A、They can be used to deliver messages in times of emergency. B、They deliver pollutants from the ocean to their nesting sites. C

Birds are famous for carrying things around. Some, like homing pigeons, can be trained to deliver messages and packages. Other birds unknowingly carry seeds that cling to them for the ride.(9)Canadian scientists have found a worrisome, new example of the power that birds have to spread stuff around. Way up north in the Canadian Arctic, seabirds are picking up dangerous chemicals in the ocean and delivering them to ponds near where the birds live.
    Some 10,000 pairs of the birds, called fulmars, a kind of Arctic seabird, make their nests on Devon Island, north of the Arctic Circle.(10)The fulmars travel some 400 kilometers over the sea to find food. When they return home, their droppings end up all around their nesting sites, including in nearby ponds.
     (11)Previously, scientists noticed pollutants arriving in the Arctic with the wind. Salmon also carry dangerous chemicals as the fish migrate between rivers and the sea. The bodies of fish and other meat-eaters can build up high levels of the chemicals.
    To test the polluting power of fulmars, researchers collected samples of deposit from 11 ponds on Devon Island. In ponds closest to the colony, the results showed there were far more pollutants than in ponds less affected by the birds. The pollutants in the ponds appear to come from fish that fulmars eat when they’re out on the ocean.(12)People who live, hunt, or fish near bird colonies need to be careful, the researchers say. The birds don’t mean to cause harm, but the chemicals they carry can cause major problems.
Questions 9 to 12 are based on the passage you have just heard.
9. What have Canadian scientists found about some seabirds?
10. What does the speaker say about the seabirds called fulmars?
11. What did scientists previously notice about pollutants in the Arctic?
12. What does the speaker warn about at the end of the talk?