Mortality Factors and Defense

Joint defense against a common enemy was noted on July 21, 1961, when

21 kites were seen swooping at a Swainson's hawk perched near the top

of a large cottonwood, where it was partly protected by foliage and

branches. When I flushed the hawk, it was pursued and harassed by the

kites, some of which followed it for nearly a quarter mile although

there were no nests of the kites nearby. On August 4 a group of six

kites was seen heckling a fledgling Swainson's hawk, which crouched

among thick foliage in the top of a tall cottonwood, as the kites

swooped at it, sometimes brushing it with their wings when they swept

past. Dr. Hibbard mentioned an instance in which a horned owl was

flushed, and was chased and heckled by a red-tailed hawk and by a

group of kites. The latter seemed to regard the owl as the greater

enemy, but ordinarily any large raptor arouses their hostility.

Because of their exceptionally swift and skillful flight, the adult

kites have few natural enemies, but the eggs or nestlings are

vulnerable to such enemies as crows, jays, the larger hawks and owls,

and to certain mammalian predators, notably raccoons. Also, many nests

probably are destroyed by the sudden and violent summer storms that

are characteristic of the High Plains. Bendire (1892:178) cited

observations by Goss that in a hailstorm in Barber County, Kansas,

eggs were destroyed in many kites' nests and some of the nests were

almost completely demolished. Several nests found by me to have

incubating eggs in the first week of June were abandoned or had

disappeared completely by July 18, but the cause was not evident. One

nest that was under observation on July 22 had nestlings approximately

two-thirds grown on that date, but on August 4 only a few sticks

remained, and the carcass of a fledgling dangled from a limb ten feet

below the nest. Even at the Park where firearms are prohibited, kites

are sometimes shot by ignorant or malicious persons. In general,

Kansas ranchers recognize the harmless and beneficial habits of kites,

appreciate their esthetic appeal and protect them, but many persons

use them as convenient targets, with utter disregard for the Federal

laws protecting them. Because of the strong popular prejudice against

raptorial birds in general, laws protecting them are usually not

enforced. Law enforcement officers do not take action even when

clear-cut violations come to their attention. Arrest and prosecution

for the killing of any kind of raptor is almost out of the question in

Kansas.

Observations on the Mississippi Kite in Southwestern Kansas · 第 12 / 17 题