Fishermen heading to cast a line out in the deep this month have been advised to consider going on days with little to no wind — to minimise the risk of a protected species of bird pilfering their bait.

Miguel Mejías, of the Bermuda Audubon Society, said that close to a million northbound great shearwaters migrate past Bermuda's southern shores from June to August.

The chances of encountering the seabirds in Bermuda's waters decline throughout July, with the last shearwaters typically moving on before the end of August.

Dr Mejías said if a shearwater is found dead or injured, it should be brought to the Bermuda Aquarium, Museum and Zoo for specimen preparation and rehabilitation.

He said the birds breed on the remote islands of Tristan da Cunha, in the middle of the South Atlantic west of South Africa. Some also nest in the Falkland Islands, east of Argentina.

Dr Mejías added: “They breed in the south between September and May.

“They are burrow-nesting birds, and once the chicks hatch and fledge, all the birds depart their breeding grounds and start moving north in May.

“They typically start showing up in Bermuda’s waters in June.”

He said the trans-equatorial journey of the birds spans more than 7,000 miles, with the peak of their appearance around Bermuda occurring this month.

Dr Mejías said some fishermen were wary of the birds because of their appetite for bait.

He explained: “The birds could actually dive down to about 60 feet deep.

“I heard stories of their encounters with the fishermen about their bait and I could understand the frustrations of the fishermen.”

While shearwaters could be an annoyance, he explained: “One has to understand that the birds could be hungry.

“They have travelled over 7,000 miles, past the equator into the North Atlantic.”

He said the birds ordinarily weigh roughly 900 grams but that by the time they arrive in Bermuda waters “they are skeletons because they are starving”.

He added: “They have a very keen sense of smell — they are very distant cousin of the cahow. They have the ability to smell their prey miles away.”

Once hungry shearwaters detect bait, they home in on the source.

Dr Mejías said the birds were covered under the Protection of Birds Act 1975.

The legislation is for the conservation of wild birds as well as their nests and eggs, and outlines offences related to killing, taking or disturbing them.

Dr Mejías said that because of the warmth of the seas around Bermuda, the shearwaters encounter less of their usual food here, as opposed to colder waters.

He added: “They are not feeding until they get to their destination, which is the northern temperate waters, like the eastern seas of the US and Nova Scotia.

“That’s their destination, where the water is cooler, with more nutrients for them and more things for them to actually eat.”

Flocks of juvenile and adult shearwaters will look for a quick meal as they pass the island.

Dr Mejías suggested that anglers take care fishing in the immediate south of the island in June, and look out for shearwaters on the prowl during southeasterly winds, which the birds ride for a boost on their journey north.

He said the birds typically did not perceive humans as a threat, and could fly close to fishermen.