Journey North Robin Migration

Ups and Downs: Counting Robins
Citizen Scientists At Work
By Laura Erickson, Ornithologist and Journey North Robin Expert

Counting Individuals

Photo Laura Erickson

A census to count the population in the United States will be conducted in 2010, and in Canada in 2011. Every adult human will be required to fill out a census form. The forms will provide accurate information about exactly how many people live in our countries, and where the people live.

People count animals too. As far as we can tell, robin numbers ARE increasing, and it's fairly widespread. How do you suppose we know how many robins there are? (Even if we could give census forms to robins, they wouldn't fill them out!)

Counting Robins
Researchers use several kinds of counts. Three well known counts are the Christmas Bird Count in late December, the Great Backyard Bird Count (GBBC) in mid-February, and the Breeding Bird Survey in early June. These counts don't keep track of every single robin. Rather, volunteers ("citizen scientists" like you) cover small areas year after year. These numbers are not precise. But by comparing counts from year to year or decade to decade, we do get a general idea of what's happening with the robin population.

Photo Karen DeMusey

The Ups and Downs of Counting
Robins wander widely during winter. This shows up in the variation of numbers from year to year. For example, In 2007 robins as a species "won" the Great Backyard Bird Count. Of 2,800,223 robins counted, St. Petersburg, Florida had 1,698,550 robins! They were in a gigantic roost; the observers just happened to be in the right place at the right time, as the wandering robins had found a big food source. If nobody was counting in St. Petersburg FL, the 2007 robin count would have been only 381,000 robins total in the U.S. Imagine that!

In 2008, snow geese were the Great Backyard Bird Count's most counted birds, with 927,059. Does that mean robins declined between 2007 and 2008? Sometimes the winter counts won't happen in the right place to see a huge flock. Any data that includes a humongous wintering roost of robins is going to throw numbers off a bit. After all, no one knows (1) whether that roost was a unique one-time thing or (2) whether each year brings equally humongous roosts, but in places where birders don't see and count them. No wonder robin counts go up and down! In 2008 robins came in fourth in the Great Backyard Bird Count, with 534,560. As of Feb. 15, 2009, robins were in second place with 279,000 reports.

Stay Tuned!
It will take many years, and information from lots of "citizen scientists" like you, to know what's happening with robins. Isn't it amazing that such a common, easy-to-see backyard bird still holds so many mysteries?