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Orientation behaviour studies have been traditionally carried out using variants of a setup known as the Emlen funnel, which consists of a circular cage with the top covered by glass or wire-screen so that either the sky is visible or the setup is placed in a planetarium or with other controls on environmental cues. The orientation behaviour of the bird inside the cage is studied quantitatively using the distribution of marks that the bird leaves on the walls of the cage. Other approaches used in pigeon homing studies make use of the direction in which the bird vanishes on the horizon.

What is studied quantitatively inside the cage?
Answer: The orientation behaviour
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From the years 1500 to 1850, an estimated 3.5 million captives were forcibly shipped from West/Central Africa to Brazil; the territory received the highest number of slaves of any country in the Americas. Scholars estimate that more than half of the Brazilian population is at least in part descended from these individuals. Brazil has the largest population of Afro-descendants outside of Africa. In contrast to the US, during the slavery period and after, the Portuguese colonial government and later Brazilian government did not pass formal anti-miscegenation or segregation laws. As in other Latin countries, intermarriage was prevalent during the colonial period and continued afterward. In addition, people of mixed race (pardo) often tended to marry white, and their descendants became accepted as white. As a result, some of the European descended population also has West African or Amerindian blood. According to the last census of the 20th century, in which Brazilians could choose from five color/ethnic categories with which they identified, 54% of individuals identified as white, 6.2% identified as black, and 39.5% identified as pardo (brown) a broad multi-racial category, including tri-racial persons.

How much of the Brazilian population are descendants of slavery?
Answer: more than half
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Tracks of the Northern Pacific Railroad (NPR) reached Montana from the west in 1881 and from the east in 1882. However, the railroad played a major role in sparking tensions with Native American tribes in the 1870s. Jay Cooke, the NPR president launched major surveys into the Yellowstone valley in 1871, 1872 and 1873 which were challenged forcefully by the Sioux under chief Sitting Bull. These clashes, in part, contributed to the Panic of 1873 which delayed construction of the railroad into Montana. Surveys in 1874, 1875 and 1876 helped spark the Great Sioux War of 1876. The transcontinental NPR was completed on September 8, 1883, at Gold Creek.

When did the Northern Pacific Railroad reach Montana from the west?
Answer:
1881