The Forest in Fall: Waterfowl
The first questions one might ask are “why do waterfowl migrate south?” or “where do they go?” Like many other processes related to phenology, waterfowl migrations are believed to be related to photoperiod and temperature. Photoperiod is the length of daylight in each day of the year. Biologists and ecologists may often refer to the photoperiod and equinoxes as nature’s calendar. Some species of waterfowl such as blue-winged teal and wood ducks prefer warmer temperatures and may migrate well before the temperatures drop during fall. Where other species such as mallards and Canada geese will hold tight into the late fall before beginning their journey south. Once these birds decide it’s time to migrate, they use geographic features like rivers, mountains, and coastlines to find their way to a new resting place. As we look at the individual species themselves and their physical biology, this will help us determine where they are headed.
Waterfowl biologists often call these birds “sampling specialists” as they seek areas that fit their needs for periods of time until resources and conditions no longer suit their needs. Each species has different needs that ultimately dictate their survival and reproduction. In general, the smaller bodied birds like teal migrate well before the cold weather hits the northern regions. Some species like teal and wood ducks may already be in the panhandle of Florida by Labor Day, where mallards and Canada geese might not begin to head south until Veteran’s Day. Groups of mallards and Canada geese are common visitors in Black Rock Forest and can be seen regularly throughout spring, summer and well into fall. The habitat that Black Rock Forest provides fits the needs of larger bodied waterfowl for longer periods of time. Other species like wood ducks and teal are much rarer and it is quite the treat to catch them as they drop in one day and are gone the next. This trio of mallard ducks in the picture were photographed at the Upper Reservoir on a late October afternoon in 2018. The birds spent the entire afternoon dabbling for whatever food scraps were left and by nightfall, were gone with the wind.
As waterfowl begin to migrate in the fall, the current conditions and seasonal variation in temperatures might impact their destination. The recent increase in wintering temperatures across the country has created some interesting findings. Migration comes with a high physical cost as flying thousands of miles requires large amounts of energy. If waterfowl from the northern US and Canada find suitable wintering habitat before reaching the southern states, they may opt to make a long-term pit stop in their migration. Migration is an adaptive strategy that varies based on the current conditions with one goal in mind, survival, which is a prerequisite for reproduction. As 2020 continues to create challenges for both humans and wildlife, it will be interesting to see how the current dry conditions impact migration and habitat suitability for waterfowl in our area.