Ornithological Note 35
On 7 September 2013, while filming a Bristle-thighed Curlew (Numenius tahitiensis) on Henderson Island in the Pitcairn group, one of us (JH) observed the bird grasp a snail shell in its beak and repeatedly slam it against the hardened-coral ground. The slamming eventually dislodged a small hermit crab, which the curlew immediately consumed (see video ).
Use of ‘slamming’ behaviour by Bristle-thighed Curlews apparently is unique among the genus Numenius and is used to help process for consumption a variety of food items that include bird eggs, crabs, snails and small rodents (Amerson & Shelton 1976, Marks & Hall 1992, Marks et al. 2002). Child (1960) was the first to describe use of the behaviour on hermit crabs, noting that curlews invariably slammed in a clockwise direction when viewed from behind. To our knowledge, no one has examined the directionality of slamming since. The video footage shows the curlew making seven counter-clockwise slams and one clockwise slam, thus providing irrefutable evidence that slamming is not confined to one direction, even within individual birds.
References
Amerson, A.B. Jr. & Shelton, P.C. (1976). The natural history of Johnston Atoll, Central Pacific Ocean. Atoll Res. Bull. 192: 1–479.
Child, P. (1960). Birds of the Gilbert and Ellice Islands colony. Atoll Res. Bull. 74: 1–38.
Marks, J.S. & Hall, C.S. (1992). Tool use by Bristle-thighed Curlews feeding on albatross eggs. Condor 94(4): 1032–1034.
Marks, J.S., Tibbitts, T.L., Gill, R.E. Jr. & McCaffery, B.J. (2002). Bristle-thighed Curlew (Numenius tahitiensis). No. 705 in: Poole, A. ed. (2002). The Birds of North America. Cornell Lab of Ornithology, Ithaca, New York.