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Immature hard ticks from the genus Amblyommafeed on blood from a wide range of Neotropical avian hosts. They serve as vectors for pathogens of medical and veterinary importance, such as Rickettsiaagents of the spotted fever group (SFG). Hence, determining ecological factors that increase encounter rates between immature ticks and their avian hosts may contribute to the understanding of tick-borne diseases transmission. Here, we used 720 individual birds from 96 species surveyed in the Brazilian Pantanal to test whether host breeding season influenced tick infestation probabilities. Additionally, collected ticks were screened for Rickettsiaagents to describe new avian-tick-bacteria associations. Our models revealed that the probability of an individual bird being infested with immature ticks was similar during the breeding and pre-breeding season, but higher loads of immature tick stages were found during the breeding season. Host sex did not predict infestation probability, but Rickettsiaagents recovered from ticks were more prevalent during the pre-breeding season. The new records of host usage by larvae and nymphs of Amblyommain Pantanal and the growing body of tick surveys in Neotropical avian communities, suggest that immature ticks may benefit from avian blood sources during their annual cycle. The low number of infected ticks with Rickettsiaagents on Pantanal birds suggest that this vertebrate group are likely not acting as reservoirs for these microorganisms. However, long-term surveys at the same site are imperative to determine which tick species are acting as reservoirs for Rickettsiaagents in Pantanal and determine whether birds are playing a role in dispersing ticks and tick-borne pathogens.

The removal of ectoparasites is a common behavior found across animal taxa and is a determinant to avoid the negative effects of parasites’ presence. Eventually, the elimination of ectoparasites is associated with mutualistic interactions. Cleaner birds remove ectoparasites, providing benefits to its mutualistic host by reducing parasite burden while they obtain a protein food source. Here we report some evidence that giant cowbirds (Molothrus oryzivorus) may have an important role as a cleaner bird. We found 74 adult ticks inside the ventriculus of one male giant cowbird. The ticks belonged to three different species: Amblyomma dubitatum, A. sculptumand A. triste. We found that the sex-ratio of the consumed adult ticks was not different from 1:1. Although additional data are necessary, the large number of ticks found suggests that the giant cowbird may have developed a mutualistic association with large, social mammals such as capybaras (Hydrochoerus hydrochaeris), since this animal is an important host species for the three tick species found in the present study.