Author: Elva Manquera

by Sam Webb

This spring marked the 4th year of our Purple Martin project. Klamath Bird Observatory has partnered with USFS and USGS to learn more about the western subspecies of Purple Martin. Our goal this year was to place GPS tags on 8 adult Purple Martins in order to track their migration routes and learn more about where they spend the winter.

Prior to banding, our crew boated out to check the nest boxes at the U.S. Army Corp of Engineers (USACE) Fern Ridge Reservoir to determine which were being used by Purple Martins. We checked each box for nesting activity so that we knew which ones were the most likely to have an adult Purple Martin roosting in it for the night.

Purple Martins naturally nest in cavities or old nest holes in snags or dying trees originally created by woodpeckers. Nesting locations become limited when snags are removed, or other bird species outcompete for nesting areas. The nest poles and boxes at Fern Ridge were made by USACE to provide Purple Martins with structures to roost and build their nests in. Designed to be removed with a unique tool, these nest boxes allow us to carefully bring them down, check for eggs or chicks, and catch adults.

While we were out checking nest boxes in the daytime, we took the opportunity to band any chicks that were old enough with a red band that had three easy-to-read numbers and an aluminum federal band. This will allow us to resight those individuals next year and learn more about the return rate of young Purple Martins or learn where else they might return to for their first breeding season.

After determining which nest boxes were likely to have adult Purple Martins roosting in them that night, we returned at dusk to try to catch and band the adults. We did this by floating quietly up to the poles and standing in the bow platform to quickly block as many cavity entrances as we could reach without the adults escaping. Once we caught an adult, we carefully took it out of the box and banded it using an aluminum federal band and the 3-numbered red band. We took additional measurements, looking at the health and size of the adult before choosing an appropriately sized GPS tag.

We fitted the GPS tag on the adult by slipping one loop of a harness made of stretchy jewelry cord around each of its legs and placing the tag on its back, similar to wearing a backpack. After the adult was banded and received its GPS tag, we double-checked the harness fit, carefully placed the martin back in its nest box, and set it back into position.

The following day, we paddled out once more to resight the adults that we banded the previous night. We spent time at each nest box to confirm that the adults still had their tags from the previous night and were comfortably delivering food to their young as usual.
These GPS tags that each Purple Martin received will take a location point every few days for up to the next year (depending on battery life) while the individual migrates to and from its wintering grounds. Due to its lightweight and compact size, the GPS tag is only able to collect location coordinates but not send them. Next year, we will return to find the adults with tags and catch them to retrieve the tags and data. Little is known about the migration route of the west coast population of Purple Martins or where they spend the winter. These data are critical for understanding their complete life cycle and for informing conservation efforts across their entire range. To read more about our first returnee and where she went, click here!

Our 2023 field efforts were supported by the Greenfield Hartline Habitat Conservation Fund and the Purple Martin Conservation Association.