Map depicting the region of the Brazilian Pantanal, on the border Brazil-Bolivia-Paraguay. Star represents the study area where the nests of Laughing Falcons were monitored, in the Pantanal, Mato Grosso do Sul, Brazil. 

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... Falcons ( Herpetotheres cachinnans ) are widespread falconids that occur in the Neotropical region and marginally in the Nearctic American continent. In Brazil they are encountered throughout the country, with a few scattered records in the extreme southern part of their distribution (White et al. 1994, Ferguson-Lees and Christie 2001). They are medium-sized falcons, weighing , 600 g (male) to 700 g (female), and are characterized by a white or pale buff plumage overall, brown wings, a tail with three or four buff bands, and a large head with a distinctive black mask extending from the eyes to the nape, traits that make the species unmistakable (White et al. 1994, Ferguson-Lees and Christie 2001, Parker et al. 2012). In spite of being widespread and considered common throughout most of their range, they can be considered rare and even in decline in some regions (White et al. 1994, Ferguson-Lees and Christie 2001), perhaps because of a decline of their specialized diet, composed primarily of snakes, venomous (e.g., Micrurus spp., Crotalus durissus ) and non-venom- ous (Wetmore 1965, Ferguson-Lees and Christie 2001, DuVal et al. 2006, Specht et al. 2008), and/or because of reduced availability of cavities for nesting that may limit their success in areas with high human disturbance (Wetmore 1965). The breeding season of this species may vary across its distribution, occurring in April in Mexico, February in Guatemala south to Costa Rica and January in northern Argentina (White et al. 1994). In Brazil, the breeding biology of the species is poorly known – one nest was reported with nestlings in September (Specht et al. 2008). The species nests in cavities or depressions, placed in somewhat exposed situations, either in an isolated tree or above the height of the surrounding vegetation (Parker et al. 2012). One or two eggs are laid, and the female does all the incubating, though both parents take care of the nestlings. Nestlings leave the nest 50–59 days after hatching (Skutch 1999, Ferguson-Lees and Christie 2001, Parker et al. 2012). The vocal repertoire of the species is composed by a variety of different songs and calls. In general, the species delivers mostly short nasal laughing calls and a full advertisement song consisting of a long, rhythmic, broadcasting series that can last . 9 min when a pair is duetting (Ferguson-Lees and Christie 2001). Few data exist concerning vocalizations of juveniles or nestlings, but some calls are reported for nestlings from the second week after hatching (Parker et al. 2012). Here, we present new data on the breeding biology of Herpetotheres cachinnans based on eleven nests from the southern Pantanal near Miranda, Brazil, and provide novel data on the use of nest-boxes by the species, as well as details on the eggs, nestlings, plumage of the juveniles, and an undescribed vocalization of nestlings. METHODS Study Area.— The data presented here were collected in the Pantanal region, at the Ref ́gio Ecol ́gico Caiman (19 u 51 9 –19 u 58 9 S, 56 u 17 9 – 56 u 24 9 W) and nearby localities, in the munici- pality of Miranda, State of Mato Grosso do Sul, Brazil (Fig. 1). The region is located in the Cerrado domain (Ab’Saber 2003), and represents a mosaic of habitats which includes different vegetation types, such as Cerrado stricto sensu (savanna woodland, with trees reaching up to 7 m high), gallery-forests, grasslands, open areas, and the typical Cap ̃ es or Cordilheiras, which consist of large woodlots of tall Cerrado forest, situated close to aquatic habitats such as saline lakes and fresh- water lagoons (Eiten 1991, Harris et al. 2005). Data Collection.— The data presented here were collected under the auspices of the Hyacinth Macaw Project, which has been monitoring nests of Hyacinth Macaw ( Anodorhynchus hyacinthi- nus ) in the Pantanal region, mainly in the state of Mato Grosso do Sul, since 1990 (Guedes 2004a). One aspect of the project has been to provide artificial nests for the Hyacinth Macaws, in order to mitigate a possible shortage of natural nest cavities for the species. In addition to A. hyancinthinus , these artificial nests have been used by 17 bird species, including H. cachinnans (Guedes 2004b). The wooden nest-boxes are rectangular in structure and measure 40 3 50 3 60 cm, with a circular entrance 15 cm wide. The floor of the nest-boxes are covered with wood- chips and installed in large trees (see Guedes 2008 for more details on the project and the artificial nests). Between 2007–2008, we monitored natural cavities previously known to be occupied by Hyacinth Macaws during the reproductive season, which occurs mostly between July–December. The nests were monitored on average once a month with observations made using binoculars and by climbing trees using ascending and rappelling techniques. The nests, eggs, nestlings, and juveniles were photographed with digital cameras SONY DSC-P73 and NIKON E4600. Vocalizations of a nestling were extracted from a video recording and corresponding spectrograms produced using Adobe Audition 3.0 and MS Photoshop. The recording is available at Xeno- Canto.org under the access number 126969. RESULTS AND DISCUSSION We found a total of 11 nests occupied by Laughing Falcons - seven natural cavities and four artificial nests (information about each nest is depicted in Table 1; Fig. 2). All nests were found between early July–December and one of them was occupied in 2007 and 2008. This result is in accordance with a nest reported in southeastern Brazil, which was recorded between early September and late October (Specht et al. 2008). All the Laughing Falcons’ nests, both natural cavities and nest-boxes, reported here were also previously used by Hyacinth Macaws. The nests were in big trees surrounded by vegetation in the typical cap ̃ es or cordilheiras , with one nest recorded on the border of a cordilheira , close to a pasture, in a nest-box installed on a Bra ́na tree ( Schinopsis brasiliensis ). Most of the natural cavities were found in Manduvi trees ( Sterculia apetala , Fig. 2a), a species known to host more than 95 % of the Hyacinth Macaws’ nests (Guedes and Harper 1995). In the Pantanal, this tree grows in natural forest fragments, cordilheiras and cap ̃ es , and in order to be able to provide a potential cavity nest, it needs to be older ...