Theories and Methods
Generally undertaken during fall migration, notable movements of waterbirds can occur as early as mid-August and run through the end of the year. Even beyond this broad time frame, fall migrant shorebirds can be spotted as early as the start of July - and although more difficult to predict, spring movements of various waterbirds can be very rewarding. Here we do our best to cover some high-level concepts of fall lakewatching and how they may improve your in-field experiences.
Sources for weather information can be found here.
Weather
Cold fronts in fall generally stimulate waterbird movements in the Great Lakes both over water and land. Some considerations may include:
Rain and/or low cloud can ground high flying migrants, and possibly restrict overland movements, improving your chances of seeing species like shorebirds or loons along the lakeshore.
Consider the origin of the front. Viewing winds at 850mb-700mb heights (1.5-3 km above ground) provides a better indication of the "origin" of winds (i.e., from James Bay, or the prairies - see images below) which can provide insight on potential species compositions. For example, very-early-season migrants like Willet or American Avocet in July may require a more western-origin for passing fronts and associated winds.
Strong winds may help concentrate birds closer to shore. Generally onshore, but offshore winds can still stimulate near-shore movements and feeding activity.
Squalls or squall lines appear to stimulate flee-responses from many waterbirds, leading to noticeable concentrations immediately prior to their arrival. Note however that snow or heavy rain can reduce visibility significantly.
Consider seasonality:
Early-season birds can be stimulated into migration during seasonally strong cold fronts or winds.
Late-season birds may move more readily during calmer conditions between our stronger late fall storms.
Note on species- or family-specific seasonality will be included on the lake watching identification page.
Weather and Geography
While waterbirds will likely be undertaking visible migration on most days in the fall, a combination of strong winds and geography can maximize the near-shore viewing experience for an observer. Two key concentration effects, based around a rough theory that waterbirds do not like to fly straight into the wind, include:
Dead-End Catch Points (tailwinds)
Strong winds can concentrate birds at "dead end locations" where a lake narrows to a fine location ideal for birders. This is particularly strong for pelagic species such as Jaegers or Phalaropes, which are not comfortable moving overland like Larus gulls, loons or puddle ducks.
Counting birds at these locations is very difficult, as the same birds may become "trapped" here and return into view several times while circling the area.
Along-Shore Migration (headwinds)
Assuming birds are reluctant to fly right into a headwind, they may tack slightly left or right.
Top Image: although the winds are onshore, birds tacking slightly right of the wind can easily move offshore if they desire.
Bottom Image: If shorelines and winds line up just right, an atypically high percentage of birds may choose to follow an "along-shore" route well within viewing distance, leading to an improved birder experience. Presumably it becomes more counterproductive for them to make migratory progress pushing back offshore.
Along-shore migration spots are well suited for counting birds, as they pass and (generally) do not return. However, beware staging or wintering birds which undertake daily movements in productive habitats.
Further Viewing Considerations
Shelter: Rain soaked optics or wind shake reduce your ability to spot or identify birds. Consider vantage points with adequate visibility and shelter to improve your experience.
Heat Shimmer: Occurs when there is a strong difference between water temperatures and air temperatures. Websites such as windy.com can provide short-range forecasts of water surface temperatures and air temperatures. The closer the temperature of air and water, the better the long-range visibility.
