First photographic records of aberrant white feathers in the threatened Lear’s macaw Anodorhynchus leari, with further notes on its breeding behaviorAbstract
The Lear’s macaw Anodorhynchus leari is a globally threatened species, native to the sandstone cliffs of the Caatinga biome in northeastern region of Bahia, Brazil. The population in Canudos consists of a large breeding subpopulation and is protected by the local authorities. In August 2022 and January/February 2025, we obtained the first documented records of white aberrant feathers in three apparent breeding adults of the endangered Lear’s macaw during short visits to the breeding grounds. Here, we provide photographic records from the field along with other anecdotal observations concerning reproductive behavior, adding unpublished information from captive individuals to complement possible knowledge gaps about the breeding biology and sexual behavior of the species.
Keywords:
breeding parameters; Canudos; Lear’s macaw; sexual behavior; white aberrant feathers
Resumo
A arara-azul-de-lear Anodorhynchus leari é uma espécie globalmente ameaçada, nativa das falésias de arenito do bioma Caatinga no nordeste da Bahia, Brasil. A população em Canudos consiste em uma grande subpopulação reprodutiva e é protegida pelas autoridades locais. Em agosto de 2022 e janeiro/fevereiro de 2025, obtivemos os primeiros registros documentados de penas brancas aberrantes em três adultos aparentemente reprodutores da arara-azul-de-lear, ameaçada de extinção global, durante breves visitas ao local de reprodução. Neste trabalho, apresentamos registros fotográficos de campo, juntamente com outras observações anedóticas sobre o comportamento reprodutivo, além de informações inéditas de indivíduos em cativeiro, para complementar possíveis lacunas de conhecimento sobre a biologia reprodutiva e o comportamento sexual da espécie.
Palavras-chave:
parâmetros de reprodução; Canudos; Arara-azul-de-lear; comportamento sexual; penas brancas aberrantes
1. Introduction
The Lear’s macaw Anodorhynchus leari represents one of three extant true ‘Blue macaws’, which entire population is geographically confined to two breeding colonies located in the northeast part of Bahia, in Brazil (Birdlife International, 2019a). The species is considerably smaller in body size (64-73.5 cm; n = 5 vs. 83.5-93.5 cm; n = 12, Abramson et al., 1995) than the congeneric Hyacinth macaw A. hyacinthinus, differing also in weight (1200-1700 g, Abramson et al., 1995), with males and females in Lear’s macaws having an average weight of 863.2 ± 80.77 g (761-994, n = 10) and 779.7 ± 71.78 g (715-966, n = 11, VM unpub. info.). In addition, the Lear's macaw has a smaller mean wingspan of 95.37 ± 7.12 cm (83.1-103.4, n = 6, n = 2 Abramson et al., 1995, n = 4 VM unpub. info.) in comparison to the A. hyacinthinus with 117-127 cm (n = 12, Abramson et al., 1995). In addition, the Lear’s macaws show notable differences in plumage coloration (A. leari: indigo blue plumage with greenish tinge vs. A. hyacinthinus: cobalt blue plumage, lack of greenish tinge) and shape of the ocular patch (A. leari tear drop vs. A. hyacinthinus round, Abramson et al., 1995). The Glaucous macaw A. glaucus, which remains poorly known, is now considered as ‘Possibly Extinct’ (Birdlife International, 2019b).
The occurrence of A. leari has long remained an unresolved mystery, resulting in the fact that the species was considered to be on the verge of extinction (IBAMA, 2006), with the population in 1990 believed to consist only of 60 individuals (Brandt and Machado, 1990). Later population assessments showed larger population sizes. For example, 570 individuals were counted in 2004 (Pacifico et al., 2014). In response to intensive research efforts and conservation measures (Barbosa and Tella, 2019), the species showed a steady increase in the population size, with current estimates indicate that the global population consists of 2.548 individuals (Projeto Arara-azul-de-lear, 2025) – albeit it is suspected that only a small proportion is actively breeding (Pacífico et al., 2014). The population near the observation site at the Estação Biológica de Canudos is currently estimated to consist of approximately 300 individuals, with individuals recorded to forage 60 km away from the natal territory (pers. comm.). The site is located in the north-eastern part of Bahia. The two main subpopulations are currently concentrated in Serra Branca, Jeremoabo, south of the Raso da Catarina plateau and in Toca Velha, Canudos, respectively (Birdlife International, 2019a). Conservation practices, like the reintroduction of captive bred individuals, continuous monitoring and protection of the nesting sites along with the identification of threats (e.g., power lines, Barbosa and Tella, 2019; Biasotto et al., 2023) helped to boost the wild population growth in the past decades.
The plumage coloration of birds is determined predominately by two forms of color pigments: melanin and carotenoids (van Grouw, 2021). In parrots, an additional unique pigment, the psittacofulvin, determines the coloration (Berg and Bennett, 2010; Hume and van Grouw, 2014; Neves et al., 2020). For the “Blue macaws”, psittacofulvin is, however, lacking to a larger extent (albeit marginally present in the Lear’s macaw due to its green tinge), while the vast majority of plumage coloration is determined by eumelanin. In parrots, where psittacofulvin is lacking, the inhibition or absence in melanin producing cells (primarily color) will result in the presence of white feathers in the associated areas (van Grouw pers. comm.). In contrast, in parrot taxa, where psittacofulvin is predominately determining the plumage coloration, the absence of melanin producing cells would result in only the color determined by the remaining color pigments (e.g., yellow, orange, red). The absence of psittacofulvin (e.g., inheritable, through captive breeding of mutations) results in contrast, produce blue feathers, which intensity will differ depending on the wild coloration of the respective species (Hume and van Grouw, 2014)
In general, the terminology of color aberrations is interspersed with inconsistencies. According to van Grouw (2021), leucism is a strictly heritable aberration that persists permanently, while singular or concentrated patches of white feathers that are present only temporally (e.g., poor diet, injury, poor physical condition) or are the result of progressive greying – should not be considered as partial leucism or leucism by any means. Partial leucism remains a rare phenomenon in wild bird species, while aberrant white feathers occur more frequently (Molina et al., 2018, van Grouw, 2021). Records of leucistic parrots or parrots with aberrant white plumage/feathers remain, on the other hand, undocumented in the wild. Nonetheless, other color aberrations were reported for a few parrot species in the wild and also for parrots likely originating from captivity (Hume and van Grouw, 2014; Smith and Ríos, 2017; Kushwaha and Kumar, 2018; Moura et al., 2018; Grajales and Silva, 2023; Ramos et al., 2023). In other avian species, the absence, either fully or partially, of both melanins in cells are suspected to originate from heritable mutations (Hume and van Grouw, 2014; van Grouw, 2021), age (progressive greying, Hume and van Grouw, 2014; Camacho et al., 2022), physiological or environmental constraints (Hume and van Grouw, 2014; Izquierdo et al., 2018). In August 2022 and January/February 2025, we were able to observe color aberrations in three wild Lear’s macaws, providing here the first photographic evidence of aberrant white feathers occurring in wild “Blue macaws”.
In contrast to the presence of color aberrations, the ecology of A. leari remains considerably well known (Pacífico, 2012; Pacífico et al., 2014). The breeding biology was studied in detail at Estação Biológica de Canudos (Pacífico, 2012), with breeding season is reported to lasts between December to July (Pacifico, 2012). Due to the inaccessibility of the nesting cliffs, the predation rate is low and thus breeding success is high (80% of the breeding attempts, Pacifico et al., 2014). While the breeding biology is well studied in the wild, some breeding parameters and aspects of sexual behavior remaining inadequately known. Therefore, our second objective is to add some anecdotal observations about the sexual behavior from wild and captive birds and complement possible knowledge gaps regarding the breeding parameters using data from an ex-situ population.
2. Methods
2.1. Study site and observations
The photographic records were obtained during opportunistic visits at the colony located at the Estação Biológica de Canudos (9°57'22” S, 38°59'55” W, 450 m a.s.l, Figure 1) near an observation platform opposing (c. 30 m) the active nesting site on the 15/08/2022, 16/01/2025 and 01/02/2025. We visited the sites during the sunrise hours (04:30-08:00 h, Figure 2), where most pairs disperse to the feeding sites as well as in the evening hours (16:00-18:30 h), when the breeding pairs are returning to the roosting/nesting sites, inspecting the sites using Binoculars (10 x 50) from the observation point. Photographs were taken using different camera setups, with the picture on the 15/08/2022 were taken with a Canon EOS 600D (300 mm) and on the 16/01/2025 with Nikon Z9 (380 mm), respectively.
Map showing the approximate location of the study site at Estação Biológica de Canudos (9°57'22” S, 38°59'55” W) and position, where the two birds where photographed. Map compiled in QGis 3.40.3 using map material from Instituto Brasileiro de Geografia e Estatística and distribution data from Birdlife Distribution Map Data 2022.
Left Several nesting cavities with breeding pairs along the nesting cliff right Landscape view of the nesting site at Estação Biológica de Canudos. Photos by Vladislav Marcuk.
2.2. Breeding data and sexual behavior
Information concerning the breeding parameters and behavior were in majority obtained at the facility of the Association for the Conservation of Threatened Parrots, in Brandenburg, Germany between 2018-2025 by VM. During the aforementioned period, breeding parameters, like clutch size, egg laying intervals, incubation and fledging periods were recorded using HD camera systems (Vicon V988D-W311MIR Dome Camera). The cameras allowed us to determine several breeding parameters like the time of laying, hatching and fledging to the exact minute, which is difficult to achieve in the wild due to the limited access to the nesting cliffs. Behavior observations were also conducted non-invasively using the same camera systems. Video recordings of the sexual behavior were stored in AVI format and analyzed with Avidemux (v. 2.7.4). The egg mass was determined shortly after the egg was laid, using a Kern precision scale (error 0.01 g). Egg measurements were taken using a GOSCIEN digital caliper (error 0.02 mm). Sexual behavior was also documented during our visit of the wild population on 01/02/2025 for three apparent breeding pairs. All descriptive parameters are given in the form of mean ± SD (range, sample size).
3. Results
3.1. First documentation of aberrant white feathers in the Lear’s macaw
On the 15/08/2022, the first adult was documented during the morning hours, accompanied by its mate, featuring at least three fully white secondary feathers on its right wing (Figure 3). No other color aberrations were noticed, although the bird was recorded from a far distance, making closer inspection of the plumage unfeasible. The second individual was photographed on the 16/01/2025, featuring a full-white left inner rectrices (Figures 4a and 4b). The same individual was observed on 01/02/2025 by the authors. Territorial calls and close cohesion between the accompanying individuals indicate that the alleged birds were in fact breeding individuals. We observed this individual on the 01/02/2025 for approximately 20 min, without noticing any other aberrations while the bird was allopreening. Both individuals were known to the field staff, who reported that in 2025 an individual was spotted again by the field staff with white feathers present among the secondaries (pers. comm.). However, we were unable to confirm if it is the same individual as the one photographed in 2022. The third individual was observed only briefly on the 16/01/2025 in flight by other visitors (Figure 4c, K. Nigge/J. Fiebig pers. comm.), featuring partial discoloration in a single primary of the left wing. We were unable to spot that individual on the 01/02/2025.
First individual photographed on the 15/08/2022, showing partial leucism with full white secondaries interspersed with normal colored feathers on the right wing. Photos by Tyson Chapman.
(a, b) Left/Right top Second individual photographed on the 16/01/ 2025 with a left all-white inner rectrices along normal colored rectrices to both sides; (c) Bottom Showing the third individual with partial leucism in one primary of the left wing. Photos by Klaus Nigge.
3.2. Notes on sexual behavior and breeding parameters
In the morning hours, between 05:45-06:30 h, we were also able to observe three copulations that were performed on the landing platform at the base of the nest tunnel entrance. Copulations were accompanied by pulsing cracking calls that lasted until the copulation was terminated. Some pairs required several attempts before initiating a successful copulation, maybe because of the confined spacing on the landing platform. Pseudo-copulations, in form of a displacement behavior, were observed on two occasions, where the nesting sites of two neighbor pairings were located less than 1 m apart. Pseudo-copulations were likely used for intimidatory display and were not accompanied by copulation calls, also the duration usually lasted in accordance with the presence of the opposing pair or individuals.
Copulations recorded for the three pairs in question lasted on average 122.7 ± 12.58 s (111-136, n = 3). Copulations of one breeding pair in captivity lasted, in comparison, on average 74.84 ± 12.02 s (n = 42). Two other copulations observed in a wild-caught pair breeding successfully in 2023 lasted 124 and 117 s, respectively.
During our visit on 01/02/2025, we were able to observe several active breeding pairs, recording at least three family groups containing between 1-2 fledged chicks (one pair with two fledged chicks and two pairs with one chick). For the captive breeding pairs, we recorded an average clutch size consisting of 2.71 ± 0.62 eggs (2-4, n = 24). In the events, where the time of egg laying was determined to the nearest minute, the average egg laying interval between two consecutive eggs averaged 78.42 ± 13.75 hours (68.21-120.36, n = 22). Eggs of the Lear’s macaw are in general uniform white and ovate in shape, with the size averaged 42.88 ± 1.25 (39.10-45.01) × 35.43 ± 0.96 mm (32.67-37.66, n = 67). A fresh egg weighs on average 29.69 ± 1.67 g (26.07-34.36; n = 65). For the incubation period, where the egg laying and hatching was determined to the nearest minute, we documented an incubation period of 27.50 ± 0.70 days (26.54-28.67, n = 11). Four parent-raised chicks were recorded to fledge in captivity after 98.75 ± 4.99 days (92-104, n = 4). In captivity, pairs were recorded to feed the chicks up to four months after fledging and these chicks remained with the parents until the onset of the next breeding season.
4. Discussion
4.1. Aberrant white feathers in parrots
The occurrence of white feathers in wild psittacines seems to be an extraordinary phenomenon, with little data existing for wild psittacine populations in general. In captive populations, aberrant white feathers are more frequently encountered (Hume and van Grouw, 2014) and are also known to occur in Spix’s macaws Cyanopsitta spixii (pers. obs.). In C. spixii the authors observed several possible triggers. Temporally, white feathers can occur in young birds, especially if growth is altered (e.g., malnourishment, physiology) or the parents show a tendency to pluck feathers (e.g., injury). Usually, weight loss, poor body condition (Hume and van Grouw, 2014), pathology or a deficiency in nutrition (Hume and van Grouw, 2014) can cause patches to emerge after the molting cycle along with stress lines. These patches vanish after the next molting cycle, when the body condition improves. Injuries, like open fractures or wounds, were also recorded to cause permanent absence of melanin producing cells in damaged skin layers or pathology (e.g., dermatitis etc.). Progressive increase of white feathers, especially on the breast, shoulders and neck were observed in aging individuals of C. spixii and are usually permanent. In Lear’s macaws, the authors did not observe white feathers in captivity, so it is speculative to explain the observed phenomenon. Captive Vasa parrots Coracopsis spp. can develop white feathers when infected with Psittacine Circovirus (Girling, 2003). Since, as shown above, different parrot species can show various degrees of feather abnormalities, such as feather discoloration, it is not possible to exclude that the presence of white feathers is related with this viral infection (Raidal, 2011). Therefore, it is recommended that samples from the roosting site of the Lear’s macaws with white feathers are identified and sampled for the presence of PBFDV. On top of the aforementioned causes, pathology, injury or physiological constraints that restrict the dissemination in the affected part could be a proximate cause, however, it is unclear if the white feathers are permanent or are replaced by normal colored feathers after completing the molting cycle
4.2. Comparative note on the breeding behavior
We provided little complementary information about the sexual behavior and breeding parameters of A. leari. Both, the breeding biology (Pacífico, 2012; Pacífico et al., 2014) and the behavior are described in detail for the species (Favoretto et al., 2024). The recorded brood size of 1.67 ± 0.60 (n = 60, Pacífico et al., 2014) is in consensus with the brood size we observed in the family groups. The average clutch size consisted of 2.62 eggs in the wild (n = 110, Pacífico, 2012), which is very similar to the clutch size recorded in our data set. Egg size and mass also resemble the data presented by Pacífico (2012). The incubation period is reported to last around 28 days for A. leari in the wild (Pacífico, 2012), which is not differing from the records outlined here. The nestling period for wild chicks is reported to be 12-15 weeks (Pacifico, 2012), which is also within the range of the given fledging dates here.
The copulation was qualitatively described by Favoretto et al. (2024), so we focused here more on the quantitative aspects of the copulations that remain poorly documented for most extant psittacines. Pseudo-copulations, used in both A. hyacinthinus and A. leari for intimidation, seems to be specific for this genus (pers. obs.). In comparison to the data provided above, we recorded also for two captive A. hyacinthinus pairs an average copulation duration of 146.88 ± 29.46 s (103.84-199.8, n = 23). While our captive records show considerable variation, that seems to be the norm also for other parrots and were also recorded for C. spixii, where duration can vary between pairs (VM unpub. info.)
In general, our note adds some novel information about the behavior of the species, along documenting the first occurrence of aberrant white feathers in the wild for any of the extant “Blue macaws”. Further observations, including studies of color aberrations in wild psittacines could be improve our knowledge about their native occurrence and possible factors determining such color aberrations.
Acknowledgements
We are indebted to the Estação Biológica de Canudos field team for permitted us to visit the nesting sites of the Lear’s macaw. We are also thankful for the permissions of Klaus Nigge to use the pictures for the publications along the helpful comments and observations shared by Klaus Nigge and Jürgen Fiebig. We are indebted to Hein van Grouw for his helpful comments about the correct use of terminology and insight in the color aberrations, that significantly improved the quality of the manuscript. We also would like to thank the anonymous reviewer that helped us to improve the manuscript significantly.
Data Availability Statement
The research data are available upon request to the corresponding author.
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Edited by
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Editor:
Takako Matsumura Tundisi
