PART II. SOOTY TERN STUDIES 
A. Sooty Tern Populations 
No census of sooty terns (Sterna fuscata) could be conducted 
at Midway this year because of the disturbance caused by a killing 
program designed to discourage the nesting of these birds on Sand 
Island. Populations during the 1958 season appeared to be approxi- 
mately the same as during the 1957 season -- about 150,000 birds on 
each island. 
The following rough estimates of breeding populations of 
sooty terns on the islands in the western half of the Leeward Chain 
are based on ground observations at Kure, Midway, and Laysan, and on 
aerial observations at Pearl and Hermes Reef and Lisianski: 
Kure Atoll Oo 
Midway Atoll 300, 000 
Pearl and Hermes 
Reef 50,000 
Lisianski Island 150,000 
Laysan Island 500,000 
Total 1,000, 000 
Elsewhere in the Hawaiian Archipelago, smaller colonies 
breed on French Frigate Shoals, Necker, Nihoa, Moku Manu, and Manana. 
The entire Hawaiian population is conservatively estimated as well 
over a million. The species is abundant and widespread throughout 
the tropical Pacific, Indian, and Atlantic Oceans. 
On Sand Island, Midway Atoll, clearing operations along the 
north side of the east end of runway 6-24 reduced to bare sand a large 
portion of the terns! former nesting ground. This the birds shunned, 
and the entire colony moved about 100 yards farther back from the run- 
way. However, they still flew in large numbers back and forth across 
the runway on their way to and from the sea. 
On Eastern Island, sooty terns were nesting in areas where 
they did not nest last year. It is possible, but not proved, that 
some of the harassed birds on Sand Island moved to Eastern Island to 
nest. : 
B. Sooty Terns and Aircraft Operations 
Unfortunately the Air Control Tower stopped keeping records 
of bird strikes at the time the sooty terns returned in April. Be- 
cause of the tern killing program, the strike frequency was apparently 
below that of the previous season, when an average of 1.15 birds were 
killed per landing or takeoff. No damage to aircraft caused by sooty 
tern strikes was reported. 
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