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North Shore corridor important to fall migration


NorthShoreCorridor_090110.mp39.67 MB
Chel Anderson is a botanist and plant ecologist from the Minnesota Department of Natural Resources. She lives here in Cook County and joins us periodically to talk about phenology or what’s going on in the woods right now. Welcome, Chel.
Anderson: Hey, Jay.
Now, listen, bird migration continues. We’ve talked about nighthawks, we’ve talked about loons. The North Shore is a real migration corridor, so who else is on the move?
Anderson: Yes, the migration is definitely underway. Let’s maybe start by talking about the corridor and what an amazing phenomenon for migration the corridor is and why it’s so important. People have known for a long time how important the North Shore was to the migration of raptors, so hawks and eagles and ospreys and birds of prey, in part because of all the long-term observations that have been going on at the Hawk Ridge Bird Observatory in Duluth. So, people have been documenting numbers of raptors there for a number of years now and banding birds. So, it’s been a great resource, but it’s really only recently that, other than anecdotally, people have really begun to look at how important is the North Shore migration corridor for other kinds of birds, particularly song birds. So, these are the birds that inhabit our forest during the breeding season, but don’t stay here for the winter. They also inhabit the forest to the north of us during the breeding season, but don’t stay there for the winter. So, they’re all going to head south. Recently, in the last three years, I believe since 2008, the Natural Resources Research Institute began a study to really try to get a better picture of how important the North Shore corridor is for birds of all kinds, and what’s emerging is the value of the corridor to birds migrating in the fall has been way underestimated. We literally have hundreds of thousands to millions, potentially millions, of birds that use the North Shore corridor in the fall as part of their migratory route south. So, this is a much more massive concentration of birds than really had been documented or could have been estimated in any kind of accurate way up until now.
What makes a corridor a corridor? What are they following, the lake?
Anderson: Yes, that’s a great question and an important one to consider. So, birds in migration have to find both food and cover as they make their way. Well, if you’re coming from the north and you get to Lake Superior, you don’t find any cover, and unless you’re some kind of water bird, water fowl, you don’t find any food. So, birds that are migrating during the day, as they come to Lake Superior, they change course and they orient along the shore, and birds that are migrating at night, if they find themselves at dawn out over the lake, they immediately reorient to the shore that they can see, the closest shore that they can see. Then, the second thing that plays a major role in that funneling effect, are the ridges that are parallel to Lake Superior, these high ridges. So, that creates kind of a funneling effect, and they tend to stay between the shore and the tops of the ridges. So, we’re right in one of the premier migration routes of all of North America.
Well, besides the obvious raptors. Name a few that we’re apt to see coming through right now.
Anderson: Well, I mentioned before that the insect feeders are the first to start to move out. And other than nighthawks, we’ve already had several species of warblers like Nashville Black and Whites, Red Starts, Tennessee Warblers; they’ve been on the move already along with Nighthawks and Tree Swallows and the really heavily focused on insect-type birds. The birds that are starting to move now, in motion already, from further north like from the arctic, that nest in the arctic, are a lot of waiting birds like sandpipers, for instance. Yellow Legs would be other species that have been moving through already. I was out recently and saw a number of solitary sandpipers and some of the larger sandpipers, in addition to the spotted sandpipers that are here all summer. Then, other birds like flickers, the thrushes, the tanagers, all the other warblers, kinglets, and then of course sparrows, are all starting to form these feeding groups and flocking together. Eventually, once these birds get on the move, many of them will be moving at night and then they feed during the day. This is how they keep themselves going, right? They’ve got to get some nourishment to get through the migration. So, they fly at night and feed during the day. And when birds from outside of our area come through here on migration, and they stop to feed during the day, they often hook up with groups of local birds, like chickadees and nuthatches, that are going around in their little bands feeding, because these are the birds that know the local scene for food, right? So, these passing-through birds, these migrant birds, will hook up with these little groups during the day and follow them around and chickadees seem to, you know, be OK with that.
Chel Anderson, DNR botanist and plant ecologist. Thanks for helping us understand what’s going on around us this late summer.
Anderson: You’re very welcome.