Preliminary Assessment of Avian Stomach Oils: A Vector of Contaminants to Chicks and Potential for Diet Analysis and Biomonitoring KAREN L. FOSTER,* ,† SHIWAY W. WANG, ‡ DON MACKAY, § MARK L. MALLORY, | AND JULES M. BLAIS † Program for Chemical and Environmental Toxicology, Department of Biology, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada, Sedna Ecological, Inc., P.O. Box 74280, Fairbanks, Alaska 99707, Centre for Environmental Modelling and Chemistry, Trent University, Peterborough, Ontario K9J 7B8, Canada, and Canadian Wildlife Service, Environment Canada, Iqaluit, Nunavut X0A 0H0, Canada Received March 29, 2010. Revised manuscript received July 10, 2010. Accepted July 15, 2010. Bird species from the order Procellariiformes or petrels, including the northern fulmar ( Fulmarus glacialis), produce high lipid and high energy content stomach oils from the prey they consume, which enables them to exploit distant marine food sources. Stomach oils are also used as a food source for chicks and for defensive purposes. Samples of stomach oils from two Arctic colonies, St. George Island Alaska, USA and Cape Vera, Devon Island Nunavut, Canada, were collected and analyzed for organochlorine contaminants. ΣPCB concentrations ranged from 13 to 236 ng g -1 wet weight (ww) and ΣDDT concentrations from 5 to 158 ng g -1 ww and were similar in both sites, though differences in chemical signatures were apparent. Stomach oils are a rich energy source; however, they may also provide a higher dose of contaminants per unit energy than the direct consumption of prey items, as illustrated using mass and energy balance calculations to estimate chick exposure to ΣDDT for hypothetical stomach oil and whole prey diets. The results of this study suggest that stomach oils are an important vector of organochlorine contaminants to chicks and should be considered in future risk assessments of northern fulmars and other species of petrels. To our knowledge this is the first study of stomach oils as an overlooked vector of organochlorine contaminants to chicks and as a potentially valuable medium for dietary analysis and noninvasive biomonitoring both of petrel dietary exposure and of marine contaminant concentrations. Introduction Avian stomach oils are a readily transportable form of energy- rich food that enables certain species of seabirds to exploit distant, often pelagic, food supplies and return to the nesting site with a source of energy both for themselves and their nest-bound young (1, 2). Stomach oils are produced by both male and female adults and chicks of most species from the order Procellariiformes, commonly referred to as tubenoses or petrels. This order contains 108 species and includes a broad range of seabirds including diving petrels, storm petrels, albatrosses, shearwaters, and fulmars - the northern fulmar (Fulmarus glacialis) is the subject of this study. Petrels are the most widely distributed order of birds, with species occurring in all oceans from the Arctic to the Antarctic (1, 2). Stomach oils are produced from prey items in an organ, the proventriculus, or glandular stomach (Figure 1 3-7). In the proventriculus the oil fraction of the partially digested prey (chyme) is concentrated and retained longer than the aqueous fraction due to slower rates of gastric emptying, enabling oils to be accumulated (8, 9). Components in the chyme are partitioned between the oil and aqueous phases based on relative water-lipid solubilities (8). This process concentrates the energy density of stomach oils by a factor of 5 to 35 over that of the prey items from which they were produced, making them a highly concentrated and readily transported food source (7, 10). Indeed, the average energy density of over 30 stomach oil samples representing 11 different species of petrel was 40 kJ g -1 (39.2 kJ g -1 for northern fulmars (10)), consistent with the energy density of pure fat (40 kJ g -1 (11)). In addition to being a source of energy to feed both themselves and their young, stomach oils are also used for defensive purposes. For example, fulmars will expel stomach oils during agonistic interactions with conspecifics for nest sites and as a defense against predators (12, 13). In some cases the oil-laden plumage of the intruder will render it unable to fly, decrease plumage water repellency, or decrease its ability to thermoregulate possibly resulting in death by drowning or hypothermia (7, 14, 15). The benefits to chick health and development of con- suming stomach oils provided by the parents have been well documented (7, 16). Similarly, the composition of stomach oil has been well-studied and is known to consist of a mixture of hydrocarbons, wax esters, various acylglycerols, alcohols, cholesterols, and free fatty acids (3-5, 10, 17, 18). The fatty acid signatures of stomach oils correspond to those of prey items, thus enabling diets to be determined. This use of stomach oil fatty acids as a qualitative indicator of diet has been investigated and applied to northern fulmars and other petrel species (19-22). However, in addition to concentrated * Corresponding author e-mail: kfoster411@gmail.com. † University of Ottawa. ‡ Sedna Ecological, Inc. § Trent University. | Environment Canada. FIGURE 1. Location of the avian proventriculus, the site of stomach oil formation. Environ. Sci. Technol. 2010, 44, 6869–6874 10.1021/es1009983  2010 American Chemical Society VOL. 44, NO. 17, 2010 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 6869 Published on Web 08/13/2010