Skip to main content

Tag: GPS

KBO tracks the first Oregon Vesper Sparrows!

Written by Dr. Sarah Rockwell

Vesper Sparrow (c) Frank Lospalluto

The unique Oregon subspecies of Vesper Sparrow, roughly estimated at just 2,000 birds, is of conservation concern. It is currently under review for listing under the Endangered Species Act because of its small population size and declining trend. One of the biggest challenges in identifying ways to help migratory species is the fact that we don’t know where they are for most of the year. Vesper Sparrows breeding in Oregon are only here for about half the year, from mid-April to early October. Because different subspecies of Vesper Sparrow mix on the wintering grounds in California and are not visually distinguishable, until now, we only had a rough idea of where Oregon Vesper Sparrows spend the non-breeding months. This study will help answer questions essential for future conservation efforts – where are these birds going during migration and winter, and what challenges might they face there?

To address this critical knowledge gap, we expanded KBO’s ongoing Oregon Vesper Sparrow research to include using miniaturized archival GPS tags to track the migration of sparrows breeding in the Rogue Basin. In 2020, we captured 10 males via target-netting at our Lily Glen study site, color-banded them, and deployed GPS tags using a leg-loop harness attachment (for more details and photos of this process, see here ). In 2021, we located and recaptured four of these birds to retrieve tags and stored data. Three of the tags successfully recorded these individuals’ fall migration and/or wintering locations; one also contained the spring migration track!

Non-breeding season movements have never been tracked in this subspecies before, and results from these first three birds are incredibly interesting in their variation. You may have already followed the adventures of Po, Gram, and Affy in our recent series of Facebook posts, where we learned where they traveled during migration, but we will recap the highlights here and below in a video. One male (Po; in green) departed Lily Glen on Sept 19 on what appears to be a “false start” migration attempt – he spent one night about 25 km southwest of Tule Lake and then headed right back to Lily Glen – a behavior that we hadn’t recorded before, and in fact, would have been nearly impossible to observe without the GPS tag data. He left Lily Glen again on Sept 24 and sped down to his wintering grounds in just two days. This was also the only individual for whom we also captured spring migration – Po left his overwintering area on the evening of Apr 9, made two short stopovers just east of Vina, CA, and Redding, CA, and was back setting up his territory at Lily Glen by Apr 15.

Another male (Gram, in blue) left Lily Glen on Sept 19 and spent two weeks on an extended fall stopover outside of Chico, CA, before arriving at his wintering grounds in October. A third male (Affy; in pink) chose a more westerly route and had multiple short fall stopovers, including at Sutter Butte, an interesting geological formation made of eroded volcanic lava domes outside of Yuba City that provides a habitat island in the highly developed Central Valley. Unfortunately, Affy’s GPS tag stopped functioning mid-October, so we do not know his final wintering location. The two birds we have wintering locations for (Po and Gram) spent the winter near Raymond, CA, and El Rancho, CA, in what appears to be oak savannah habitat in the western foothills of the Sierra Nevada.

This study is the first to identify precise migratory stopover sites and overwintering areas used by this imperiled subspecies, and it addresses a critical information gap for future conservation efforts. So far, it seems like the Oregon Vesper Sparrows are using grassland and oak savannah habitat in the foothills east and west of the Central Valley as a stopover and overwintering habitat and avoiding the heavily agricultural Central Valley. We retrieved additional GPS tags in 2023, and after analyzing the data, we will use this information to assess whether conservation actions are warranted at non-breeding sites.

The Bureau of Land Management, Carpenter Foundation, Oregon Conservation and Recreation Fund, and Oregon Wildlife Foundation supported this GPS-tracking work.



Cover photo: Oregon Vesper Sparrow (c) Frank Lospalluto

Purple Martin Banding Efforts

by Sam Webb

Sarah Rockwell checking nest boxes with the box remover tool (c) Sam Webb

This spring marked the 4th year of our Purple Martin project. Klamath Bird Observatory has partnered with USFS and USGS to learn more about the western subspecies of Purple Martin. Our goal this year was to place GPS tags on 8 adult Purple Martins in order to track their migration routes and learn more about where they spend the winter.

Prior to banding, our crew boated out to check the nest boxes at the U.S. Army Corp of Engineers (USACE) Fern Ridge Reservoir to determine which were being used by Purple Martins. We checked each box for nesting activity so that we knew which ones were the most likely to have an adult Purple Martin roosting in it for the night.

Purple Martins naturally nest in cavities or old nest holes in snags or dying trees originally created by woodpeckers. Nesting locations become limited when snags are removed, or other bird species outcompete for nesting areas. The nest poles and boxes at Fern Ridge were made by USACE to provide Purple Martins with structures to roost and build their nests in. Designed to be removed with a unique tool, these nest boxes allow us to carefully bring them down, check for eggs or chicks, and catch adults.

While we were out checking nest boxes in the daytime, we took the opportunity to band any chicks that were old enough with a red band that had three easy-to-read numbers and an aluminum federal band. This will allow us to resight those individuals next year and learn more about the return rate of young Purple Martins or learn where else they might return to for their first breeding season.

Collaborator Joan Hagar of USGS banding a Purple Martin nestling (c) Sam Webb

After determining which nest boxes were likely to have adult Purple Martins roosting in them that night, we returned at dusk to try to catch and band the adults. We did this by floating quietly up to the poles and standing in the bow platform to quickly block as many cavity entrances as we could reach without the adults escaping. Once we caught an adult, we carefully took it out of the box and banded it using an aluminum federal band and the 3-numbered red band. We took additional measurements, looking at the health and size of the adult before choosing an appropriately sized GPS tag.

Sarah Rockwell and Sam Webb banding adult Purple Martin (c) Daniel Farrar

We fitted the GPS tag on the adult by slipping one loop of a harness made of stretchy jewelry cord around each of its legs and placing the tag on its back, similar to wearing a backpack. After the adult was banded and received its GPS tag, we double-checked the harness fit, carefully placed the martin back in its nest box, and set it back into position.

Adult male Purple Martin with its GPS tag (c) Sarah Rockwell

The following day, we paddled out once more to resight the adults that we banded the previous night. We spent time at each nest box to confirm that the adults still had their tags from the previous night and were comfortably delivering food to their young as usual.
These GPS tags that each Purple Martin received will take a location point every few days for up to the next year (depending on battery life) while the individual migrates to and from its wintering grounds. Due to its lightweight and compact size, the GPS tag is only able to collect location coordinates but not send them. Next year, we will return to find the adults with tags and catch them to retrieve the tags and data. Little is known about the migration route of the west coast population of Purple Martins or where they spend the winter. These data are critical for understanding their complete life cycle and for informing conservation efforts across their entire range. To read more about our first returnee and where she went, click here!


Our 2023 field efforts were supported by the Greenfield Hartline Habitat Conservation Fund and the Purple Martin Conservation Association.

KBO tracks the first Western Purple Martin with GPS tag technology

By Sarah Rockwell

Spoiler alert: Our first recaptured Martin flew almost 8,000 miles to southeastern Brazil and back again!

Retrieved GPS tag – photo credit Joe Metzler

The unique western subspecies of Purple Martin is of conservation concern, roughly estimated at just 3,500 pairs. Relatively little is known about the Western Purple Martin compared to the more abundant eastern subspecies. One of the biggest challenges in identifying ways to help migratory species is that we simply don’t know where they are most of the year. Western Purple Martins breeding in Oregon are only here from about April to August, and until recently, we only had the slightest idea of where they spend the non-breeding months. From 2020-2023, a small team of researchers from KBO, USFS, USGS, and Cape Arago Audubon Society captured adult Western Purple Martins and outfitted them with lightweight archival GPS tags that fit like a backpack with two leg loops to track their movements. Our goal is to track martins that nest in Oregon to discover their migratory pathways and winter roost locations and assess whether conservation actions are needed at these non-breeding sites. This is the first study of its kind with the western subspecies and the first to track them with GPS technology throughout the year!

There is one important catch – to have a battery small and lightweight enough for a small songbird to carry safely, the tags cannot transmit GPS data, only store it on board. Returning tagged birds must be recaptured following a year-long round-trip migration to retrieve the tag and its precious geospatial data. It can be very challenging to find these birds again, not to mention recapture them! So, we were thrilled to recapture our first female, whom we nicknamed Roxa (‘purple’ in Brazilian Portuguese – pronounced more like “hosha”), in the summer of 2021.

Joe is watching for Purple Martins to return to their nesting boxes. Photo Credit Karen McGuire.

Roxa returned with fascinating information, revealing new discoveries about her incredible 8,000-mile journey. After she left her nesting area in coastal Oregon in August, Roxa first headed south to Baja California, where she spent about a month from mid-Aug to mid-Sept on an extended fall stopover – although somewhat unusual for a songbird, this long pause was not totally unexpected, as it matched hints from earlier research using geolocators on a few martins from British Columbia (Fraser et al. 2017). She then continued south through western Mexico, with GPS points taken every 5 days, including stops in Nicaragua, Costa Rica, Colombia, and Venezuela before entering Brazil, where she passed over many of her Eastern Purple Martin cousins in their wintering area in the Amazon. She then spent another multi-week stopover in late November in northern Minas Gerais, near Parque Nacional do Peruaçu – which was unexpected! Roxa finally completed the last leg of her trip to the southeastern Brazilian coast, where she spent Christmas in Linhares in the state of Espírito Santo. She even made it to the beach city of Praia do Morro in time for Carnaval before winging her way back north and graciously returning her GPS tag to us.

Joe uses a specialized pole that traps the Purple Martins in their nesting box so the box can safely lowered and the Martins extracted. Photo Credit Karen McGuire.

We now have an amazing window into what Roxa and other Western Purple Martins are up to after they leave Oregon and the incredible voyages they undertake. These insights also lead us to more questions. Why does she stop for so long in Baja California Sur, Mexico, and Minas Gerais, Brazil? Could she be molting and regrowing feathers at one of these locations where the insect food resources are especially abundant? Does she use the same route every year, and do other Western Purple Martins use similar or different routes? What changes are occurring in the habitats she occupies along the way? Are any of these places threatened by deforestation, pesticide use, or other conservation challenges? We hope to apply what we have learned to help make sure the Western Purple Martin’s migratory journey, connecting people and places across continents, remains a phenomenon we can all marvel at well into the future.

Female Purple Martin recaptured – Photo credit Joe Metzler

In summer 2023, we recaptured two more returning Purple Martins with new data to add to our understanding of their migration routes and winter homes – we are so excited to process these data and see how they compare to our first recapture! We also deployed 8 more GPS tags on Purple Martins nesting at Fern Ridge Reservoir near Veneta, OR. Those individuals have finished their nests for this summer and will be leaving soon for parts unknown – but a little less unknown than before – so we will also have more chances to add data to this study next summer.

The USFS, USGS, Purple Martin Conservation Association, and the Greenfield Hartline Habitat Conservation Fund supported this work. The research team comprised Sarah Rockwell from KBO, DeAnna Williams of USFS, Joan Hagar of USGS, and Joe Metzler from Cape Arago Audubon Society. Watch the short video On the Wings of Roxa and join her 8,000-mile journey.