I relocated to NC from Oregon 2 years ago, and have my own cormorant demonization experiences from there. I will say that I have seen trees (Sitka Spruces and others) killed in as little as 2 years by guano accumulation from roosting cormorants. Of course, among the various things that kill trees, cormorants are a very minor one. In fact, in Pennsylvania browsing by deer has a far greater effect on forest health than cormorant guano.
And - when cormorants displace other colonial birds from tree colonies, the others usually do not have much trouble finding new colony locations. Maybe in areas with few trees this is significant, but not in North Carolina or Pennsylvania.
In Oregon and adjacent states a bunch of human endeavors have greatly disrupted the habitat and life cycle of Pacific Salmon, including water diversions for irrigation and domestic use, dams for hydro power, stream channelization and habitat simplification to benefit boating and shipping etc. etc. The agencies and others who benefit from these water uses have been blaming birds and other predators for salmon declines for decades, in order to deflect attention from their own actions.
And in the local context, the "Seabirds" research paper made a point of reporting their consumption estimates in Menhaden tonnage. Cormorants eat lots of kinds of fish (including Menhaden), but I doubt it was accidental that they expressed their results in terms of a species that is overfished and subject to hard management decisions.
From: "badgerboy" <badgerboy...> To: "carolinabirds" <carolinabirds...> Sent: Wednesday, January 13, 2021 12:46:46 PM Subject: Re: NC Seabirds
Please excuse the soapbox, and click "delete" now if only interested in rare bird sightings.
I checked the link provided about the cormorant killing ("culling") in PA. Very difficult to say whats going on there, but it seems likely to be a great example of exactly the kind of scapegoating I was warning about.
They start by demonizing cormorants because of their appearance and numbers, describing them as "an all-black seabird that has risen from once-obscure numbers here to a genuine pain in the butt".
They then cite vague and unsubstantiated worries about negative impacts on other wildlife, stating that "Cormorants don't take over the egret and heron nests or plunder the eggs. But they are taking up the available trees for their own stick nests" and "Moreover, studies show the droppings of cormorants can kill trees." (Emphasis my own) There seems to be no direct causal evidence of harm provided, and not even any indirect evidence that I can see.
Finally they throw in purported economic harm as a clincher, with "Certainly, cormorants have become the bane of many anglers because they eat fish. They raid fish hatcheries and commercial aquaculture operations. Their burgeoning numbers have had negative impacts on vegetation."
This one small instance of wildlife targeting is not likely in itself to have any impact whatsoever on overall cormorant numbers or ecosystem function. It might even have a very small and positive local influence on heron and egret numbers. What is problematic is the complete dismissal of any possible positive role in the ecosystem, the absence any acknowledgment that wildlife has a job to do, a valuable feedback function to perform, and the narrow focus on the negatives, which justify people's innate urge to control. I think the real danger is that public attitudes and psychology, which are already slanted against wildlife, will be reinforced and amplified by this official sanction for violence against wildlife.