The breeding biology of Suiriri affinis (Campo Suiriri) and S. islerorum (Chapada Flycatcher) is described for the first time. The nest of S. affinis is a basket constructed mainly with vegetable fibers and lined with a thick layer of silk cotton. All its exterior is ornamented with lichens and dry leaf fragments. All those layers are firmly attached to each other by a large amount of spider web. The nest is supported by its bottom and sides between two or more divergent branches. Although superficially similar, the nest of S. islerorum present many differences, being shorter, shallower, and supported only by its sides between a forked branch. Its interior is also lined by an additional layer of vegetable fibers over the silk cotton layer. The nest of both species is constructed exclusively by the females. The eggs of S. affinis (mean of 20.8 x 15.1 mm, 2.5 g) are pearl white, and those of S. islerorum (20.4 x 15.4 mm, 2.4 g) are light cream, presenting a wreath of small brown blotches around its thicker end. The fledglings of S. islerorum are very similar to the adults, while those of S. affinis present the head, back and wing coverts largely tipped white. The incubation is performed only by the female, lasting 15.2 days for both species. The nestling period of S. affinis and S. islerorum is of 18.9 and 18.3 days, respectively. Some evidences suggests that S. affinis may be a cooperative breeder.
Breeding biology; nest; Suiriri affinis; Suiriri islerorum; Tyrannidae; Cerrado
