New developments in tracking changes in bird populations
Our recent studies have been showing how bird populations have been changing over time using lake sediment cores as archives. This research is showing promising new approaches for conservation biology and wildlife management.
One of the main challenges in wildlife conservation biology is to understand what factors affect vulnerable populations. Often, wildlife population surveys are limited and only extend back a few decades at most, challenging our ability to understand what factors affect populations over time. These problems are most pronounced in remote areas like the Arctic, where wildlife monitoring is limited. For example, the population of the common eider, a seaduck long sought by Inuit for its meat and down, once numbered in the millions in the Eastern Canadian Arctic-Greenland region, but reports by northerners and some wildlife surveys suggested substantial reductions by the late 20th Century. By contrast, cormorant populations in in the Great Lakes has seen a resurgence, likely because of measures to reduce industrial pollution.
Our lab is working to develop new ways to track how water bird populations have changed over time, and even when birds first colonized certain areas.
Our method involves taking lake sediment cores from small lakes and ponds on islands near the nesting bird colonies. Over time, sediments slowly accumulate at the bottom of lakes, archiving a detailed history of biological and chemical changes in those lakes, much like tree rings reveal historical information. When birds colonize a new area, they begin to fertilize the local environment, changing the nutrient levels in the water. In recent years, we have been discovering new and more sensitive ways to detect how birds alter the environment where they nest, allowing more detailed historical interpretations of how and when bird populations increased or collapsed.
By examining a range of chemical compounds recorded in pond sediments, including sterols, stanols, bile acids, and stable isotopes of nitrogen and carbon, we found evidence that common eider populations in Hudson Strait near Cape Dorset, Nunavut, collapsed in the mid to late 20th Century, during a period of intense hunting pressure by Greenlanders and the relocation of nearby Inuit communities.
In another recent study, we confirmed that pond sediments were able to record the dramatic increase in cormorant populations recently observed in Lake Ontario.
This technique of using lake sediment cores to reconstruct the history of bird colonization and population changes will allow us to determine how colonial bird populations responded to environmental stressors like hunting, chemical contamination, and climate change, and will have applications for wildlife management and conservation.
Collecting a lake sediment core on East Brother Island, Lake Ontario, near a cormorant colony.
Photo: Chip Wesseloh
