In general, to find maps transporting statistics in a well-behaved way, it is useful to try [FindStat][1]. In the case at hand, go to http://www.findstat.org/StatisticsDatabase/St000021/ (which is the statistic "number of descents of a permutation") and click on "Search for values". After a short while, you will be presented with a list of candidates, each of the following type: 1. a statistic $stat$ on (possibly different) combinatorial objects, and 2. a map $\phi$ such that $$ des(\pi) = stat(\phi(\pi)) $$ (possibly $\phi$ is in fact a composition of several maps) You then only have to check which of candidates have maps that are bijective. Furthermore, you will have to check that not only the *number of descents* but also the descent set itself is preserved. In the case at hand, Ira's example of standard Young tableaux is found, there is possibly a well behaved bijection to increasing trees, to ordered trees,... [1]: http://www.findstat.org