Photo by Saulo Cortés Arévalo (left to right)
Back: Jorge Amador González, Juan Carlos Carranza , David La Puma, Kyle Shepard, Jenifer Andrea Rojas Leguizamón, German Miguel Quijano Chacón, Oscar Rangel Middle: Sarahy Contreras Martínez, Melani Paulina Vázquez López, Michael Lanzone, Phoebe Lanzone, Fernanda Damayanti López Torres, Ana Luisa Santiago Pérez Front: Oscar G. Cárdenas Hernández, Saulo Cortés Arévalo

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Before diving into the details, I think it's important to understand the context within which this breakthrough fits. At CTT we're constantly innovating, and from a public-facing standpoint, it probably appears like a very rapid process. But, like anything worth doing, these innovations take time to conceptualize, to design, to refine, and to eventually produce something that's worthy of becoming a final product. It's simpler to make a one-off of something; an experimental bespoke device; it's entirely something else to make something that can be produced at a scale appropriate for distribution to many researchers worldwide. Nearly every day we talk with researchers looking to study species in ways never before possible. In many cases we have to tell them that it's not possible today, but we are working on something for the future. Developing the BlūMorpho tag technology was one such case.

This story begins in February of 2019, when I was invited to give a talk on the Motus network to the Partners in Flight (PIF) Western Working Group in San Diego, California. During that meeting I met Dr. Sarahy Contreras-Martinez, eminent hummingbird researcher and professor in the Department of Ecology and Natural Resources at the University of Guadalajara’s CUCSUR campus in Autlán de Navarro, Jalisco, Mexico. Actually, we had previously met briefly around 2013 when I was a postdoc in the SILVIS lab at the University of Wisconsin, Madison, and Sarahy was visiting the lab where she had completed her Master’s degree back in 1999. But it wasn’t until the 2019 PIF meeting  that we discussed a dream for tracking small hummingbirds. I had recently become a hummingbird bander myself and hoped eventually to be able to attach transmitters to Ruby-throated Hummingbirds (Archilochus colubris), while Sarahy had spent decades studying many species of hummingbirds in Mexico, including her main focal species of concern: the small Rufous Hummingbird (Selasphorus rufus). At the time, the smallest tag that CTT produced was the 0.35g PowerTag, a battery-powered radio transmitter that could last ~20 days beeping every 15 seconds. Still, that tag was over three times as heavy as could be carried by either Rufous or Ruby-throated Hummingbirds, which weigh only 3.1 grams on average. “Not now” I told her, “but soon,” I added. I continued, “We’re working toward developing a tag for tracking Monarch butterflies which have to be less than a tenth of a gram. We’re not sure whether the current technology we’re using will be capable of that weight, but we’re trying. As soon as we have something, you’ll be the first person I call.”  Sarahy smiled her signature smile, and said “That will be a great day for hummingbird research!” 

Fast-forward to 2023, following a global pandemic, microchip shortages, and all of the travel and shipping delays and headaches that came with it, and CTT’s engineers were still searching for and testing the next generation of transmitters. In the early days of 2023, they found a tiny chip that could transmit data over a new frequency: 2.4GHz. Actually, it’s not a new frequency at all, as it’s the same frequency as Bluetooth transmissions, allowing for many other receiver options, like smartphones and tablets, in addition to the ones that CTT produces. The best part, though, was the size. Using this tiny chip, CTT engineers were able to design a solar-powered tag weighing the same as a grain of rice, or 60 milligrams . . .  That’s 0.06 grams. It was during the 2023 spring PIF meeting at the Desert National Wildlife Refuge in Las Vegas, Nevada, when David sent Sarahy an email with a photo of the tag titled, simply, “new tag for tiny birds”. Within the email was the following:

Dear Sarahy,

I often think about when we were walking back to the hotel in San Diego after the 2019 meeting and talking about transmitters for small hummingbirds. Well, we are almost there! I’ve attached a photo, please keep it private for now, of our upcoming 2.4GHz tag which we’ve tentatively called the "Morpho”. It is a solar-only tag, like our LifeTag, which means it does not have a battery, so can last indefinitely, and will only beep when there is light on it...

By the time of the American Ornithological Society annual meeting in London, Ontario, in August of 2023, the BlūMorpho tag was finally in production, and various receivers to pick up the tag were being designed, manufactured, and tested. At this point David and Sarahy convened again, along with Susan Bonfield, Miguel Matta and Deanna Williams of the Western Hummingbird Partnership, to discuss the BlūMorpho tag as a viable option for tracking Rufous Hummingbirds. At this meeting a plan was hatched for David to join Sarahy in January of 2024 where they could visit the Las Joyas field station and potentially test deployment of these tags on hummingbirds. As the planning evolved, a full-fledged research team was assembled with some wonderful multidisciplinary talent to ensure a successful field experiment testing the effectiveness of harnessing hummingbirds with these new tags.

This research team brings over a century of collective experience and expertise in field ornithology: one of the world’s leading experts on hummingbirds, Dr. Sarahy Contreras-Martinez (University of Guadalajara - Cucsur); GIS professor Dr. Oscar G. Cárdenas-Hernández (University of Guadalajara - Cucsur); Michael Lanzone, a global leader in wildlife telemetry and attachment techniques (Founder and CEO of Cellular Tracking Technologies, New Jersey, USA); conservation ecologist and hummingbird bander, Dr. David A. La Puma (VP of Cellular Tracking Technologies, New Jersey, USA); and hummingbird bander and manufacturer of hummingbird banding tools, Kyle Shepard (Director of Banding Coalition of the Americas, Alabama, USA). In addition to the above, the full team included four graduate students, one undergraduate student, and a professor from the University of Guadalajara- CUCBA; a professional photographer and publisher (Orgánica Editores), two technicians from the Sierra de Manantlan Biosphere Reserve, and a high school student from Cape May Tech in Cape May, New Jersey, USA.

Over the course of three days, this group made great strides toward an ethical and effective methodology to attach these tiny transmitters to hummingbirds. It cannot be overstated the effort put into thinking about and designing a tiny harness light enough for the birds we are targeting, well-fitting enough to ensure the safety of the birds, and simple enough that deploying them could be reproducible by other researchers. Leading up to our trip, Mike Lanzone spent several late nights poring over materials, including cutting tiny pieces of leather with a Cricut machine, and testing various sizes of crimp beads. Even during the expedition, both Mike and Kyle worked for hours, day and night, to refine the design based on what they were learning in real-time as they tested attachments on birds.

 Here Kyle (left) and Mike (right) are sizing a harness on an Amethyst-throated Mountain-gem (Lampornis amethystinus). Photo by the Author.

In the end the team successfully attached, tested, observed, and deployed a total of 11 BlūMorpho (2.4GHz coded radio) transmitters on hummingbirds of five species (see Table 1). These 0.06g tags lack a battery, but are instead powered by a single solar panel providing an unprecedented lifespan for a transmitter of this size. When attached to a harness made of ultralight materials, the final weight was less than or equal to 0.1 grams, or less than 3% of the mass of any hummingbird tagged. In four of 11 cases the team glued the transmitter onto back feathers, which provides a much faster and lighter transmitter option, with the tradeoff being a shorter-duration deployment (as birds will most likely molt or shed the tag within a few weeks to months). Depending on the research questions being asked, and the species being targeted, both techniques provide ample options for discovery. 

These ultralight tags transmit the digital ID, temperature (of the transmitter), and solar voltage, once per second when in full sun, and in varying intervals when in shade (for instance, we witnessed tags beeping every 2-5 seconds when birds were perched in dense cover). The tags do not store data onboard, so in order to receive the information being transmitted, researchers need a receiver within range of the tag (range can vary from a couple hundred meters to over two kilometers depending on line of sight and whether birds are flying or perched). Receiver options include handheld manual devices and autonomous tower-based stations, the latter of which can be registered to the international Motus Wildlife Tracking Network so that tags detected at other locations will be relayed back to the original researcher. 

A recently tagged White-eared Hummingbird (Basilinna leucotis) preparing for release. Photo by Phoebe Lanzone.

Transmitter testing protocol

In order to evaluate transmitter attachment techniques for the birds, we established the following protocol. We first set up a flight cage: 6’ long x 4’ high x 3’ wide. To understand the effect of the flight cage alone, we assessed “normal” behavior by placing newly banded birds in the flight cage and observed them for up to 30 minutes. In each case birds were offered nectar from a hummingbird feeder and, once fed, were released into the flight cage. Behavior was classified as perching on netting, perching on branches, active flight, and feeding from a feeder at one end of the cage.

University of Guadalajara undergraduate Fernanda Damayanti López Torres and U.S. high school student Phoebe Lanzone observe and classify the behavior of a recently tagged hummingbird within the mesh flight cage. Photo by Sarahy Contreras-Martinez.

 

In general, birds appeared to take ~6 minutes to acclimate to the flight cage and begin perching on sticks and free-flying normally. In the case of one White-eared Hummingbird, it actively fed from the feeder provided in the flight cage during testing. Because birds in this locale are not accustomed to feeders, use of the feeder was not considered a milestone for “normality”, but seeing the White-eared Hummingbird take to it quickly was indeed exciting! For birds outfitted with transmitters, the process was the same but the birds were kept in the flight cage for 10-20 minutes post-attachment and evaluated. If the behavior was consistent with non-transmittered bird, they were removed from the cage and checked again for transmitter fit (checking all of the harness lines and attachment points, position of transmitter on back, etc.) and if everything looked good, the hummingbird was again offered food, returned to the capture location, and released.

A recently tagged White-eared Hummingbird (Basilinna leucotis) perches before heading back to defend its territory. Photo by Michael Lanzone.

 

Birds fitted with transmitters were followed with a handheld tracking device to confirm normal behavior and flight. Additionally, a permanent SensorStation (Motus compatible base station) was installed at the Las Joyas field station to continue monitoring presence and movement in the absence of manual tracking.

Next Steps

It is important to note that this endeavor was more about assessing various methodologies than it was about deploying transmitters, and the luxury of such a high density and diversity of hummingbirds available at Las Joyas meant the team was able to evaluate many variations in harness style over the three days. In the end the team arrived at a point where they feel comfortable building and deploying several harness variants which can and should now be tested and evaluated over a longer period of time and in controlled settings as well as in the field. In the case of the 11 birds tagged during this endeavor, students of Dr. Contreras-Martinez will be actively hand-tracking and attempting to resight those tagged birds to assess their health as well as tag longevity. In cases where tagged birds are recaptured during subsequent banding efforts, harnesses will be evaluated for any long-term effect such as abrasion or feather wear.

It is important to stress that this effort is only the beginning of the process of drawing up recommendations for harnessing techniques of these smallest of birds. This effort would not have been possible without the contributions of those mentioned above who assisted in this process. On the final evening of the trip a full debriefing occurred in one of the classrooms at the field station, describing in detail the evolution of the harnessing process over the course of the trip. In the coming months this information will be distilled into a living document which will form the foundation for a harnessing manual. A special thanks to German Quijano-Chacón for translating from English into Spanish during the debriefing; his skill and dedication elevated the ability of the group to communicate very technical information quickly and efficiently.

 

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Table 1. Hummingbird transmitters deployed during expedition, in order of deployment. #s 1-2 on Jan 25, #s 3-7 on Jan 26, and #s 8-11 on Jan 27, 2024.

Scientific Name	English Name	Mig Class	Attachment
Basilinna leucotis	White-eared Hummingbird	Resident	Backpack Harness
Saucerottia berylina	Berylline Hummingbird	Altitudinal Migrant	Backpack Harness
Selasphorus rufus	Rufous Hummingbird	Long-distance Migrant	Glue-on
Saucerottia berylina	Berylline Hummingbird	Altitudinal Migrant	Backpack Harness
Eugenes fulgens	Rivoli’s Hummingbird	Resident	Backpack Harness
Selasphorus rufus	Rufous Hummingbird	Long-distance Migrant	Backpack Harness
Basilinna leucotis	White-eared Hummingbird	Resident	Backpack Harness
Lampornis amethystinus	Amethyst-throated Mountain-gem	Resident	Glue-on
Lampornis amethystinus	Amethyst-throated Mountain-gem	Resident	Backpack Harness
Lampornis amethystinus	Amethyst-throated Mountain-gem	Resident	Glue-on
Saucerottia berylina	Berylline Hummingbird	Altitudinal Migrant	Glue-on

Full List of Participants

Mexico

• Universidad de Guadalajara CUCSUR Campus
• Sarahy Contreras Martínez
• Oscar G. Cárdenas Hernández
• Juan Carlos Carranza Rodríguez
• Melani Paulina Vázquez López
• German Miguel Quijano Chacón
• Jenifer Andrea Rojas Leguizamón
• Fernanda Damayanti López Torres
• Universidad de Guadalajara CUCBA Campus
• Ana Luisa Santiago Pérez
• Saulo Cortés Arévalo
• Administration from la Reserva de la Biosfera Sierra de Manantlán
• Jorge Amador González
• Oscar Rangel

USA

• Cellular Tracking Technologies
• David La Puma
• Michael Lanzone
• Phoebe Lanzone
• Banding Coalition of the Americas
• Kyle Shepard

Acknowledgements

We, the team, would also like to thank the following entities for both financial and logistical support, without which this effort would not have been possible:

• Las Joyas Scientific Station
• The administration of the Sierra de Manantlán Biosphere Reserve
• Devil’s Mountain Audubon
• Environment and Climate Change Canada & Klamath Bird Observatory
• Cellular Tracking Technologies

The focal species for a larger future project, a Rufous hummingbird (Selasphorus rufus), wearing a glued-on BlūMorpho transmitter and about to take off! Photo by the Author.