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Red-footed booby

The Red-footed booby (Sula sula) is a medium-sized, highly pelagic seabird in the family Sulidae, distinguished by its vivid coral-red webbed feet, which males prominently display during courtship displays.^[1] Measuring 69–79 cm in length with a wingspan of 130–150 cm and weighing 850–1,100 g, it is the smallest of the six booby species and features a streamlined, torpedo-shaped body adapted for aerial and diving pursuits, along with a pale blue bill and wedge-shaped tail.^[2] The species exhibits notable plumage polymorphism, with adults appearing in white morphs (predominantly white body with blackish flight feathers) or brown morphs (entirely dark brown), and both forms often co-occurring in the same breeding colonies.^[1] Native to tropical and subtropical oceanic waters across the Atlantic, Pacific, and Indian Oceans—but absent from the eastern Atlantic—this booby forages over vast pelagic areas, plunging from heights up to 10 m to capture small fish like flying fish and squid averaging 8.8 cm in length, often chasing prey in flight or swallowing them mid-air.^[3] It breeds in dense colonies on remote islands and atolls, favoring tree canopies or low scrub for nest-building rather than ground sites to avoid competition with other species, with monogamous pairs laying a single egg every 15–18 months and incubating it for 41–45 days.^[4] Highly social and diurnal, these boobies communicate through calls, postures, and sky-pointing displays, while also resting on floating debris or boats and cooling themselves by panting and wing-spreading in hot conditions.^[1] With an estimated global population of around 1.4 million mature individuals (as of 2019), the red-footed booby is classified as Least Concern on the IUCN Red List, though trends indicate a decreasing population due to threats like illegal hunting, habitat destruction from vegetation clearance on nesting islands, and potential impacts from introduced predators and climate change.^[3] The largest colonies occur in the Galápagos Islands, and the species is non-migratory within its range, with juveniles dispersing widely after fledging at 2–3 months.^[4]

Taxonomy and systematics

Etymology and naming

The scientific name of the red-footed booby is Sula sula, with the genus Sula derived from the Old Norse word súla, referring to the northern gannet (Morus bassanus), a close relative in the family Sulidae.^[5] The specific epithet sula is a tautonym, redundantly repeating the genus name, a practice sometimes used in binomial nomenclature for emphasis. Originally described by Carl Linnaeus in 1766 under the name Pelecanus sula based on a specimen from Barbados, this early classification placed it among pelicans before reassignment to Sula.^[6] The common name "booby" stems from the Spanish term bobo, meaning "fool," "stupid," or "clown," applied by 17th-century Spanish and Portuguese sailors who exploited the birds' lack of fear toward humans and their clumsy terrestrial movements, making them easy prey.^[7] The descriptor "red-footed" directly alludes to the species' prominent coral-red feet, a trait highlighted in 18th-century European exploration accounts, such as those from Captain James Cook's Pacific voyages.^[8] Historical synonyms include the original Pelecanus sula and, for certain populations, Sula rubripes proposed by John Gould in 1838, reflecting early attempts to distinguish regional variations before modern taxonomic revisions.^[9]

Subspecies and classification

The red-footed booby (Sula sula) is classified within the order Suliformes and the family Sulidae, which encompasses gannets (Morus) and boobies (Sula). Molecular phylogenetic analyses using multiple nuclear and mitochondrial loci have resolved the Sulidae as monophyletic, with Papasula abbotti (Abbott's booby) as the basal lineage, diverging from the remaining sulids approximately 22 million years ago in the Early Miocene.^[10] Within Sulidae, the genera Morus (gannets) and Sula (boobies) form sister clades that diverged around 17 million years ago (95% highest posterior density interval: 16.0–19.4 million years ago), also in the Early Miocene, based on fossil-calibrated relaxed molecular clock models.^[10] This divergence reflects the family's adaptation to diverse marine foraging niches, with boobies specializing in tropical and subtropical waters.^[11] Three subspecies of the red-footed booby are currently recognized, though their validity has been questioned due to minor differences, and further genetic and morphometric studies are needed; distinctions are based primarily on geographic distribution, subtle morphological variations in size and bill proportions, and differences in plumage morph frequencies. The nominate subspecies S. s. sula occurs in the Caribbean Sea and western Atlantic Ocean, typically exhibiting a higher proportion of white morphs with brown tail and flight feathers, and possessing intermediate body length (69–79 cm) and bill length (about 82–94 mm); wingspan is approximately 134–150 cm across subspecies.^[2] S. s. websteri is found in the tropical eastern Pacific, including the Galápagos Islands and extending to the Gulf of California, where it is slightly smaller (length ~66–77 cm) with a shorter bill (around 78–85 mm) and tends toward darker brown morphs or black-tailed white morphs in some populations.^[12] S. s. rubripes inhabits the central and western Pacific Ocean as well as the Indian Ocean, showing slightly smaller overall size (length ~66–77 cm) and similar bill length (about 80–90 mm), with variable plumage but often more frequent brown morphs in Indian Ocean colonies.^[12]^[2] These distinctions, while minor, correlate with isolation by ocean basins and are supported by morphometric data from breeding colonies, though S. s. websteri has been suggested as a potential separate species in some analyses.^[12] Recent genetic studies, including multilocus DNA analyses post-2010, have confirmed the monophyly of the genus Sula, with S. sula forming a well-supported clade distinct from other boobies such as the brown booby (S. leucogaster) and masked booby (S. dactylatra).^[10] Phylogeographic research using mitochondrial control region and nuclear markers indicates low genetic differentiation among S. sula populations across ocean basins, suggesting ongoing gene flow despite geographic barriers, but with no evidence of significant hybridization with other Sula species.^[13] This contrasts with documented interspecific hybridization in other sulids, such as between blue-footed (S. nebouxii) and Peruvian boobies (S. variegata), highlighting S. sula's reproductive isolation.^[14] The fossil record of Sulidae dates to the Early Miocene, with the earliest known ancestors appearing in marine deposits from the Chilcatay Formation in Peru around 13–14 million years ago, representing primitive sulids with morphologies akin to modern Sula.^[15] No direct fossils of S. sula have been identified, but related species in the genus Sula, such as S. brandi and S. figueroae from the Late Miocene Pisco Formation (approximately 9–10 million years ago), exhibit similar small to medium body sizes and rostrum shapes, indicating evolutionary continuity within the booby lineage in the eastern Pacific.^[15] These Miocene records underscore the family's long-term presence in tropical seabird communities.^[16]

Physical characteristics

Morphology and measurements

The red-footed booby (Sula sula) is a medium-sized seabird characterized by a streamlined body adapted for aerial efficiency and aquatic foraging. Adults typically measure 69–79 cm in total length, with a wingspan ranging from 134–150 cm and a body mass of 850–1,100 g.^[17] These dimensions reflect its status as the smallest species within the Sulidae family, enabling agile flight over vast oceanic distances.^[18] Key anatomical features include long, pointed wings suited for dynamic soaring and gliding, a short wedge-shaped tail for maneuverability, and a large, conical bill with a slightly decurved tip and serrated edges for grasping prey during dives.^[18] Its feet are large, totipalmate (fully webbed between all four toes), and positioned far back on the body, facilitating propulsion in water and secure perching on branches.^[18] Skeletal adaptations support its plunge-diving lifestyle, including a robust sternal keel that anchors powerful flight muscles for sustained soaring and strong neck musculature to withstand impact forces during dives. The bones are hollow to minimize weight while maintaining structural integrity, and extensions of the bronchial air sacs provide buoyancy and cushioning to protect internal organs.^[18] Sexual dimorphism is evident, with females slightly larger than males and averaging 10–15% heavier in body mass, a pattern consistent across populations. Males exhibit brighter red foot coloration during the breeding season, enhancing visual displays. Juveniles are smaller overall, with proportionally shorter bills and paler feet compared to adults.^[19]^[18]^[20]

Plumage and color variations

The red-footed booby (Sula sula) exhibits notable plumage polymorphism, with three primary adult morphs: the white morph, characterized by predominantly white plumage except for blackish flight feathers and tail; the brown morph, featuring overall dark brown plumage with a paler brown head; and the white-tailed brown morph, which has a brown body but white tail and undertail coverts.^[21] Globally, the white morph predominates at approximately 85% of the population, while the white-tailed brown morph comprises about 15%, and the brown morph is rarer overall but reaches high frequencies in specific colonies, such as up to 90% brown on Genovesa and Wolf Islands in the Galápagos Archipelago.^[21] In the eastern Pacific, brown morph prevalence is elevated compared to other regions, potentially linked to camouflage advantages that reduce kleptoparasitism by frigatebirds in vegetated nesting habitats.^[21] Juveniles emerge with a downy white fluff covering their naked skin, which is soon replaced by mottled brown-gray plumage resembling the brown adult morph, including sooty brown overall tones with a lighter tan or white belly and a faint darker chest band.^[22] This juvenile plumage transitions gradually to adult morphs over 3–4 years through successive molts, with all individuals initially acquiring brown-like feathers before differentiating into white or other morphs.^[21] Distinct color changes occur in non-plumage features across life stages and seasons. Juvenile feet are gray or brown, shifting to vivid red in adults through deposition of carotenoid pigments derived from their seafood diet; similarly, the bill transitions from grayish-brown to pale blue, and facial skin from dull bluish to more vibrant tones.^[21] During the breeding period, the bill, facial skin, and gular pouch intensify in coloration—becoming brighter blue and rosy—to signal reproductive readiness, a pattern observed across morphs.^[23] Regional variations in morph frequencies are pronounced, particularly in the Indian Ocean, where the white-tailed brown morph is more common than globally; for instance, it constitutes 98.5% of adults on Europa Island and about 30.6% on Tromelin Island, contrasting with predominantly white (>80%) populations in most other Indian Ocean colonies.^[24] These differences may reflect historical isolation and limited gene flow among island populations, with higher brown morph prevalence potentially aiding camouflage in certain habitats.^[24] Subspecies, such as S. s. websteri in the Galápagos, influence morph distributions by featuring a unique black-tailed variant of the white morph.^[2]

Distribution and habitat

Global range

The red-footed booby (Sula sula) has a pantropical distribution, occurring in tropical and subtropical waters across the Atlantic, Pacific, and Indian Oceans, with breeding colonies primarily on remote oceanic islands. This species is absent from the eastern Atlantic but is widespread elsewhere, nesting in more than 20 countries including Mexico, Ecuador, Costa Rica, Panama, Colombia, Brazil, the United States (Hawaii and Pacific territories), Australia, Indonesia, the Philippines, Micronesia, Mauritius, and the Seychelles.^[3]^[25]^[18] The largest breeding colonies are concentrated in key regions such as the Galápagos Islands (Ecuador), where populations exceed 400,000 pairs, primarily on Genovesa and San Cristóbal islands; Johnston Atoll (United States), which supports one of the most substantial aggregations in the central Pacific; and Christmas Island (Australia) in the Indian Ocean, with over 12,000 breeding pairs. Vagrancy records extend beyond the core range, including multiple sightings in Washington State, USA, during 2024 and 2025—such as live individuals off Dungeness Spit and Port Townsend—and rare occurrences in Europe, with a confirmed adult in East Sussex, United Kingdom, in 2017.^[26]^[27]^[28]^[29]^[30]^[31] During non-breeding periods, red-footed boobies undertake post-breeding wanderings, dispersing up to 1,500 km from their colonies, as documented by satellite and GPS tracking studies in the Pacific and Indian Oceans. These movements often involve juveniles exploring new areas, contributing to occasional vagrancy far from breeding sites.^[32]^[33]^[34] Historically, the species' range expanded in the 20th century following the cessation of guano mining on several Pacific atolls, which permitted vegetation regrowth and the establishment of new colonies; for instance, populations increased on islands like Johnston Atoll after mining activities ended. However, recent contractions have occurred in some regions, driven by habitat degradation and invasive species, leading to an overall moderate population decline.^[35]^[36]^[3]

Breeding colonies and habitat preferences

Red-footed boobies form large, dense breeding colonies on remote tropical islands and atolls, where they nest primarily in trees or shrubs to avoid ground-based predators. These colonies can include from a few hundred to hundreds of thousands of pairs, often coexisting with other seabirds in mixed-species groups, and the birds exhibit high sociality with synchronized breeding peaks in many locations. Nests are typically constructed from twigs, grasses, and leaves in the canopy of trees such as Pisonia grandis or in low shrubs, providing elevated perches; ground-nesting is rare and usually occurs only on sparsely vegetated sites or artificial structures when trees are unavailable.^[37]^[18]^[38] The species prefers tropical coral atolls and oceanic islands characterized by low human disturbance, with nesting habitats generally at elevations below 100 m to ensure accessibility and protection from extreme weather. These sites are selected for their proximity to deep pelagic waters, facilitating efficient foraging trips, and feature vegetated microhabitats that offer some wind protection through dense foliage, though nests are often placed in exposed, sunny positions within the canopy. Vegetation cover, particularly from native trees like Pisonia grandis and Tournefortia argentea, is crucial for nest support and camouflage, with birds avoiding heavily shaded or disturbed areas.^[3]^[39]^[1] Major breeding colonies are concentrated in protected, isolated locations across the tropics, such as Palmyra Atoll in the central Pacific, which hosts one of the largest populations with approximately 25,000 pairs nesting in Tournefortia groves during peak season. In the Indian Ocean, Europa Island supports 2,800–3,800 breeding pairs in dry Euphorbia stenoclada forest on the northern shore, emphasizing the species' reliance on undisturbed insular ecosystems. Other significant sites include the Galápagos Islands and Christmas Island, where colonies benefit from similar remote, vegetated conditions.^[40]^[33]^[18] Breeding habitats are influenced by stable tropical climates with warm temperatures typically ranging from 25–30°C, supporting year-round or seasonally asynchronous reproduction in many colonies. However, these sites are vulnerable to tropical cyclones, which can destroy flimsy nests, disrupt foraging, and cause temporary shifts in activity patterns, such as increased time at the colony during storms. Cyclonic events exacerbate risks in low-elevation atolls by flooding or wind damage, highlighting the species' sensitivity to climate variability in its preferred warm, oceanic environments.^[18]^[41]^[42]

Behavior and ecology

Foraging strategies and diet

The red-footed booby's diet consists primarily of small schooling fish, such as flying fish (Exocoetidae) and other epipelagic species including mackerel scads and anchovies, supplemented by squid; crustaceans appear only occasionally in regurgitated samples.^[43]^[44] In analyses of chick-provisioning regurgitations from Hawaiian colonies, fish dominated the diet numerically (82-100% of identified items), with squid comprising the remainder (up to 36% by number in some samples); seasonal variation occurs, with squid intake higher in wet seasons (up to 21% by mass).^[45]^[46] Prey items are typically small, averaging 6-15 cm in length, allowing the birds to swallow them whole underwater or in mid-air. Red-footed boobies forage exclusively during daylight hours, with activity peaking at dawn and dusk when prey schools are most accessible near the surface.^[47] Their primary hunting technique involves visual detection of prey from the air, followed by plunge-dives from heights of up to 25 m, reaching impact speeds of up to 100 km/h to pursue fish or squid underwater to depths of 2-3 m.^[46]^[37] They do not employ echolocation, relying instead on keen eyesight to spot translucent schools against the water's surface.^[37] Recent 2025 research using lightweight bird-mounted cameras on individuals from Indian Ocean breeding colonies has documented frequent mid-air captures of flying fish, revealing that boobies skim low over waves to intercept escaping prey in flight, often in tandem with wave-assisted propulsion.^[48]^[49] Foraging often occurs in flocks of 10-50 individuals, sometimes in mixed-species groups, where coordinated dives may concentrate schooling fish for easier capture, enhancing efficiency in patchy tropical waters.^[46]^[50] Trips typically extend 50-200 km from breeding colonies, with maximum ranges limited to around 150 km due to diurnal constraints, allowing return before nightfall to avoid predation risks.^[51] Foraging ranges and paths are strongly influenced by wind patterns, with boobies favoring tailwinds for outbound trips and crosswinds for efficient commuting.^[47] A 2025 study using GPS and accelerometers demonstrated that red-footed boobies optimize navigation by adjusting flight trajectories to diurnal light availability and wind gradients, enabling straight, high-speed returns that minimize energy expenditure and maximize daily provisioning.^[52]

Breeding and reproduction

The red-footed booby exhibits year-round breeding in tropical regions, influenced by food availability, though colonies often show synchronized peaks, such as April to August in the Galápagos Islands.^[37] Breeding occurs in large colonies with hundreds to thousands of pairs nesting together, typically laying a single egg per clutch.^[18] Pairs generally breed every 15 months, returning to the same nest site annually.^[18] Courtship involves elaborate ritualized displays by males, including sky-pointing postures, wing spreading, and highlighting their bright red feet to attract mates, often at prospective nest sites.^[37] Pair bonds are monogamous for one to several seasons, sometimes lasting over 10 years, with both partners participating in nest construction using twigs, grasses, and green vegetation to form a platform about 12 inches across.^[37]^[18] During breeding, plumage colors brighten, particularly in brown and white morphs, enhancing displays before fading through incubation.^[37] Incubation lasts 41–46 days and is shared by both parents, who take turns covering the chalky white egg for stints of 12–60 hours.^[18]^[53] Chicks hatch nearly naked and helpless, initially brooded on a parent's feet, and are fed regurgitated fish by both parents throughout the 90–135-day fledging period, with post-fledging care extending up to 190 days.^[18]^[53] Chick mortality is high, ranging from 30–50%, primarily due to starvation, especially during environmental events like El Niño.^[54] Red-footed boobies typically begin breeding at 3–5 years of age, with some as young as 2 years in certain populations.^[54] Average lifespan is around 17 years, though individuals can live over 40 years in the wild, with about 23 years of reproductive potential.^[18]^[1] Red-footed boobies exhibit a highly colonial social structure, forming large roosting and nesting flocks that can number in the thousands at shared sites, which facilitates communal defense and resource sharing. Within these colonies, individuals engage in agonistic interactions, including intra-species aggression at nest sites where birds defend territories through physical confrontations and displays to maintain spacing.^[55] Vocal communication plays a key role in social dynamics, with honking calls used primarily for territory defense during colony interactions and bill-clattering produced in aggressive or display contexts.^[56]^[57] In terms of movement patterns, red-footed boobies do not undertake true long-distance migration but instead display dispersive behavior outside the breeding season, with adults often showing year-round residency near their colonies. A 2024 geolocation study using light-level and saltwater immersion loggers on adults from the Chagos Archipelago in the tropical Indian Ocean revealed that these birds remain in proximity to breeding sites throughout the year, with limited seasonal shifts in colony attendance influenced by prey availability.^[32] Juveniles, however, tend to wander farther from natal colonies post-fledging, dispersing to sea and occasionally roosting at distant sites to develop foraging independence.^[58] Social interactions extend beyond conspecifics to include kleptoparasitism by frigatebirds, which chase red-footed boobies in flight to force regurgitation of captured prey such as fish or squid. Studies on tropical seabird communities have documented this behavior as a significant interaction, with frigatebirds frequently pursuing boobies though success rates are low (less than 1%), leading to occasional food loss for the boobies but rarely affecting overall colony productivity.^[59] Communication during these and other social encounters often involves visual displays, such as wing-spreading to signal aggression or submission, complementing vocal signals in maintaining group cohesion.^[55]

Predators, parasites, and natural threats

The red-footed booby faces predation primarily from introduced mammals on breeding islands, including rats, cats, dogs, and pigs that consume eggs, chicks, and occasionally adults.^[60] Great frigatebirds (Fregata minor) harass foraging adults through kleptoparasitism, forcing them to regurgitate or drop captured prey, and may also steal nest materials, sometimes dislodging the booby in the process.^[59] While sharks occasionally prey on diving seabirds like the red-footed booby during foraging dives, such incidents are opportunistic and less documented than mammalian threats on land.^[47] Ectoparasites are common on red-footed boobies, with lice such as those in the genus Pectinopygus infesting adults and nestlings across breeding sites like the Galápagos Archipelago, where up to nine louse species have been recorded among booby populations.^[61] Obligate ectoparasitic flies, including louse flies (Hippoboscidae), attach to the birds during breeding, feeding on blood and potentially transmitting pathogens, though their impact on red-footed boobies remains lower than on co-occurring frigatebirds.^[62] Endoparasites include blood protozoans like Haemoproteus, detected in adult red-footed boobies, and nematodes acquired through their fish-heavy diet, such as Contracaecum species common in piscivorous seabirds.^[63] No widespread disease outbreaks have been reported specifically for this species, though general seabird parasites like ticks (e.g., Ornithodoros capensis) can infest nests and contribute to minor stress during breeding.^[64] Natural threats to red-footed booby colonies include severe weather events that disrupt breeding. Tropical cyclones alter foraging patterns, forcing birds to avoid storm-affected areas and reducing prey availability, as observed in the Coral Sea where red-footed boobies and great frigatebirds shifted movements during cyclonic activity.^[41] El Niño-Southern Oscillation (ENSO) events exacerbate food scarcity by warming ocean waters and shifting fish distributions, leading to delayed breeding, lower chick weights, and population declines; for instance, the 1997-1998 El Niño caused significant reductions in Galápagos colonies due to diminished squid and fish resources.^[65] These events can result in fledging success dropping by up to 10-20% in affected years, highlighting the species' vulnerability to climatic variability.^[66] Red-footed boobies employ several behavioral adaptations to mitigate these risks. Colonial nesting in dense tree or shrub groups enhances vigilance, allowing individuals to detect approaching predators collectively and respond rapidly through alarm calls.^[37] At the nest, adults defend against intruders, including frigatebirds and conspecifics, via aggressive displays such as bill snapping, head shaking, and charging postures to protect eggs and chicks.^[37] Foraging in large flocks further dilutes individual predation risk from aerial or aquatic threats, while daytime-only hunting avoids nocturnal shark activity.^[47]

Conservation and threats

Population status and trends

The global population of the red-footed booby (Sula sula) is estimated at 1.4 million mature individuals, with breeding occurring across more than 100 sites in tropical oceans.^[3] This figure, derived from Partners in Flight assessments, reflects a scattered distribution concentrated in the Pacific, where the majority of colonies are found, including key sites like Johnston Atoll and the Galápagos Islands.^[67] The species is classified as Least Concern by the IUCN, though data quality for these estimates remains poor due to challenges in surveying remote island colonies.^[3] Population trends indicate an overall decrease, suspected to be moderate and driven primarily by habitat degradation rather than rapid collapse.^[3] In the Pacific, some colonies have experienced significant losses, such as an 80% decline at Christmas Island from 2,500 breeding pairs in 1967 to 500 in 1993, attributed to historical poaching.^[54] Conversely, populations at Johnston Atoll have shown stability or growth, with aerial surveys recording over 5,000 breeding pairs as of 2025—a significant colony size.^[68] In the Caribbean, numbers at Little Cayman have increased to 8,200–10,000 pairs as of 2023, comprising the majority of the regional total of approximately 10,000 pairs. Recent observations also suggest increasing vagrancy, with a 920% range expansion in the California Current after 2012, potentially signaling broader shifts linked to oceanic changes.^[69]^[70] Monitoring efforts rely on aerial surveys, such as the Cooperative Avian Survey Team (CAST) programs in the U.S. Pacific, and GPS tracking to map movements and colony dynamics across scattered sites.^[35]^[71] Demographic factors include adult survival rates of approximately 90%, a generation length of 9.4 years, and high fecundity with one egg per clutch, though chick survival varies from 60% to 80% and has shown declines in some areas due to environmental variability.^[3]^[54] These elements help offset moderate declines, maintaining overall population resilience despite ongoing pressures.^[3]

Human impacts and conservation measures

Human activities pose several significant threats to red-footed booby populations, primarily through the introduction of invasive species, climate change, and commercial fishing practices. Invasive predators such as rats (Rattus spp.) and cats (Felis catus) have devastated chicks and eggs in numerous breeding colonies, with predation leading to near-total reproductive failure in affected sites. For example, black rats introduced to Pacific islands historically consumed significant numbers of booby eggs and chicks annually in some locations, necessitating eradication efforts on a substantial number of colonies to safeguard breeding success. The successful removal of invasive rats from Palmyra Atoll National Wildlife Refuge in 2011–2012 by the U.S. Fish and Wildlife Service and partners resulted in a dramatic recovery, with red-footed booby nesting increasing substantially.^[72]^[73]^[74] Climate change exacerbates habitat vulnerability, particularly through sea-level rise that floods low-lying atolls and increases storm intensity, potentially displacing breeding sites. Historical guano mining has further degraded nesting vegetation on islands like those in the Indian Ocean, where extraction cleared trees essential for colony establishment, contributing to the loss of at least a dozen colonies over the past century. Commercial fishing, including longline operations, indirectly impacts the species via bycatch and prey depletion; while red-footed boobies experience lower bycatch rates than some sulids, incidental captures in tuna fisheries still contribute to localized mortality, with global seabird bycatch in longline fisheries estimated at over 160,000 individuals annually.^[75]^[76] Conservation measures focus on habitat protection, invasive species management, and international cooperation to mitigate these threats. The red-footed booby is classified as Least Concern by the IUCN Red List, reflecting its large global population, but it benefits from protections in key sites such as Galápagos National Park, where regulated access prevents disturbance during breeding seasons. Invasive removal programs have proven effective, with ongoing initiatives targeting rats and cats on additional Pacific islands to restore ecosystem function and boost booby populations. Ecotourism regulations in breeding areas, such as limits on visitor numbers and guided access in the Galápagos, help minimize human disturbance that could abandon colonies.^[3] Recent research, including a 2024 assessment of U.S. Pacific Island seabird restoration priorities, integrates climate modeling to identify high-risk colonies for targeted interventions, emphasizing site-specific adaptations like elevating nesting platforms. Emerging threats include a 2025 U.S. Air Force proposal for a rocket test site at Johnston Atoll, which could disturb the significant colony there. Future conservation recommendations include enhanced monitoring of sea-level rise impacts using satellite tracking and predictive modeling, alongside bycatch reduction through gear modifications in international fisheries. These efforts aim to counter ongoing population declines in vulnerable regions, ensuring the persistence of this widespread seabird.^[77]^[68]

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http://losbird.org/article.php?articleHtml=Identifying%20sulids.html
[24]
https://www.cebc.cnrs.fr/wp-content/uploads/publipdf/1999/LCJZL249.pdf
[25]
[PDF] Plumage polymorphism of red-footed boobies (Sula ... - CEBC - CNRS
Particularly, the population of Europa is the only current population of the Indian Ocean constituted almost entirely of white-tailed brown morph, suggesting ...
[26]
Distribution - Red-footed Booby - Sula sula - Birds of the World
In the e. Pacific, breeds on Revillagigedo, Clarion, Clipperton, San Benedicto, Soccorro, Cocos, Malpelo, Isla Isabella near Baja, and the Galapagos Archipelago ...
[27]
Red-Footed Booby | Online Learning Center - Aquarium of the Pacific
May 29, 2020 · Sula sula is the smallest species of booby. This species has a tapering, long, blue-and-pinkish-colored bill with serrated edges to help catch and eat prey.Missing: morphology dimorphism skeletal
[28]
Red-Footed Booby - The Nature Conservancy
The red-footed booby is a large seabird of the booby family, Sulidae. As suggested by the name, adults always have red feet, but the color of the plumage ...
[29]
Red-footed booby | Christmas Island National Park | Parks Australia
Christmas Island is a globally important breeding site for red-footed boobies, hosting more than 12,000 breeding pairs in large colonies. Females lay a single ...
[30]
October 27th, 2024 - Searching Port Townsend for the Red-footed ...
Oct 27, 2024 · Narrative. We made a day trip to Port Townsend in search of the Red Footed Booby that has been sighted there recently.
[31]
Port Townsend's Red-footed Booby: A messenger from the future
Sep 2, 2024 · Washington had three previous records – two found dead on the Dungeness Spit (2018 and 2023) and one seen on a passing vessel in the Strait of ...Missing: vagrancy Europe
[32]
British Ornithologists' Union Records Committee (BOURC)
Dec 6, 2017 · Red-footed Booby Sula sula (Linnaeus). Add to Category A. One, female, second-calendar-year or older, St Leonards, East Sussex, 4 September ...
[33]
Geolocation and immersion loggers reveal year‐round residency ...
May 28, 2024 · Here we use combined light-level and saltwater immersion loggers to study the year-round movement behaviour of adult red-footed boobies Sula sula rubripes.Introduction · Material and methods · Results · Discussion
[34]
Ontogeny of foraging behaviour in juvenile red-footed boobies (Sula ...
Oct 24, 2017 · Adults and juveniles were observed from shore and tracked at sea using GPS loggers over 3 consecutive 12-day periods. Juveniles initially made a ...
[35]
[PDF] Using GPS tracking to determine flight patterns of red-footed ...
We investigated the flight and foraging movements of red- footed boobies nesting on the north-western side of the atoll using GPS data logging tags. The birds ...Missing: breeding | Show results with:breeding
[36]
[PDF] USFWS Johnston Atoll National Wildlife Refuge
Sep 26, 2024 · As in all past years of CAST surveys, the Red-footed Booby was the most common nesting species on Johnston Island.
[37]
[PDF] RED-FOOTED BOOBY Sula sula - Bishop Museum
A booby, probably Red-footed, is present in the fossil record of Ulupau Head, indicating presence and possible breeding here for at least 200,000 years ...Missing: Miocene | Show results with:Miocene
[38]
Red-footed Booby Life History - All About Birds
The Red-footed Booby is a graceful, slim-winged seabird named for its vivid coral-red feet which males show off during courtship. Most booby species nest on ...Habitat · Food · Nesting · Behavior
[39]
Status of the Red-footed Booby on the Xisha Archipelago, South ...
The Red-footed Booby nests only in Pisonia grandis trees on the island, and the most serious threat to the breeding colony is from a herd of introduced cows ...
[40]
Pisonia grandis | Tetiaroa Society
The open branching system and size of these trees make them preferred nesting sites for birds such as Brown Noddy, White Tern, and Red-footed Booby. Because ...
[41]
[PDF] The Palmyra Atoll Research Consortium
Tournefortia at Palmyra also supports one of the largest red-footed booby colonies in the world, with around 25,000 pairs at the height of the nesting season, ...
[42]
Tropical cyclones alter short-term activity patterns of a coastal seabird
Oct 28, 2019 · Observations of the movements of red-footed boobies (Sula sula) and great frigatebirds (Fregata minor) during cyclonic activity in the ...
[43]
Cyclone avoidance behaviour by foraging seabirds | Scientific Reports
Apr 1, 2019 · Conversely, boobies may be less susceptible to the stronger cyclones ... tropical seabird, the red-footed booby, in a dynamic marine environment.
[44]
Genetic analysis of the diet of red‐footed boobies (Sula ... - USGS.gov
The diet of red‐footed boobies (Sula sula) provisioning chicks was quantified using 106 regurgitations collected from 81 adults over two study years with ...
[45]
Red-footed Booby - Pacific Rim Conservation
Taxonomic Information: There are 3 subspecies of Red-footed boobies: S.s. sula, S.s. rubripes, and S.s. websteri. S.s. rubripes breeds in the central and ...
[46]
[PDF] Donahue et al.: Diet of Red-footed Boobies in Hawai'i over decades
We describe the diet of Red-footed Boobies Sula sula nesting at Ulupa'u Crater, O'ahu, Hawai'i based on 106 regurgitations collected during 2014 and 2015. We ...
[47]
Diet and Foraging - Red-footed Booby - Sula sula - Birds of the World
Close ): in wet season, 79% (by mass) fish and 21% squid taken; in dry season, 99% fish and 1% squid. More squid in diet than taken by Brown Boobies ...Missing: composition crustaceans
[48]
The three-dimensional flight of red-footed boobies - PubMed Central
They make extensive use of wind conditions, flying preferentially with crosswinds at median speed of 38 km h−1, reaching highest speeds with tail winds. They ...Missing: skeletal | Show results with:skeletal
[49]
The three-dimensional flight of red-footed boobies: adaptations to ...
Dives were shallow (maximum 2.4 m) but frequent (4.5 dives h-1), most being plunge dives. While chasing for very mobile prey like flying fishes, boobies have ...
[50]
Wildlife Program | ʻĀ (Red-footed Booby)
The 'ā or red-footed booby is the smallest booby (Family: Sulidae), and like its Hawaiian relative, they live in tropical regions of both hemispheres.
[51]
On-board camera footage offers bird's eye glimpse into seabird ...
Aug 5, 2025 · Scientists have captured unique on-board footage of Indian Ocean seabirds speeding just above the waves to catch flying fish on the wing.
[52]
Seabird Tracking Data: Red-Footed Booby Bird-Bourne Video Data
Footage recorded via bird-borne video cameras on the backs of red-footed booby (Sula sula) adults during the breeding season, while undertaking ...
[53]
[PDF] 'Ā or Red-Footed Booby
'Ā (red-footed booby) forage alone or in mixed species feeding flocks, generally feeding further from land than congeners. 'Ā (red-footed booby) capture prey ...Missing: herding | Show results with:herding
[54]
(PDF) Foraging strategy of a tropical seabird, the red-footed booby ...
Aug 5, 2025 · By using GPS, Argos transmitters and activity recorders, we studied the foraging strategy of red-footed boobies (RFBs) Sula sula breeding on ...
[55]
Homing navigation is optimized to diurnal constraints in a tropical ...
We found that red-footed boobies navigated efficiently back to their colony on fast, straight and direct flights and adjusted their homing behaviour to arrive ...Missing: non- dispersal satellite
[56]
[PDF] Aerial Counts for Surface-Nesting Seabirds at Lehua Island and ...
Red-footed Boobies lay single-egg clutches in nests built in trees and shrubs that are incubated for 45 days; fledging may take place between 90 and. 135 days ...Missing: period | Show results with:period
[57]
Demography and Populations - Red-footed Booby - Birds of the World
Per pair with 60-65% reproductive success/yr for 15 yr, 9 young fledge successfully; 40-50% of these return to breed, so each breeding pair potentially raises 4 ...
[58]
Behavior - Red-footed Booby - Sula sula - Birds of the World
Courtship occurs at prospective nest site and adjoining perch site, and involves much nest-building (see Breeding: nest, below). No data on initial selection of ...Missing: reproduction | Show results with:reproduction
[59]
[PDF] USE OF AN HONEST SIGNAL BY RED-FOOTED BOOBIES SULA ...
The behavior was a striking behavior that visually resembled a “honking,” although no vocalization was heard because the booby was too distant. The honks also ...
[60]
Sounds and Vocal Behavior - Red-footed Booby - Birds of the World
Vocalizes mainly in nesting colony. During rest of year threat call may be used if another bird gets too close at a roost (EAS, RWS, GAS). No sexual differences ...
[61]
Movements and Migration - Red-footed Booby - Birds of the World
Initial dispersal from natal site Few data; young disperse to sea. In some areas immatures found roosting in colonies distant from natal site (EAS, RWS, GAS).Missing: geolocation studies
[62]
Kleptoparasitism in Tropical Seabirds: Vulnerability and Avoidance ...
We investigated the importance of kleptoparasitism in a population of Red-footed Boobies (Sula sula) sympatric with frigatebirds (Great and Lesser Frigatebird ...
[63]
[PDF] Boobies of the CNMI
Predators and habitat alteration are other threats to boobies. Rats, cats, dogs and pigs feed on the adults, chicks and eggs of boobies. On Rota, the Red-footed ...
[64]
Comparative ectoparasite loads of five seabird species in ... - PubMed
In this paper we describe the ectoparasitic lice ... red-footed booby Sula sula ) on the Galapagos Archipelago. We found 9 species of ectoparasitic lice ...
[65]
[PDF] Obligate fly ectoparasites on Galapagos seabirds - IRL @ UMSL
Jan 1, 2013 · Hippoboscid flies are highly specialized obligate parasites of birds and mammals that typically spend all of their adult life on the host. Most ...
[66]
Suliformes - an overview | ScienceDirect Topics
No microorganisms were detected in A. minutus (black noddy) or S. sula (red-footed booby). Haemoproteus was found in 8 of 98 adult birds and in none of the ...
[67]
Parasites of seabirds: A survey of effects and ecological implications
A range of micro- and macro-parasites can affect seabird species, including ticks, mites, helminths, viruses and bacteria in gulls, terns, skimmers, skuas, ...
[68]
Red-footed booby - Galapagos Conservation Trust
They are one of three species of booby found in Galapagos and their name comes from the Spanish word 'bobo', meaning foolish or clown – referring to their ...Missing: etymology origin
[69]
[PDF] EL NIÑO AND THE BIRDS: A RESOURCE-BASED ...
Asymptotic weights of Red–footed Booby chicks were also lower in 1982 (1178 ± 50 g) and 1983. (1165 ± 20 g) as compared with 1980 (1207 ± 20 g) and 1981 (1222 ± ...
[70]
Population Estimates Database – Partners in Flight Databases
2019. Estimates for any species or region of interest can be viewed online or downloaded as Excel files from each page. Downloadable files include all pertinent ...
[71]
Increase of tropical seabirds (Sula) in the California Current ...
First records of the Red-footed Booby in the western United States. W. Birds 11, 199–200. Available online at: https://archive.westernfieldornithologists ...<|separator|>
[72]
GPS Tracking of Red-footed Booby Seabirds - EPIC
With this in mind, in March 2023 an EPIC team outfitted GPS data loggers on 28 adult Red-footed Boobies nesting on Battowia island, Saint Vincent and the ...
[73]
Invasive Species | What We Do | U.S. Fish & Wildlife Service
red-footed boobies — now thrive at Palmyra Atoll National Wildlife Refuge after the eradication of invasive rats. We eradicated invasive black ...
[74]
Recovery: The Miracle on Palmyra - Cool Green Science
Dec 15, 2015 · Palmyra Atoll has recovered from many calamities, but it couldn't recover from rats. Can a dying ecosystem be brought back to life? Ted Williams reports.
[75]
Recovery: The Miracle on Palmyra - Island Conservation
Feb 20, 2016 · The island's native populations were struggling until invasive rats were completely eradicated. Since then, the island continues to show signs ...Missing: threats | Show results with:threats
[76]
https://www.nature.com/articles/srep35191
[77]
Decline of recent seabirds inferred from a composite 1000-year ...
Oct 17, 2016 · Specifically, there are >35500 pairs of Red-footed Boobies living on the Xisha Archipelago at present. This is approximately 10% of the world ...
[78]
[PDF] PROPOSED AMENDMENTS TO THE ACTION PLAN OF ... - AEWA
The migratory populations of the remaining 92 species were proposed for inclusion in CMS Appendix II in 1994, but only those species ... Sula sula : Red-footed ...