Swallows dying, reason unknown.

"The recent deaths of nearly 100 cliff swallows near the public dock at Lower Otay Lake – plus five deaths reported yesterday at El Capitan Reservoir – have created a stink and prompted an investigation by the county veterinarian.
“I wouldn't say this is normal to see a colony like that experience such a high number of losses,” said Nikos Gurfield, the county vet.
Gurfield is looking for West Nile virus and avian influenza, two diseases that have captured a lot of attention in recent years, as well as lesser-known possibilities. He said the deaths may be related to a lack of food for the birds, and he's asking for a review from pesticide experts. " LINK