Archived 2012-2013 topics: Rufous Crab-hawk (Buteogallus aequinoctialis): uplist to Vulnerable?

This discussion was first published as part of the 2010 Red List update, but remains open for comment to enable reassessment in 2013. Rufous Crab-hawk Buteogallus aequinoctialis is currently considered Least Concern on the IUCN Red List because it was assumed to have a large global range supporting a moderate population size that was not thought to approach the thresholds for listing as Vulnerable under criterion C of the IUCN Red List, and despite the fact that the population trend appears to be decreasing, the decline was not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion A (>30% decline over ten years or three generations). However, examination of FAO Forest Resources Assessment Working Paper 63 gives a total mangrove cover (this species is a mangrove specialist) of c.30,000 km2 in 1980 from its range states along the north-east coast of South America, and that the area of mangrove habitat declined by over half during 1980-2000 to 1,467,000 ha. A corresponding decrease in the population size over the same time frame (three generations equals 22 years based on a generation length of 7.6 years; BirdLife International unpublished data) could qualify the species as Endangered on the IUCN Red List under criterion A. If declines in suitable habitat have since stabilised the species may now qualify as Vulnerable under criterion A and possibly criterion B if the Extent of Occurrence now constitutes <20,000 km2 and it has been severely fragmented by mangrove clearance. Comments on current rates of mangrove loss and whether population declines are likely to have occurred at the stipulated rates are welcomed.

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2 Responses to Archived 2012-2013 topics: Rufous Crab-hawk (Buteogallus aequinoctialis): uplist to Vulnerable?

  1. Andy Symes says:

    Comments received during 2010 update:

    Nyls de Pracontal (GEPOG) – French Guiana (January 2010):
    There is no pressure on mangroves in French Guiana mainly due to their limited accessibility. This species is distributed evenly over the entire coastline, but its density is unknown. I note however that it does not seem huge …

    The size of mangroves varies with sediment from the Amazon River and the high dynamic coastal “enriched” and “destroyed” on a regular cycle.

    I don’t know the situation in Brazil and Venezuela for example, but their expertise is essential to have a better sense of pressure and the effective reduction of mangroves.

    Grupo Ornitológico Potiguar (February 2010):
    In Rio Grande do Norte where the formal status of B. aequinoctialis is unknown, but where great destruction of his habitat due to shrimp culture ran from 15-20 years (now almost stopped), these last eight years we found a lone locality (manguezal de Canguaretama) with a single breeding pair. At state level (RN), we gave it as critically endangered (discussion panel in CBO).

  2. Loss of mangroves along the coasts of Para and Maranhao has not been extensive, from Menezes et al. 2008:

    The overall net loss of mangrove vegetation coverage in the 1972-1997 period was 19 km2, a total net loss of 3.2%, which is approximately 0.76 km2·yr-1 (Cohen and Lara, 2003).

    I certainly see this species with some regularity and have seen it hunting in quite degraded mangrove forests, for example with suburban Salinopolis.

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