Last week, things went from bad to worse.  

It made for a bad day when I received a call about a dead barn owl. And the week got even worse when two days later a second call came in reporting another dead barn owl. These birds were found in different locations, Chilmark and Edgartown, so their demise could not be traced to a single, localized event.

The only good thing about these reports is that the barn owl population must be on the rise on the Island if we are seeing deceased birds. Plus, the establishment of a pair in the owl box at the Felix Neck Nature Center adds to the knowledge that barn owls are increasing here. It has been a few years since barn owl numbers were strong.

In the winter of 2014/2015, a majority of the Vineyard’s barn owls perished. The crash of this species occurred during a winter of heavy snowfall that persisted on the ground, creating difficulty for owls looking for the small mammal prey that are needed for their survival. Cold weather requires more food for barn owls, and long-term snow cover reduces prey availability. That winter, most of the barn owls on the Island died from starvation.

The Vineyard is one of the last holdouts for Massachusetts barn owl populations. Our mild weather and lack of sustained snow and snowy ground cover provide better conditions than the mainland for these birds. We are at the northern range for this species, so population fluctuations are a normal condition.

Starvation is a leading cause of barn owl mortality. However, it is not the only issue for these beautiful birds and likely wouldn’t be the reason for the two dead birds, as our winter has been mild with little snow.

Excessive winter rainfall can be a problem. Barn owls have soft feathers, an adaptation for silent flight. These feathers are not very water resistant, though, so barn owls prefer not to hunt during rain events. Too much rain can reduce hunting time and impede the collection of food.

The other major concerns are human-induced. Collisions with vehicles, power lines and windows cause mortality, and, sadly, a serious threat is poisoning from rodenticides.

Rodenticides are rat poisons used commercially and by homeowners to reduce or eliminate rodents. Rats ingest these toxins and die within four to fourteen days of consumption. Contaminated rats that are still active become food for barn owls and other raptors. Since raptors will eat many rats (barn owls eat more than half a dozen a day), the poisons build up and can easily cause mortality for these hungry birds. A study at a Massachusetts wildlife hospital showed that 86 per cent of raptors in their care tested positive for these poisons. The EPA recently banned a category of these poisons for use by consumers, though licensed exterminators still can employ them.

We don’t know what killed those two barn owls last week, though a necropsy could lead to the answers. We do know that the use of rodenticides is a deadly threat to barn owls and other raptors, not to mention humans, since children account for approximately 10,000 annual visits to the emergency room after inadvertently consumption of rat poisons. Always try to use alternatives to these poisons — for your family, pets, and our wild friends — because it truly can be a matter of life or death.

Suzan Bellincampi is director of the Felix Neck Wildlife Sanctuary in Edgartown, and author of Martha’s Vineyard: A Field Guide to Island Nature and The Nature of Martha’s Vineyard.