Passage: The precise distribution of the Puerto Rican amazon before the arrival of Spanish colonialists is uncertain, because of a lack of contemporary records and then the extermination of the indigenous Taíno people, but the species was apparently widespread and abundant. There is also evidence the species may have inhabited other nearby islands, such as Antigua, Barbuda and the Virgin Islands. Estimates of the parrot's early numbers vary greatly. Some authorities claim that there were once more than a million individuals, while others suggest a more modest population of 100,000. During the first 150 years of Spanish rule the human population was small, and in 1650, when the population of the island was 880 people, the species was still abundant throughout the archipelago. After 1650, human habitation increased exponentially, and by the 18th century the Puerto Rican amazon population started to be affected.  Heinrich Moritz Gaede, a German naturalist, declared that by 1836 the parrot population had noticeably declined. Even so, as late as 1864, British ornithologist Edward Cavendish Taylor noted that the parrots were still common near the island's capital, San Juan.At first, human activity had not posed a significant threat to the Puerto Rican amazon. The Taíno hunted the parrot but without much effect on its population. In the past 200 years, however, many factors have led to a drastic decrease in the birds' numbers: agricultural development, the construction of roads, hydroelectric development, and the adoption of young chicks as pets. Especially during the latter half of the 19th century, most of Puerto Rico's virgin forests, a historical habitat of the species, were cleared for agricultural development, primarily for the production of sugar, cotton, corn and rice. The amazon quickly came to rely on these crops as its main food source and so became seen as a pest; local farmers repelled or hunted the bird if possible. As agriculture expanded, the amazon's habitat disappeared further and its population declined.

Question: when had the population greatly increased?
1650