Studies in Avian Biology No. lO:l-7, 1987. GULL RESEARCH IN THE 1980s: SYMPOSIUM OVERVIEW WILLIAM E. SOUTHERN' Symposia are now a regular feature of the an- providing for mans’ environmental require- nual meetings of scientific organizations. Two ments, we must possessan in-depth understand- approaches are available for selecting themes for ing of the speciesinvolved, including their breed- symposia. The subject may be a concept, such ing biology, habitat requirements, food habits, as the mechanisms of bird orientation, and re- and long-term responses to environmental searchers working on an array of species present change. The papers presented in this symposium results tied together by the unifying conceptual contribute significantly to the development of a thread. The other option is to use a taxon as the data base that is essential for resource managers. common denominator and have the investi- In addition, many of the papers address more gators discuss a variety of concepts as they apply theoretical aspectsofbehavioral ecology for which to one or more closely related species. Both types gulls are ideal subjects because of their colonial of symposia have their advantages. The orga- nesting habits and their tendency to use nest sites nizers of the 1985 First Joint Meeting of the accessible to investigators. Pacific Seabird Group (PSG) and the Colonial Gulls as a group also have served as the sub- Waterbird Group (CWG) considered it an ap- jects of basic research that has contributed to the propriate time to review the status of gull re- formulation of many major biological concepts. search in the 1980s. Presented herein are 11 pa- Such studies have expanded our understanding pers and 10 abstracts reflecting current larid of motivational systems (Tinbergen 1953, Baer- research and the approaches investigators are ends and Drent 1970), evolutionary behavior taking. (Moynihan 1958a & b, Beer 1975), physiology Gulls stand out as appropriate subjects for con- (Tucker 1972, Howell et al. 1974), foraging be- sideration at a scientific meeting because of their havior (Andersson et al. 198 1, Curtis et al. 1985, relationship with man in the past, present and, Greig 1984, Patton 1986), territoriality (Burger more than likely, in the future. During the nine- 1984), interspecific associations (Gotmark and teenth century egging activities, the feather trade, Andersson 1980, Barnard and Thompson 1985), reduction in fish populations, use of nearshore life history strategies (see Burger et al. 1980), and islands for livestock grazing and other human a number of other subjects. Because several gull endeavors lowered gull populations in North species have been thoroughly studied, it is now America (Graham 1975). Protection in the form possible to design interesting comparative stud- of state, national and international legislation ies dealing with ecology and behavior. Even with early in the twentieth century resulted in gradual all the attention gulls have received from in- population increasesuntil about midway through vestigators, many unanswered questions remain. this century. Then there was a continent-wide The papers and abstracts presented in this vol- explosion in the population of several gull species ume provide an outstanding indication of the (e.g., Drury and Kadlec 1974, Ludwig 1974). En- directions gull research is taking and suggest ap- vironmental changes that probably made these proaches for further inquiry. population changes possible included the intro- Twenty-one species of gulls breed in North duction of forage fishes (smelt and alewives) in America and three other species regularly visit the Great Lakes, the operation of large landfills the continent (Farrand 1983). Of the five genera throughout the winter ranges of North American involved, Laws includes the largest number of gulls, construction of dredge-spoil islands, and species(19). Both species of Rissa occur here and the construction of new resting habitat (numer- Rhodostethia, Xema and Pagophila each are rep- ous ponds and reservoirs) throughout the ranges resented by one species. Several species range of some species. widely over arctic waters or are nearly pelagic in In the 1980s gull populations have become the North Atlantic and Pacific oceans. Six of the large or concentrated enough to result in conflicts 21 breeding species tend to nest in inland loca- with man. The increase in competition between tions whereas 15 species are primarily coastal gulls and man has added a practical component nesters. During the nonbreeding period, consid- to gull research. In order to develop management erable overlap occurs in the ranges of the non- strategies that are resource sensitive while also arctic species. The breeding ranges, however, are more distinct and only occasionally do more than two or three species share colony sites (Southern ’ ’ Department of Biological Sciences, Northern Illinois University, 1980, American Ornithologists ’ Union 1983). DeKalb, IL 60115. Several species of gulls are good research sub- 2 STUDIES IN AVIAN BIOLOGY jects because their colonies are relatively acces- sensitivity to these factors will result in more sible and they nest in large numbers which allow accurate data collection and analysis, and con- investigators to obtain statistically important clusions that more correctly describe how a given samples. During the last two decades alone, species is performing. (1) Gull investigators are hundreds of papers have been published about becoming increasingly cognizant of the impor- gull migration and orientation, seasonal distri- tance of long-term studies (e.g., Mills 1973, Coul- bution, breeding biology, sex ratios, ecology, food son and Thomas 198 5) which take into account habits and population size. Of the 21 species what happens throughout a particular breeding breeding in North America, 6 have received most season as well as throughout the lifespan of in- of the research attention: Laughing Gull, L. atri- dividual gulls. This is particularly applicable in cilia; Ring-billedgull, L. delawarensis; California the case of studies dealing with population trends, Gull, L. californicus; Herring Gull, L. argentatus; reproductive success and habitat selection. (2) Western Gull, L. occidentalis; and Glaucous- The project designs and methods used by many winged Gull, L. glaucescens. Others such as the researchers clearly show that they are now cog- kittiwakes (Rissa spp.), have been studied thor- nizant of the effects of investigator-caused dis- oughly in the Old World. Considerably less is turbance in gull colonies (Hunt 1972, Robert and known about others (e.g., Franklins’ Gull, L. pi- Ralph 1975, Hand 1980, Fetterolf 1983). Ignor- pixcan; Bonapartes’ Gull, L. Philadelphia; Mew ing these effects when designing or conducting a Gull, L. canus; Iceland Gull, L. glaucoides; Ross ’ study can seriously bias the data collected, par- Gull, Rhodostethia rosea; Sabines’ Gull, Xema ticularly in studies measuring chick survivor- sabini; and Ivory Gull, Pagophila eburnea). ship, parental care, aggressiveness and territo- Bents’ (1947) “Life Histories” illustrates the riality. (3) Methods of marking gulls may nature of gull research prior to the middle of this influence the accuracy of data collected and se- century. Shortly thereafter, Tinbergens’ (195 3) riously bias the outcome of a study. For example, classic study of the Herring Gull stimulated nu- Southern and Southern (1985) showed that wing merous ethological studies and field experi- markers detrimentally influence the breeding be- ments. Moynihan (195 8a & b) described the vi- havior of Ring-billed Gulls. Use of this marking sual and auditory displays of several larid species method during studies dealing with mate fidelity, and provided the types of information consid- longevity, site tenacity or other studies requiring ered necessary for an ethogram. Such studies pro- unimpeded return to the site of marking should vided us with significant descriptive information be avoided. It is no longer possible for investi- but they also caused us to de-emphasize the im- gators to discount the possibility that their ex- portance of individual differences in behavior. perimental methods may influence the behavior The fixed action pattern concept of Lorenz (see of their research subjects. Ways of avoiding such translations, 1970) left the impression that much complications must be developed during the of bird behavior was inflexible. We now know planning stages rather than attempting to work that more plasticity exists in the performance of around them statistically during the analysis stage. gull displays and the components of other be- The topics covered by this volume are some haviors than earlier investigators proclaimed. For of those having the greatest importance to larid example, gull chicks can stimulate adults to feed researchers today. The papers and abstracts are them by pecking at portions of the the bill other grouped into five subject areas: life histories, be- than the salient spot or ring that adults possess. havior, foraging, habitat selection and hybrid- Also, as parental care progresses during the nest- ization. Information of these types is accumu- ing season, experienced parents may attempt to lating gradually for most gull species. Particular feed without any begging by the chick (Hender- ones are more thoroughly studied than others but son 1975; pers. obs.). Experienced parents and sufficient data exist for a comparative approach chicks show more variability in the behaviors possibly