Nest support plants and breeding season of two ibis (Theristicus) species in the Pantanal wetland, Brazil

Abstract

ABSTRACT Six species of the Family Threskiornithidae are found in the Pantanal. Despite being abundant and conspicuous birds, information on aspects of their breeding biology in this wetland remains scarce. The aim of this study was to examine breeding aspects (nest support plants and breeding season) of the two species of the genus Theristicus Wagler, 1832 that are found in the Brazilian wetland. Field work occurred in 2008, and a search for records (photographs) with evidences of breeding activities was done in the WikiAves and eBird databases in March 2020. A total of 49 records were obtained between 2007 and 2019 in four municipalities, mostly in Poconé. Records (n = 37) involving breeding Plumbeous Ibis, Theristicus caerulescens (Vieillot,1817), were obtained between March and November, and incubation has been documented mainly between May and September. Records (n = 12) of the Buff-necked Ibis, Theristicus caudatus (Boddaert, 1783), occurred between April and December, and nests with an incubating adult or nestlings were mainly found between September and December. Breeding activities of T. caudatus were delayed in relation to those of T. caerulescens. Nests of both species were platforms built with large amounts of branches. Most nests of T. caudatus were built in palms, while nests of T. caerulescens were found mainly in non-palm trees. Both species nested in tree species that are commonly found in areas where they forage.