NAIROBI, Kenya (AP) _ After days without sleep, a 1,200-mile-trek across marshes, savannahs and bush and a run-in with an upset hippo, birdwatcher Terry Stevenson feathered his cap with a new record Monday.

In a search that took Stevenson and teammates John Fanshawe and Andy Roberts from the volcanic lakes of western Kenya to the sultry Indian Ocean coast in the east, the Kenyan team sighted 342 bird species within 24 hours.

The team clipped the record of 331 birds sighted in a 24-hour period. It was set by American Ted Parker four years ago in Peru, which has the world's largest collection of bird species with about 2,000.

It was the plume of the white-bellied bustard - an ungainly, ground- dwelling bird with the equally unattractive scientific name of Eupodtis senegalensis - that pushed the Stevenson team ahead of the previous record.

''It's a fairly common bird,'' Stevenson, an ornithologist, said in an interview Monday. ''We spotted it about six o'clock Sunday evening in Nairobi National Park.

''We were seeing birds and just jotting them down on a bit of paper and when we got a break we were transferring them to the official list. We didn't realize until about half an hour afterwards that we had broken the record,'' he said.

Birdwatchers compete on an honor system, recording their own sightings.

Stevenson, 32, is a native of Bradford, England, but has lived in Kenya the past 10 years. Fanshawe is a lawyer and Roberts is a farmer who served as recorder, pilot and driver for the winning team.

Seven teams of world-class birdwatchers - two each from Kenya and Britain and one apiece from the Netherlands, the United States and Zimbabwe - set out at midnight Friday on a birdwatching marathon called Birdwatch Kenya '86.

The contest was divided into two 24-hour periods, with the victory going to the team with the highest total. The lure was a bronze trophy and two shots at breaking the record.

Kenya, about the size of Texas, boasts 1,068 of the 1,750 bird species found in sub-Saharan Africa. Only Peru, Ecuador and Colombia have more bird species.

The competitors used motorboats, planes and four-wheel-drive vehicles to crisscross Kenya in search of the birds.

''We didn't see anything really rare,'' Stevenson said. ''But on these kind of competitions you're not worried about what's rare, it's much better to see five common ones.''

The search took the contestants through wild game parks and some crocodile- infested waters, but the closest anyone got to danger was the Stevenson team's encounter with a hippopotamus while sloshing through a marsh.

''There was a tremendous noise and we looked around and there was a hippo galloping back to the water,'' Fanshawe said. ''We were galloping in the other direction, of course.''

In the 48-hour, overall competition, the Kenyan team of Don Turner, David Peason and Allan Root recorded 323 birds Saturday and 171 Sunday to take first place with 494 birds.

The U.S. team of William Russell, Dale Zimmerman and Brian Finch tallied 317 birds Saturday and 160 Sunday to finish second overall with 477 birds.

Russell, leader of the American team, is managing director of Wings Inc., one of the largest birdwatching tour companies in the United States.

Zimmerman is a professor of biology at Western New Mexico University in Silver City. Finch, recorder for the American team, lives in Kenya where he instructs birdwatching guides.