Review of the breeding biology of rufous crab hawk Buteogallus aequinoctialis (Aves: Accipitridae) across its distribution

ABSTRACT

The rufous crab hawk (Buteogallus aequinoctialis) is a crab-eating specialist restricted to South American mangroves. Even though it is considered Near Threatened, with presumed population declines, its breeding biology remains poorly studied. Here we combined a comprehensive review of literature, museum and citizen science data to address its breeding biology, gaps in our knowledge, and conservation implications. The species lays one egg on a large stick nest placed on mangrove trees 6 to 11 m above the ground. The ovoid eggs averaged 57.5 × 44.0 mm in size (n = 25), overlapping partially with B. anthracinus and B. gundlachii eggs. The breeding period differs among regions, starting earlier in the northern parts of the distribution and progressively later in the southern ones. This review also shows that the species nests only in mangrove trees, a vegetation type under threat, and that breeding records are unevenly distributed across its range. Very little has been published on the reproduction of the rufous crab hawk in the last 50 years, and we still lack proper information on most aspects of its breeding biology. Our review shows that we can improve our understanding of a species’ reproduction by using multiple sources of previously available data and therefore provide a better basis to assist in conservation measures.

KEYWORDS:

• Egg sizes
• mangroves
• nesting season
• reproduction

Acknowledgements

We thank all of the museum curators for kindly allowing us to study specimens under their care. JABM thanks PLÁ Figueiredo and RP Félix for field support in Itapicuru River, and G Abuchahla for the identification of mangrove trees. We also thank all the anonymous reviewers, whose remarks and suggestions greatly improved this paper.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The authors confirm that the data supporting the findings of this study are available within the article and its supplementary material. Originally, some of these data were openly available in the Citizen Science databases WikiAves (https://www.wikiaves.com) and Macaulay Library (https://www.macaulaylibrary.org). Additional information is available from the corresponding author, JABM, upon reasonable request.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00222933.2024.2311956

Additional information

Funding

Research funding was provided by Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPQ) [under # 473281/2013–9], Fundação de Apoio a Pesquisa do Distrito Federal [under # 0193.000839/2015], and Program CAPES-PrInt. CNPq provided fellowships to MÂM and JABM. We thank Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for a post-doctoral scholarship [under # 88882.314922/2019-01] received by NMH.