29th annual Colonial Waterbird Meeting

Last week was the 29th annual meeting of the Great Lakes Area Working Group on  Colonial Waterbirds (GLAWGCW). Having just recently begun my own research on colonial waterbirds in the the Great Lakes, this was my first year in attendance. Overall, it was a great experience because I was able to meet other biologists working on similar research and the meeting provided a platform to  share our work and discuss important population trends for colonial birds in the lower Great Lakes.  And I have to say that I find considerable satisfaction in knowing that some old bearded biologists have dedicated the last several decades to colonial waterbird monitoring in the Great Lakes.



Colonial waterbirds are birds that nest in groups (colonies) and are dependent upon aquatic environments at some point of their lives for food or nesting habitat. Some of the major colonial waterbirds of the lower Great Lakes include, double-crested cormorants, ring-billed, herring, and blackbacked gulls,  common and caspian terns, black crowned night herons, and great white egrets. Some of these colonies range from the very small (2 black crowns), to the very large (5,000+ cormorants).

There are many hypothesized advantages to nesting in colonies. One explanation is that colonial nesting developed as an evolutionary response to a shortage of available nesting sites. Another explanation is that it is a predator avoidance strategy - nesting in large numbers decreases the likelihood of any individual to be depredated.

In the Great Lakes basin, historic numbers of colonial birds have fluctuated widely. Many species experienced sharp declines in the 1960's and 70's, when many contaminants were released unchecked into the Great Lakes. Other causes for populations perturbation include, habitat loss or alteration, species competition, exotic species introductions, and resource limitations.

Common tern pair. St. Lawrence River

Common tern populations experienced a significant decline during the middle-to-late part of the 20th century. Their population went from an estimated 15,000 pairs in the 1950, to less then 5,000 in 1980. It was during this period that the more generalist gulls were able to adapt more quickly to the increasing human population. And as the larger bodied gulls increased, they began to out-compete terns for nesting substrate.

Cormorants have also undergone similar perturbations, yet they have recovered much better then terns in recent decades. Populations in the Great Lakes were thought to have crashed in the 1960's primarily due to inceasing levels of DDT. Once DDT was banned in the early 70's, the population began to recover quickly and today there are over 45,000 breeding pairs of cormorants in the lower Great Lakes//St. Lawrence river.  Anglers often blame the increasing cormorant population for the recent fisheries decline, but this may be unfair. As the population continues to increase, its hard to say that they are limiting available resources. Fishermen fail to realize they may also be a part of the problem.

Cormorant colony. Lake Ontario

These, and many other issues were discussed at  the waterbird meeting. I am already looking forward to next year because we have a plan to assess the impact of the Deep Horizon Oil spill on Great Lakes breeding birds that overwinter in the Gulf of Mexico. Stay tuned for that information.