The Purple Martin is the largest of the Western Hemisphere swallows that breed in North America. As a cavity nester, this swallow now needs artificial nests to survive and reproduce. It can be seen occasionally in summer over the waterfront and the marsh because a small population nests in wooden boxes attached to the Point Wells pilings, about a mile south of Marina Beach. The Purple Martin was a staple on the Edmonds waterfront for about five years starting in 2004, to the delight of summer visitors.
It is possible that the plastic gourd attachments, which were the same as those used for the earlier natural gourds, failed because of the domino effect. Cormorants had perched in large numbers on the Union Oil dock. The dock was removed in late 2008. That displaced a large population of birds. Some of the remaining cormorants began to perch on the rebar we had installed on the Olympic Beach pilings. Cormorants have large feet. After just so many take-offs and landings, the attachments failed.
The local Audubon chapter next decided to install painted plastic gourds in the marsh. Purple Martins never showed any interest in those gourds. They were taken down last fall.
Stan Kostka, an independent Purple Martin researcher and Snohomish County resident, had been installing wooden nest boxes throughout the northern inland marine waters. Once installed, they required no maintenance and could be used for years. The Point Wells boxes, installed by Kevin Li about 20 years ago, are still in use. Stan agreed to build nest boxes for Edmonds if I would assist.
The entrance holes of the nest boxes are designed to deter entry by House Sparrows and European Starlings. The interior floors and exterior perches are scored so that adult martins can pull themselves in and out. Scoring also prevents hatchlings from developing splayed feet, which can happen on a smooth surface. Each box has been seeded with straw as nest material. The boxes have been numbered one through six on both sides. Numbering allows observers to identify for others which boxes are in use. Wire has been stapled to the top of each box to discourage perching by larger birds, such as the cormorants.
Male birds are the first to arrive and they establish nesting territories. The female lays 4 – 5 eggs and incubates them for 15 – 18 days. Both parents feed the nestlings. The young birds remain in the nest for nearly a month before they fledge. Flying insects make up the bulk of the Purple Martin diet. These include wasps and winged ants, many true bugs, both house and crane flies, beetles, moths and butterflies. There is no guarantee, of course, that a Purple Martin colony will use the new nest boxes this summer. We should all know by some time in June. It may take another year for enough adult birds to form a new colony at Olympic Beach.