Sam Christopher, Field Observation 1: ID and Flight Physiology

My birding expedition took place on February 3, 2019, from 8:10 am to 9:50 am. From 8:10 am until 9:20 am I birded on the East Woods Natural Area Loop in South Burlington, Vermont. East Woods is an old growth forest with varied terrain including steep inclines and flat paths that followed closely to the Potash Brook. During my walk, there was at least a foot of snow cover on the forest floor. From 9:20 until 9:50 am I moved across the street to Farrell Park in the hopes of increased sightings. Farrell Park was more integrated into a human environment. There was a paved path in between open fields, sparse trees, and recreational areas including a dog park, playground, and sports fields. The environmental conditions during this time consisted of 100% cloud cover, no wind, and a temperature of 19 °F throughout the hour and forty minutes spent birding.
Throughout my time in East Woods there were few sightings, but many audio cues describing which birds were in the vicinity. Within five minutes of entering the nature trail a Black-capped Chickadee, a White-breasted Nuthatch, and a Tufted Titmouse could be heard in the trees surrounding us. I continued to walk along the path in an attempt to get a better vantage point to spot the birds visually; however, I couldn’t get a glimpse of them. The first birds I saw I was unable to identify. Three Black-capped Chickadee sized birds flew out of the top of an approximately twenty foot tall tree. Their quick escape didn’t allow me time to view them in my binoculars. Continuing down the nature trail I heard another Black-capped Chickadee in addition to a Blue Jay. Again, neither of these birds were spotted. Possibly they were hidden in the dense trees, or too far from the path to see. As I continued on the loop I spotted another unidentified bird. This individual was approximately the size of an American Robin and had an undulating flight pattern. This led me to think that it was possibly a White-breasted Nuthatch. I reached the end of the nature loop without any more sightings; however, next to the road outside of the woods I immediately saw two American Crows flying overhead. The lack of sightings in East Woods could possibly be due to weather conditions. It was extremely cold and there was no sun due to cloud cover. Also, the dense tree coverage could have prevented me from seeing some of the birds I heard. Another thought as to why there were limited sightings could be the noise pollution in this area. Specific parts of the loop were very close to the highway, 189, and the noise from the cars was extremely loud. This could influence which habitats a bird chooses to spend time in.
I changed location to Farrell Park which is directly across the road from East Woods. Immediately there was an increase in bird sightings. Within five minutes of arriving, I saw three Black-capped Chickadees within the branches of a tree next to the parking lot. These three stayed in the uppermost branches and did not take on many long flights. Mainly they took short flights between nearby branches. Continuing on, a dog walking group passed me on the path. As soon as this group passed I saw a Downy Woodpecker, a White-breasted Nuthatch, and three Black-capped Chickadees. One of my hypotheses is that the presence of the dogs brought the birds out towards the bike path. All of these species were calling and were seen in the branches directly next to the bike path where the dogs were walking. Possibly the birds were becoming territorial and saw the dogs as a threat. I observed that both the Downy Woodpecker and the White-breasted Nuthatch remained on one tree. Neither flew between trees and only moved up and down the initial trees that I saw them on. Both species could effortlessly climb vertically up the trunks. It was surprising to me that I saw more birds in the more humanized environment than in the more isolated and preserved environment. Comparatively, I saw three times as many birds on the walking path in Farrell Park than in the more secluded East Woods. This could be due to limited noise pollution from the highway or maybe these species preferred more open habitats.
The presence of the dogs gave me a good opportunity to look at these species and observe their flight patterns. Black-capped Chickadees had extremely fast wing beats. Almost impossible to see an individual flap of the wing as they moved from branch to branch. The Black-capped Chickadees tended, as I mentioned earlier, to only attempt short flights between branches. Sometimes these even appeared to look as though the bird was just hopping from branch to branch. They could quickly change direction amongst the trees. Possibly this species would be considered to have a low aspect ratio which describes short and wide wings. This allows for speed and maneuverability. This flight pattern is extremely different than the flight pattern of the American Crow which I saw earlier near East Woods. The American Crow utilized steady wing beats that could each be individually detected, unlike the Black-capped Chickadee. The American Crow did not change direction and was seen in open air instead of a habitat that requires maneuverability around branches or other obstacles. A key feature to identify the American Crow would be its steady wing flaps and slotted primary feathers. Slotted primaries allow for each feather to become an independent airfoil. This is oftentimes seen in birds that undergo long distance travel. This characteristic is an indication that American Crows may undertake longer distance flights than Black-capped Chickadees. This matches my observation of the Black-capped Chickadees only flying short distances between branches while the American Crow was flying constantly during my observation of it. Flight shape and pattern can indicate species and behavior. Low-aspect ratio emphasized the maneuverability and speed of the Black-capped Chickadee and reaffirmed the idea that this species is oftentimes located within dense trees. In contrast, slotted wings and a steady wing beat indicate the American Crow can be found in more open habitats and allow for long distance flights.

Publicado el febrero 15, 2019 05:37 TARDE por sgchrist