Double-crested Cormorant (Phalacrocorax auritus) 



World Breeding Range 



Double-crested Cormorants are the most 

 widespread of all cormorants in North America. 

 They are also the only cormorant in the United 

 States and Canada regularly found in freshwater 

 habitats. In California, Double-crested Cormo- 

 rants are found breeding along the coast and 

 inland near large rivers and lakes. Despite their 

 widespread breeding distribution, they are 

 probably the least abundant of the cormorants in 

 California. 



Double-crested Cormorants nest in a variety 

 of habitats. Along the coast they nest on offshore 

 rocks and islands, on abandoned wharf timbers, 

 and on power poles in coastal bays. Cormorants 

 living inland nest in trees or snags, around lakes, 

 or on islands within the lakes. They construct 

 nests of sticks or matted vegetation gathered near 

 the colony. 



Double-crested Cormorants are sleek and 

 strong swimmers that prey on shallow-water fish 

 (Robertson 1974). After their fishing sessions, 

 they are frequently seen extending their wings to 

 dry. Cormorant feathers become completely 

 saturated during underwater swimming and 

 require periodic drying (Rijke 1968). Many 

 Double-crested Cormorants which nest on coastal 

 rocks and islands feed in nearby bays and rivers of 

 the mainland. Even birds nesting as far offshore 

 as the Farallon Islands (429 012) may come to 

 the coast to feed if local food supplies are poor 

 (Ainley pers. comm.). 



CALIFORNIA COLONIES 



Double-crested Cormorant colonies are 

 located in the Channel Islands and Farallon 

 Islands and on nearshore rocks and islands north 

 of San Francisco. There are 17 coastal sites listed 

 in this catalog. The largest of these sites is Prince 

 Island (325 003) with 450 birds. Other large 

 colonies are Old Arcata Wharf (325 038) with 

 340 birds and the Farallon Islands (429 012) with 

 180 birds. The remaining 14 coastal sites have 

 150 or fewer birds. The total breeding population 

 on the coast of California now contains about 

 1,900 birds. The largest inland population in 

 California breeds near Tule Lake, Siskiyou 

 County (Kelly pers. comm.). 



HISTORICAL STATUS AND VULNERABILITY 



Populations of Double-crested Cormorants 

 on the Channel Islands may have declined in size 

 significantly since the turn of the century, but 

 numbers may now be increasing (Hunt et al. 

 1979). The reasons for the prolonged decline are 

 unknown. However, in the late 1960's and early 

 1970's pesticide contamination caused thinning 

 of eggshells of Double-crested Cormorants and 

 Brown Pelicans in the Channel Islands, 

 considerably lowering the reproductive success of 

 these two species (Gress et al. 1973). Eggshell 

 thinning in Double-crested Cormorants has also 



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