THE SHINY COWBIRD (MOLOTHRUS BONARIENSIS) IN CHILE:INTRODUCTION OR DISPERSION? ITS HOSTS AND PARASITICTRENDS

I analyzed the origin, distribution, and hosts of the Shiny Cowbird (Molothrus bonairensis) in Chile, using specimen records and the literature. It is more likely that the species was introduced to Chile before natural dispersal could take place from Argentina. The earliest specimens are from mid-1865 and from around Santiago in central Chile. In the early 1900’s, the Shiny Cowbird was a very popular cage bird, and large-scale importations took place from Argentina to the markets in the Rancagua-Santiago area. Not coincidentally, the species began to be more common around 1910-1920 in the Santiago-Rancagua area. By the 1940s, it had dispersed as many as 1100 km to the north and 1300 km to the south of theSantiago-Rancagua area and in the 1980’s it reached the extreme north of the country and the Magallanes area in the far south. Only 15 species are known as a host for this species in Chile, of which six are known to rear young Molothrus. Its slow expansion northward might be due to the decrease in number of birds species that rear young Molothrus and to the reduction of suitable habitat. As it disperses northward Molothrus bonariensis will probably need to find new hosts that are able to rear its young.

Manuel Marin, ORNITOLOGIA NEOTROPICAL 11: 285-296, 2000