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Nathan Cooper and Pete Marra, our friends at the Smithsonian Migratory Bird Center, have a new paper in Current Biology that started out to be one thing and, well, turned into something else.


Cooper originally set out to document Kirtland's Warbler movements on the wintering grounds to correlate their winter health to breeding success. So Cooper fitted more than 100 warblers with radio tags that weigh only one-third of a gram. Signals from the tags are picked up when a bird mounted with the tag flies past a tower that is part of the Motus Wildlife Tracking System.


Cooper thought tracking movements would be as simple as migrating from the Bahamas to the jack pine breeding grounds, around the breeding grounds, and back. But when Cooper analyzed the data, was shocked to find out that certain birds moved around a whole lot more than he thought.


It turns out that a small number of birds fail to find mates. So instead of just hanging around in one territory, they move around on the breeding grounds, sometimes from area to area that are many miles away.


What are these birds up to? Cooper believes that they are looking around for good places to breed in the future, and assessing how successful the current breeding birds are at raising their young. That is important because it's an indication of the level of resources.


Cooper says the big clue to decoding the behavior of the floaters: they were most active during the few weeks when hatchlings of the breeding birds were in the nest.


Cooper believes if we better understand the movements of Kirtland’s Warblers, we can better plan for which areas we will need to protect. Based on this information, it looks like simply protecting summer and winter habitat won't be enough. Based on this study, it looks like birds might need more than just one place to live.


“If many birds are moving around at larger scales than we realize, then we may not be protecting the right areas,” Cooper told the Smithsonian website.


You don't need to read the entire article to get a good feel for their research. Cooper and Marra have developed a video abstract that explains their work in just a couple of minutes. You can find that video here: https://www.youtube.com/watch?v=QMS0YIfiovs.


The coronavirus has changed pretty much everything around us, including this year’s efforts to monitor and manage the Kirtland’s Warbler.


But the warblers didn’t seem to mind.


The birds arrived on their Jack Pine breeding grounds a little late this spring because of cold temperatures across the northern United States. But once they arrived, they set about doing what they do best that time of year. Unfortunately, the state and federal agencies responsible for Kirtland’s Warbler conservation were limited in their field work so, it’s not known if the population has continued to grow. Here’s a quick rundown:

Michigan: Michigan Department of Natural Resources biologists are seeing the continuation of a trend of birds occupying what had previously been viewed as marginal habitat. Specifically birds are in plantations with trees that were considered too young to attract warblers and sparse habitat that has grown back through natural regeneration. If birds continue to occupy these stands it may force biologists to rethink their notions about Kirtland’s Warbler conservation.


Wisconsin: The numbers are not in yet, but it appears that the Kirtland’s Warbler population continues to expand slowly, particularly in Marinette County, north of Green Bay. Birders also found a pleasant surprise in Jackson County: at least three males and one female were recorded in that county for this first time since the late 1970s.


Ontario: Kirtland’s Warbler populations are found in three locations, Garrison Petawawa, (north of Ottawa), southern Simcoe County and Henvey Inlet (northeastern Georgian Bay). The Simcoe County population, is believed to be holding steady at around 20 pairs, while Garrison Petawawa continues to have one or two pairs/singing males and Henvey Inlet one singing male most years. One hundred forty acres of habitat was created in Midhurst and seeding and planting were completed in 2020 using herbaceous plants and Jack and Red Pine plugs. The Packard Tract, an existing 140-acre site, was enhanced through seeding and planting in 2019 and 2020. A 25-acre site adjacent to the Packard Tract is being prepared for a fall burn.


Spring planting: The Michigan DNR was able to plant young jack pines on 1,300 acres of Kirtland’s Warbler habitat. The U.S. Forest Service did no planting. The agency plans to double planting in 2021.


Cowbird: Nest parasitism from the Brown-headed Cowbird appears to have been minimal to non-existent. Over the past 10 years, there has been a steady decline in the cowbird population in the jack pine. Nobody knows exactly why there are fewer cowbirds around but the population in the jack pine has fallen so much that parasitism is not a factor. That said, the conservation plan includes contingencies for a cowbird rebound.


Census: A full census—the first in five years—is planned for 2021. You will get a full update on plans in our December newsletter.


Tours: Even though official tours were not offered this year, birders came anyway. The U.S. Forest Service is aware of people coming from as far away as California, Arizona and Maryland to see the warbler.