American Robins: Harbinger of spring or year-round resident?
When people see an American Robin this time of year, many think it is a sign of spring, but robins can be found year round in Michigan.
Robins in Michigan all year? You Bet! Just like humans, some American Robins that spend their summers in Michigan, migrate to warmer states like Florida in the winter. Not all robins that winter in Michigan, however, will stay to nest and breed in the summer (see Fig. 1).
According to Julie Craves, Avian Biologist at the Rouge River Bird Observatory, “American Robins have been present every winter at the University of Michigan-Dearborn since I started counting them in 1993”. The chart below (Fig 2) shows her findings. The bars represent the average number of robins counted per survey (visit) each year through winter 2011-2012. Overall, an average of 348 robins is counted each winter, or an average of 25 per visit.
According to Journey North, there are numerous factors that impact robin migration including:
- Not all robins are the same: The vast majority of robins do move south in the winter. However, some stick around—and move around—in northern locations.
- Robins migrate more in response to food than to temperature: Fruit is the robin’s winter food source. As the ground thaws in the spring, they switch to earthworms and insects. While the robins may arrive when temperatures reach 37 degrees, this is because their food becomes available not because the robins themselves need warm temperatures.
- Robins wander in the winter:Temperatures get colder as winter progresses. Robins need more food when it is cold and more and more of the fruit are eaten. Robins move here
and there in response to diminishing food supplies and harsh weather. If all robins wintered at their breeding latitude, there would not be enough fruit for them all. So, robins tend to spread out in the winter in search of fruit. Most hang out where fruit is abundant, but some take the risk of staying farther north where smaller amounts of fruit remain.
- Robins sing when they arrive on territory: Robins sing when they arrive on their breeding territories. Sometimes, robins even sing in winter flocks, due to surging hormones as the breeding season approaches. However, in the majority of cases, robins really do wait to sing until they have reached their territory.
Has all this talk about migrating birds and potential winter sightings piqued your interest? Get out and search for birds in your area. In southeast Michigan and southwest Ontario, you can use the ByWays to FlyWays Birding brochure created in 2008 by Michigan Sea Grant in partnership with Metropolitan Affairs Coalition and the International Wildlife Refuge Alliance.