There have been several days in the past few weeks that have felt like spring in winter. While human Chicagoans may head outdoors to enjoy the warm sun rays, some birds may see this as a signal to fly back north. As a matter of fact, seeing spring migrants in February has already raised concerns about climate change.
The good news:
Some birds actually hang around Chicago all year, they are just not known to do so. Robins, for instance, are thought to herald the arrival of spring. However, some do choose to stay in Chicago during the winter months. Plenty of Red-winged Blackbirds also stay in place. Other birds such as Great Blue Herons have irregular migration patterns, making decisions based on weather – if it is still nice in Chicago, they won’t bother to migrate. Additionally, birds such as Red-winged Blackbirds may only fly a hundred miles south, meaning they have a short distance to travel back when the temperature gets high enough.
Some American Robins stay in Chicago year-round!
Photo Credit: Xianwei-Zeng./Audubon Photography Awards
However…
There is strong evidence that the mild winters are affecting migration patterns for numerous birds, such as the Swainson’s Thrush and Black-throated Blue Warbler. A key concern is that if birds move north too soon, they may not find enough food to eat along the way. Issues also arise when a period of warmth is followed by a plunge in temperature, otherwise known as a ‘false spring’. Birds that made it to their destination thinking it was springtime may find themselves fighting the snow or cold rain while trying to find plants that haven’t frozen over and insects that haven’t died or gone dormant. The false spring may also impede plant growth, eventually making it more difficult for birds to nourish themselves for fall migration.
Black-throated Blue Warbler is one species observed as changing migration patterns due to mild winters.
Photo Credit: Lorraine Minns/Audubon Photography Awards
How to help:
Most importantly, we should be focusing on ways to avert further climate change. However, we can more directly help by putting out food such as suet feeders and water during false springs, growing native plants, and protecting important bird habitats such as parks and forest preserves. Another way is to become a community scientist by sending observations to eBird so there is more data to understand migratory changes.
Sources:
https://vt.audubon.org/news/shifting-timelines-warming-world-changing-how-birds-migrate