'Snorkeling' by the chicks of the wattled jacana

The chicks of the Wattled Jacana (Jacana jacana) exhibited an unusual predator escape behavior in the floodplains of Venezuela. When approached by a human, chicks dove and remained completely immobile while entirely submerged with just the beak protruding vertically above the water line. Since breathing should continue while hiding, we reasoned that it would be advantageous for the bird to have the nostrils placed in a forward position along the bill to facilitate breathing while submerged. To examine this expectation we compared the relative position of the nostrils of the Wattled Jacana with those of species belonging to phylogenetically related Scolopacidae. In accordance with expectations, Wattled Jacanas have nostrils that are placed significantly more forward along the bill than all species of Scolopacidae measured. Nostril placement in species belonging to other phylogenetically related families, Thinocoridae, Pedionomidae, and Rostratulide is also basal as in Scolopacidae. Forward placement of nostrils seems to be a derived character in jacanas. The 'snorkeling' behavior of Wattled Jacana chicks is a behaviorally elaborate predator escape mechanism, seemingly accompanied by anatomical adaptations.
Predation is often the major mortality factor of young birds and is therefore an important selective force shaping the behavior of young birds and their parents (Rickleffs 1969, Martin 1992). [...]