Bird of the Month: April 2002

Pelagic Cormorant

Phalacrocorax pelagicus

by David Fix

When I was a kid, going about my brand of nature study without a field guide, I often tide-pooled at Haystack Rock, a seastack at Cannon Beach on the northern Oregon coast.  While poking sticks at (colonial) pink sea  anemones and happily imprisoning innocent hermit crabs in Miracle Whip jars, I saw various nesting seabirds...all in a non-birder-ish sort of way.  One kind of bird most intrigued me.  It marked itself in my memory for nesting on absurdly small ledges high on the cliffy sides of the rock.  As a shy child, I think I must have felt a twinge of empathy for the unglamorous, seeming ‘outcasts’ at their harsh redoubts on Haystack.  I later learned I had made the acquaintance of Pelagic Cormorants. I think often of the value of simple, formative experiences such as these when doing murrelet surveys in summer.  Gazing from the boat, the slow passage of each whitewash-splotched coastal cliff decorated with Pelagic Cormorant nests brings those days back, if only dimly now.

Of the three species of cormorant breeding along the coast of the Redwood Region, the Pelagic Cormorant (Phalacrocorax pelagicus) is the smallest and most slender.  It is a sinuous blackish bird about 28 inches in length, with a wingspan of slightly more than three feet, and weighing about three or four pounds.  As well as being smaller than Double-crested and Brandt’s cormorants, Pelagics differ in having comparatively thinner necks, strikingly thin bills, and—from January to late summer—a conspicuous white patch on each flank.  Subdued red facial skin is visible at close range, as are appealing purplish and greenish highlights.  The noticeable iridescence of the adults gave rise to the old vernacular for our local subspecies, P. p. resplendens:  the ‘Violet-green Cormorant’.

How can three species of cormorants nest on the same rocks?  In what ways do their habits ensure both coexistence and separation?  Answers can readily be found with a quick look at their respective life histories.  While Brandt’s and (marine-nesting) Double-crested Cormorants each prefer to nest in fairly dense colonies on flat or sloping tops of rocks, Pelagic Cormorants place their nests only on ledges, niches, and in shallow hollows on the steepest and tallest rock faces available.  Further, they forage very near the shore, diving to the bottom to find gunnels, greenlings, sculpins, small rockfish, and crustaceans in the rough waters of the surf zone (Ainley and Boekelheide 1990, Seabirds of the Farallon Islands).  Brandt’s Cormorants spread out north and south over the innermost continental shelf, and Double-cresteds fly to freshwater or to estuaries to fish—seldom ever foraging in the ocean in our area.  By apparent family agreement, the spoils of their chosen environment are available to each bird nation, such that all may pursue life with minimal interspecies conflict and maximum efficiency.

Pelagic Cormorants are common residents, confined to the nearshore ocean coast.  A few birds regularly feed in the lower reaches of estuaries, especially in winter.  They construct compact nests of marine algae, grass, moss, and debris—all cemented to the precarious ledge with their excrement.  Three to five light blue eggs are incubated for about four weeks. Young hatch asynchronously---those without a good headstart are likely to perish as nestlings. They are fed regurgitated meals until they depart their nest sites at 45-50 days.  Following breeding, they abandon nest sites and assemble in small groups with other cormorants on offshore rocks, jetties, and breakwaters.  Pelagic Cormorants distribute themselves over the water at low density, and are never seen flying in flocks.