Hidden long-distance movements by KWs
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.