British officials said Monday that a spill at one of Shell's North Sea platforms that began last Wednesday has become one of the worst in their waters in the last decade. While the flow has been "greatly reduced," it was not stopped completely, government officials admitted Monday. Conservationists worry that the leak could harm birdlife during a time when thousands of young razorbills, puffins, and guillemots are flightless and settling throughout the North Sea for the summer. Shell estimated the spill to be around 1,300 barrels, with five barrels continuing to leak. In comparison, the Gulf of Mexico oil spill last year leaked up to 70,000 barrels a day. Government advisers asserted that wildlife risk would be small and that Shell was working hard to fix the problem.