3/15 Openlands Lakeshore Forest Preserve

My bird walk began in the late afternoon at 4:50 pm at the Openlands Lakeshore Forest Preserve in Fort Sheridan, Illinois. The sun was shining, but it did little to warm up the brisk air rolling off of Lake Michigan. I was excited to see what birds I could find in the preserve, because while the majority of the acreage is classified as an oak savanna, there is also a deep ravine on the northern border and the coast of Lake Michigan to the west.
From the moment I stepped out of the car, I was surrounded by a cacophony of different calls and songs. Off to my right I heard a short, loud trill that I didn't recognize from the species we learned in class. Fortunately, a few moments later I saw the bird fly from a shorter tree to a large oak, where I could clearly see its all-black body and the bright red splotches on its wings that identified it as a male Red-winged Blackbird. While I stood there watching him, he seemed perfectly content to sit on the low-hanging branch and sing. Perhaps, due to their coloring, Red-winged Blackbird males developed this behavior in the winter to help absorb heat from the sunlight on their black feathers. A minute later, an American Robin flew over to perch on a nearby fence-post.
As I started walking down the grassy path, I heard the call of a Northern Cardinal and I spotted a large flock of sparrows up ahead. At first glance, they appeared to be House Sparrows. However, upon closer observation, I saw that they had lighter colored underbellies and a brighter brown-orange at the top of their head. My best guess is that these were American Tree Sparrows, but I'm not completely certain. Most of the sparrows could be seen on either side of the path up ahead, foraging in the grass and then retreating to the larger plant and grass stalks when I got too close. I think foraging in a group could be a behavior that evolved to help increase foraging efficiency and safety during winter. I imagine they were looking through the ground vegetation for seeds or insects.
As I kept walking, I heard several other Red-winged Blackbirds off in the distance. Black-capped chickadees also could be seen flitting over the tall grasses or through the tree branches, and I heard a single Mourning Dove somewhere in the trees when I was walking through the ravine. I expected to find more snags around that area, because I hadn't seen any on the path walking through the oak savanna. While there were not many trees on the savanna, the sides of the ravines were covered in oaks and smaller deciduous trees. However, I only found two snags in the entire ravine, and neither had any cavities I could spot. Interestingly, I didn't find a lot of birds near the ravine despite the higher stem density. While snags play essential ecosystem roles, by providing shelter to various species of wildlife, as well as a place to find or store food. I think in ecosystems that are dominated by grassland species of plants, the birds and other wildlife depend more on different structural or biological ecosystem components other than snags. This can be contrasted with Vermont, where the birds probably depend more on snags because of the predominance of forest ecosystems.

Publicado el marzo 16, 2018 07:15 TARDE por asmolens