The latest cell phone technology allows billions of people around the world to keep tabs on family, communicate with friends, monitor health and exercise levels, and much more. Now the same technology is being used by scientists to learn more about the behaviors, movements, and habitat preferences of ducks and geese. In these studies, birds are captured and fitted with lightweight backpack transmitters and then released. The transmitters are equipped with solar-powered batteries, GPS tags, and accelerometers that collect a wealth of data about bird activities and locations. Just like your phone, each transmitter has a data plan that allows information to be uploaded to nearby cell phone towers, and researchers receive the data on their computers hundreds or even thousands of miles away.
These transmitters are being used across the globe to answer questions that have puzzled wildlife ecologists for decades. In waterfowl behavior studies, scientists have mostly focused on observing individual birds for a moment in time, but until recently they have been unable to follow birds throughout the year. Moreover, researchers have been unable to connect how certain behaviors (such as feeding and resting) on migration and wintering areas might influence subsequent reproductive outcomes later in the year. Duck distributions often span thousands of miles, and understanding how these behaviors are connected could help us focus limited conservation resources in high-priority areas that demonstrably improve reproductive success for specific species.
Our lab at the University of Saskatchewan has been exploring these information gaps in American black ducks and eastern mallards for several years. Black ducks breed primarily in the eastern Boreal Forest in Canada and in the northeastern United States. In contrast, eastern mallards largely breed in more temperate environments in rural and urban areas from eastern Canada to South Carolina. While black ducks and mallards may breed in different areas, their wintering ranges overlap.
Black duck studies are helping to answer long-standing questions about whether conditions on breeding or nonbreeding areas have a greater impact on reproductive success. Studying eastern mallards is important because breeding populations of these birds appear to be stable in eastern Canada, while their counterparts in the United States are declining. To learn more about what’s driving these populations, numerous conservation partners have launched an unprecedented study of black ducks and mallards in the Atlantic Flyway. As part of this effort, more than 2,000 female black ducks and mallards have been equipped with transmitters over the past five years.
Using accelerometer data, we monitored how much time these birds spent resting, feeding, flying, and preening (spreading oil on their feathers for waterproofing). Data from these studies show that, throughout their full annual cycle, mallards rested the most right after migration, preened the most right before fall migration, and flew the most during spring and fall migration. Black ducks showed similar behavior, although the amount of time they spent resting each day showed less variation throughout the year. However, we noticed that some individual birds of both species spent significantly more time feeding than others. This was likely due to weather and environmental conditions encountered by those birds, as well as the energetic requirements of migration and other activities.
Overall, we found that resting was the most common activity for mallards and black ducks, and that black ducks spent more time feeding than mallards did. Both species spent the same amount of time preening, and flying accounted for only 1 percent of their activity (see charts). How might these behaviors impact future breeding success? These studies suggest that black ducks that fed more in late winter, just before spring migration, were more likely to attempt to nest when they returned to breeding areas, but we did not observe a similar pattern in mallards.
To understand the factors that impact breeding success, we needed to know if the ducks in our study bred successfully. We monitored and collected data on individual females settling on breeding areas, navigating nesting attempts, and raising ducklings. Our first measurement of breeding success was nesting propensity—whether or not hens attempted to nest and lay eggs. We developed a model that used GPS and accelerometer data to identify egg-laying behavior in individual birds. We also focused on the movements of hens and their behavior shortly after sunrise, which is when most ducks lay eggs.
After hens finish laying eggs, they begin incubation. Thus, the second stage of breeding success that we measured was nesting success, or whether hens successfully incubated and hatched their eggs. Not surprisingly, incubating hens remained largely stationary throughout the day.
After the eggs hatch, hens leave the nest within about 24 hours and lead their ducklings to nearby wetlands to feed. Accordingly, the third stage of breeding success that we measured was fledging success, or whether broods survived to 30 days of age. We developed a model to classify brood-rearing behavior. Because ducklings are flightless during the first 30 days of life, hens with broods moved shorter distances and spent less time flying than hens without broods did.
By analyzing transmitter data from hens that we visually confirmed to be nesting and rearing broods in the field, we were able to test how accurate our models were in classifying breeding behaviors. These observations revealed that our models had an accuracy of 95 percent. What were the results? We found that breeding success differed by species and age. Overall, breeding success was higher for mallards than it was for black ducks. This was due to mallards having higher nesting propensity and fledging success than black ducks. Nesting success, however, was similar for mallards and black ducks. Hens of both species had lower breeding success during their first year than during their second and subsequent years. This was largely due to lower rates of nest initiation, nest success, and brood-rearing success among first-year birds compared to older, more experienced hens.
Now that we know how to classify the behavior and breeding success of the hens equipped with transmitters, the next step will be to incorporate habitat and environmental data matched to our location data for each bird. We will then use models to identify when and where habitat, behavior, and weather have the greatest influence on subsequent breeding success and compare these results between black ducks and mallards. This information will help guide future conservation efforts for these species as well as other species that rely on similar habitats across North America, ensuring that limited financial resources are used in areas where they will have the greatest benefit for waterfowl populations for years to come. Who would have guessed that we could learn so much about ducks with the same technology that we use every day on our mobile phones?
Cassidy Waldrep and Ilsa Griebel are PhD students at the University of Saskatchewan studying the ecology of black ducks and mallards. Dr. Mitch Weegman is an associate professor and the Ducks Unlimited Canada endowed chair in wetland and waterfowl conservation at the University of Saskatchewan.
