the humboldt current system of northern and central chile - figema

THE HUMBOLDT CURRENT SYSTEM OF NORTHERN AND CENTRAL CHILEconditions), would be most likely to decline in numbers. In order to develop the models to testthese predictions, a long-term research programme is necessary to assess (1) breeding populations,(2) feeding ecology, (3) reproductive biology and (4) energy budgets, under different environmentalconditions. In particular, it appears to be important to examine the breeding biology of seabirds.There is an indication that populations of seabirds in northern and central Chile may be limited bythe availability of undisturbed breeding islands (see Schlatter 1984, 1987, Schlatter & Simeone1999). While additional research is necessary, present knowledge already identifies the protectionof undisturbed breeding sites as one of the highest priorities for seabird conservation in the HCSof northern and central Chile.Sandy beachesSandy beaches are a common feature of the Chilean coast between 18°S and 41°S (Figure 9), wherethey offer breeding habitats and important food resources for migrating shorebirds. The extent anddistribution of sandy beaches offers unique opportunities for studying the factors driving thepopulation dynamics of invertebrate consumers along the coast of northern and central Chile.Beaches are found along exposed shorelines, sheltered bays and coastal islands and their total extentand average length show a clear latitudinal trend, increasing toward southern-central Chile(Figure 9). Sandy beaches of the coast of Chile show a general zonation pattern of three zones thatdiffer both in their physical characteristics and biological communities (Figure 10) (Jaramillo 1987,Average distancebetween beaches (km)Average lengthof beaches (km)Total extentof beaches (km)6 4 2 0 6 4 2 0 300 200 100 0−18°−20°−22°−24°−26°−28°−30°−32°−34°−36°−38°−40°−42°Southern latitudeA B CFigure 9 (A) Average distance (mean ± standard error) between beaches, (B) average length of individualbeaches, and (C) total extent of sandy beaches within each sector; individual sectors correspond to the coastlinebetween two subsequent degrees of latitude (information extracted from GOOGLE-EARTH, a total of 810sandy beaches were measured between 18°S and 42°S).227