Source-sink Dynamics

I’m trading in my insulated hip waders and freezing morning temperatures for humidity and endless spider webs. I accepted a position as field supervisor for the Smithsonian Migratory Bird Center. My new study species will be my first study species—wood thrushes. I’ll be moving to Bedford, Indiana in a couple of months (I think).

The project is interested in looking at source-sink dynamics of a species of special concern on military lands (Wood Thrush). Source-sink dynamics is a theoretical model used by ecologists to describe how variation in habitat quality may affect population growth or decline of a species.  Let’s say some species of bird occupies two patches of habitat. One patch, the source, is high quality habitat that on average allows the population to increase (has more births than deaths)--there are many successful nests and lots of little fledglings at the end of the season. The second patch, the sink, is very low quality habitat that, on its own, would not be able to support a population (has more deaths than births). However, if the excess individuals from in the source frequently move to the sink, the sink population can persist indefinitely. Birds (and other organisms) are generally assumed to be able to distinguish between high and low quality habitat, and to prefer high quality. It’s also typically believed that sources have older birds that are better able to win better territories, etc. That’s the gist anyway—but it gets more complicated than that.

For willow flycatchers, it was believed that the meadows along the south end of Lake Tahoe were a huge source for the central Sierra population, and when they turned those meadows into the Tahoe Keys Marina only small nearby sinks were left and it contributed to the decline of the species. There are only a few pairs still breeding in the South Lake area.

So, I’m excited to get to work to a new project—especially one that has the potential that this one does (for a bunch of reasons I won’t get into). I’ll be supervising about 18 people from May-August on the intensive demography part of the study. And I miss wood thrushes—since they were the first birds I studied they have a special place in my heart. They have a beautiful song. And I think it’s about time to get back to those eastern migrants that I loved so much. More on the project here: http://nationalzoo.si.edu/scbi/migratorybirds/research/marra/wood-thrush.cfm