Birds in V formations are frequently observed and two main hypotheses have emerged in the biology/ornithology literature to explain this particular geometry: (i) it offers aerodynamic advantages and (ii) it is used to improve visual communication. Both explanations require a bird to track its predecessor. Observations of flocks suggest that this task is difficult for birds in large formations. We explain this phenomenon using a simple bird model and systems theory. This result has implications for the coordinated control of unmanned aerial vehicles. In particular, predecessor-following is an inherently poor strategy for formation flight.