Photo: Trumpeter Swans foraging in corn stubble by Bob Boekelheide
New Research to Advance Migratory Swan Conservation
by Laura Davis and Liam Antrim, Co-leaders, OPAS Swan Study
Whether weekly, monthly or annual in frequency, all of our OPAS Swan Study surveys are just snapshots of the current numbers and usage locations of the swans in our area through periods of migration and the more stable winter season. While our surveys typically have no ability to track individual birds, we have that potential when we can recognize individual swans.
We sometimes recognize the few Tundra Swans here that have fallen off the Tundra migratory path somewhere along the flyway; the amount of yellow near the bill in the adults can vary. We can learn to distinguish them well enough to know when we see a new individual. Since October this season, we have observed a single juvenile Tundra Swan here. That we continue to see this individual may indicate the Trumpeters it flocks with have remained in our area from this season's start. Most recently, it has been seen roosting at Kirner Pond and foraging on the harvested corn fields west of Carlsborg Road.
Juvenile Tundra Swan on October 23. Photo: Steve Koehler
Concurrent with our surveys, methods of following and understanding wild species’ usage and movements through the landscape are changing radically with state-of-the-art tracking technologies. Another swan recognizable here since late November is a Trumpeter adult, this one marked and tracked with a GPS collar. The marked swan is part of a collaborative research study of CalPoly Humboldt and the WDFW Waterfowl Section. Their study is attempting to characterize the requirements of migratory waterfowl that are here in Washington during the non-breeding season.
Trumpeter Swan GPS collared for WDFW–CalPoly Humboldt study, dawn of December 4. Photo: Sally M. Harris
In the March/April 2024 Conservation Matters column, we introduced this academic study. Trumpeter Swan nutritional needs and overwintering habitats in the Pacific Flyway are neither well understood nor are data up to date. It has been 30 years since a couple of regional studies of Trumpeter Swan forage focused on the two areas of their greatest overwinter use: in the Skagit River valley and the Comox River estuary. Using GPS data from collared Trumpeter Swans wintering in the Skagit, analysis from this project will focus on swans' spatial distribution among crop types in relation to all available food resources. The researchers expect that quantifying forage resources will inform swan conservation.
Last winter's warm El Niño weather delayed the swans' arrival to the Skagit River valley and the start of the collaring. Following the mid-January arctic storm, the study team successfully collared 19 Trumpeters, representatives of the Skagit swan population numbering several thousand. Prioritizing females to avoid tracking more than one per family, they might have gotten a few males. It has been fascinating for the researchers to watch the swans' broad distribution as they returned this early-winter – not yet a full year on these transmitters. Swan fidelity to particular areas seems to be looser than expected; our lower Dungeness study has certainly shown significant variability too.
In a northerly latitude wintering site like Washington, weather patterns can quickly alter how many individuals of multiple waterfowl species co-occur with other wildlife and land uses; all compete for the same space on the map. Deciphering these patterns in dynamic habitats such as wetlands (changing month by month and year by year) or with species that use multiple features of a landscape in a single day (such as a roost and a foraging field) may require observations repeated at intervals that capture that frequency of change. How tightly do they hold to particular areas?
The Pacific Coast Population of Trumpeter Swans who breed in interior Alaska and winter west of the Cascade Mountain Range experienced tremendous population growth until their population peaked in 2017. Their breeding grounds hit capacity several years ago. Identifying the location and timing of staging and stopover sites used during migration between Washington and breeding areas in Alaska and Canada are also part of the study focus. The transmitter devices provide a unique ability to “see” birds in more remote, cool-season landscapes like British Columbia; data are offloaded to cellular networks whenever within range.
Although most study swans returned directly to the Skagit Valley this fall, one remained on the BC coast until 8am on December 8, when it skirted the Vancouver Island shoreline flying southeast, crossed over the San Juans and landed north of Mount Vernon on the Skagit River floodplain four hours later. Another Trumpeter continued from the Skagit down to the Columbia River. The collared individual we observe here summered in the Copper River drainage just north of Glenallen Alaska. It left there on September 4, then arrived in Washington the afternoon of November 26 where it touched down in the Skagit for two nights. Then, this swan, its mate, and likely other Trumpeters made their way over to Sequim on the morning of the 28th. Unlike the more familiar banding studies that rely on birders' observations of numbered bands, these collars gather real-time GPS-quality location data at regular intervals, currently every 30 minutes.
As the researchers approach a full year cycle of data, they look forward to providing presentations on preliminary results and insights that these marked individuals have provided to date. (Thanks to Kyle Spragens, WDFW Waterfowl Section Manager for the information in this article; errors are my own. ~LD)
Nearly all of our midday observations of swans foraging have been on harvested corn fields (stubble) overplanted with cover crop winter grains. The residual grains of corn provide carbohydrates, and the winter grains provide green protein. Photo: Bob Boekelheide
Our swan team is highly alert to potential disturbance to the swans' sense of safety. Disturbance may send them elsewhere, and safe roosting is especially in short supply in our area. Loss of vegetated wetlands is why swans started targeting agricultural crops, and water needed for digestion and safety is a primary limitation to swans in our area. It's important that folks observing or photographing the swans avoid unnecessary movements or standing in the swans' flight path. Consider keeping distance from roosting or foraging swans as a core conservation practice.