We study the behavior of sources and sinks in an experiment where left and right traveling waves are excited on the free surface of a fluid that is heated by a wire stretched under the surface. To study phenomena very close to threshold the experiment is made very long (2 in), while a precise linear map of the free surface is provided by a scanning device. The observed dynamical behavior of the sources is in agreement with a recent prediction based on the coupled complex Ginzburg-Landau equation [Physica D 134 (1999) 1]. However, the behavior of the sinks disagrees with it. When sources turn unstable they eject holes which are believed to be of homoclinic type.