THE SELECTION OF SAFE BREEDING SITES IS AN IMPORTANT BEHAVIORAL COMPONENT OF AVIAN POPULATION ECOLOGY (NEWTON 1998), AND NEST PREDATION IS A MAJOR ECOLOGICAL FORCE LIMITING REPRODUCTIVE SUCCESS AND SHAPING THE SPATIAL DISTRIBUTIONS OF BREEDING BIRDS (RICKLEFS 1969, MARTIN 1995). AVIAN NESTING SITES CAN BE EXAMINED AT MULTIPLE SPATIAL SCALES, FROM BROAD LANDSCAPE LEVELS, TO NEST AND PATCH CHARACTERISTICS, TO MICROSITE FEATURES SUCH AS OVERHEAD CONCEALMENT AND NEST ORIENTATION (MARTIN 1993, PATON 1994). MICROHABITAT FEATURES OF THE VEGETATION USED AS NEST SUBSTRATES ARE ESPECIALLY IMPORTANT FOR CAMOUFLAGE AND PROTECTION FROM INCLEMENT WEATHER (MARTIN 1995, DEEMING 2002, KOLBE AND JANZEN 2002). NUMEROUS STUDIES HAVE LINKED SPECIFIC ASPECTS OF NEST MICROSITES AND NESTING SUCCESS IN A VARIETY OF BIRDS (E.G., MARTIN AND ROPER 1988, LIEBEZEIT AND GEORGE 2002, AGUILAR ET AL. 2008, POWELL ET AL. 2010, MILLER 2014). WHILE MANY STUDIES OF AVIAN NESTING SUCCESS FOCUS ON PREDATION OR BROOD PARASITISM (E.G., LI AND MARTIN 1991, LARISON ET AL. 1998, LIMA 2009), IN SOME SPECIES, PARTICULARLY SPECIES WITH NARROW PHYSIOLOGICAL TOLERANCES LIKE HUMMINGBIRDS (CALDER AND BOOSER 1973, CALDER 1994, 2002), NEST PLACEMENT MAY ALSO BE IMPORTANT FOR MAINTAINING THE MICROCLIMATE AROUND THE NEST (DEEMING 2002).