Avian wildlife as sentinels of ecosystem health.

Birds have been widely used as sentinels of ecosystem health reflecting changes in habitat quality, increased incidence of disease, and exposure to and effects of chemical contaminants. Numerous studies addressing these issues focus on the breeding period, since hormonal, behavioural, reproductive, and developmental aspects of the health can be observed over a relatively short time-span. Many body systems within individuals are tightly integrated and interdependent, and can be affected by contaminant chemicals, disease, and habitat changes in complex ways. Animals higher in the food web will reflect cumulative effects of multiple stressors. Such features make birds ideal indicators for assessing environmental health in areas of environmental concern. Five case studies are presented, highlighting the use of different species which have provided insight into ecosystem sustainability, including (i) the consequences of anthropogenic disturbances of sagebrush habitat on the greater northern sage grouse Centrocercus urophasianus; (ii) the high prevalence of disease in very specific passerine species in the Canary Islands closely paralleling deterioration of formerly productive desert habitat and ensuing interspecific stressors; (iii) fractures, abnormal bone structure, and associated biochemical aberrations in nestling storks exposed to acidic tailings mud from a dyke rupture at an iron pyrite mine near Sevilla, Spain; (iv) newly presented data demonstrating biochemical changes in nestling peregrine falcons Falco peregrinus and associations with exposure to major chemical classes in the Great Lakes Basin of Canada; and (v) the variability in responses of tree swallows Tachycineta bicolor to contaminants, biological and meteorological challenges when breeding in the Athabasca oil sands.