Sam Christopher, Field Observation 6: Reproductive Ecology

On April 21, 2019, I went birding from 1:20-3:00 pm on the Island Line Trail in Colchester, Vermont. The habitat consisted of both a forested bike path and an open bike path surrounded by water. The weather during this trip started as approximately 67 °F with a cloud cover of approximately 40% and ended with a temperature of 65 °F with a cloud cover of 30%.
The first part of my walk started in a closed woodland. Mainly American Robins and Northern Cardinals were observed in the nearby trees. The male Northern Cardinal’s bright red coloration is a visual mate selection cue. Having these bright colors can signal to female Northern Cardinals the level of fitness a male has. Brighter colors often indicate resistance to parasites, resistance to disease, and access to resources. Based off of this information, females can determine which male to select. I continued to walk to the edge of this woodland toward the marsh environment that is located right before Lake Champlain. Black-capped Chickadees sang their “cheeseburger” or “hey sweetie” song. This is an oral cue for mate selection. This song is used to attract females. In addition to hearing this song, Black-capped Chickadees were seen entering and leaving small cavities in trees. This could possibly be a nesting site. Another visual behavior that indicates mate selection could be the defense of breeding and nesting habitats. A male Black-capped Chickadee might be chosen for his ability to defend a nest and based off of his choice of a specific cavity. This would be considered a visual mate selection behavior. In this same area, male Red-winged Blackbirds surrounded me on all sides of the path. These individuals sang back and forth to each other constantly. These vocalizations could be another oral mate selection cue for females which may indicate to a female that the male is looking for a mate. These calls also serve a dual purpose as a way to advertise territory boundaries. The males calling back and forth to each other around the path could have been communicating about territory locations.
Continuing on my walk, I reached the more open bike path surrounded by Lake Champlain on either side. Immediately to my left I spotted a lone Canada Goose in the water as well as a group of eleven Buffleheads. This mixed flock of males and females also emphasized mate selection based on visual cues. Females are a dark brown color with a white patch under the eye. Males, on the other hand, have a white stomach, dark back, and an almost iridescent purple and green head with a white patch on the back of the head. This coloration is flashier than the females’. Again, this coloration could play a large roll in female mate choice. Continuing down the bike path I took note of the multiple Herring Gulls circling on the air currents overhead, the two Double-crested Cormorants floating and occasionally diving into the water, and the two Tree Swallows flying around the bridge about a mile and a half from my starting location. Another interesting sight was the multiple Song Sparrows observed. At least three separate Song Sparrows were seen moving in and out of the rocks along the side of the causeway. Individuals would stay low to the ground and move in and out of rock crevices. Possibly this species uses this as a nesting location.
Multiple nesting locations were observed throughout the entirety of my birding expedition. Black-capped Chickadees were seen entering and exiting small cavities in trees. This nesting location could be specifically tailored to this species. The entry and exit hole is extremely small allowing for protection from large species of birds. The cavities also are difficult to spot which enhances the protection of young within the cavities. The small entryway also minimizes the young’s exposure to the environment. This could allow Black-capped Chickadees to survive and breed in harsher environments. Another type of nest seen was a small nest of sticks and mud located about halfway up a tree. This possibly belonged to an American Robin that was seen in close proximity to the nest. This nest is larger than the Black-capped Chickadees nest and would hold more offspring. This could be a trade off of having a nest that is more exposed to the environment. In exchange for more eggs, the American Robin must face more predators, more environmental conditions, and may need to put more energy into nest defense. Song Sparrows had a different tactic for nesting. Their nests were hidden amongst the rocks of the causeway close to the ground and water. This nest location might protect offspring from predators if hidden in vegetation or crevices. Nest niche partitioning allows all of these species to become more successful if they are not fighting over nesting locations amongst species.
Mini Activity:
This activity was helpful in organizing the species heard within this area. By listening for 5 minutes I was able to get a better idea of what individuals surrounded me. There were approximately eight different species that I could hear while standing in that location. Some of the species written down such as the Canada Goose and gull species only had one call heard during this time which emphasizes that they were possibly just flying overhead or quickly left the area. Other species called multiple times and it could be determined that there were multiple individuals. For example, there were multiple Red-winged Blackbirds on either side of me and a few Black-capped Chickadees calling in front of me. Writing down the species and their direction allowed me to determine how many individuals of each species were present in the area. I was unable to identify the unknown calls written down and marked with symbols. The symbols were not descriptive enough to allow me to remember the exact call; however, the variation in symbols did help me determine the diversity of birds in the area.

Publicado el abril 22, 2019 02:28 MAÑANA por sgchrist