PEARL Paleoecological Environmental Assessment and Research Laboratory
Department of Biology, Queen's University, Kingston ON, Canada, K7L 3N6
Birds and other organisms such as bats, often form large breeding colonies or roosts where they can number in the tens or even hundreds of thousands. Because many species feed almost exclusively off shore but nest on land, water birds can act as potent biological vectors of nutrients from marine or aquatic ecosystems to terrestrial ecosystems. The wastes released from water bird colonies provide critical nutrient subsidies for many coastal ecosystems, often creating thriving biological communities that would not exist otherwise. An unfortunate irony is that this transport pathway also concentrates contaminants that are biomagnified and bioaccumulated through the marine or aquatic food webs, thereby threatening the very ecosystems it supports and sustains. The biological transport of contaminants by water birds is of global concern as they are the dominant form of wildlife along coastlines worldwide.
Lake and pond sediments archive a wealth of information about past water bird population dynamics (a rare commodity in most regions), and can be used to better understand the fate and transport of environmental contaminants because the water bird inputs have direct effects on downstream water chemistry, biological communities, and sediment geochemistry. Sediment cores from water bodies that take drainage from nesting sites can be used to track past water bird inputs over long timescales. They can also potentially be used to monitor for more recent impacts and new contaminants coming from the increased shipping that Arctic ice conditions now permit, for example. These are relatively new applications of paleolimnology, the science that deals with reconstructing past ecological and environmental conditions using physical, chemical, and biological information stored in sediments.
We track water bird inputs through time by analyzing lake and pond sediment cores for: (1) stable isotopes of nitrogen (δ15N), which reflect food web dynamics and trophic structure and can also be used to track marine-derived nutrients; (2) the remains of biological indicators such as algae and aquatic invertebrates, which change in response to past nutrient and/or contaminant inputs; (3) fossil pigment such as chlorophyll a, which reflects past aquatic production; and (4) contaminants, such as persistent organic pollutants (POPs) and metals, which we can link to past water bird inputs.
In some instances, the actual guano deposits can be used as the environmental archive, much in the same way as sediment cores. This is not restricted to water birds. Guano deposits from any bird species can build up over time at the base of nesting or roosting sites. These deposits create natural archives that can be sampled and analyzed for changes in diet (via insect remains, for example), or contaminants through time. Chimney swifts are one such species that leave deposits of guano and egested pellets that archive a record of diet and environmental contaminants.
The Paleoecological Environmental Assessment and Research Laboratory (PEARL), in collaboration with colleagues at the University of Ottawa, University of Alberta, Acadia University and the Canadian Wildlife Service of Environment Canada, have been developing and applying some of these approaches to studying bird populations from different regions. Follow the links below for details and publications on each project.
Click on each image below to link to a page with publications and descriptions of our various projects.