FJ3

The weather today was a balmy 18 degrees with about 60% cloud cover at 9 am (we walked until 10:30 am). We left the Davis Center circle and walked down to Centennial woods, taking a short route into the woods and back over the hour and a half walk. We walked through a mix of urban environments (prior to the woods), and coniferous and deciduous forest.

The first thing we saw was a flock of about 14 Red Crossbills flying over the parking lot. They could be returning from a short nonbreeding winter season in more southern states - the main strategy that migratory birds use to survive the winter. However, I think most of the birds we saw today were year-round residents that had their own ways of handling the cold. We saw many smaller birds with their feathers fluffed up into little balls, such as the Dark-eyed Juncos who were perched in a dense shrub, likely to stay warm. Most of the birds we saw were in areas of Centennial Woods dominated by coniferous trees, whose needles provide extra insulation compared to the leafless deciduous trees. They were concentrated in large groups there - walking through we would hear the calls of 10 or more different birds who were likely staying together to work together in finding food. This highly populated area had plenty of snags and cavities - valuable resources for staying warm in the winter (more on that later). There was also evidence of squirrels pulling apart pine cones for food, which birds likely scavenge afterward because that is a food source they wouldn't otherwise be able to get at. Birds rely more heavily on fruit, seeds, and nuts during the winter because many of the insects they eat during the summer aren't around. We saw several different species, including the American Robin and Darke-eyed Junco, eating shriveled up berries that had fallen off various shrubs.

One of the most interesting things we saw today was a Barred Owl swooping away in the canopy. We didn't get a great look at it, but a small murder of American Crows followed soon after, squeaking loudly at it to move it away. I could imagine that some smaller birds are more at risk of predation during the winter from larger raptors and birds of prey because the lack of foliage leaves them more vulnerable and many of the other food sources have migrated south. That is why mobbing the predators in the way the American Crows did to the Barred Owl is an important way to fend off predators.

Mini-Activity: Snag Watch
Over the course of the walk, I saw about 15 different dead trees with cavities. They were in various states of quality - some trees were very rotted and the cavities looked to be unoccupied and falling apart. Other trees, particularly white pine, still had bark and the cavities looked to have been made more recently, evidenced by cleaner wood around the cavity entrance. Some of them had blong shapes, showing they were made by Pileated Woodpeckers. In the area we walked through that had a lot of birds, we heard a number of different species that likely used some of the surrounding cavities, including Black-capped Chickadees, White and Red-breasted Nuthatches, Tufted Titmice, and the Barred Owl. Since most of these birds aren't capable of making their own cavities, there is aggressive competition for the best sites. We didn't see any birds going in or out of cavities, but I would bet given the limited nature of them as a resource, most of the cavities I saw were occupied (except for the ones on overly rotted trees). In the winter, they're primary use is roosting to stay warm and protected at night, but during the breeding season they're main purpose is for nesting.

Posted on March 7, 2021 04:54 PM by grady_jakobsberg