Waterbird Ecology and Movement in the Saline Lakes

Overview: 

USGS scientists are tracking the movement of migratory water birds in the Great Basin to understand how they rely on terminal lakes and wetlands. Migratory birds go between and use multiple terminal lakes and wetlands over the seasons in the basin. Linking detailed bird movement data to critical water conditions is an important component for future management of water and habitats. A primary goal of this research is to provide context for decision makers regarding the outcomes of water management actions on migratory bird populations. 

Background: 

The Great Basin is North America’s largest endorheic watershed, meaning there is no drainage to the ocean. All the water flowing into the region evaporates, sinks underground, or flows into terminal lakes. Terminal Lakes are land-locked bodies of water generally with a higher salinity – or saltiness, like an ocean, bay, or salt-water estuary. Terminal lakes in the Great Basin are a vital rest stop for migrating birds. They provide habitat and resources to support them during various life-stages like migration, breeding, molting, and wintering. In the last 150 years, Great Basin terminal lakes shrunk by as much as 90 percent. Terminal lake wetlands decreased by as much as 47 percent. Decreased water levels in terminal lakes and wetlands are due to water diversions, lake and groundwater use, and drought. Understanding how changing conditions influence vulnerable bird populations requires more water monitoring and ecological data. Available information on waterbird movement is not enough to understand bird use across the terminal lakes or among all bird guilds of interest. 

The Bird Movement project launched in 2023 with a plan to track up to 10 species of waterbirds as they travel through and use the terminal lakes of the Great Basin. Scientists are already tracking the movement of American Avocets, White-faces Ibis, and a few waterfowl with more to come. 

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How are birds tracked? 

The birds are captured using remote triggered nets placed in areas where they forage. They are carefully removed from the netting and basic physical measurements are taken, such as weight and size. A GPS tracker is attached to the back of the bird using elastic and Teflon straps, like a little backpack. Depending on the bird type, other attachment methods include a leg loop, or with the help of veterinarians, placed under the skin. The GPS trackers send high resolution location data via the cell phone network to cloud-based storage where it can be retrieved and analyzed by researchers. 

What story can the data tell?  

Monitoring bird movement highlights exactly how the birds are interacting with the landscape. Terminal lakes and wetlands need to provide habitat, food, and water at the right places at the right time. When one of those needs isn’t met, birds or management decisions need to adjust if possible.  

Drought can lead to food web instability. If too much water evaporates that is not replaced with inflows, salinity increases to extreme levels and degrades vital food resources, like brine shrimp and pile worms. If not enough water and food is available at one lake, birds may move to another terminal lake to feed. 

What if a bird population cannot leave an area during a drought? For instance, Eared Grebes spend 3-4 months flightless in the fall while they molt their wing feathers. During this process their body mass changes and they become flightless. Eared Grebes can choose where to molt, often at Mono Lake, Great Salt Lake, and Lake Abert - to a lesser extent - but after becoming flightless they are vulnerable to ecosystem disfunctions. In this scenario, resource managers could choose to divert less water away from the lake to protect the birds. 

Migratory birds use the terminal lakes as a network to meet their needs. Bird movement data can show how that network ties together in the Great Basin and how it connects to the larger picture of the Pacific and Central flyways. Tracking multiple species at multiple lakes is necessary because different species require different resources and each lake offers a unique landscape. The data can show patterns and variation in habitat use over space and time; as well as how the birds are responding to stresses from drought, water-quality, water availability and salinity.  

Project Objectives: 

1. Collect and combine the data necessary to quantify bird dispersal and use across the terminal lakes as a network. 

2. Identify habitat characteristics that are important to representative bird species and quantify the birds’ use and/or selection of habitats. 

3. Develop a water sampling design that links collection of habitat and water-quality data to regions of recent high-intensity bird use.  

No one agency can do this work alone. This project is just a small portion of a larger collaboration and coordination effort with other federal and state agencies, non-profit groups, and universities who collect similar bird movement, habitat characteristic, and water-quality data across the Great Basin terminal lakes system. 

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GPS Tracking Progress: 

All of the 2023 transmitters are deployed! Birds captured and tracked in the spring and summer of 2023 include: 

• American Avocets at Great Salt Lake, Lake Abert, Summer Lake, and Malheur National Wildlife Refuge. 

• White Faced Ibis at Summer Lake and other locations across the west. 

• Wilson's phalaropes at Mono Lake and Tule Lake National Wildlife Refuge.

Bird Movements Highlights:

• 80 thousand and counting Avocet locations collected.

• 800 thousand and counting White Faced Ibis locations from Western US as far as Louisiana. 

• One Wilsons phalarope traveled an incredible 1,800 km in two days between Tule Lake Wildlife Refuge, passing over Channel Islands, before arriving in Baja California Sur, Mexico.

• Every bird species tagged in the Saline Lakes region (Wilson’s Phalaropes, Avocets, White Faced Ibis) are showing signs of migration.

As work progresses, stay tuned for updates on this ambitious project! 

All animal studies were performed under the auspices of the USGS Western Ecological Research Center and University of California Davis Institutional Animal Care and Use Committees.