Cormorants are famously controversial and, as with crows, large numbers are culled by fishermen mainly but also conservationists (illegally culled in Scotland, where salmon fisheries matter more than bird welfare). But the most widespread culling is in America so why would Labradoran cormorants make their nests conspicuous with gew-gaws? Can they not un-learn behaviour?
The situation in North America is reminiscent of the passenger pigeon story. In the 19th century there were huge numbers
...after birdwatching near Natchez, Mississippi, in December of 1820, John James Audubon reported: “We saw to day probably Millions of those . . . Cormorants, flying Southwest—they flew in Single Lines for several Hours extremely high.”
By the 20th century numbers were small enough for the species to be officially endangered until some protection was allowed (though wider measures such as the banning of DDT were more effective) and nesting sites were, inadvertently, provided by engineering projects to stabilise small islands. Artificial islands in distant lakes have recently been built to lure them away from fish stocks.
Artificial islands for cormorants rings a bell. The difference seems to be the islands were intended to be visible.