Appeared to have been ejected by cormorants.
Bird guano comes mainly from islands off the coasts of Peru, Baja (Lower) California, and Africa heavily populated by cormorants, pelicans, and gannets.
As we sailed out of Provincetown harbour, we left the calm protected waters, passing breakwaters colonised by cormorants and lounging seals.
The rock has long since been reclaimed by cormorants and common murres, and the lighthouse is now the privately owned Eternity by the Sea Columbarium.
Indeed, there are so many yellow perch in the lake that their growth is stunted -- a sign of overpopulation -- and some biologists say their consumption by cormorants is a good thing.
Islands used by cormorants comprised a small proportion (n = 90, 3%) of the U.S. Great Lakes island resource, and < 1% of the total island area.
It is documented that high predatory pressure by cormorants can lead to a mass development of small fish species like bullhead, loach or minnow [60], which obviously was not the case at the investigated Argen River sections.
Propulsion underwater can be provided by wings (as used by penguins, auks, diving petrels and some other species of petrel) or feet (as used by cormorants, grebes, loons and several types of fish-eating ducks).
Figs 5 and 6 show two examples from this modelling using a prey item of a size (10 cm total length) commonly taken by cormorants [24], [25].
We then used these data to model the appearance of a typical target fish viewed by cormorants at a range of distances, target contrasts, and illuminations representative of those encountered by naturally foraging birds.
