What does "nesting failure" mean?
Actually, nesting failure means that nesting trial fail before offspring could even leave the nest. In case of precocial species (where chicks leave nest immediately after hatching, like swans) it means that eggs was destroyed or parents abandoned nest, as @nico point out. In case of altricial birds (offspring stay in nest) nesting failure may also mean that all nestlings died before leaving nest.

for example among House wrens (Belles-Isles &amp; Picman 1986):


  About 81%
  of nesting failures (n = 30) were due to predation (contents disappeared before the expected fledgingdate). Females abandoned seven nests, and starvation (presumably because
  of desertion by parents) accounted for one nesting failure.