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HomeNest Box Program


Providing Good Homes to Feathered Families Since 2012 

Western Bluebirds with Mom
Yosemite Area Audubon Society began a long-term program to build, install, and monitor nest boxes placed in the open grasslands of the lower foothills Madera, Mariposa, and Merced counties. The first year of the program focused on American Kestrels, made possible through a generous donation from The Peregrine Fund, which partially funded this program through the American Kestrel Partnership whose support continues to this day. During 2013, the program was expanded to include Barn Owls, Wood Ducks and cavity-nesting passerines, Western Bluebirds in particular although other many other species can and do use the boxes. In 2017 and 2018 more owl boxes were installed and monitored. 

The nest boxes are built in-house with the help of volunteers and material contributions from sources like General Wood Products. The program also owes its success to those who approved our use of private and public lands where the boxes have been installed.

In 2019, the Nest box Program saw 528 nestlings, owlets and ducklings fledged, bringing the total for the 8-year-old endeavor to 2331 birds.

Why Install Nest Boxes?
Habitats are shaped by many factors, and science is just beginning to discover how much our oak woodlands have been shaped by its native inhabitants.  This unique California landscape has shrunk dramatically over the past 230 years. Widespread destruction for intensive agriculture, rangeland and urban development have eliminated oak woodlands from much of their former range and continues to this day. 

A few struggling remnant trees along creeks, or the occasional oaks scattered in agricultural fields or on grassy hillsides sometimes provide the only hints of the extent of former range. 

As this precious habitat shrinks or becomes isolated, so to does the diversity of species in those areas. 

The introduction of invasive species, particularly the aggressive House Sparrow and European Starling that evicts or kills native nesting birds, as well as the increase in feral and free-roaming domestic cats, has also played a huge role in hastening the demise of these unique Californian landscapes and their inhabitants. 

By installing nest boxes, especially with predator safeguards, in areas that have fewer trees and tree cavity creators, such as Acorn Woodpeckers and Northern Flickers, we increase the chance of keeping a healthy natural balance of native birds and the other species that interact with them, which in turn supports a diverse natural habitat.  Agricultural lands offer few natural cavities, so artificial cavities allow more birds  to help with pest control.

Many of the birds that use our nest boxes are natural ‘pest control specialists’, eating volumes of insects and/or rodents. On average, Bluebirds consume about 12 percent of their body weight daily, much of that being insects. That’s the equivalent to a 200-pound human eating 24 pounds of food a day.  A family of Barn Owls can consume about 3000 rodents in a breeding season alone. The U.S. Fish and Wildlife Service believes the barn owl is the most economically beneficial species to humans.  Imagine how much more beneficial it would be for our landscapes to support these creatures with nest boxes, instead of using pesticides and poisons as our method of rodent control.

Data Collection

We look at a number of variables besides number fledged. We examine nest initiation, nest starts, successful nests, fecundity, number of abandoned and predated nests. In 2018, Bill Ralph, the YAAS Conservation Chair, became a Master Bander for American Kestrels and Barn Owls, and records the number of banded adults and nestlings as well as the number of recaptured (previously banded) birds.

We happily make this research available to educational institutions on request and are looking to build additional research opportunities and partnerships for long term monitoring projects.

Monitoring and Maintaining Nest Boxes

With the unfortunate introduction of aggressive House Sparrows and European Starlings into the United States in the 19th century, it became much more difficult for native birds to survive and breed. In many areas, they now rely heavily on nest boxes provided by humans.  Bad things can happen in boxes that are not monitored.  For example, House Sparrows  and European Starlings may attack and destroy eggs, nestlings, and incubating adults.  Flickers enlarge entrance holes, or make their own entrances that then allow starlings and other predators access to eggs or nestlings. Wasps and bees can invade boxes, preventing nesting altogether, driving parents away, or killing young birds.  

Mites can infest nests, preying on the nestlings, weakening them, and causing the adults to abandon the nest. Rodents can take over boxes and kill sleeping adults, chicks, and eat the eggs. Snakes and raccoons can raid nests. With regular monitoring and box maintenance we can prevent and deter these problems with use of baffles and other means of keeping predators out, increasing the odds of successful outcomes. Another reason for monitoring nests is the information that is gleaned from our careful note taking. Data gathered by our citizen scientists during nest box monitoring is absolutely needed to increase our understanding of our natural spaces, and learn more about how to help and support native birds.

Community Support
Though we work year around on the building and repairing of the nest boxes we monitor, our greatest need for volunteers in from late February through late July and even August, when the breeding and nesting seasons are in full swing.  If you are interested in participating in the building, installing, or monitoring activities, or would just like to tag along, contact our Conservation Chair and we’ll contact you with more information on how to help.

We are particularly interested in developing partnerships with schools, including high schools and universities, that would like to use this program as an opportunity for education, community service and scientific research projects. 

We would love to hear from you. 

Our thanks to the following generous contributors. Our success belongs to you.

General Wood Products donated wood for the nestboxes.

The Peregrine Fund provided partial funding for this program through the American Kestrel Partnership.

We are also deeply grateful for all of those who approved our use of private and public lands where the boxes were installed, and have generously supported this program. If you or your business would like to get involved, please contact our Conservation Chair.

We are raising funds continuously for our expanded nest box program  All your contributions are fully tax deductible.

Support YAAS Nest Box Program

We are raising funds continuously for our expanded nest box program  All your contributions are fully tax deductible. We also need volunteers to assist in monitoring.