feeders. However, since birds can transmit other diseases to humans (e.g. salmonellosis), people who feed birds should routinely clean their feeders and bird baths as recommended by Audubon and the USGS National Wildlife Health Center. People who come into contact with wild bird excreta should thoroughly clean up with soap and water.

Additional Resources

Centers for Disease Control

United Nations Food and Agricultural Organization

ProMED-mail Program for Monitoring Emerging Diseases

USGS National Wildlife Health Center

BirdLife International Statement on Avian Influenza

Wetlands International Statement on Avian Influenza

Ducks Unlimited - Avian Flu