Priorities for Future Research

For such a familiar and much-discussed species, there are substantial gaps in available knowledge. In addition to those already mentioned, 8 priority topics reflect different interests (the numbers follow the sequence of this account and are not ranks):

1. The genetic distinctiveness of the diverse populations and the extent of gene flow are prime targets for the modern tools of population genetics, combined with field observations. This information is an important basis for regional management.

2. Cormorant species are most distinctive in the colors of eye, face, and throat, yet the significance of these bright colors has not been studied in the field.

3. For clearer understanding of local impacts on prey populations and ecosystem dynamics, it will be important to know more about foraging behavior (including range and diving performance) and predator-prey interactions at different scales.

4. Anatomical and physiological adaptations and constraints for diving are worthy of study, and measures of field metabolic rates will contribute to improved estimates of fish consumption.

5. Study of cormorants killed during management activities, especially banded birds of known age, would yield useful information on molt and maturation.

6. For population modeling, and to develop life tables, numerous parameters need to be established reliably. Winter survival and distribution of nonbreeding birds are notably poorly understood. An extensive banding program coupled with intensive long-term study of marked individuals will be required. Although difficult to study because so sensitive to disturbance, cormorants may readily habituate (Mendall 1936) and become rewarding subjects. Modern analyses of existing banding records would be rewarding.

7. Coordinated rangewide censuses will enable the size of breeding populations to be tracked; at present major sections are poorly known, notably Manitoba, Florida, and Mexico.

8. Better understanding of the conflicts requires careful design of studies, including experimental manipulations to quantify impacts, as well as to develop new nonlethal methods of population control that minimize conflicts: by changing stocking procedures, by dispersing the birds, or by reducing their take of fish.

For additional suggestions of research needs and divergent views of goals, see Erwin 1995 and Nisbet 1995; and for opinions of midwestern wildlife managers, see Weseloh and Lewis in press .