Tracking How Waterfowl Respond to Western Drought

By Luke Matthews

Drought has been a common occurrence in California over the past 10 years. These dry cycles typically impact the number of planted acres on many annual crops, including rice, and the annual variation of dryness is almost expected by both people and wildlife. However, the extreme conditions leading up to the spring of 2022 set the stage for an unprecedented reduction and distribution of planted rice acres in the Sacramento Valley (the Valley). 

In a “normal” year there are about 500,000 acres of rice planted in the Valley, but this year that number was cut down by more than half to roughly 250,000 planted acres. The last time planted acres were this low in the Valley was in the late 1950’s; however, the distribution of these acres may have an even larger environmental impact than the sheer reduction. Typically, rice is planted in a fairly even distribution on both the east and west sides of the Valley, creating a region critical to supporting wildlife. But this year, due to drought and lack of water in the Lake Shasta watershed, the west side accounts for less than 10% of the total planted acres in the Valley. This dramatic change in both reduction and distribution has never been seen before and could have significant, long-term impacts on wildlife that rely so heavily on rice agriculture. 

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Waterfowl that travel into the Sacramento Valley, along ancient routes of the Pacific Flyway, are heavy users of rice fields in the winter. In fact, rice makes up a huge proportion of the diets of ducks and geese in the Valley; to be specific it is responsible for 74% and 95% of their diets respectively. This reliance coupled with the reductions of planted rice acres has lead waterfowl biologists and researchers to question how waterfowl will navigate this landscape that is largely void of their primary food source. To answer this question, the Rice Commission teamed up with the U.S. Geological Survey in requesting financial support from the Department of Water Resources to purchase bird tracking devices through the Drought Relief Waterbird Program.  

On short notice, a massive collaborative effort between the Rice Commission, U.S. Geological Survey, U.S. Fish and Wildlife Service, California Department of Fish and Wildlife, Ducks Unlimited and California Waterfowl Association kicked into high gear in preparation for annual fall waterfowl migration and to launch this new study. Together this group has been working tirelessly to capture birds and deploy 160 GPS transmitters on four species of waterfowl: Mallard, Northern Pintail, Greater White-fronted Goose and Snow Goose. The objective has been to capture birds on the west side of the Valley as they arrive from their breeding grounds and deploy the transmitters, which will allow researchers to collect real-time location data on the marked birds and get a better understanding of how they are responding to the lack of rice as a once reliable food and habitat source. The data has already revealed some predictable trends, with many of the marked birds leaving the west side and heading for areas with more rice and water. However, this is only a small part of the story as these transmitters will continue providing crucial information for months and possibly years to come. This information will help determine how we can best support waterfowl populations during future dry years. 

pintail with transmitter tag