Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

If you need an accessible version of this item please contact JSTOR User Support

Feeding Behavior and Ecology of the Goliath Heron

Douglas W. Mock and Karilyn C. Mock
The Auk
Vol. 97, No. 3 (Jul., 1980), pp. 433-448
Stable URL: http://www.jstor.org/stable/4085837
Page Count: 16
  • Read Online (Free)
  • Download ($15.00)
  • Subscribe ($19.50)
  • Cite this Item
If you need an accessible version of this item please contact JSTOR User Support
Feeding Behavior and Ecology of the Goliath Heron
Preview not available

Abstract

We studied the feeding methods of Goliath Herons (Ardea goliath) in Lake St. Lucia, Natal during the September-December 1977 breeding season. The herons captured very large fish (estimated mean length of 30 cm and wet weight of 500-600 g), which they impaled on their bills. In general, Goliath Herons hunted well away from the lake's edge, usually among beds of floating macrophytes. The plants probably attract greater fish populations; they also make the surrounding water clearer for visual penetration. Goliath Herons moving to new feeding sites frequently landed on the macrophytes to effect splashless entry into the water. Finally, the plant mats were used extensively by herons as a place upon which to lay struggling prey for additional killing measures. Goliath Herons are passive hunters, standing motionlessly about three-quarters of the time. They sometimes adopt very tall postures that allow deeper visual penetration during initial scanning. Prey are usually caught near the bottom of the lake and apparently struggle violently. Goliath Herons direct stabs to the fish's gill regions, presumably to stun them. The entire handling process lasts an average of 109 s, with hard-spined fish requiring more time. While thus engaged with the prey, Goliath Herons are commonly attacked by various fish-pirates. Of the captures we observed, 11% were lost during the harrassment. Only Fish Eagles (Haliaeetus vocifer) seem capable of taking fish away from Goliath Herons, but other piscivores sometimes position themselves nearby to get any unattended prey. We suspect that Fish Eagles are effective pirates because they are fast and formidable enough to pose a potential threat to the heron itself. In our study, Goliath Herons consumed an average of 2.3 fish per day, an estimated 23-34% of their body weight. It seems likely that such a low capture frequency is related to the large average prey size, a pattern we call "jackpot strategy." We conclude that the great body size of the Goliath Heron (1.5 m tall, 5 kg) is adapted to efficient handling of these profitable prey and probably not strongly related to interspecific competition with other ardeids.

Page Thumbnails

  • Thumbnail: Page 
433
    433
  • Thumbnail: Page 
434
    434
  • Thumbnail: Page 
435
    435
  • Thumbnail: Page 
436
    436
  • Thumbnail: Page 
437
    437
  • Thumbnail: Page 
438
    438
  • Thumbnail: Page 
439
    439
  • Thumbnail: Page 
440
    440
  • Thumbnail: Page 
441
    441
  • Thumbnail: Page 
442
    442
  • Thumbnail: Page 
443
    443
  • Thumbnail: Page 
444
    444
  • Thumbnail: Page 
445
    445
  • Thumbnail: Page 
446
    446
  • Thumbnail: Page 
447
    447
  • Thumbnail: Page 
448
    448