Surface densities found in our z ~ 7 z ₈₅₀-dropout (upper left) and z ~ 8 Y ₀₉₈-dropout (lower left) selections over the wide-area ERS observations (black histograms, with 1σ errors) and in our z ~ 7 z ₈₅₀-dropout (upper right) and z ~ 8 Y ₁₀₅-dropout (lower right) selections over our HUDF09 observations (histograms). For comparison, we show the predicted surface densities based upon the Bouwens et al. (2007, 2008) determinations of the UV LF at z ~ 6 (cyan lines) and z ~ 7 (magenta lines). The solid red lines are the surface densities predicted extrapolating the Bouwens et al. (2008) LF results to z ~ 8 (based upon the fitting formula in that paper). The two H _{160, AB} ~ 26 Y ₁₀₅ dropouts seen in the lower right panel—while exceeding the predicted surface densities for z ~ 8 star-forming galaxies—may be part of an overdensity (see Section 5.3).