THE OSPREY. 



An Illtastrateci Pvlagazine of Popialar Orn^ithiology. 



Published Ivlontlnly ©accept in July and Axagust. 



Volume 2. 



JUNE, 1898. 



Number 10. 



TERNS OF SOCORRO ISLAND. 



W. ANTHONY. 



NE of the many surprises 

 experienced in exploring 

 the R e V i 1 lagigedo Is- 

 lands the past summer 

 was the great rarity of species of 

 the order Loiii^iprnues. After 

 leaving Cape St. Lucas, where 

 only a few Western Gulls were 

 seen late in April, we met with 

 no gulls or terns until we neared 

 Socorro Island of the Revillagi- 

 io group. Socorro, the largest of this 

 ttered group of three small islands, 

 5 about 240 miles southwest of Cape 

 Lucas and 280 from Maria Madre of 

 the Tres Maria group near San Bias. 

 On May 4 as our schooner rounded the west end of 

 Socorro Island, small straggling flocks of Noddy Terns 

 were seen flying low over the water, and occasionally 

 another species with light lower parts was seen ; but 

 unlike the Xoddys, they were flying high, and with 

 harsh, scolding notes turned aside to enter vigorous 

 protest at the unprecedented intrusion upon their do- 

 main. 



As we ran down the rocky, broken coast of the west 

 end of Socorro both species became more and more 

 abundant, the flocks all radiating toward a low, flat- 

 topped rock lying about a mile off the southwestern 

 end of the island. Above this rock thousand.s of terns 

 were hovering, their nests well protected by the angry 

 breakers that dashed about the perpendicular walls 

 from all sides. Anchoring in a small rocky cave near 

 the southwestern end of the island — which cave, by 

 the way, I would advise future explorers to avoid 

 unless they want to walk home — we pulled in the surf 

 boat to the tern rookery on May 6, and obtained a 

 nearer view. Thousands of angry birds met us half 

 way and escorted us to the rock with anxious cries. 



Several specimens of each species were shot, the 

 lighter species proving to be the race of the Sooty 

 Tern described by Prof. Baird as crissa/is, but not 

 recognized by recent authors. It is quite probable, 

 however, that the form will eventually be recognized 

 as perfectly distinct. The Noddys taken have since 

 formed the basis for the new sub-species ridgwuyi. As 



we neared the nesting ground a pair of Red-billed 

 Tropic birds joined the mob of scolding Terns, add- 

 ing their shrill pipe to the chorus, and one of them 

 paid the penalty for his boldness. Arriving at the 

 rock we examined all likely landing places, and al- 

 though the sea was unusually quiet, we found a heavy 

 swell dashing against the face of the rock, which rose 

 direct from the water from seven to thirty feet, and 

 landing seemed out of the question. 



On May i we left the south side of the island, in- 

 tending to visit the north coast where a favorable 

 anchorage had been discovered on the ist. We were 

 becalmed, however, and day-break of the 12th found 

 us but a stone's throw to the leeward of the terns' 

 rock. The sea was as placid as a mill pond, and the 

 landing apparently easy ; but when Mr. McGregor 

 and I attempted it a few moments later, we discovered 

 it was a decidedly hazardous undertaking, the swell 

 threatening to crush the boat against the rock or 

 swamp it with water thrown back from the ledges. A 

 landing was accomplished, however, and the entire 

 top of the rock, some 300 feet by 100 feet, was found 

 to be fairly covered with birds and eggs. Many of 

 the Sooty Terns were still setting on single eggs laid 

 on the bare rock, and several birds were easily caught, 

 as they would not fly until forced to do so. On all 

 sides were seen hundreds of young in various stages 

 of growth, ranging from those just hatched to a few 

 showing feathers through the down and nearly as 

 large as their parents. At our approach the young 

 scurried for shelter under overhanging rocks or into 

 corners between the boulders of lava, as many as 

 fifteen or twenty sometimes trying to hide under a 

 rock no larger than a man's hat. In the depressions 

 between the rocks were windrows of addled eggs 

 which had rolled there from the nests above. 



The most of the Ridgway's Noddys were nesting 

 on the north and east sides of the rock, each incubat- 

 ing a single egg laid on the bare rock, often on a shelf 

 but little larger than the egg which was so nicely bal- 

 anced that it was a wonder that it was not rolled ofif 

 into the sea. Hundreds of large crabs shuffled about 

 in every direction, and the well-picked bones of dead 

 birds, as well as empty egg shells, bore testimony as 

 to their bill of fare. 



