Field Observation 6: Reproductive ecology and evolution
On April 22, a Monday, at about 2:00 PM I walked over to Centennial Woods for my birding excursion. The weather was really nice. It was only partly cloudy with a few cool breezes here and there. The temperature fluctuated around 60 degrees Fahrenheit. I was heading to the very first entrance of Centennial which consisted of dry coniferous woods. I happened to stumble upon a bird feeder with a variety of frequent visitors. My excursion consisted of mostly walking along the trails and observing any birds I came across until roughly after 3:30 PM.
As I walked up to the bird feeder, one of the first birds I noticed was a Black-capped Chickadee. After spotting one individual, I noticed more flying back and forth from the nearby eastern hemlocks. They were very vocal and there had to be at least 10 individuals in direct proximity of the feeder. Picking out one particular individual I observed it for a couple minutes as it foraged from the feeder. I noticed that each time it picked a seed from the feed it would fly up to a branch and peck the branch with its beak. I am unsure if it was storing seeds for later or pecking the branch for other reasons. I also noticed some males in particular pick out certain perches and sing for a few minutes. I was unable to distinguish males from females so I assumed that every Chickadee that sung was a male.
After a while more birds started visiting the feeder. One of the new birds I saw was a Gold-headed finch. There was only one male in the area that let out a very low volume call. This individual perched very close to the feeder and made it his singing perch. The lone male was very calm and did not show much activity except to hop down into the feeder. That all changed when I imitated his song. When I started making a similar whistle, the male became more active, started singing much louder than before, and flew to more locations as if trying to secure more territory.
Overtime another species made its appearance. At first I had no idea what this brown, discrete robin-sized bird was. Confused of what bird I was observing I unsuccessfully tried to snap pictures. Though I was unsuccessful on capturing a photo of the brown bird, I accidentally caught a glimpse of a black bird. This black bird was much more bold and a lot easier to take a picture of. I was not entirely sure what this black bird was until it sang. Once I heard its vocalization I knew immediately it was a Brown-headed Cowbird. After making that realization, I soon noticed the male was hovering by the brown bird which I now knew was also a Brown-headed Cowbird. I did not see any mating behavior, but the male and female were very close and seemed to share the same territory. There were a couple times they both perched on the same branch and the male displayed some dominating behaviors like raising his head or looking bigger. Seeing these two together made me want to inspect the tree and surrounded area for a nest. I had no luck finding their nest if they had one but I saw a very large nest in a somewhat further away tree. No clue what made that specific nest, but I know it has to be larger than a cowbird.
After discovering the nest, I decided to continue down the trail. I did not see much on the trail, but I definitely heard a variety of calls and songs. At one point I followed the vocalizations and found myself under an eastern hemlock teamed with black-capped chickadees. Unsurprisingly, the chickadees in this area behaved the same as the ones by the feeder as they sang, foraged, and pecked the branches beneath them. After a while, I resumed my journey along the trail. I met a dead end, made my way back, noticed it was 3:30, and decided to call it a day.
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