"The latest of these, “A phylogeny of birds based on over 1,500 loci collected by target enrichment and high-throughput sequencing” by John E. McCormack et al., isn’t even officially published yet, but its authors made it available this month on a manuscript server called arXiv (a practice which, by the way, is still regarded with some uncertainty but appears to be gaining popularity)."
I was not familiar with arXiv but this manuscript must be accepted for publication I reckon. Systematic Biology or something?