A new prey-detection mechanism for kiwi (Apteryx spp.) suggests convergent evolution between paleognathous and neognathous birds

Kiwi (Apterygidae: Apteryx spp.) are traditionally assumed to detect their soil-dwelling invertebrate prey using their sense of smell. The unique position of the nares at the tip of the bill and the enlarged olfactory centres in the brain support this assumption. However, studies designed to show the importance of olfaction in prey-detection by Apteryx have provided equivocal results. Another family of probing birds, the Scolopacidae, detect their buried prey using specialised vibration and pressure-sensitive mechanoreceptors embedded in pits in the bill-tip. We found that aspects of the foraging patterns of Apteryx mantelli are like those of scolopacid shorebirds, suggesting that Apteryx may be using a similar prey-detection mechanism. We examined specimens of all five Apteryx species and conducted a morphological and histological examination of the bill of A. mantelli. We discovered that Apteryx possess an arrangement of mechanoreceptors within pits similar to that in Scolopacidae species and may therefore be able to localise prey using a similar vibrotactile sense. We suggest that this sense may function in conjunction with, or be dominant over, olfaction during prey-detection. The Apterygidae and the Scolopacidae are members of the two different super-orders of birds: the Paleognathae and the Neognathae, respectively. Therefore we cite the similar bill-tip anatomy of these two families as an example of convergent evolution across a deep taxonomic divide.