We are co-hosting a workshop about using “nodes”, essentially mini Motus stations, to detect tagged animals, register their activities, and triangulate their movements. These devices can detect radio tags near them and send the data to Motus.org via a nearby Motus station (see this page for more information on Motus). This workshop is the day before the main meeting of The Wildlife Society, Western Section in Monterey, CA, USA. There may be spots left if you want to register.
In celebration of all of our recent work tracking Western Yellow-billed Cuckoos in the Kern River Valley, we are releasing new merchandise (t-shirts and a bandana, for now) on Bonfire.
Check them out at our Bonfire store
If you would just like to donate to support out work, look for the donate button on our web page.
It is important that people do not try to find these birds this season as it might cause them to abandon the nest. If you are interested in trying to see cuckoos here, contact us through our contact form.
In 2025, we have 4 tagged cuckoos. These birds were captured early in the season in giant mist nets as they flew through the tall cottonwoods and willows. Then they were tagged with a radio tag and given colored leg bands to be able to identify them through binoculars. The tag allows us to estimate the location of the birds in the habitat so we can understand the movement and activity of the birds as they go about their daily activities.
We give the birds nicknames to help field observers talk to each other about individual birds so that they can record data on location, and behavior based on visual and auditory detections. This year’s birds are nicknamed using part of the genus of known food items. In the image below, White is referred to as Hyla, Green is Papilio, Red is Schisto, and Purple is Neo. Observer data is used to match up with data from tag detection “nodes” described below.
Estimated locations of four cuckoos from July 7 to August 7, 2025. Black dots represent ground detectors or nodes that detect tags. Colored dots represent location estimates from one time interval. Colored outlines represent an estimate of home range (based on 80% kernel density estimate) for each tagged bird.
Using the signal strength recorded at adjacent nodes and a time stamp, a location estimate can be generated for a given time. The tags generate very large numbers of location estimates, as you can see (30 day period pictured). These locations can be used to estimate the home range used by individual birds to find food. Home ranges change as the birds move through different phases of their breeding cycle: from nest building, to incubating eggs, to feeding chicks, to feeding fledglings. We can look at these data in almost real time to understand which birds are being observed in the field. These data can also be used to find nests. We have successfully placed an additional node below the nest and have been able to use the signal strength patterns to understand what the birds are doing, for how much time in their day. The signal strength pattern can also tell us what phase of breeding they are in and when the transitions between phases happens.
To see how we have used signal strength data to estimate activity and breeding cycle phase, click on or download one of our recent posters: A novel way to monitor nests using Motus tagged birds and a CTT node
We have a video of location-tracking over time and of the giant mist nets on our Youtube channel. (Murrelet Halterman and others developed the canopy netting methods.)
We are thrilled to announce that at least two of the Western Yellow-billed Cuckoos that we tagged over the past three summers in the Kern River Valley (KRV) have returned. One of these birds, affectionately nicknamed Stroopwafle, was tagged in summer 2022. In 2023, it was detected by a Motus station at Mad Island Marsh, north of Corpus Christi, Texas on its northbound migration on June 15, 2023. It seemed to stay in the KRV for the summer during 2023, with the last tag detection being in August 2023. During this time we were able to track the bird’s movements using a network of tag detectors called nodes that can be used to estimate tag locations. Its tag has now stopped transmitting or has fallen off, but it has been identified using leg color bands.
June 2023 Stroopwafle position estimates based on node network detections.
Another tagged cuckoo, nicknamed Sphinx, that was tagged in 2023 has also been detected. Its Motus tag has stopped working but we can identify it by its colored leg bands.
A map of Stroopwafel’s 2023 migration detections: Motus Wildlife Tracking System
Not sure what Motus is? Curious to learn more? Check out our page explaining it and SSRS’s involvement here: Motus Tracking | Southern Sierra Research Station
See a 2024 post on last years cuckoo detections here: Our Yellow-billed Cuckoos are on their way back to the breeding grounds!
Our cuckoo work in the Kern River Valley, CA is currently unfunded, if you want to help support our work, we would greatly appreciate donations of any amount! We’re hoping to raise funds for 3 cuckoo tags for 2026.
We have been invited to purchase some of the first of a new type of tag. The exciting thing about these new tags is that they can be detected by cell phones and other IoT devices (think AirTags) as they travel. In addition, they are detectable by both the increasing numbers of Motus stations equipped to detect relatively new 2.4 GHz tags as well as home-based stations on the Terralistens network. These tags have been successfully used to track Monarch Butterflies as they travel down the East Coast of the US. Our hope is that these tags will allow tracking of birds like the Western Tanager pictured that migrate through areas with few Motus stations. Our goal is to purchase 10 of these tags to test on Western Yellow-billed Cuckoos, Western Tanagers, and possibly Tri-colored Blackbirds.
We are trying to raise $3,500 for this project. Can you help us by donating to SSRS? Click the Donate button and indicate Motus program.
More details about the new tags can be found on the manufacturers web pages:
https://celltracktech.com/pages/blu-bluseries-tag-detection-service
We are thrilled to announce that one of the Western Yellow-billed Cuckoos that we tagged last summer in the Kern River Valley, affectionately nicknamed Baba Ganoush, was detected by a Motus station near Corpus Christi, Texas on its northbound migration on June 16th, 2024.
This is particularly exciting because last year another of our tagged cuckoos (this one nicknamed Stroopwafel, tagged in 2022 along the South Fork Kern River) was detected by the very same Motus station on the Texas coast– the two detections were just one day and a year apart. The Mad Island Marsh Preserve, where both cuckoos were detected, is a nature preserve protected by The Nature Conservancy. Both cuckoos appeared to land at this site based on tag detection patterns, rather than just flying over, indicating that this may be an important spring stopover site for this federally threatened bird! Identifying migratory stopover sites is just one of the ways that tracking birds with the Motus Wildlife Tracking Network can help support conservation efforts.
From Corpus Christi, Stroopwafel subsequently made the 1,600 mile westward journey to return to Audubon California’s Kern River Preserve, where we picked it up on our local Motus towers 2 weeks later.
Will Baba Ganoush make the same trek? Stay tuned for updates! You can also check yourself on the Motus website:
A map of Baba Ganoush’s 2024 detections: Motus Wildlife Tracking System
A map of Stroopwafel’s 2023 detections: Motus Wildlife Tracking System
Not sure what Motus is? Curious to learn more? Check out our page explaining it and SSRS’s involvement here: Motus Tracking | Southern Sierra Research Station
Our cuckoo work in the Kern River Valley, CA is currently unfunded, if you want to help support our work, we would greatly appreciate donations of any amount! We’re hoping to raise funds for 3 cuckoo tags this year.
Check out this great new Audubon Magazine article featuring Hummus the cuckoo and findings from our research using the Motus Wildlife Tracking Network!
This work was done on and around the Audubon Kern River Preserve
(run by Audubon California).
The data is in… and our Motus tower at Canebrake Ecological Reserve detected one of the Tricolored Blackbirds we tagged at a breeding colony April 2022! (The bird in this photo to be exact!)
While the 10 mile movement from its original tagging location to Canebrake may not seem like a big deal, it’s actually the timing of the detection that we’re all excited about. Tricolored Blackbirds are highly nomadic, moving almost year around to follow abundant food resources, and their post-breeding movements (especially in foothill populations like ours) are still poorly understood. There are scattered sightings of Tricolored blackbirds in the area during the winter, but this November 2022 detection represents the latest post-breeding record of a tagged Tricolored Blackbird in the Kern River Valley.
We now know that this bird bred in a patch of Himalayan Blackberry in Weldon and remained in the valley until at least late fall. By piecing together data from individual tagged blackbirds we hope to get a picture of where our population goes throughout the year. We hope to use this data to facilitate the protection of habitat and food resources for the species throughout the annual cycle. The bird seems to have moved on from the site, but we hope to catch up with him again soon at the local breeding colonies in March.
Winter flocks of blackbirds, including Tricolored blackbirds, are often seen in the Canebrake Ecological Reserve, East of SSRS.
We had a special visitor to our MAPS bird banding station this June! This is a male Summer Tanager in its first alternate plumage (FCA).
This first photo shows a nice example of juvenal1 (yellow) vs non-juvenal (red, alternate plumage in this case) tail feather shape.
The next photo shows the typical mottled red and yellow plumage of a male in the summer following the year it hatched.
To nerd out on molt even further… this bird left its nest last year in yellowish juvenal plumage, and did a partial “pre-formative” molt of body feathers at the end of the summer (replacing yellow juvenal feathers with yellow formative feathers). Before this summer, he did an incomplete “pre-alternate” molt, replacing some body feathers and much of the tail with red alternate plumage, resulting in the mottled red and yellow coloration sported here. By next summer this stud will be entirely red.
