Basin Notes - March 2013

Lazy Birds

The recent sighting of a white-tailed eagle (also known as sea eagle) on the Basin has produced a great deal of interest. This was one of the 85 young birds released by the RSPB re-introduction programme in Fife since 2007. This bird has a red wing tag with a white "E" on it showing it was released in 2011.

The re-introduced birds not only have wing tags, for easy identification, but also radio transmitters to allow them to be tracked accurately. Up until now the tracking data for Red-E showed it was staying around Perth, but clearly it has decided to scout out Angus and only time will tell if it settles here.

White-tailed eagles are not fussy about their feeding habits and will happily take any carrion that they can find, which might include dead whales and dolphins washed up on the shore line. They will catch live fish from the surface of the water and also water birds. Like skuas, they will also force other birds to release their own food catches to save them the effort of finding their own.

It will be interesting to see if there is any interaction between the sea eagle and the ospreys, when they return in a month or so. There have been reports that sea eagles will rob ospreys of the fish they have caught. Ospreys fishing in the Basin have often have to run the gauntlet of gulls that want to grab their prey, so having something as large as a sea eagle taking an interest as well would be fascinating to watch.

For all this active behaviour, sea eagles often spend a lot of their time sitting in trees or on the ground looking around for an easy meal. This makes sense in a marine environment when the rising tide might bring in and the falling tide might reveal, a dead animal that will be food for the eagle.

Another bird which also spends a lot of time standing on the mud doing nothing is the cormorant. Recent research suggests that they will spend less than an hour each day fishing and can find enough food in that time to satisfy them for that day. So once their hunger is satisfied they can rest and use minimum energy as they are in a safe place in the middle of the Basin.

Also, a safe roost at low tide is high on the priorities for common seals which join the cormorants on the mud banks and stay there until the tide comes in again 6 hours later.

This behaviour shows how larger birds and animals can afford to spend time resting each day as they lose less heat than smaller ones who have to forage for food for much longer periods each day to satisfy their energy needs.

Another recent sighting has been of black-necked grebe. This migrant species has been known to breed in Scotland, but only time will tell whether this bird will move on or stay on the Basin. Together with long-tailed ducks the Basin has been a fruitful place for wildlife watching recently.