As nesting seabirds become more concentrated on a few managed colonies, nutrient inputs from their guano encourage the growth of vegetation in nesting areas. Common terns, which require a matrix of open ground and standing vegetation cover at nest sites, are rapidly losing habitat due to overgrowth of vegetation. Managers often address this problem on a case-by-case basis, with little or no formal research.
I compared the effectiveness of controlled burning and weed barriers for creating Common tern nesting habitat, assessing both vegetation characteristics and tern nesting success in treated areas, vegetated control plots, and unmodified nesting habitat.
Although burning created usable habitat at nest initiation, it quickly became unsuitable as annual plants invaded the open soil. By the time tern eggs hatched, the vegetation was too dense to allow adults to access their nests, leading to near-complete nest failure. However, weed barriers-- particularly second-hand artificial turf (AstroTurf) from miniature golf courses-- created nesting habitat with similar vegetation characteristics and tern productivity to existing habitat. Artificial turf represents an inexpensive, promising short-term solution to overgrowth and overcrowding in tern nesting areas.
I also compiled a review of vegetation management techniques and their relative effectiveness throughout the North Atlantic by surveying seabird researchers and colony managers in the Eastern United States, England, Ireland, and France. In general, researchers found that maintaining open habitat for a full nesting season required applying a barrier treatment, although the methods varied widely from landscape fabric, to gravel, to a full stone terrace.
Lamb, J.S., C.S. Hall, S.W. Kress and C.R. Griffin, 2014
Waterbirds 37: 286–297
Review of vegetation management in breeding colonies of North Atlantic terns
Lamb, J.S., 2015
Conservation Evidence 12: 53-59.
If you're interested in reading more, here's my thesis.