Field Observation 6: Reproductive Ecology and Evolution

It was an overcast and drizzly day in the mid 50 degree range.

I started my walk under a tree that is frequented by a pair of Northern Cardinals. Both birds will sing repetitively, and this time it was the female singing and flicking her tail. The male joined her, and she seemed annoyed by him and moved to a more distant branch. He stayed below her chirping. I suspect that this breeding pair has a nest nearby, as they are so often found in this tree and around the property. I expect that if I had permission to root around in the bushes in backyards I would find their nest in some dense leaves.

Across the road, a pair of Mourning Doves sang dolefully from a high branch. One of them flew off with its fussy call. I do not know whether these were breeding birds, but Mourning Dove song is also common in the neighborhood, and I suppose they might defend it as a territory. Mourning Doves build simple nests with little sophistication or insulation. Evergreens are common around the neighborhood, and their needles would be easy for these birds to obtain for lining, as would the twigs for structure.

I walked in the direction of the Cemetery, and came across a horde of American Crows. Three flew over head, another two chased each other. One would fly at the other’s tail, or they would tumble with feet outstretched, and they called occasionally. I lost sight of these two behind some trees and houses, but three more flew past to join the first three. Not being an ethologist, I hesitate to assume the meaning behind this exchange, but it did seem aggressive to an untrained observer. I know that American Crows prefer the higher portions of evergreens as nesting spots, and these birds may have been members of a family unit with at least one breeding pair.

Further along, I came across a few American Robins and European Starlings. The unpleasant, whistley song of the Starlings is always heard near the bus stop, which they probably congregate at for warmth. I do not know whether they nest there as well, but if there is a cavity I am sure they have occupied it. As for the Robins, I expect that they choose a more secluded spot for their nests.

I managed to find another Northern Cardinal, but only by ear. It sang loudly from a stand of tall trees, but was too distant to find (and would have required trespassing). This area tends to be louder than the one occupied by the first Cardinal pair, it is closer to the main road and to the trains. It also has fewer fruiting trees but more evergreens. I am hesitant to assign territory quality when I do not know how Northern Cardinals assess quality, but I predict that the more secluded spot used by the noisy pair is the better territory. Perhaps this Cardinal is younger, weaker, or less healthy and it could not obtain a better territory.

As I moved on, I heard an American Goldfinch calling from a dense tree. I also heard the persistent song of a bird I could not identify (I have a recording if you want to try).

Posted on April 29, 2018 08:20 PM by tesshall