þÿ<html> <head> <meta name=Title content="SURMAN, C"> <meta name=Keywords content=""> <meta http-equiv=Content-Type content="text/html; charset=unicode"> <meta name=ProgId content=Word.Document> <meta name=Generator content="Microsoft Word 11"> <meta name=Originator content="Microsoft Word 11"> <link rel=File-List href="37_2_129-138_files/filelist.xml"> <title>SURMAN, C</title> <style> <!-- /* Font Definitions */ @font-face {font-family:"Times New Roman"; panose-1:0 2 2 6 3 5 4 5 2 3;} @font-face {font-family:Arial; panose-1:0 2 11 6 4 2 2 2 2 2;} @font-face {font-family:"MS Mincho"; panose-1:0 0 0 0 0 0 0 0 0 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {margin:0in; margin-bottom:.0001pt; font-size:12.0pt; font-family:Arial;} table.MsoNormalTable {font-size:10.0pt; font-family:"Times New Roman";} @page Section1 {size:8.5in 11.0in; margin:1.0in 1.25in 1.0in 1.25in;} div.Section1 {page:Section1;} --> </style> </head> <body bgcolor=white lang=EN-US style='tab-interval:.5in'> <div class=Section1> <p class=MsoNormal><span lang=EN-CA style='font-family:"Times New Roman"'>SURMAN, C.A. &amp; NICHOLSON, L.W. 2009. The good, the bad and the ugly: ENSO driven oceanographic variability and its influence on seabird diet and reproductive performance at the Houtman Abrolhos, Eastern Indian Ocean. <i>Marine Ornithology</i></span><span lang=EN-CA style='font-family:"Times New Roman"'> 37: 129 138.</span></p> <p class=MsoNormal><span lang=EN-CA style='font-family:"Times New Roman"'>&nbsp;</span></p> <p class=MsoNormal><span lang=EN-CA style='font-family:"Times New Roman"'>Each spring/summer more than a million pairs of seabirds breed at the Houtman Abrolhos, Western Australia, the most significant seabird breeding site in the Eastern Indian Ocean. The southward-flowing Leeuwin Current is the dominant oceanographic feature influencing the region, in conjunction with the northward-flowing Leeuwin Undercurrent and the Capes Current. Seabirds at the Houtman Abrolhos are reliant wholly upon marine sources of food, and several species feed predominately upon larval ichthyoplankton species, the availability of which has been found to play a pivotal role in their reproduction. We conducted a comparative study of the timing of breeding, breeding participation and reproductive success over a 17-year period of four tropical pelagic seabird species in relation to the regional oceanographic conditions affecting the Leeuwin Current. Three tern species, the Lesser Noddy <i>Anous tenuirostris</i></span><span lang=EN-CA style='font-family:"Times New Roman"'>, Brown Noddy <i>A. stolidus</i></span><span lang=EN-CA style='font-family:"Times New Roman"'> and Sooty Tern <i>Sterna fuscata</i></span><span lang=EN-CA style='font-family: "Times New Roman"'>, and the Wedge-tailed Shearwater <i>Puffinus pacificus</i></span><span lang=EN-CA style='font-family:"Times New Roman"'> comprised our study species at the Houtman Abrolhos between 1991 and 2007. The diet of these species was also investigated between 1991 and 2000. Life-history traits determined the response of these seabirds to fluctuations in marine resources caused by variation in the flow of the Leeuwin Current. During El Niño Southern Oscillation (ENSO) events, reproductive effort and output were severely reduced in all species, which coincided with reduced volumes of key prey species in regurgitates. Between 1991 and 2000, ENSO driven changes in the Leeuwin Current resulted in lower participation rates and reduced breeding success or catastrophic breeding failure for all four seabird species and delayed timing of breeding for the tern species. Between 2000 and 2007, the relationship between each ENSO event and a subsequent poor reproductive season was not as strong. Increasing years of poor breeding performance were recorded outside El Niño periods, accompanied by a significant seasonal delay in the onset of breeding in the three tern species. Based on our seabird observations, we postulate that in recent years the high number of ENSO events have resulted in a regime shift in offshore and oceanic planktonic food chains off central Western Australia. The use of seabirds as an upper-trophic-level indicator of change in marine productivity as a result of variability in the Leeuwin Current system is discussed. The possibility that tropical seabirds in the region are adapting to a new suite of prey, dictated by a Leeuwin Current system which is influenced by more frequent ENSO events, is also discussed.</span></p> </div> </body> </html>