Research Interests -

Research Interests - Peter C. Frederick

I am interested in the ecology and conservation of wetlands, and particularly of wetland vertebrates. These creatures are adapted to environments that are extremely productive, yet often very unpredictable, and whose nutrient cycling is completely different from terrestrial, oceanic or lacustrine environments. The field of wetland science is dominated by studies of energetic flow, plant ecology, and nutrient flux, in which wetland vertebrates are often assumed to play minor roles. Yet animals, even vertebrates, are often key in the healthy functioning of these ecosystems, and the conservation and restoration of these ecosystems depends strongly upon an understanding of how larger animals use them, especially in terms of movement behavior, foraging ecology, and reproduction. For vertebrates, this often requires understanding various aspects of ecosystem function at once, and often at regional and international scales. In my research program, wetland birds have been used intensively and extensively as indicators of ecosystem health, ecosystem function, and as guides for the spatial and temporal scale at which conservation and restoration should occur. My work has included vertical studies of long-legged wading birds in the Everglades (health, reproduction, foraging ecology, energetics, flight behavior, communication, movements, demographics, feedback nutrient loops), comparisons of ecosystems (Everglades, Miskito Coast, Okavango Delta, Brazilian Pantanal), measuring anthropogenic effects (human disturbance, nutrient pollution, powerlines, construction, contaminants), multidecadal studies of population dynamics and movements, and ecosystem/regional planning for conservation.

Examples of current and recent research projects:

Long-term dynamics of wading bird populations as indicators of ecological change. Using a combination of aerial and ground search techniques, myself and my research team have systematically monitored nesting by wading birds during the past 15 years in the 1,300 square miles of the freshwater Everglades, where over 90% of the wading birds nest. This work has included studies of reproductive success, nesting effort, survival of young, and energetics. Along with information on nesting effort by wading birds begun in the 1930's, the resulting database provides a rare glimpse at how wading bird populations have changed in size, location, timing and success as a result of structural changes in the hydrology of the Everglades. For example, we have demonstrated a strong link between severe droughts and exceptionally large nesting events in the Everglades, underscoring the need to retain natural fluctuations in hydrology in the restored ecosystem. This information collectively has helped to provide a roadmap for restoring wading bird populations, and has aided in devining the historical hydrological functioning of the marsh.

Colony of Wood Storks in the Everglades, 2000

Consequences of methylmercury contamination on wading bird reproduction and survival. In this 7-year project, we have used a combination of lab and field studies to investigate the effect of ambient methylmercury contamination levels in the Everglades on health, survival and reproduction of wading birds. This work has demonstrated significant effects of mercury on appetite, production of red blood cells, disease immunity, blood and liver enzyme chemistry, and behavior of young. We have also identified a critical period for mercury exposure that occurs as birds have finished growing feathers and are fledging. This work has led to a re-examination of current effects assessment for piscivorous birds. We have also established dose response curves for several tissues of wading birds, allowing us to monitor mercury exposure through nondestructive sampling of the feathers of young birds. This process has allowed us to identify a 73% decline in mercury exposure between 1994 and 2000, thought largely to be a lagged effect of regulatory reductions in mercury emissions in municipal waste incineration in the Miami metropolitan area.

Reproductive endocrinology of White Ibises. Endocrine events in avian reproduction are represented by studies in a very few, mostly temperate species. White Ibises are both nomadic and explosive breeders, with a subtropical and tropical distribution, and it is unclear how species like the ibises use external cues and internal mechanisms to come into reproductive condition. PhD student Julie Heath is working out the endocrine and physiological events that lead up to breeding in ibises, using the Everglades as a study area. This work may help us to answer why a large proportion of birds in the Everglades do not come into reproductive condition in many years, when resources need to be available to stimulate breeding, and whether environmental contaminants such as mercury are having an effect on the ability of birds to come into reproductive condition.

Effects of ecotourism on wading bird reproduction in the Brazilian Pantanal. This project was initiated by Shannon Bouton, who experimentally measured strong disruptive effects of ecotours in and around a large wading bird colony. The interesting part of this work was that the birds showed no behavioral reactions to ecotours - yet later abandoned nesting in far higher proportions than undisturbed birds. This work has led to a socioeconomic analysis of the use of wading bird colonies by people, and a followup study of the birds responses to changes in tourist visitation protocol.