Fish populations play a critical role in the feeding habits of seabirds. Healthy populations of fish provide subsistence to many species of birds, some of which are threatened, or in dire straits. A recent article by Philippe M. Cury and others (2011) analyzes the trophic relations between birds and fishes, and ponders on the impact of fishing on the prey of seabirds. The authors conclude that the ecosystem approach to management must put into action to allocate resources (“one-third for the birds” *) for the sustenance of bird populations and to maintain the “integrity of predator-prey interactions and marine food webs for the benefit of both natural predators and humans.” (Cury et al: 1706)
Ricardo López-Ortiz, from the Puerto Rico Department of Natural and Environmental Resources, studied the foraging and feeding habits of seabirds of the genus Sula in the Monito Islet of the Mona Channel near the island of Puerto Rico (López-Ortiz, 2009). The study (supported by UPR Sea Grant) is perhaps one of the few descriptions of the foraging habits of boobies (Figure 1; p. 115) that suggests that the feeding habits of seabirds could also serve as a mechanism for monitoring the population of epipelagic species at their juvenile and post-larval stages. Seabirds could provide (through regurgitation) samples of epipelagic fishes that could, otherwise, be difficult to obtain.
In the large scheme of things, seabirds compete with fishers, fishes, and other marine species for a number of their target preys, and thus must be factored into the management equation as Cury et al. (2011) suggests.
* – “…a practical indicator would be to maintain forage fish biomass above one-third of the maximum observed long-term biomass. The application of such a management guideline will depend upon local circumstances, such as the need to implement spatial management around breeding colonies or the conservation status of species.” (Cury et al: 1706)
Cury PM, Boyd IL, Bonhommeau S, Anker-Nilssen T, Crawford RJM, Furness RW, Mills JA, Murphy EJ, Österblom H, Paleczny M, Piatt JF, Roux J, Shannon L, and Sydeman WJ. Global Seabird Response to Forage Fish Depletion—One-Third for the Birds. Science, 23 Dec 2011: 334 (6063), 1703-1706.
López-Ortiz, R. 2009. The Diet of Masked, Brown and Red-Footed Boobies (Sulidae: Pelecaniformes) in the Mona Passage, Puerto Rico. Ph.D. Dissertation. Marine Sciences, University of Puerto Rico, Mayagüez. (Figure 1, p. 115)
Written by: Dr. Manuel Valdés-Pizzini
Edited by: J. Seda Miró