iMi 



m'^n 



.Vv«J 



In the midst of glaciers and volcanoes, 

 Kuril Lake, below, remains ice-free all 

 winter An adult S teller's eagle, left, 

 reveals its fully mature plumage as it 

 hoists a scrap of salmon aloft. At six or 

 more pounds, whole salmon are too hefty 

 to allow even the mighty Steller's to 

 become airborne. 



six pounds and are sheathed in tough skin. 

 Unless a salmon is dead and decomposing, 

 this hide is difficult for birds other than 

 Steller's eagles to penetrate. The golden 

 and white-tailed eagles that live at Kuril 

 Lake may take hours to pry an opening 

 around a salmon's gills, front fin, or anus, 

 and for the most part, they depend on the 

 massive-billed Steller's eagles to open a 

 fish carcass. Salmon is unusual prey for 

 white-tailed and golden eagles, which in 

 most of their range, and in summer in 

 Kamchatka, prey on other birds and on 

 mammals. They have no specific adapta- 

 tions for capturing large live salmon and 

 tend instead to scavenge dead fish on the 

 gravel bars of the lake or feed on the left- 

 overs when the Steller's eagles have had 

 their fill. The existence of the golden and 

 white-tailed eagles on the salmon spawn- 

 ing ground is attributable to the presence 

 of the more brawny, fish-eating special- 

 ists, the Steller's sea eagles. 



In contrast, Steller's sea eagles are ac- 

 tive predators on the spawning ground. 

 They can catch and pull live salmon from 

 the water, but sockeye salmon carcasses 

 are simply too heavy for even Steller's ea- 

 gles to carry away, and they more often 



feed on dead fish deposited on the gravel 

 bars and icy edges of the lake. One salmon 

 is more than enough to satiate several ea- 

 gles. The birds seldom bother with rotting 

 fish being picked apart by other species of 

 raptors. While golden eagles form small 

 feeding groups of three or four members, 

 and white-tailed eagles tend to hunt alone, 

 wintering Steller's eagles are attracted in 

 great numbers to other Steller's eagles. 

 The degree of attraction and interaction 

 reaches a peak when dozens of birds con- 

 verge on a mound of dead salmon — often 

 ignoring other carcasses — and harass and 

 fight one another in an attempt to steal the 

 spoils. 



From my snow cabin, I have witnessed 

 some impressive squabbling from just ten 

 to twenty yards away. Although physical 

 injury, or even contact, is rare, the eagles 

 use a number of ritualized displays to con- 

 vey dominance, submission, and a variety 

 of moods. Wing, tail, and head displays 

 are most common. Sometimes one or 

 more eagles will stretch out their wings 

 and wave their tails to signal their determi- 

 nation to feed on a particular fish. Steller's 

 eagles and their cousins the bald eagles 

 regularly force other birds to give up prey, 

 as when a bald eagle harasses an osprey 

 into dropping its catch. Because of their 

 penchant for feeding together, Steller's ea- 

 gles also often engage in piracy and steal 

 fish from one another on the lakeshore. 

 Piracy takes place only when the fish is 

 sizable; small fish are not worth the energy 

 expended in a fight or are simply con- 

 sumed too quickly to allow piracy to 

 occur Moreover, even though its massive 

 beak enables a Steller's eagle to snatch 

 and swallow large chunks of fish, eating a 

 salmon takes a long time; before it has fin- 

 ished eating, any eagle partaking of such a 

 banquet is likely to be seen by another 

 hungry eagle. 



For a long time I wondered why the ea- 

 gles preferred robbing one another to feed- 

 ing independently, especially when the 

 lakeshore teemed with living and dead 

 sahnon. 1 now beUeve that even for such a 

 mighty bird as the Steller's sea eagle, 

 opening large, tough-skinned carcasses is 



31 



