National Geographic

Scientists surveytightly packed nestsof guano left behindby guanay cormorantsat Punta San Juan,a peninsula in south-ern Peru transformedinto a virtual island bya six-and-a-half-foot-high concrete wall builtby the guano industryto protect the breed-ing site from preda-tors. With three or fournests per square yard,guanays are among thedensest nesting sea-birds in the world.``````NEXT PHOTOFarther north, guanaycormorants make roomfor a few Peruvian pel-icans to roost on IslaGuañape Norte, one ofPeru’s most productiveguano islands. This col-ony of over 80,000 gua-nays leaves the island atmidmorning to preen inoffshore waters beforeflying farther out to seato forage for anchovyand other prey in thePeru Current.The capes and offshore islands washedby the fertile Peru Current are hometo millions of seabirds. Their guano oncesupplied fertilizer to the world.SEABIRDS 133