Brown boobies and masked boobies are two similar species of seabirds in the Sulidae family. While they have some similarities, there are several key differences between these two types of boobies in terms of their physical characteristics, habitat, diet, breeding behaviors, and conservation status.
Physical Characteristics
The most noticeable difference between brown and masked boobies is the coloration of their plumage.
Brown Booby
As their name suggests, brown boobies have mostly brown plumage. Their heads, necks, backs, wings, and tails are a rich chocolate brown color. Their undersides are a lighter tan or white shade. Brown boobies have pale grayish-blue bills and feet.
Masked Booby
Masked boobies have more striking black and white plumage. They have white undersides, rumps, and tails. Their heads, wings, backs, and necks are snow white as well, contrasted by blackish-brown “masks” around their eyes and across the top of their wings. Their bills and legs are yellow.
Size
Brown and masked boobies have similar body sizes.
| Species | Length | Wingspan |
|---|---|---|
| Brown Booby | 24-32 in (60-81 cm) | 58-68 in (150-173 cm) |
| Masked Booby | 25-32 in (65-82 cm) | 59-71 in (150-180 cm) |
Brown boobies tend to be very slightly larger, but there is extensive overlap in their size ranges.
Habitat and Range
Brown and masked boobies have broadly overlapping ranges in tropical and subtropical oceans globally. However, there are some habitat differences.
Brown Booby
Brown boobies have an extremely wide distribution across tropical oceans. They can be found across the Caribbean, off the coasts of Central and South America, throughout the Hawaiian Islands, and scattered across the Pacific and Indian Oceans.
Brown boobies mainly nest on rocky cliffs and offshore islands, rarely venturing inland. They only come ashore to breed. At sea, they favor deep, offshore waters.
Masked Booby
Masked boobies also range across tropical oceans, but their distribution is centered more solidly in the Pacific. They are abundant in the tropical East Pacific, around Hawaii, and across Micronesia and Polynesia.
In contrast to brown boobies, masked boobies regularly nest on beaches and coral atolls as well as cliffsides. They also forage closer to shore than brown boobies.
Diet
Both species are piscivores, meaning fish make up the majority of their diet. However, brown and masked boobies show some differences in prey preferences.
Brown Booby
– Primarily eat flying fish, mackerel, herring, anchovies, and other schooling fish
– Sometimes eat squid and crustaceans
– Forage by plunge diving from heights of up to 100 feet
Masked Booby
– Eat more squid and pelagic fish like mahi mahi
– Less likely to eat schooling fish than brown boobies
– Dive from lower heights around 60 feet
The brown booby’s greater diving heights allow it to catch faster schooling fish, while the masked booby is better adapted for capturing squid and lone predatory fish at shallower depths.
Breeding
Brown and masked boobies have similar breeding behaviors with a few key differences:
| Breeding Trait | Brown Booby | Masked Booby |
|---|---|---|
| Nest Type | Depression in ground | Mound of vegetation |
| Clutch Size | 1-3 eggs | 1-2 eggs |
| Incubation | 41-45 days | 41-46 days |
| Fledging Period | 70-100 days | 100-120 days |
Key differences:
– Masked boobies build nests, while brown boobies lay eggs directly on the ground.
– Masked booby clutches are smaller.
– Masked booby chicks take longer to fledge.
Courtship
Their courtship rituals also differ somewhat:
– Brown boobies have an elaborate, acrobatic courtship display involving bill-fencing and synchronized flying.
– Masked boobies have a simpler courtship display. Their most impressive ritual is “sky-pointing” where males point their bills straight up towards the sky.
Conservation Status
The brown booby has a stable, healthy global population and is classified as a species of Least Concern by the IUCN Red List.
In contrast, the masked booby has experienced population declines due to habitat loss, harvest for food, and predation. The IUCN Red List categorizes it as Near Threatened.
Brown boobies face fewer threats overall and adapt readily to disturbances, while masked boobies are more sensitive to human activity and environmental changes. Creating protected breeding areas will be important for masked booby conservation.
Conclusion
While brown and masked boobies are closely related seabirds with many common traits, they differ in their plumage, habitat preferences, foraging behaviors, breeding rituals, and conservation status. The brown booby is widespread and abundant, while the masked booby has a more restricted range and is nearing threatened status. Understanding these key differences can help inform management efforts for both species.
