Today was a whale-seeking day at Boca de Soledad at the northern tip of Isla Magdalena in Baja California, Mexico. But it was also a day for hiking over the picturesque sand dunes of this area and for walking the endless beaches that front the Pacific Ocean. Those of us awaiting a second round of whale seeking ventured over the dunes and close to this huge colony of nesting Double-crested Cormorants (Phalacrocorax auritus). Scattered among the cormorants were a few stately Great Blue Herons (Ardea herodias) and skulking Black-crowned Night-Herons (Nycticorax nycticorax). The cormorants leave the colony early each morning, flying in lines and seeking concentrations of schooling fish in the calm waters of Magdalena Bay or outside the breakers of the Pacific Ocean.
Natural forces are threatening this colony, however. The warm, desert winds that prevail out of the northwest quickly dry the sand that is pushed up onto the beaches by the breakers, and then drive it into tall dunes, which march across the island. The semi-circular slip-faces of the barchan dunes are slowly but surely engulfing the mangroves on which these birds nest. Marine birds usually seek isolated islets or lofty mangroves for nesting and roosting so that they will be out of the reach of mammalian predators - in this case the coyotes that prowl the island. Perhaps in a few months, perhaps in a few years, the shifting sands will triumph. This colony of 200 or more pairs will lose its nesting "platforms" and will have to seek another stand of mangroves somewhere else. Eventually, the new colony may suffer a similar fate, as nature imposes what might appear to be unfair forces on the wildlife of a delicately balanced desert ecosystem.
