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Brown-Necked Raven Predation Remained the Main Suspected Cause of Osprey Nest Failure on Boa Vista

Osprey parent with chicks in a nest
Conservation · Threats

Monitoring on Boa Vista recorded 25 osprey (Pandion haliaetus) pairs and 21 active nests during the 2026 breeding season, but only six nests produced young. Those successful nests produced nine chicks in total, while field evidence continued to point to brown-necked raven (Corvus ruficollis) predation as the leading suspected cause of nest failure, according to preliminary results released by Bios Cabo Verde on 6 June.

Pair numbers remained stable, but few nests succeeded

Surveys ran from December 2025 through May 2026. Cabo Verde holds the most important osprey breeding population in Macaronesia, and Bios Cabo Verde said the Boa Vista population had remained relatively stable for about 14 years, usually at roughly 20–22 breeding pairs per season. Six previously unrecorded nests were found in 2026, three of them with breeding activity, and six newly ringed adults — three males and three females — joined the recorded breeding population.

All nine chicks were ringed, and two were fitted with GPS-GSM transmitters to follow their movements after leaving the nest. The organisation has monitored the Boa Vista population with support from Cabeólica since 2012.

Raven predation remains the leading suspected cause

Breeding success nevertheless remained limited. Bios Cabo Verde said nests attributed to raven predation showed a recurring pattern of apparently normal incubation followed by brood loss around the hatching period. The evidence did not document every predation event directly, and the organisation said the evidence continued to suggest brown-necked ravens were the main cause of nest failure.

Bios Cabo Verde described action on this threat as important for the long-term conservation of Cabo Verde’s osprey population. The 2026 results are preliminary, and continued monitoring of nests and marked birds will provide the next evidence on how the local population develops.

Sources and image credit

  1. Bios Cabo Verde. (2026, June 6). Preliminary data from the 2026 osprey and Egyptian vulture monitoring activities in Boa Vista [Facebook post]. Facebook.Official preliminary monitoring update. Surveys from December 2025 through May 2026 recorded 25 osprey pairs, 21 active nests, six newly detected nests, six successful nests producing nine chicks, ringing and GPS-GSM deployment, and field evidence identifying brown-necked raven predation as the continuing main cause of nest failure.

Image: Amaury Laporte / Wikimedia Commons — osprey parent with chicks in a nest, photographed 22 February 2024; representative nest image, not birds from Boa Vista · CC BY 2.0 — https://creativecommons.org/licenses/by/2.0/ · Source

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