Yellow-rumped warbler, red-shafted flicker prepare for breeding
On Jan. 16, Lois Richter, a docent for the UC Davis Arboretum, led a tour highlighting winter birds in Davis. Richter has been giving this tour every year for five years, and she explained that the Arboretum did not have any outdoor winter events before hers.
Richter did a presentation including a slideshow of the birds and then went for a walk in the arboretum to point out the birds that she had been talking about.
Two birds that Richter indicated as her favorites were the Colaptes auratus and Setophaga coronata, commonly known as the red-shafted flicker and yellow-rumped warbler, respectively. The yellow-rumped warbler, among other migratory birds, changes its appearance in the winter.
“Yellow-rumped warblers look different in the winter than in the summer,” Richter said. “The plumage is very bright in the summer and in the winter their plumage is much duller and grayer.”
The yellow-rumped warbler flies all the way to Canada and Alaska in the summer and flies down to California, Arizona and Mexico in the winter.
The red-shafted flicker, also known as the northern flicker, is very widespread across the United States, according to Richter. The species migrates into Canada and Alaska in the summer and flies down into the southern states and Mexico in the winter. There are even some parts of the U.S. where they can be seen year-round.
“Each individual bird has a place it likes to hang out in the summer and then another place it likes to hang out in the winter,” Richter said. “One [red-shafted flicker] might go from Oregon to Mexico and another one might go from Alaska to Davis. You don’t know which bird is doing which.”
Marilyn Ramenofsky, a professor at UC Davis studying the physiology and behavior of migratory birds, indicates that migratory birds are traveling long distances in order to breed. The breeding season is only one and a half months for migratory birds and before they travel, the birds must undergo an increase in muscle mass.
“When [a migratory bird] arrives at a great distance, it must be ready to start to breed. A lot of the changes, although we don’t see them on the surface, are getting started here in the wintering grounds,” Ramenofsky said.
The migratory birds need a month to prepare for breeding before they migrate and therefore, need an environmental cue to initiate these physiological changes. These birds start feeding more, fattening and changing once photoperiod, the period of time during the day that there is light, starts to increase.
Comparatively, non-migratory birds have to respond to local cues, such as precipitation, weather, bud bursts and insect emergence. The nuttalli, a subspecies of the Zonotrichia leucophrys, commonly known as the white-crowned sparrow, does not have to change its weight as much as migratory birds before breeding. Not only do native birds not have to travel to breed, but they also breed for six to eight months.
According to Ramenofsky, there are also different types of migrant birds, such as long-distance migrants and middle-distance migrants. Alison Kent, a board member of the Yolo Audubon Society, indicates that Davis is an important winter destination along the Pacific Flyway.
“Birds in general move to where there’s food,” Kent said. “The Central Valley, where Davis is, is a very important wintering place on the Pacific Flyway especially for water birds, such as ducks and geese.”
On the Yolo bypass, hundreds of ducks and geese can be seen during this time of the year. Additionally, birds such as the yellow-rumped warbler can be found in the Arboretum until late April.
Written By: RIVA BALLIS – city@theaggie.org
