Breeding Seasons of Cuban Gulls and Terns Revealed
New study finds seabird reproduction largely synchronised with the rainy season, with habitat features shaping success across cays
Seasonal synchrony in the tropics
A new study of seabird colonies in Cuba has shed light on the breeding phenology and reproductive success of gulls and terns, showing that most species nest in a relatively tight seasonal window from May to August. This synchrony contrasts with the more aseasonal or episodic patterns seen in other tropical seabird communities, and appears linked to the rainy season - when prey is more abundant and vegetation cover higher, offering shelter from predators.
Researchers surveyed three small cays in the Sabana-Camagüey archipelago during the 2021 breeding season, monitoring seven species: Laughing Gull, Brown Noddy, Sooty Tern, Bridled Tern, Roseate Tern, Royal Tern, and Sandwich Tern. Camera traps supplemented weekly counts of nests, eggs and fledglings.
Different strategies, similar timing
Most species reached peak egg-laying within three to five weeks of starting, producing a high degree of overlap between colonies. Sooty, Roseate and Sandwich Terns were especially synchronous, while Laughing Gulls were more staggered, taking up to five weeks to peak. Several species attempted two laying periods, though Roseate Terns failed to fledge chicks in the second.
Clutch sizes varied by species and site. Laughing Gulls often laid two or three eggs, while terns generally produced single-egg clutches. Roseate Terns stood out with a high proportion of two-egg clutches, though chick survival per egg was lower than per pair. This highlights how measures of breeding success can shift depending on whether they are calculated by egg or by breeding pair.
Success and setbacks
Reproductive outcomes were mixed across species and cays. Laughing Gulls, Sooty Terns and Roseate Terns all achieved high reproductive success (=50% per pair). Sandwich Terns performed moderately, while Bridled and Royal Terns fared well at some sites but suffered notably poor success at Paredón de Lado, where fledging rates fell below 30%.
The differences appear tied to habitat features. Denser vegetation and larger colony sizes favoured higher success, likely by shielding nests from predators and weather, and by bolstering group defence. In contrast, sparse cover and small colony sizes at Paredón left eggs and chicks more exposed to predation and climatic extremes.
Implications for seabird conservation
The findings underscore how seabird breeding success in the Caribbean is shaped by both seasonal cycles and local habitat conditions. Rainfall-driven changes in vegetation and prey availability seem to synchronise reproduction, while microhabitat features at colony sites strongly influence outcomes for individual species.
Protecting these fragile cay ecosystems is therefore critical. The study shows that even small differences in vegetation cover or colony size can make the difference between successful fledging and widespread breeding failure. As threats such as hurricanes, invasive predators and climate-driven shifts in rainfall increase, monitoring and safeguarding these seabird colonies will be essential to securing the future of Cuba’s gulls and terns.
September 2025
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