Posted on 10/23/2010 by Michael Schummer
Not too long ago, waterfowl hunters and other enthusiasts only had weather forecasts from the newspaper, radio, or TV to help them plan for arrival of birds from the north. Nowadays, with the internet and long-term weather forecasts, we have better ability to plan our outings. Such planning is important because other activities may increasingly attract our attention away from outdoor recreation. Thus, we watch the weather channel and seek information regarding waterfowl migration from the internet to increase the likelihood our limited days afield are successful. Additionally, increased availability of weather data and predictions also are important for conservation planning by waterfowl managers who need to understand distributions of ducks and provide habitat for them throughout the flyways.
To aid waterfowl hunters, ‘watchers,’ and managers in prediction of migration and fall-winter distributions of ducks, Drs. Rick Kaminski and Michael Schummer, Department of Wildlife, Fisheries and Aquaculture at Mississippi State University (MSU), in collaboration with Drs. Mike Brown and Charles Wax, MSU Department of Geosciences (Climatology Unit), and Andy Raedeke and Dave Graber, Missouri Department of Conservation, have been busy analyzing temperature and snow data to evaluate their combined effects on duck migration during fall-winter. The research team further evaluated how atmospheric teleconnections, such as El Niño, La Niña, and the Arctic Oscillation Index, influence annual differences in weather severity and thus duck migration in the Mississippi and Atlantic Flyways. They developed and published a weather severity index (WSI = - [average daily temperature oC ] + number of consecutive days with average temperature <0 o C + snow depth + number of consecutive days with snow cover; Schummer et al. 2010, Journal of Wildlife Management 94:94-101) that explained significant variation in changes in relative abundance of ducks at mid-continent latitudes across Missouri during fall and winter migration, 1995–2005. As WSI values approach 8 for mallards and zero for other dabbling ducks, there was increased likelihood of migrations by these ducks from Missouri to southern locations. At values above WSI thresholds, rate of change in relative abundance of ducks became increasingly negative indicating increased likelihood of migration to southern latitudes.
Based on the WSI threshold for mallards, the team of researchers have been evaluating if the WSI differed among decades and the effect of atmospheric teleconnections on annual changes in WSI from 1950– 2008. Severity of weather has been mild during the 2000s when compared to previous decades and differed substantially from the more severe 1960s and 1970s. Most winters during these decades were typified by cold and snowy conditions known to cause migration of mallards to southern wintering grounds. Further, the Arctic Oscillation Index explained substantial variation in weather severity during El Niño and La Niña episodes but not when the Oceanic Niño Index was neutral. Because we can forecast El Niño and La Niña episodes nearly 3 months in advance of their occurrence, we can develop season-long forecasts of annual distributions of ducks in the Mississippi and Atlantic Flyways.
El Niño and La Niña winters are typified by specific weather patterns, but frequency and intensity of these weather patterns can be modified greatly by the Arctic Oscillation Index. The MSU researchers found that severity of weather (indexed by WSI) increased with decreasing Arctic Oscillation Index during winters with El Niño and La Niña conditions. Increased weather severity likely resulted from decreases in temperature and increased snowfall at northern and mid-latitudes of North America that generally accompany a decreasing Arctic Oscillation Index. However, the Arctic Oscillation Index can only be reliably predicted approximately 7 days in advance. Therefore, knowing if we are trended toward an El Niño and La Niña winter is important, but watching the Arctic Oscillation Index for short-term fluctuations in weather patterns also aids our understanding of weather severity and thus potential periods of duck migration.
Based on published literature, we provide the following duck migration forecast for fall-winter 2010-2011. Our prediction is developed using available research and literature regarding reaction of ducks to weather severity and long-term weather forecasts. However, weather severity in North American should not be considered an absolute predictor of duck migration. A multitude of other factors potentially influence migration and winter distributions of ducks, including food and habitat availability, evolutionary and ecological mechanisms, body condition, and human disturbance. Presently, La Niña conditions exist over the equatorial Pacific and are expected to influence weather patterns throughout North America through fall-winter 2010-2011.
Warm conditions are likely to occur in the northeastern U.S. much later into fall-winter than normal; whereas, when cold air intrudes into the mid-continent, weather will be colder than normal but may often be followed by extremely mild and possibly wet conditions. These alternating cold and warm conditions may "flip-flop" several times this fall-winter. Much of the change in conditions will rely on the status of the Arctic Oscillation Index and the latitude of the boundary between cold arctic air and the warm southerly flow. Specific and local conditions are difficult to predict accurately this far in advance. Thus, reviewing the Weekly Weather Severity Index for Mississippi Flyway Duck Migration will be important for planning your hunting activity.
In summary, we may see cold, stormy conditions that influence duck migration in the mid-continent, but as warm conditions return and snow quickly melts, ducks that "stick it out" at northern latitudes may find available food and fewer competitors following such weather events. In the Mississippi Alluvial Valley (the Delta) and southeastern U.S., dry conditions will likely persist well into winter as will warmer than normal conditions. Areas in the southeastern U.S. with permanent water or where water can be pumped or flowed from sources may see increased abundance of ducks this season because of reduced availability of natural wetlands from lack of precipitation. Sustaining waterfowl on areas also will likely be related to food availability, potential competition for food among concentrated birds, and human disturbance. Overall, duck migrations this year may be sporadic, and a classic "grand passage" of waterfowl is doubtful. Increased rainfall and mild temperatures will increase likelihood that ducks migrating from the prairies will remain in northern to mid-latitude regions of the Mississippi Flyway (e.g., upper Midwest and Missouri) whereas those from the Great Lakes region may not leave until late in fall and then remain in areas with abundant water at the Illinois-Ohio latitude.
The Waterfowl Breeding Population and Habitat Survey by the U.S. Fish and Wildlife Service and the Canadian Wildlife Service indicates that the 2010 total duck breeding population was 41 million, and the majority of species were above their long-term average. However, availability of these birds to hunters is dependent upon many factors, particularly weather. Although historical patterns during La Niña episodes normally result in conditions less than ideal for large-scale early season migrations of ducks to the southern end of the Mississippi and Atlantic flyways, a strongly negative Arctic Oscillation Index can cause movements of ducks throughout these flyways. Thus, pay close attention to weekly duck migration forecasts on this website and tell your friends to visit the site. The duck migration forecast is updated each Monday morning November–January and provides a 5-day forecast for duck migration for the coming week using weather data available on the internet.