Landlords who don't conduct weekly nest checks may never know martins, nestlings, or eggs are disappearing. Martin houses that have become regular targets for hawks, owls, or crows should be equipped with owl guards. Since martins feed solely on flying insects, they are extremely vulnerable to weather conditions that affect insect availability. If poor weather persists for more than 2 or 3 days, martins begin to die of starvation. Heat waves and droughts can also be a problem.
Prolonged drought can also adversely affect insect numbers.
Some weather conditions may contribute to a population explosion of external parasites normally found in martin nests, including fleas, nest mites, and blowfly larvae. Never use pesticides in nests or boxes. First, remove the nestlings to a temporary container. Throw out the old parasite-infested nest. Shape a shallow bowl in the new material and place the nestlings back in the nest.