angustifrons) destroyed cacique eggs and killed young,
leaving nests empty. Finally, Venezuelan Troupials
(Icterus icterus), which are large, aggressive orioles,
both destroyed cacique eggs and young and took over
their nests. Robinson hypothesized that the piracy is
not related to competition for food, because each of
the nest pirate species has a diet different from that of
caciques. Instead, the presence of many nearby empty
cacique nests serves to confuse potential predators and
confer protection on the nest pirate species.
Oropendolas and caciques are also routinely
parasitized by Giant Cowbirds (Molothrus oryzivorus;
plate 15- 128), which are brood parasites. A female
cowbird will surreptitiously (and quickly) lay an egg
in an oropendola or cacique nest, and the oropendolas
and caciques (which do not know the egg is not one
of theirs) actually raise and fledge the young cowbird.
Of course, if they catch the cowbird in the act, the nest
owners usually evict the egg.
Orioles are among colorful blackbird species, their
plumage usually various combinations of orange,
yellow, and black (plate 15- 129– 130). They are not
colonial, like the oropendolas or caciques, but nest as
territorial pairs. Several oriole species migrate to North
America to nest, but most remain in the tropics.
Orioles, oropendolas, and caciques feed on fruit and
nectar, mixing various arthropods into an otherwise
vegetarian diet.Finches, Seedeaters, and Others:
Taxonomy in FluxThere are many species of Neotropical birds with thick,
strong, seed- cracking bills. Typically seed- eating birds
inhabit areas such as grassy, disturbed sites and forest
edges. They also occur in marshes and around human
habitations. Some inhabit forests.
The classification of birds has become increasingly
complex, and taxonomic sequences have changed as
more molecular- based data have been analyzed. Such
complexity is illustrated, for example, with a subfamily
of common birds that comprises the genera Euphonia
and Chlorophonia.
Euphonias (plate 15- 131), long believed to be allied
with the tanagers, are a group of 27 small, multicolored
species. On the basis of DNA studies, they have been
reclassified and placed in the large family Fringillidae,
with the so- called true finches, such as goldfinches andPlate 15- 128. Giant Cowbirds (37 cm/14.5 in), here bathing in
a pasture, are brood parasites that frequently lay their eggs in
oropendola and cacique nests. Photo by John Kricher.
Plate 15- 129. The well- known Baltimore Oriole (Icterus
galbula), a migrant that breeds in eastern and central North
America, shows the strikingly colorful plumage pattern typical
of most orioles. Baltimore Orioles winter in the Neotropics.
Photo by John Kricher.
Plate 15- 130. Look for the Yellow- hooded Blackbird
(Chrysomus icterocephalus) along marshes and wet areas from
Central America to northern South America and along the
Amazon River. Photo by Jill Lapato.
306 chapter 15 neotropical birds: the bustling crowd