An earlier post on the Long-tailed Shrike (Lanius schach) shows the adult with a cross bill, claimed to be a birth defect.
Dr Jeff Lim queried whether this condition was consistent or only momentary, “…say perhaps after preening or beak cleaning? It may not necessarily be a ‘birth defect’ since picture captures a moment in time (although as judged from the image the tip of its beak does exhibit some unusual curvature).” And according to Kennie Pan the photographer, “…the cross bill does not occur all the time…”
To resolve the controversy, Kennie provided his videos (see comments in earlier post) so that images via video grabs could be examined. As shown in all the images posted here, the bill is consistently crossed all the time the bird was in the nest brooding its chick (top left).
Hope this will, once and for all, convince everyone that the Long-tailed Shrike’s bill is permanently crossed,
due to a birth defect.