a case of beak deformity in the Shiny cowbird Molothrus bonariensis and a review on beak deformities in wild birds in Brazil

Beak deformities in wild birds are rarely reported. Here, I described a case of beak deformity in Shiny Cowbird, Molothrus bonariensis, and also provide a review on beak deformities recorded in wild birds in Brazil. In October 2016, I observed a M. bonariensis with a grossly elongated maxilla in the east region of the Mato Grosso state, Brazil. The literature review revealed 60 records of beak deformities in the Brazilian avifauna. The most common types of deformity were crossed maxillae or mandibles (38%), probable accidental injuries (27%), and elongations (15%). Deformities were reported in 35 bird species of 22 families. The most affected species was Ramphastos toco with 21 records. The number of published reports from Brazil was low overall, and are not related as an epizootic episode recorded in some bird communities. KeY-WorDS: avian keratin disorder, beak abnormality, bill deformity, crossed beak, elongated beak. still unclear whether this virus is involved in the epizootic episodes recorded in other regions of the world. In Brazil, despite its extensive geographical area, there has been little research on the occurrence of beak deformities in wild birds, and few cases have been reported (Sazima et al. 2016, Souza et al. 2016). In the present study, I described, most probably, the first report of a case of a beak deformity in a Shiny Cowbird Molothrus bonariensis for Brazil. I also present a review on the published records of beak deformities in Brazil, based on a comprehensive literature search. I used the bibliography identified in Google Scholar (https://scholar.google.com) to make a compilation on beak deformities cases in wild birds in Brazil, and other specific bibliographic sources not indexed as scientific journals of restricted circulation to Brazil and technical books. The literature search was performed using multiple combinations of the words in English and Portuguese: avian keratin disorder, beak abnormality, beak deformity, beak deformities, bill deformity, crossed beak, elongated beak, bird, wild bird and Brazil. On the afternoon of 11 October 2016, I briefly sighted a female M. bonariensis with a heavily deformed beak on the campus of Mato Grosso State University (14o41'25''S; 52o20'55''W), located within the Bacaba Municipal Park in Nova Xavantina, Mato Grosso state, Brazil. I sighted the female again at the same site on Review of beak deformities in wild birds in Brazil Purificação 213 Revista Brasileira de Ornitologia 27(3): 2019 Revista Brasileira de Ornitologia 27(3): 2019 the following day, at around 15:00 h, local time. This individual was part of a flock of five M. bonariensis. On this occasion, I could confirm that the bird had a grossly elongated maxilla (Fig. 1). In addition to being elongated (approximately three times longer than the normal length of the beak), the maxilla was quite curved downward, and had some wear at the extremity. I also observed a contrast in the coloration of the beak, which was greyish black (the standard color) at the base and brown in the elongated portion of the rhinotheca. Despite this deformity, the bird appeared to be healthy, with well-groomed plumage, and similar in size to other adult females. During the short period that I was able to monitor the bird (~4 min), it captured food in a distinct manner in comparison with the other members of the flock. I observed the bird tilting its head to one right side and using the base of its beak to catch insects (apparently ants) in the grass, while the other members foraged normally. Individual adaptations in feeding behavior have been observed in birds of other species with deformed beaks (Pomeroy 1962, Van Hemert et al. 2012). I found 60 recorded cases of beak deformities in wild birds for Brazil from 11 publications (Table 1). Deformities were recorded in 35 bird species, belonging to 22 families, of which 11 families were Passeriformes. Ramphastidae and Thraupidae had the highest number of species with deformities, with 4 each, followed by Thamnophilidae, with 3. The species with the most records were the Toco Toucan Ramphastos toco (n = 21) and the Picazuro Pigeon Patagioenas picazuro (n = 3). With the table 1. Cases of beak deformities in wild birds registered in Brazil. taxon type of deformity municipality-state Date Source


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Beak deformities are rarely reported in wild birds, which may be due to the fact that they are infrequent (Pomeroy 1962, Craves 1994. Beak deformities may be either permanent or temporary, and are caused by a range of factors (Pomeroy 1962). The main causes are genetic mutations, injuries (e.g., collisions with windows), diseases, nutritional deficiencies, contact with chemical pollutants (e.g., agricultural pesticides), problems during incubation, and the inadequate wear of the rhinotheca (Pomeroy 1962, Craves 1994. Most cases of beak deformity are records of isolated cases (Pomeroy 1962, Craves 1994. One notable exception is the case of the wild birds in Alaska, USA, in particular since the 1990s. In this region, beak deformities have been recorded in more than 2500 birds of 30 species . Recurrent sightings of birds with deformed beaks were also reported in the United Kingdom in subsequent years (Harrison 2011) and in the Patagonia, Argentina (Gorosito et al. 2016). Following these epizootic episodes, considerable research efforts have been invested in an attempt to identify the possible causes of these deformities, known as avian keratin disorder , Handel & Van Hemert 2015. The most recent evidence indicates that the deformities observed in Alaska are associated with a viral infection (Zylberberg et al. 2018 In Brazil, despite its extensive geographical area, there has been little research on the occurrence of beak deformities in wild birds, and few cases have been reported (Sazima et al. 2016, Souza et al. 2016). In the present study, I described, most probably, the first report of a case of a beak deformity in a Shiny Cowbird Molothrus bonariensis for Brazil. I also present a review on the published records of beak deformities in Brazil, based on a comprehensive literature search.
I used the bibliography identified in Google Scholar (https://scholar.google.com) to make a compilation on beak deformities cases in wild birds in Brazil, and other specific bibliographic sources not indexed as scientific journals of restricted circulation to Brazil and technical books. The literature search was performed using multiple combinations of the words in English and Portuguese: avian keratin disorder, beak abnormality, beak deformity, beak deformities, bill deformity, crossed beak, elongated beak, bird, wild bird and Brazil.
On the afternoon of 11 October 2016, I briefly sighted a female M. bonariensis with a heavily deformed beak on the campus of Mato Grosso State University (14 o 41'25''S; 52 o 20'55''W), located within the Bacaba Municipal Park in Nova Xavantina, Mato Grosso state, Brazil. I sighted the female again at the same site on the following day, at around 15:00 h, local time. This individual was part of a flock of five M. bonariensis. On this occasion, I could confirm that the bird had a grossly elongated maxilla (Fig. 1). In addition to being elongated (approximately three times longer than the normal length of the beak), the maxilla was quite curved downward, and had some wear at the extremity. I also observed a contrast in the coloration of the beak, which was greyish black (the standard color) at the base and brown in the elongated portion of the rhinotheca. Despite this deformity, the bird appeared to be healthy, with well-groomed plumage, and similar in size to other adult females. During the short period that I was able to monitor the bird (~4 min), it captured food in a distinct manner in comparison with the other members of the flock. I observed the bird tilting its head to one right side and using the base of its beak to catch insects (apparently ants) in the grass, while the other members foraged normally. Individual adaptations in feeding behavior have been observed in birds of other species with deformed beaks (Pomeroy 1962, Van Hemert et al. 2012. I found 60 recorded cases of beak deformities in wild birds for Brazil from 11 publications (Table 1). Deformities were recorded in 35 bird species, belonging to 22 families, of which 11 families were Passeriformes. Ramphastidae and Thraupidae had the highest number of species with deformities, with 4 each, followed by Thamnophilidae, with 3. The species with the most records were the Toco Toucan Ramphastos toco (n = 21) and the Picazuro Pigeon Patagioenas picazuro (n = 3). With the Based on the published photographs and the case descriptions, I was able to determine that 38% of the cases of beak deformity involved crossed beaks, due to some type of deviation of the maxilla or mandible. A further 27% of the cases appeared to be the result of accidental injuries. This type of deformity was found primarily in three species of toucans, which can be explained by the large size of the beak of these species. First, in theory, the large beak of toucans probably becomes more vulnerable to accidental fractures. Second, a large, colorful beak provides more visual conspicuity, which facilitates field registration in relation to the other bird species. Birds with elongated beaks corresponded to 15% of the records. Altogether, other types of deformity contributed with 17% of the records, while the deformity was not described specifically in the cases of Brown Booby S. leucogaster and Pale-breasted Thrush Turdus leucomelas (Table 1).
Despite the large number of icterid species found in Brazil, beak deformities have been recorded in only three taxa, including the present case. Recently, a case of crossed beak was recorded for M. bonariensis in Argentina (Bianchini & Arenas 2018). I evaluated the photographic record of this case and observed that, in addition to the crossed beak, at least the upper mandible was also elongated. Apparently, this record and that of the present study are the only two records of beak deformity in M. bonariensis. In both cases, the elongation of the upper mandible and the difference in color of the elongated part of the beak is notable. Considering only the two isolated cases, the similarities found do not reveal much at the moment, but can serve as a basis for possible future observations.
As in most of cases recorded in Brazil, it was not possible to monitor the specimen over a long period to determine whether the deformity was permanent or temporary, nor to collect it for analysis. At first, it seems unlikely that this case of beak elongation, or any of the others recorded in Brazil, has an etiological origin similar to the alarming cases of beak deformity recorded in Alaska . In fact, the number of published reports from Brazil were low overall, and the events did not appear to be related to epizootic outbreaks. However, beak deformities are more common than suggested by the literature, given that not all cases are reported in scientific publications (Vasconcelos & Rodrigues 2006). Moreover, without systematized research efforts on the subject this issue cannot be elucidated. Laboratory analyses, the long-term monitoring of affected individuals, even in a small number of cases, and formal publication of records may help to better clarify the causes and consequence of beak deformities in birds. These approaches will contribute to the detection of possible threats to the wild bird fauna.

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This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior -Brazil (CAPES) -Finance Code 001.