DU, Partners Use New Tech to Study Mottled Ducks

Light-level geolocation used to study breeding propensity

© Chris Nicolai

The Western Gulf Coast (WGC) is home to approximately 90 percent of the worldwide population of mottled ducks (Anas fulvigula), a non-migratory species that satisfies its annual cycle needs from a small geographic range. Available population survey data suggest the WGC mottled duck population has experienced a long-term, steep decline in Texas, is stable or slightly increasing in Louisiana and is stable to declining across the entire WGC range.

The Gulf Coast Joint Venture Mottled Duck Conservation Plan was developed to provide guidance on conservation strategies and research needs for mottled ducks. Recent investigations have bolstered our understanding of mottled duck ecology and vital rates responsible for driving population growth.

Although our understanding of annual and seasonal survival has improved, breeding propensity (the probability that a hen will attempt to nest) remains poorly studied despite it having potential to greatly influence annual production. A primary reason for our poor understanding is the difficulty of collecting reliable data to measure it, as it typically relies on intensive data collection from individually marked birds.

The emergence of a new tracking technology – light-level geolocation – provides an exciting opportunity to use minimally invasive methods for studying breeding propensity of individually marked birds. The miniature devices employ geolocators which weigh as little as 1 gram and contain tiny sensors that measure the timing and duration of ambient light.

Geolocators were originally designed to track large-scale movements based on geographic patterns of sunrise and sunset (https://goo.gl/JEbJcw). Yet researchers have discovered that when attached to leg bands the light patterns captured by geolocators may be used to infer nesting activity as the devices are hidden from sunlight when a hen is nesting. The greatest drawback to this technology is individual birds carrying the device must be recovered to retrieve the data.

With funding received from the Gulf Coast Prairie Landscape Conservation Cooperative, Ducks Unlimited is working with our partners along the Gulf on a 2.5-year pilot study to investigate the feasibility of using geolocators to measure breeding propensity of mottled ducks.

This summer, geolocators will be attached to 220 female mottled ducks captured during banding operations in coastal Louisiana and Texas. Recoveries are expected to occur over three to four years via harvest and recaptures during banding. If this technology proves useful, the opportunity may exist to expand this into a long-term effort to monitor mottled duck breeding propensity.