Ash plume from Eyjafjallajokull Volcano / NASA/MODIS Land Rapid Response Team
Much of the coverage I have seen of the Eyjafjallajökull Volcano's eruption has focused on the problems caused by flight cancellations, its possible effects on Europe's weather, or the spectacular images documenting the eruption. So far there has not been much (or at least not much that I could find) on whether the volcano might affect wildlife generally or birds specifically. The information I have seen is rather fragmentary. One story, from Iceland Review, mentions a possible impact for wildlife: birds flying into the ash plume.
One of the most terrible consequences of an eruption like this is the effect on animals. Most domestic animals are still in house, but the birds have no shelter. They fly into the dark cloud, flap their wings like they have lost their bearings and then fall down and die. Our reporters saw a flock of geese fly straight into the deadly ash. Farmers have told of the desparate [sic] sound coming from the birds battling death. This is the season when birds are migrating back to Iceland.Unfortunately this is rather vague and does not elaborate on why the ash kills birds (presumably suffocation) or how much of a threat the ash plume represents. Like North America, Europe is in the midst of its spring migration season. Birds will be flying the same skies deemed too dangerous for airplanes. At least one Whooper Swan carrying a satellite tracking device passed near or through the plume successfully. However, the current eruption is still a concern for migrating birds.
On Iceland itself, the volcanic eruption is causing concern for the returning waterfowl. A report from WWT’s colleague Dr Olafur Einarsson in Reykjavik confirms that that there is dense ash and total darkness to the southeast of the volcano, near the area dubbed “Whooper Airport” because it is where most of the birds land after their migration.The BBC reports that farmers have had to keep their domestic animals indoors to prevent them from being poisoned by the falling ash.
Dr Einarsson reports that bird deaths have occurred during previous eruptions of other volcanoes in Iceland, when the feeding areas were covered with ash, causing major problems for farmers and birds. Fortunately at the moment the main area affected, between Vik (in the west) and Kirkjubaejarklaustur (in the east), is primarily an area of sand and gravel, leaving internationally important whooper swan staging or breeding sites still suitable for swans.
The fluoride in the ash creates acid in the animals' stomachs, corroding the intestines and causing haemorrhages.If this poses a threat to domestic animals, it probably applies to wildlife too. In fact, wildlife may be at greater danger because they rely on the outdoors for food. It is possible that they could relocate temporarily, but I am not sure if they would know to do that. The BBC article does not mention much about wildlife, but it does mention that some geese had difficulty flying because their wings were caked with ash.
It also binds with calcium in the blood stream and after heavy exposure over a period of days makes bones frail, even causing teeth to crumble.
Since volcanic ash reduces sunlight passing through the atmosphere, volcanic eruptions in the past have been followed by colder winters. Earlier this year, parts of Europe experienced a historically cold winter, and that caused noticeable changes in local bird life. If Eyjafjallajökull does cause a harsh winter this year, I would expect to see some effect on birds.
Update: Grrlscientist also wrote about how ash clouds might affect birds's lungs.