Purple Martin Nest Box Update – October 2020

The 2020 Purple Martin season began in February with construction and installation of 5 new and 2 replacement nest boxes, on pilings in the Squamish estuary central channel. An experimental 3-story nest box (#13) was installed on the south piling, with a camera to monitor activity outside the nest box. Wire predator guards were installed on all existing nest boxes.

Observations were collected from April through September, by spotting scope from shore and from non-motorized watercraft.

  • The first recorded sighting was on May 1, by Chris Dale, with at least 4 purple martins at the nest boxes.
  • By the end of May, up to 11 individuals were seen flitting around the nest boxes.
  • Activity increased again during the third week in June, with 19 individuals counted on June 21 and birds seen at the new nest boxes.
  • June 28 an estimated 22 individuals were seen moving in and out of the nest boxes and carrying nesting material into the boxes.
  • Numbers and activity stayed fairly constant through August. Feeding activity, disposal of fecal sacs, and young chirping, all indicated presence of nestlings.
  • Third week in August, young poking their heads out of the nest boxes.
  • First week of September, fledged young being fed by parents, others still inside nest boxes.
  • Mid-September activity falling off at nest boxes.

John and Rachel went out on September 20, October 4, and October 12, to inspect and clean the nest boxes. We found 8 successful purple martin nests, 6 failed nests (unhatched eggs or dead young), 6 empty nest boxes, and 3 nest boxes used by tree swallows. Several boxes contained a small amount of starter nest material.

Photo and video documentation was sent to Bruce Cousens, Senior Biologist with the Georgia Basin Ecological Assessment and Restoration Society. Mr Cousens kindly reviewed and annotated some of the photos, to help us interpret our field data. The high number of nests that failed during incubation was apparently typical for the region this year, especially with late subadult nests, due to a prolonged cool wet late spring and early summer, and a very late nesting season as a result. Mr Cousens noted that the entrance height on some boxes was slightly over, or under, the recommended height of 1-3/16″. These will be replaced in 2021, to meet the specifications.

More about our Purple Martin Nest Box Program

Photos and video: John Buchanan