I did my Ph.D. in Zoology at the University of North Carolina under the supervision of the late, great Nelson G. Hairston, Sr. (By the way, Nelson Jr. is also a superb evolutionary ecologist, on the faculty at Cornell.)
Nelson Sr. told his students that they could work on anything except birds. Why? Because too many people love them (as did he) and, more importantly, because birds were just too difficult to study – especially if one intended to pursue an experimental approach, which for Nelson was the best kind of biology, even in the field. Working with Nelson, you could study salamanders, protozoa, insects (like my carabid beetles) … any animals except birds.
I may not have all the details right after all these years, but I recall Nelson telling about an ecologist who was trying to manipulate the density of a bird population (this was back in the day when there were still intense debates about the importance of density dependence in ecological dynamics) by shooting birds, only to have other birds from neighboring areas immediately move back onto the study plot, thereby defeating the intended manipulation.
So it’s interesting that now, 30+ years later, juncos and Darwin’s finches are the stars of two of the greatest long-term eco-evolutionary studies.
There are at least two lessons here. First, young scientists should not always accept what their advisors say. Listen carefully and discuss, but make your own decisions. Second, it’s amazing what extraordinary people like Ellen Ketterson and Peter & Rosemary Grant can accomplish when they put their minds, energy, and professional lives into understanding the evolving world in which we live.