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LUCY’S WARBLER

Just four inches long and very active, Lucy’s Warblers (Leiothlypis luciae) have been known in the past as Mesquite Warblers due to their close ties to these trees. Being one of the only two cavity-nesting warblers we have in the United States, they choose old woodpecker holes as well as peeling bark crevices as their nesting sites. While fairly common during breeding season, Lucy’s Warblers are in population decline and listed as a Species of Conservation Concern by Arizona Game and Fish – primarily due to the loss of available nesting sites which occurs most commonly in dense mesquite bosque along major waterways. Even in an urban environment, Lucy’s Warblers seek out mesquite trees for nesting and foraging.

To learn more about this little warbler click here: allaboutbirds.org/guide/Lucys_Warbler/overview

Nestboxes and Lucy’s Warblers

Secondary cavity-nesting species (those that cannot excavate their own holes) appear to be limited by the lack of available nesting sites which have been helped by the creation of appropriate nestboxes, for a long time no one knew exactly what type of nestbox Lucy’s Warblers would prefer. Over the last few years Tucson Audubon has received reports of Lucy’s Warblers nesting in decorative birdhouses, gourds and other small cavities. Knowing that there’s an opportunity to make a big conservation effort and to increase the state of scientific knowledge on this species, we’ve undertaken a project to better understand Lucy’s Warbler nesting and to develop nestboxes that they’ll readily use. Our study efforts aim to determine the nesting preferences of Lucy’s Warblers with the ultimate goal of increasing Lucy’s Warbler populations by creating functional habitat especially via viable nestboxes in Tucson’s urban areas.

Nestbox Preference Experiment

In order to figure out the best design of nestbox for Lucy’s Warblers, we first studied the dimensions and physical attributes of member-reported nests in artificial cavities. They ranged from small wren houses to big metal pipes. We also located and measured their natural nests in peeling bark or splitting branches of mature mesquite trees. One thing that stood out the most is the apparent preference of two points of exit. Ventilation and escape routes may be the two benefits of such a design. Thus we created 8 designs of nestboxes with varying dimensions which we installed at 60 points across Arizona to test which one gets the most use. After 4 years of collecting data, it was solidified that the design based on their natural nests, the triangle box, is the most selected out of all available.

We then used the triangle design to look further into Lucy’s Warbler nesting preferences. We tested different installation techniques varying height or direction of nestbox placement. The results show that when presented with choices, Lucy’s Warblers will select the highest available nestbox. In our case it was 15 feet high. As for compass direction preference, north exposure was least selected for while the rest had a fairly equal distribution. Our recommendation is to install Lucy’s Warbler nestboxes between 6-15 feet off the ground. Opt for higher of the range if the area receives a lot of foot traffic. Overhead shade and small branches near the nestbox installation spot remain the most important factors from our experience.

So what’s next? We are planning to publish our findings to contribute to the scientific knowledge about this species. We are planning on expanding our project to more locations in southeast Arizona and beyond, turning stands of young mesquites into suitable nesting habitats with the help of nestboxes. We live in the center of the Lucy’s breeding range, so there is no better place to study their nesting behavior. We want to see a Lucy’s Warbler nestbox in every eligible yard!

Get Involved

  • Purchase a Lucy’s Warbler nestbox at our Nature Shop or construct your own using this plan.
  • Regardless of whether you purchase or build your nestbox, please register your nestbox to help us learn more about this secretive species.
  • Please consider showing your support of the Lucy’s Warbler Nestbox Project by donating your skill, materials or funds for construction of more nestboxes.

If you are already involved in this project in any way, thank you! You make it possible to have a community science effort that yields significant scientific results.

For more information or to get involved please contact us at nestbox@tucsonaudubon.org

Lucy’s Warbler Study Sponsors:

A special thank you to the organizations and individual donors who make our projects possible!

By purchasing this license plate for your vehicle, a portion of the proceeds go to fund on-the-ground conservation projects in Arizona.