Notes and Double Knocks from Arkansas

Abstract

In the search for ivory-billed woodpeckers ( Campephilus principalis ) in the Big Woods region of eastern Arkansas [“Ivory-billed woodpecker ( Campephilus principalis ) persists in continental North America,” Reports, 3 June, p. [1460][1]], our unattended digital autonomous recording units (ARUs) recorded over 17,000 hours of ambient sound at 153 sites between 18 December 2004 and 31 May 2005. Review and analysis of these recordings are ongoing, and a full account will be published when analyses are complete. Here we briefly describe examples of the possible nasal “kent” notes and “doublek-nock” display drums mentioned in our Report and provide them as supporting online material (SOM) ([1][2]). ![Figure][3] A painting of the ivory-billed woodpecker and the device used to record its calls.CREDITS: (PAINTING) LARRY CHANDLER; (PHOTO) SUSAN SPEAR, CORNELL LABORATORY OF ORNITHOLOGY On four different mornings in January 2005, a single ARU in the White River National Wildlife Refuge (NWR) recorded a sequence of kent-like vocalizations. The four sequences, which lasted 8 to 41 s and contained between 11 and 26 notes, are extremely similar; the recording of 29 January (audio S2) is typical of them. In the same area, experienced observers have heard blue jays ( Cyanocitta cristata ) produce atypical notes resembling these ARU recordings. Quantitative comparisons of these kent-like sounds with sounds of known ivory-bills (SOM text; audio S1), white-breasted nuthatch ( Sitta carolinensis ), and the most kent-like notes of blue jay in the collection of the Cornell Laboratory of Ornithology's Macaulay Library indicate that the notes recorded by the ARU are most similar to those of ivory-bills. Sounds that are strikingly similar to the double knocks of other Campephilus woodpeckers (SOM text; audio S3) were recorded by ARUs in several areas of the White River and Cache River NWRs. One recording (audio S4), made 1.3 km from the site of the kent-like notes discussed above at 0645 local time on 24 January, includes a low-amplitude, apparently distant double knock followed 3.5 s later by a higher-amplitude, apparently closer double knock. Although the sequence and cadence of this recording match an exchange between two individuals of a Campephilus woodpecker, the relative amplitude of the separate strikes in each double knock is atypical (SOM text). Additional descriptions and discussion of our acoustic data are available at [www.birds.cornell.edu/ivory/field/listening][4]. Further acoustic monitoring and field observation (including intensive efforts to record a large sample of the vocal repertoire of local blue jays) are planned for the areas where these recordings were made. 1. [↵][5]The SOM is available on Science Online at . [1]: /lookup/doi/10.1126/science.1114103 [2]: #ref-1 [3]: pending:yes [4]: http://www.birds.cornell.edu/ivory/field/listening [5]: #xref-ref-1-1 View reference 1 in text