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Desert Purple Martin Nestbox Design Challenge

We Need Your Help!

Desert Purple Martins (Progne subis hesperia) are a subspecies of Purple Martins whose breeding range spans the southwestern United States and northwestern Mexico. They nest primarily in cavities created by woodpeckers in columnar cacti (saguaros and cardons). Availability of these nest cavities appears to limit their productivity and, by extension, total population size. Drought, coupled with invasion by non-native grasses into desert areas, has increased the frequency and intensity of cactus-killing wildfires. Saguaros can take 100-150 years to achieve the size necessary to host desert Purple Martin nests. Unlike their eastern counterpart, desert Purple Martins do not currently use nestboxes within their range, but they could benefit from a design that allows them to nest in artificial cavities as saguaro cactus face many current and ongoing threats leading to substantial losses in nest availability.

  • That’s where you come in – We need your creativity and ingenuity in creating a nestbox design the desert Purple Martins will love!
  • Tucson Audubon and project partners are sponsoring a nestbox design competition with $2000 in cash prizes! 

Nestbox Design Challenge

In an effort to provide additional nesting cavities for desert Purple Martins, we are opening a nationwide contest to solicit nestbox designs that would aid conservation of this imperiled sub-species. The goal is to use a biomimicry approach to design a nestbox that effectively replicates a saguaro cavity enhancing the chances that martins will adopt them. These nestboxes will provide shelter from harsh summer conditions in the Sonoran Desert. Our research shows temperatures in saguaro  cavities, which are protected from outside conditions by inches of thick, water-storing flesh, may buffer ambient temperatures by 10 degrees F or more.

Please read through the requirements and suggestions to participate in this nestbox design challenge.

Deadline: February 15th, 2023.

Design Guidelines:

Based on field measurements of saguaro cavities that Desert Martins have nested in, general Sonoran Desert conditions, and local ecological knowledge.

  • Opening size: round or oval shape of approximately 2 – 3.5 inch diameter.
  • Drop (the distance from the bottom of the entrance to the bottom of the internal cavity): 7.25 – 11 inches.
  • Internal Dimensions: 5.5-6.2 x 5.5-6.2  inches and for cylindrical cavities ~5.5-6.2 in diameter.
  • Nest cavity access – rounded entrance cleared of thorns.
  • Insulation: Average outside temperatures during nesting season range from daytime highs of (95-110 deg F) to overnight lows of (70-90 deg F). On average, a saguaro cavity buffers  daily minimum and maximum ambient temperatures in summer by 6-10 degrees F (see figure below).
  • Desert Martins nest during July-August, that’s during the summer rainy season. Consider taking steps to prevent water collecting inside as wet nests can lead to nest failure.
  • Nestboxes will be exposed to direct sun and rain, so consider this when selecting your materials.
  • In many areas (post burn and on the edge of current saguaro habitat) there will be a ~100 year need for successful nestboxes – long-term durability is key. Ultraviolet light in the desert is extremely intense and rapidly degrades many materials, especially plastics. 
  • Mounting hardware is not needed with submission, only an explanation of how the nestbox could be mounted on a pole. Boxes will be installed between 15-25 feet off the ground.

Left: Temperatures measured inside and outside of a saguaro cavity over a 3-day period in August 2022. Note how the cavity buffers ambient temperatures. Right: A “saguaro boot” is the internal structure of a saguaro cavity. Woodpeckers excavate the hole, then it scars over leaving a fully formed “boot” for birds to nest in.

Potential Considerations: 

Things to consider that may or may not have relevance for replicating a cavity within a saguaro.

  • Traditional nestboxes have drainage holes in the floor and ventilation holes on the upper portions of the sidewalls to vent excess heat. 
  • A perch directly outside of the entrance hole may provide access to predators.
  • The desert is hot – avoiding heat accumulation is key. Dark colors absorb heat, so keep designs a light, neutral color to prevent overheating.

Designs will be evaluated by a panel of experts based on the following:

  • Dimensions
  • Cost-effectiveness
  • Ease of installation
  • Durability / longevity
  • Temperature buffer of at least 6-10 degrees F

Prizes:

Cash prizes will be awarded after rating all designs based on the above criteria.

  • Youth Category (Individual or group 18 y.o. and under): 1st place $500, 5 runners-up $100 each.
  • Adult Category (Individual or group 18 y.o. and up): 1st place $500, 5 runners-up $100 each.

Submission portal: forms.gle/k23vYqWYE9ThXwQSA 

Deadline: 11:59 pm, February 15th, 2023

  • Each person or group can submit an unlimited number of designs.

  • Upload your detailed plan as a single file and include a list of materials, a sketch with dimensions, and indicate installation method. Finally, attach a paragraph describing the reasoning behind the design. Make sure file names include the name used on the submission form. For example: Purple_Martin_NB_plan_by_Joe_Smith.pdf. 

  • You have the option to submit a physical prototype of your design. Prototypes are not required unless submitting designs that use non-standard materials, or materials that are difficult to procure.  Prototypes for other designs are not required but encouraged to help us with production times. You can drop off the prototype at our Nature Shop in Tucson or mail it to us. Address for both: Attn: Olya Weekley 300 E. University Ave #120, Tucson AZ, 85705. Make sure your prototype is labeled with your name as listed in the submission form. It should arrive no later than February 15th, 2022.
If designing nestboxes isn’t your thing, consider sponsoring a saguaro hotel or newly planted seedling! More information here

For questions please contact Olya Weekley at oweekley@tucsonaudubon.org

This work is made possible through the Wildlife Conservation Society’s Climate Adaptation Fund, the Disney Conservation Fund, Arizona Game & Fish, and private donations.

Learn more about Desert Purple Martins and Tucson Audubon’s Purple Martin Project at tucsonaudubon.org/purplemartin

Top photo by Henry T. McLin, saguaro boot by Matt Griffiths, bottom by Richard Fray