It has also been reported that large numbers of the same species feed unusually near the coasts and venture several miles into Scottish rivers in search of fish to eat.

The Scottish Government’s Marine Scotland branch has now collected water and plankton samples from the seas off eastern Scotland, from Aberdeenshire to the Firth of Forth, to investigate the possible presence of harmful algae species.

A so-called “large county-sized” algal bloom has been identified off the northeast coast. Near some seabird feeding hot spots, one theory is that some of the stranded birds may have been feeding there and absorbing algal toxins through the food chain.

Samples taken by the Marine Protective Vessel (MPV) Hirta are currently being analyzed at the Scottish Government’s Marine Laboratory in Aberdeen to determine if they contain toxic algae.

Scientists in the management of Marine Scotland are also gathering information on the abundance and quality of major prey fish populations to see if prey availability is a potential factor.

Tests carried out for avian influenza on a sample of dead seabirds gave negative results.

A Scottish Government spokesperson said: ‘We are aware of reports of unprecedented numbers of seabirds stranded on the Scottish coast.

“We are working closely with various other organizations to investigate a number of potential causes for this unusual event.

“The Scottish Government’s Marine Scotland vessels have collected water and plankton samples off the east coast of Scotland to investigate the presence of harmful algae species.

“These samples are currently being analyzed and we will communicate the results in due course.

“Further work is also underway to determine whether changes in the abundance or quality of prey are a potential factor.”

Dr Francis Daunt, a seabird ecologist at the UK Center for Ecology and Hydrology (UKCEH), said this week the number of reported dead murres and razorbills has exceeded 1,000.

The dead birds weighed an average of 550 grams – barely half their usual body weight of 1,000 to 1,100 grams – suggesting that they starved to death at a time when conditions are generally good for the species.

Murres have also been reported searching for fish in very shallow water, among swimmers and people wading in places such as Portobello and Cramond in Edinburgh.

Dr Daunt added: “This is a very unusual behavior that we hadn’t really seen before and, coupled with this docility, we also saw a lot of birds moving up rivers.

“We have bird watchers who have been following their plot for 20 years and they have never seen them before.

“We even got a little further upstream from Stirling, very far from the sea. These birds seem desperate. They call, sitting by the river, really doing nothing because they are probably hungry and cannot find food.

The phenomenon adds to an already dire situation for Scotland’s globally significant seabird populations.

The latest NatureScot indicator, which tracks 11 species of seabirds, showed an overall decline of 49% since 1986, linked to climate change.

Members of the public who find sick seabirds should report their whereabouts to the Scottish SPCA.

Dead seabirds should be reported to UKCEH.

The Scottish Government spokesperson added: “Wild birds can carry several infectious diseases to humans, so members of the public should not touch or pick up dead or visibly sick birds they find along the Scottish coast. ”

• Anyone who finds a sick or injured seabird in Scotland is urged to contact the Scottish SPCA on their dedicated animal helpline 03000 999 999. Dead seabirds should be reported to UKCEH, which collects data on the ‘event, at https: // www. ceh.ac.uk/form/general-contact-us