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Designed by Paul Smith 2006. This website is copyrighted by law.
Material contained herewith may not be used without the prior written permission of FAUNA Paraguay.
Photographs on this web-site were taken by Paul Smith, Hemme Batjes, Regis Nossent,
Alberto Esquivel, Arne Lesterhuis and Hugo del Castillo and are used with their permission.
SHINY COWBIRD Molothrus bonariensis
Decked out in glossy black plumage, the Shiny Cowbird looks like an undertaker, and if an egg-carrying female is in your territory then she might as well be an undertaker, for her presence likely signals the end of your own brood and the beginning of a hard labour sentence to raise her baby - the cowbird is a brood parasite (she lays her eggs in other birds nests, in the same way as the European Cuckoo Cuculus canorus). The expansion of the cowbird has been blamed on the decline of many native species including the much-loved Rufous-collared Sparrow. In some areas as many as 50% of the nests may be parasitised by the marauding flocks of pregnant female cowbirds, and watching a tiny parent struggling hard to satisfy the voracious appetite of her much larger offspring is a pitiful sight (VIDEO B).
FIGURE 1 - Adult male, Costanera Sur, Buenos Aires, Argentina (Paul Smith November 2006).
FIGURE 2 - Adult male, PROCOSARA, PN San Rafael (Paul Smith December).
FIGURE 3 - Same individual head detail (Paul Smith December).
FIGURE 4 - Same individual upperwing (Paul Smith December).
FIGURE 5 - Same individual underwing (Paul Smith December).
FIGURE 6 - Adult male landing, Central Chaco (Marcelo Bombaci October 2007).
FIGURE 7 - Adult female, Costanera Sur, Buenos Aires, Argentina (Paul Smith November 2006).
FIGURE 8 - Pair, Asunción, Departamento Central (Frank Fragano undated).
FIGURE 9 - Immature male, Encarnación, Departamento Itapúa (Paul Smith October).
FIGURE 10 - Juvenile, Villa Florida, Departamento Misiones (Paul Smith December 2007).
FIGURE 11 - Cowbird chick in nest of Rufous-collared Sparrow. Encarnación, Departamento Itapúa (Paul Smith December 2006).
FIGURE 12 - Same chick, estimated 6 or 7 days old. (Paul Smith December 2006).
FIGURE 13 - Same chick, estimated 12-13 days old.(Paul Smith December 2006).
FIGURE 14 - Eggs (top row) found in a nest of Rufous-collared Sparrow (bottom row). Note similarity to host of 2 of the 3 cowbird eggs. Shiny Cowbirds in southern South America exhibit two colour morphs in their eggs, and both were present in this nest. These eggs had failed to hatch and a large Cowbird chick was already being fed by the parents. Encarnación, Departamento Itapúa (Paul Smith December 2006).
FIGURE 15 - Flock, Pilar, Departamento Ñeembucú (Arne Lesterhuis June 2004)
VIDEO A - Adult male, PROCOSARA, PN San Rafael (Paul Smith December).
VIDEO B - Juvenile soliciting food from host Rufous-collared Sparrow Villa Florida, Departamento Misiones (Paul Smith December 2007).
Molothrus bonariensis ski-lee call by female recorded Encarnación, Departamento Itapúa (Paul Smith August 2007).
Click the link to hear the call. Longer versions of this call can be downloaded from the Paraguay page of our partner website Xeno-Canto - the largest collection of freely downloadable Neotropical bird calls available online.