Research Spotlight: California Central Valley Ducks Move Shorter Distances and Use Smaller Areas Than Expected

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In a new publication, U.S. Geological Survey biologists report the results of real-time tracking of three species of dabbling ducks in California’s Central Valley with GPS to examine the ducks’ fine-scale 24-hour movement patterns.

Nine ducks in flight above a grassy area

Flock of northern pintail at Yolo Bypass Wildlife Area, in California's Central Valley

(Credit: Andrea Mott, USGS Western Ecological Research Center. Public domain.)

By attaching small, light transmitters to the ducks, the scientists were able to determine how far the ducks moved, how much space they used when not flying (e.g. when foraging or roosting), and how their time was allocated across the day. Results showed that the ducks moved shorter distances and used smaller areas than previously thought, indicating that these ducks benefit from small, resource-rich habitat patches.

The researchers captured 109 ducks in Suisun Marsh, fitted them with small harnesses with solar-powered GSM-GPS transmitters attached, and released the ducks. The species tracked included gadwall (Mareca strepera), mallard (Anas platyrhynchos), and pintail (Anas acuta). During the study period of 2015 to 2017, the transmitters attached to the ducks recorded their locations every 30 minutes. For each 24-hour period, each duck’s movement pathways were analyzed to estimate distances moved, space used, and associated behaviors, resulting in 118,829 recorded locations for the 109 birds.

Movements distances and space-use were smaller than expected based on previous tracking studies, with a third of tracked movements categorized as short duration. Distance moved and space used varied by species, sex and season. Gadwall tended to move less than the other species, with foraging flight distances of 0.5–0.7 km, spending their time in a small number of large habitat patches. Pintails were the “flightiest” ducks, with foraging flight distances of 0.8–1.1 km. Pintails were most likely to conduct flights > 300 m, had more flight segments than other species, and used more habitat patches per day, resulting in the longest daily total movements. Females and males differed only for pintails during the post-hunt season, when females moved greater distances and used more habitat patches than males, which may reflect females switching ponds to elude male pursuit.

The shorter distances traveled and lower area use relative to other studies may reflect the higher resolution of the GPS trackers or other methodological differences, but the results may also be driven by regional differences in behavior, habitat, and resource availability. The prevalence of short duration movements and relatively low area use indicates that resources are currently plentiful for ducks in California’s Central Valley, reducing the ducks’ need to travel far to acquire enough food.

 

This Spotlight Refers To:
McDuie, F, Casazza, ML, Overton, CT, Herzog, MP, Hartman, CA, Peterson, SH, Feldheim, CL and Ackerman, JT. 2019. GPS tracking data reveals daily spatio-temporal movement patterns of waterfowl. Movement Ecology, 7(1), p.6. 
https://doi.org/10.1186/s40462-019-0146-8

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Maps of female gadwall and northern pintail locations over a 24-hour period, with locations recorded by GPS.

Maps of female gadwall (left) and northern pintail (right) locations over a 24-hour period, with locations recorded by GPS transmitters every 30-minutes in the California Central Valley.

(Public domain.)

 

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