Field Observation 6: Reproductive ecology and Evolution

Friday, April 27, 2018 from 4:3 to 7:15pm

Today was a warm, overcast day with temperatures hovering around 58oF. We went to Redrocks, which has quite the diverse habitat. From Lake Champlain, to the rocky bluffs, to a variety of mature trees including red maple, eastern cottonwood, eastern white pine, white ash, and eastern redcedar, to name a few.

We started off by exploring the vernal pools, looking for herp eggs. As we wandered, we heard a group of Black-capped Chickadees chipping to each other while foraging and an American Crow indignantly squawking, as if threatened. We soon discovered the source of the crow’s distress, a Barred Owl began calling from the eastern white pine stand that the crow had just been sitting in. After listening for a while, I was able to triangulate the location of the Barred Owl and spend some time watching the lovely specimen.

We then headed over to the rocky bluffs, and were met with a symphony of birds, singing out their territory lines and communicating with potential mates. The first bird we observed was a Pine Warbler!! These birds build nests from late March to early June, with females doing most of the nest-building while males sing to mark the territory. Nests are built at the top of large conifer trees. The male we observed was singing in a large eastern white pine, likely guarding his mate as she worked. The habitat that this particular Pine Warbler had found was very prime habitat, as the eastern white pine was very large and appeared to be very healthy. Although the trees were near a few foot trails, the area is relatively undisturbed and surrounded by mature trees. Holding a prime habitat location, such as this one, shows that the male is a very fit individual, as he is able to expend that energy to defend his territory against other males that would be seeking this location. Pine warblers make their nests out of stems, bark, pine needles, spider webs and other materials, which are then lined with feathers. These nests are shaped as deep cups and are located near the end of branches.

As we listened, we heard Tufted Titmice, a Northern Carinal, a Pileated Woodpecker, and two Brown Creepers foraging. All of the birds were just chipping as thy foraged, except for the male Brown Creeper, who was giving his territorial call. Male Brown Creepers generally only call on their breeding groups, but will occasionally sing during migration. Their high, tremulous call is always a treat to hear. The last birds we heard as we stood and listened were a Wood Thrush and a Winter Wren. Male Winter Wrens sing vigorously during the spring breeding season to attract females. Once they have attracted a female, they will flutter around and show her different nests they have built in their territory so she can pick which one she wants to use. They nest in natural cavities that are close to the ground, and tip-up mounds created by fallen trees are very important habitat to them. Within the cavity, a nest is created of grass, moss, and rootlets, which is then lined with animal hair. Male Winter Wrens also sing to defend their territory.

Posted on 29 de abril de 2018, 10:07 PM by jpupko