University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Symposium on Double-Crested Cormorants: Population Status and Management Issues in USDA National Wildlife Research Center the Midwest Symposia December 1997 The Problems of Being Successful: Managing Interactions Between Humans and Double-Crested Cormorants Douglas Siegel-Causey Follow this and additional works at: https://digitalcommons.unl.edu/nwrccormorants Part of the Ornithology Commons Siegel-Causey, Douglas, "The Problems of Being Successful: Managing Interactions Between Humans and Double-Crested Cormorants" (1997). Symposium on Double-Crested Cormorants: Population Status and Management Issues in the Midwest. 3. https://digitalcommons.unl.edu/nwrccormorants/3 This Article is brought to you for free and open access by the USDA National Wildlife Research Center Symposia at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Symposium on Double- Crested Cormorants: Population Status and Management Issues in the Midwest by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Symposium on Double-Crested Cormorants 4 Managing Interactions Between Humans and Double-Crested Cormorants Keynote Address The Problems of Being Successful: Managing Interactions Between Humans and Double-Crested Cormorants By Douglas Siegel–Causey Abstract: The natural history, behavior, and ecology of economic impact is greatest with aquaculture and least in double-crested cormorants (Phalacrocorax auritus) predis- sport fisheries. Research during the past 5 years suggests pose this species for conflict with human sport and commer- that some control methods like culling and egg spraying are cial fisheries. Cormorants breed early in life, have large effective but must be balanced against the actual impacts on broods, are efficient predators even in marginal conditions, humans. seem to be able to adjust colony sizes quickly in response to local conditions, and have limited requirements for feeding Keywords: aquaculture, conflict, diet, double-crested and nesting habitats. A survey of the past history of suc- cormorant, feeding ecology, fisheries, natural history, pests, cesses and failures in managing cormorants reveals that Phalacrocoracidae, Phalacrocorax auritus, management This paper is meant to provide a brief look into the our world with the diversity of birds, and most would natural history, behavior, and conservation ecology of agree that this would be a drab and dismal world an increasingly common water bird of continental North without them. America and to examine how these aspects place it in Those birds achieving the rare status of a prob- conflict with human activities. I will partially survey the lem species have, therefore, done so by factors that history of successes and failures in how humans have are entirely extrinsic and anthropocentric. That is, a dealt with double-crested cormorants (DCCO’s) as a pest is acknowledged as such by human perceptions problem species and review some of the developments based on many personal assessments of sociological in approaches undertaken in the past 5 years since the and economic value, desirability, and even beauty. I 1992 symposium on this topic held in Oxford, MS, that think that most people would agree that neither these was sponsored by the Colonial Waterbird Society nor other such criteria are the result of evolutionary (Nettleship and Duffy 1995). Finally, I will provide selection or ecological process but instead are a some insights that may help alleviate the impact of consequence of human activities, culture, and behav- current and future problematic consequences of ior. Where human perceptions and natural history human activities on the natural activities of the DCCO. clash, the conflicts usually result in severe impacts on From the beginning, the scientific and popular individuals and populations of the pest species— literature on cormorants has been dominated by sometimes to its ultimate detriment. practical and domestic topics of management and pest There is a fairly extensive literature associated control, which relate ultimately to the ubiquity of these with the issues of pest or problem species (see Kellert birds, their natural history and ecology, and their 1985 and Wagner and Seal 1992 for helpful reviews), proximity to human activities. Of the roughly 10,000 and there have been several recent symposia dealing species of birds, only a few have achieved the status specifically with human–cormorant conflicts (Nettleship of pests. Depending upon the gaze of the beholder, and Duffy 1995, van Eerden et al. 1995). This paper most are seen as being critical components of local will serve instead as a survey of those aspects of ecosystems, as unique subjects for scientific investiga- DCCO biology that create conditions for pestiferous tion, or as pleasant components of the natural world. status and as an introduction for the following papers Even those of us with little interest in environmental which focus on developments, positive and negative, issues or wildlife ecology seem to appreciate sharing that have occurred in the past 5 years. 5 Symposium on Double-Crested Cormorants Cormorant Systematics and wide (except in polar regions), and often far inland Evolutionary Relationships following major freshwater drainages. The Family Phalacrocoracidae has long been Cormorants and shags (Phalacrocoracidae) are the considered to be a homogeneous group. Recent most successful family of the Order Pelecaniformes systematic study revealed instead that there are two and comprise at least 35 species worldwide. Birds of well-defined groups in the family: cormorants and this family are generally found near coastal and shags (Siegel–Causey 1988). Shags characteristically nearshore waters, and they are common dwellers in are compact, offshore foragers that are flat- and cliff- marine and freshwater littoral habitats. They are nesting birds with fair flight abilities. By contrast, restricted from oceanic habitats chiefly because of their cormorants can be generalized as heavy-bodied, unique wettable plumage, a feature well suited for deep-feeding near-shore foragers that prefer flat- and underwater pursuit of shallow-bottom-dwelling fish but tree-nesting and have indifferent or labored flight. one that requires perching sites for drying and thermo- There are four taxonomic groups within cormo- regulation. Consequently, members of this group are rants (fig. 1): the microcormorants (“Little”), the marine found along most of the productive coastlines world- cormorants, the macrocormorants (“Great”), and the Cliff Subantarctic Inland Great Blue-eyed Marine Guanay Little “Shags” “Cormorants” A Phalacrocoracidae Pied Indian Double-crested Neotropic European Japanese “Inland” “Great” B Cormorants Figure 1—Phylogenetic relationships of cormorants. A = genera of varius), indian cormorant (P. sulcirostris), double-crested cormorant (P. shags and cormorants; B = species of inland and great cormorants. auritus), neotropic cormorant (P. brasilianus), European or great Latin names of cormorant species are pied cormorant (Phalacrocorax cormorant (P. carbo), and Japanese cormorant (P. capillatus). 6 Managing Interactions Between Humans and Double-Crested Cormorants mesocormorants (“Inland”)(Siegel–Causey 1988). The extending from Tierra del Fuego to Canada, from the latter group is composed of entirely black or dark birds Atlantic and Caribbean shores to the Pacific and, with having broad geographic distributions. With a few the great cormorant (P. carbo), are undoubtedly the exceptions, these are the only members of the family most studied members of the family (Lewis 1929, to inhabit the continental interiors extensively. The Mendall 1935, Palmer 1962, Hatch and Weseloh mesocormorants include two of the most common 1999). cormorants of the New World: the olivaceous cormo- The DCCO is commonly considered to comprise rant (Phalacrocorax brasiliensis) and the DCCO. six allopatric breeding populations that serve as the These two species have complementary distributions basis for the current taxonomy of five subspecies (see 5 ★ ★★★ 2 ★ 6 ★ 1 Breeding Pairs/ 1° × 2° Quadrangles ★ >10,000 5,001–10,000 3 4 500–5,000 < 500 Figure 2—Populations of double-crested cormorants: 1 = Atlantic Salvador, 5 = Alaska, and 6 = west coast. The symbols indicate (northeast coast), 2 = Interior, 3 = Florida and Caribbean, 4 = San numbers of breeding pairs in 1:250,000 quadrangles (1°N. by 2°W.). 7 Symposium on Double-Crested Cormorants Siegel–Causey and Litvinenko 1993, Hatch 1995, and Natural History and Behavior of Hatch and Weseloh 1999 for greater detail). P. a . DCCO’s auritus, the nominal race, is found throughout most of interior and northeast North America. P. a. albociliatus Nests and pestilence are terms essentially relating to breeds extensively on the west coast of North America human interactions, although there is some biological up to southern British Columbia. P. a. cincinatus is justification for using these terms to characterize found from southern British Columbia up to Alaska. DCCO’s. Several features can distinguish biological P. a. floridanus is found in the eastern gulf coast pests, including the following nonobjective anthropo- regions, eponymously in Florida. And P. a. heuretus, centric criteria: overabundant populations, rapid resides on San Salvador Island and other islands of population growth, noisome behavior, impacts on the Caribbean (fig. 2). Most of the populations