Potential New Ways to Determine the Movement of Phalaropes

One of the defining characteristics of birds is that they never stay in one place. This can be maddening when catching a quick glimpse of a hard-to-identify bird. It is awe-inspiring given that many species, such as Wilson’s Phalaropes, journey hundreds or thousands of miles between areas where they breed and raise young and areas they depend on for food, refuge, and survival during other seasons. For those tasked with conserving birds, this movement is challenging. To better conserve and manage Phalarope habitats, we need to know how and when they use those sites.

A group of North and South American researchers, resource managers, and other conservation professionals recently convened at California’s Mono Lake, to discuss the status of, threats to, and research needs for Wilson’s and Red-necked Phalaropes. Among other priorities, this group identified a need to better understand what sites these species use and how they move among these sites to cope with natural (e.g., droughts) and human-caused stressors (e.g., diversions of rivers).

There is a variety of approaches to studying bird movement. One traditional approach is to capture birds temporarily and place uniquely numbered aluminum bands around their legs at breeding, migration, or wintering sites. The recapture or recovery of a banded bird at a site connects that site to the original capture location. Unfortunately, recapture or recovery rates for banded birds can be extremely low.

Alternatively, researchers can attach radio transmitters to birds using harnesses and follow the bird’s progress with an antenna. However, it can be difficult to track birds, especially large numbers of radio-tagged birds that are on the move, even with an antenna.  Rather than manually tracking tagged birds, researchers might affix satellite tags to collect data on long distance movements, but the weight of these tags can prohibit studies of small birds like Phalaropes.

The Motus network is overcoming barriers in tracking movements of small birds as described by Taylor and colleagues in 2017. Motus (Latin for movement) relies on a network of automated radio-telemetry systems connected to fixed or mobile receivers to continuously record data on tagged birds.  Motus was established and continues to grow through researchers and organizations who are setting up and operating independent receiving stations across a wide geographic area, including North, Central, and South America, as well as Europe and Australia. A map of current Motus receiving stations is available here.

The Motus network’s automated collection of data alleviates the need to devote staff time to manually track birds in the field, and the network relies on lightweight radio-transmitting tags that can be affixed to small birds like Phalaropes. Researchers are using Motus to answer a wide range of questions such as arrival and departure times at particular migration sites, whether birds are faithful to a site, as well as flight distance, time and speed.  Audubon’s Water and Birds in the Arid West report and Connecticut Audubon Society’s 2018 Connecticut State of the Birds report, have recognized the potential of Motus to increase our understanding of bird movements.

One example of this can be found in a study at Texas Tech University. Researchers there are using Motus to study breeding, migratory, and wintering locations of Snowy Plovers associated with saline lakes of the Texas High Plains. One question they seek to answer is where birds are being exposed to high levels of selenium, which potentially can affect bird reproduction. Exposure to elevated selenium levels may be occurring during the birds’ stay at the saline lakes, waterbodies that are drying due to droughts, diversions, and a changing climate.

Despite the recognized and realized potential of Motus, no approach to studying bird movements is without challenges. Because of the bottom-up growth of Motus, there are large and important gaps in the geographic areas it covers. There are currently no receiving stations at the saline lakes in the Intermountain West, the fall staging grounds for Wilson’s Phalaropes. Small tags, such as those used for Phalaropes, have a limited lifespan between 10 and 90 days, and transmitted signals may be easier to detect when birds are in flight rather than near ground. Without multiple stations or antennae, it is difficult to precisely determine the location of a detected bird. Finally, establishing and maintaining a Motus station requires thousands of dollars for equipment and staffing.

The tremendous potential and challenges associated with Motus underscores the importance of thoughtful design and implementation of Motus projects to supply information of critical conservation importance. At Mono Lake, a group of dedicated individuals began conversations that may lead to more Motus stations, which will fill in some of our information gaps, especially in the Intermountain West. This would help the wildlife and land management communities guide Phalarope conservation and management. Audubon looks forward to continuing these conversations.