John Picard reports that three of the 31 tree swallow nest boxes at Hammonasset Beach State Park were repeatedly raided by house sparrows and the resident swallows killed.
House sparrows are attracted to the same sort of cavity that tree swallows are. And house sparrows are very aggressive.
John has been able to keep the deaths to a minimum with constant monitoring of the boxes. And the results over the last four year have shown increased fledge rates as shown in this spreadsheet.
As to the deaths this year, John has posted posted some pictures of the carnage. Warning: they are graphic.
