The statistics of bird arrivals

Posted by Libby Ellwood

 "'But,' says one, 'you do not mean that the students should go to work with their hands instead of their heads?' I do not mean that exactly, but I mean something which he might think a good deal like that ... 

How could youths better learn to live than by at once trying the experiment of living? 

Methinks this would exercise their minds as much as mathematics." 

-Henry David Thoreau, Walden

(Photo of a magnolia warbler by Richard Primack)

Last spring Richard Primack and I visited our friend and colleague Trevor Lloyd-Evans at Manomet Center for Conservation Sciences. For over 40 years researchers and volunteers have been banding birds at Manomet and have compiled an impressive dataset of migration dates at this beautiful coastal location. These unique records provide many details of the migration including first and mean arrival dates of particular species, population size, and morphological information such as mass and wing length. Members of the Primack lab have found these data incredibly useful for answering questions of how bird migrations have changed over time and in relation to warming temperatures (Miller-Rushing et al. 2008).

At Manomet we met up with the creative team of Chedd-Angier Production Company, a group working with the Annenberg Foundation to develop educational videos that explore statistical concepts through real-life examples. They thought our research on bird arrivals at Manomet would be a good fit for the "Normal Curves" segment. When the number of captured birds of a given species is graphed over the course of a migration season a "normal curve" is created and this is an important tool for understanding migration patterns and changes.

After a morning of banding, we spoke with them about how the analyses we do can answer questions about changes in bird migrations and populations, and how this is important for conservation efforts.

You can watch the full video here:

Against All Odds: Normal Curves

(Photo of Trevor and a common grackle by Patrick Roberts)

Miller-Rushing, A. J., T. L. Lloyd-Evans, R. B. Primack, and P. Satzinger. 2008. Bird migration times, climate change, and declining population sizes. Global Change Biology 14: 1–14.