The fall and rise of white-tailed kites
In 1966, a young birder looked through the air disturbed by heat rising over the agricultural fields in Monterey, California. It was difficult to make out the shimmering form of the white bird sitting on the ground, but it belonged to a white-tailed kite.
It wasn’t a great look, but it was the first I had ever seen. I recorded the sighting in my growing life list in less than tidy handwriting. I still have that list.
The white-tailed kite is a small, elegant bird of prey about the size of a crow but with more graceful proportions. It has long pointed wings and is a striking white with a pale gray back and a black patch on the wing. Kites favor open areas where they can be seen hovering over pastures searching for prey.
The family friend who took me birding in the Monterey area explained that, for unknown reasons, white-tailed kites were in severe decline, and this area was one of the last places you could hope to see them along the West Coast.
White-tailed kites were not in danger of extinction. They occurred (and still do) in several widely separated populations in North and South America, including along the Gulf Coast of Texas and Mexico, northern South America, and Argentina. However, the West Coast population was in real trouble.
Since that time, the kite population has increased tremendously. By the early 1970s, they had arrived in Oregon. Several pairs took up residence in Jackson County, most in and around Denman Wildlife Area. A few have since moved into the Willamette Valley and along the coast. Jackson County is still the best place to find kites in the state. The reason for their population expansion is just as mysterious as their decline. It’s not like there has ever been a shortage of meadow mice.
The 1970s was a time of recovery for many birds of prey and fish-eating birds. The pesticide DDT, more specifically its break-down product DDE, interfered with the calcium metabolism of birds sitting atop the food chain, including bald eagles, osprey, peregrine falcons and brown pelicans. Eggs were laid with thin shells or none at all, leading to reproductive failure. With the ban on the use of DDT in the 1960s, populations recovered rapidly.
This explanation does not apply to white-tailed kites. They feed on meadow mice, which make up nearly 90 percent of their diet. Meadow mice are “salad eaters,” feeding low on the food chain. Pesticides such as DDT become more concentrated in tissues with each link up the food chain. “Grass, mouse, kite” is a very short food chain, not allowing for the acute accumulation of toxins.
In the last 10 years, I have found it increasingly difficult to find white-tailed kites in the Rogue Valley. Three pairs that I followed for years have abandoned their territories. This may or may not signal the beginning of another decline. Populations of all species fluctuate in abundance, although kites seem to take it to the extreme. It is something I will watch with interest. I would hate to see this beautiful bird disappear from the Rogue Valley.
Stewart Janes is a biology professor at Southern Oregon University. He can be reached at email@example.com.