Named after the British naturalist William Svenson, this bird of prey is a skinny bird of prey with a long tail and long, pointed wings that soar in a distinctive shape similar to the "V" when soaring. It is a typical bird in open areas, especially in grasslands, and its breeding core is in the savannahs of western North America. Although its range extends as far north as the Alaskan tundra and as far south as northern Mexico, it is most commonly found on the Great Plains of North America.
"Single-minded" raptor
The Scythorn migrates as far as other North American predators, spending about a third of their lives migrating. Every year, most populations move from the Great Plains of North America to the steppes of Argentina in thousands of large gangs, and then return. This is a widely distributed bird, and in North America from April to September, people can often see them on telephone poles, fence poles and some dead trees. Data from field observations show that the Scythorn is very specific to its mate and nesting address.
The spouses have a seven-month period of separation, and the total distance of the entire migration journey has reached 300,000 kilometers, but every spring, both spouses return to the same region to reconfirm their relationship through a series of chirping calls and circular and subductive courtship. Such a high degree of specificity to the breeding ground as they do is very rare in species that migrate over long distances.
Excellent little killer
Sisi's grebe is a master predator of rodents, feeding on rodents throughout the breeding season, initially only male Scythians preying on rodents, and then both parents regularly bring back squirrels, weasels, house rats and rabbits to the land. But other times, these birds of prey only prey on insects. In the steppe wintering grounds of Paraguay and northern Argentina, the Scythorn feeds mainly on locusts and migrating dragonflies, and hovers over vast grasslands to track insect swarms. Soar in the updraft
The Scythian is highly gregarious during the four-month migration period. They can form huge flocks, like swarms of insects from distant places, that are easy to observe at traditional eagle-watching sites such as Hazel-Badsmore County Park in Texas. Every year from March to April and from October to November, about 1 million Scythorn pterophores throughout South America pass through Mount Amkong near Panama City. These large-scale migrations only occur when the weather is warm and dry and the hot air currents are formed, and the Scythorn can soar with minimal energy consumption.
In Panama, the Scythorn group is able to take advantage of long-haul flights created by a series of updrafts, gliding tens of kilometres or more at the bottom of clouds with little flapping of its wings. Compared with flapping flight, the soaring period and sliding period can save about 95% to 97% of energy. This way of conserving energy is important because the Scythorn does not feed during the 60-day journey to Argentina, and ornithologists rarely see the S. Sissy quarry feeding during the journey, nor does it observe its excrement in public settlements. The fact that these birds are able to migrate without a single feed indicates that their energy consumption for long-distance migration journeys is very low.
The migration bottleneck of birds
Every autumn, including the Scythorn, about 500,000 predatory birds pass through the Mesoamerican migratory bird migration route from southern Mexico to Panama. This passage narrows sharply at the southern end, forcing migratory birds of prey to form larger migratory flocks. The narrowest point of the land bridge is located in the Isthmus of Panama, which is only 50 kilometers wide in the Panama Canal Zone. The four bird of prey species that take advantage of this migration route are: the giant-winged dew, the red-headed Condor, the Scythorn and the Mississippi Grey Warbler. There are also a slightly smaller number of 24 other North American raptor species that also pass through here.
Spectacular flocks of migratory birds of prey can also be seen on a small land mass between Lake Michigan, Lake Huron and Lake Superior, Cape Whitefish, Michigan; It can also be observed in places such as the Strait of Gibraltar, a migration route between Spain and North Africa, and the Bosphorus between the European and Asian parts of Turkey.
Existential crisis
Although it is a large bird, its survival is still threatened, and in the 1980s and 1990s, the population declined significantly, due to the extensive use of organophosphate-rich insecticides in the overwintering grasslands, which led to a sharp decline in the main food of these birds of prey, and many of the birds were poisoned. Later, due to the implementation of conservation measures for this species in Argentina and the change in the migration patterns of the species itself, the population of the Scythorn warbler began to recover slowly.
Some individuals have migrated to the northern part of Brazil's predominantly grassland regions to overwinter, while a small number of Scythorn has migrated to southern Florida, California and Central America to overwinter, and this overwintering population may be growing. Whether this change in behaviour is a direct consequence of the intensification of savannah agriculture or is influenced by other factors, such as climate change, remains to be studied.