On a recent visit to Hillsborough Park to feed the geese, ducks and coots, we spotted some peas on the ground by the side of the lake. We were surprised that birds ate such things, but the Canal and River Trust are recommending that people do indeed feed water birds frozen peas, or lettuce, or grain. This story was picked up extensively in the UK media yesterday and today.
But not bread. The video in this piece from the Daily Telegraph has figures for the amount of bread that is fed to water birds. A lot of it is not eaten by the birds, but ends up as a culture medium for microorganisms, making the birds ill and encouraging rats. See also this piece from the Canal and River Trust.
A web search for avian botulism bread finds news stories from last summer and autumn, so the finger of suspicion has been pointing at bread for some time.
A quick web search and search of PubMed suggests the fingers of suspicion in the academic and government literature are pointing at a link between avian botulism and algae, although there seems to be no study directly relating bread and the disease in water birds.
There is a page from the US National Wildlife Health Center about avian botulism, discussing the conditions that the bacterium needs to grow (a protein source, warm temperatures, and no oxygen) and pointing out that there are regular outbreaks in the USA and Canada (my PubMed search turned up more than one item discussing the problem in the Great Lakes).
This What's New in Health and Safety from the Canal and River Trust (scroll down when you have loaded it) discusses what to do if a bird suspected of dying from avian botulism is discovered. DEFRA need to be informed.
Thanks to Emma Kimberley for sharing the Daily Telegraph piece via Facebook.