The red legged cormorant (Phalacrocorax gaimardi) is a large seabird found along the Pacific coast of North America. It gets its name from its bright red legs and feet. Red legged cormorants spend most of their lives in coastal waters, nesting on cliffs and rocky islands and feeding on fish and other marine life.
Where do red legged cormorants live?
The red legged cormorant has a very limited range, nesting only along the Pacific coast from the Aleutian Islands in Alaska down to central Baja California, Mexico. Their breeding habitat consists of rocky cliffs and islands, where they nest in groups called colonies. Some of the major nesting sites include the Farallon Islands off San Francisco, the Channel Islands off Southern California, and islands off Baja California. During the nonbreeding season, red legged cormorants disperse somewhat farther, ranging as far north as the Alaska Peninsula and as far south as Mazatlán, Mexico on the Pacific coast. However, their range is still concentrated within about 500 miles of the breeding colonies.
What habitats do red legged cormorants use?
Red legged cormorants utilize both marine and terrestrial habitats:
- Marine: Red legged cormorants spend the majority of their time on the ocean, resting on the surface and diving to catch fish and invertebrates. They forage in nearshore waters within a few miles of land, especially around rocky outcroppings, kelp forests, and other areas where prey congregates.
- Coastal cliffs: Breeding colonies are situated on protected cliffs and rocky islands, usually with steep faces to deter mammalian predators. Nest sites are bare rock surfaces or accumulations of guano.
What features make good red legged cormorant habitat?
The key features that red legged cormorants require for nesting and foraging habitat include:
- Nesting sites: Steep, rocky cliffs or islands relatively isolated from mainland predators. Ledges or flat areas for nests.
- Marine foraging areas: Nearshore waters within a few miles of breeding sites. Areas with rocky reefs, kelp forests, or other submerged structure that aggregate prey.
- Food supply: Abundant populations of small fish and invertebrates like rockfish, sculpin, lingcod, crustaceans, and echinoderms.
- Undisturbed habitat: Free from excessive human disturbance and mammalian predators.
How do red legged cormorants use marine habitats?
Red legged cormorants are pursuit divers that catch prey underwater. They typically forage within a mile or two of the coast, diving to depths of up to 130 feet to pursue schooling fish. Though they occasionally venture farther from shore, most foraging takes place near kelp forests, rocky reefs, underwater pinnacles, or other areas where prey congregates. Their diet consists of small, schooling fish like rockfish, greenlings, and midshipman as well as invertebrates like crabs and sea urchins. Cormorants are able to dive deep and stay underwater for extended periods due to anatomical adaptations like dense bones, muscular legs for propulsion, and long, hooked bills for catching slippery prey.
Diving Behavior
Red legged cormorants typically make dives lasting around 30-90 seconds. However, they are capable of staying submerged for over 5 minutes when pursuing prey at depth. Cormorants propel themselves with their large webbed feet while underwater. They chase after individual fish or swim through schools with their hooked bill held open to snatch prey. After a successful dive, cormorants will surface and often swallow prey before diving again.
Flock Feeding
Cormorants frequently feed in groups or flocks near areas of high prey abundance. Working together increases their ability to herd fish into tight balls where they are easier to catch. It also allows the birds to surround schools so fish have nowhere to escape. Flocks lift off the water one after another when giving chase underwater. The presence of multiple predators underwater simultaneously makes it harder for prey to evade attack.
Nocturnal Foraging
Cormorants have excellent vision during daylight. But some red legged cormorants also feed at night, using their tactile senses and ability to capture prey in dark or silty water. Nocturnal feeding might take advantage of certain fish and invertebrates that migrate toward the surface or exhibit less evasive behavior under cover of darkness. Their nocturnal prey includes species like rockfish, greenlings, midshipman, sculpin, octopus, squid, and shrimps.
How do red legged cormorants use terrestrial habitats?
Red legged cormorants use terrestrial habitats solely for nesting and resting. Their nesting habitat occurs on steep cliffs and rocky islands that offer protection from predators. Nests consist of accumulated guano and debris scraped together into mounds. While the nests themselves are very rudimentary, the birds are very faithful to nesting sites and colonies, often reusing the same areas year after year. When not actively diving for food, red legged cormorants spend a lot of time perched on rocks or cliff ledges close to their nest sites. Here they rest, preen their feathers, and dry their wings following foraging bouts.
Nesting Colonies
Red legged cormorants nest in dense colonies numbering from just a few dozen to over 1,000 pairs. Some of the largest colonies occur on islands off Baja California with over 25,000 breeding birds total. Nesting is highly synchronized, with most eggs laid within a 2-3 week period. The colonies form a nearly continuous carpet of nests built side-by-side on ledges and cliffs. While crowded, the density offers some protection from aerial predators. Both parents share in incubating the eggs and provisioning the chicks after they hatch.
Roosting and Hauling Out
When not actively diving or attending to nests, red legged cormorants spend time perched on rocks and cliff ledges near their colonies. These areas serve as important roosts and haul-out sites where the birds rest, preen, and dry their feathers. Cormorants’ feathers are not waterproof, so they must regularly haul out to dry and maintain their insulating properties. Favorite haul-out sites allow easy takeoff to return to the ocean to catch more prey.
How do red legged cormorants interact with their habitats?
Red legged cormorants interact with both marine and terrestrial habitats in the following ways:
- Foraging: Cormorants dive underwater to pursue and capture fish, impacting prey populations. Their guano deposits can also raise nutrient levels around colonies.
- Nesting: Breeding activities concentrate nutrients from guano at colony sites. Nests scrape together guano and debris. Their presence influences habitat for other species.
- Roosting: Repeated use of haul-out sites and cliff ledges can accelerate erosion and leave deep guano deposits.
- Disturbance: Red legged cormorants are very sensitive to human activities near breeding sites and may abandon colonies if disturbed.
Overall, cormorants play an important role as top predators in nearshore food webs. Their presence also influences habitat for other species and accelerates nutrient cycling where large colonies form.
Threats to red legged cormorant habitat
Some of the major threats to red legged cormorant breeding and foraging habitat include:
- Human disturbance at nesting sites
- Introduction of mammalian predators to nesting islands
- Expanded development along coastlines
- Oil spills and water pollution
- Declines in fish stocks from overfishing
- Entanglement in fishing lines and nets
- El Niño events that reduce prey availability
Protecting isolated, undisturbed nesting sites and maintaining healthy fish populations in nearshore waters are key conservation priorities for the species. Monitoring and management may also be needed at frequently visited haul-out sites and foraging areas that are vulnerable to human impacts.
Conservation of red legged cormorant habitat
Some important conservation measures that help protect and maintain red legged cormorant habitat include:
- Protecting nesting areas through site management, access restrictions, and monitoring
- Eradicating introduced mammalian predators from breeding islands
- Establishing marine protected areas around important foraging and rafting sites
- Enforcing regulations on oil spills and discharge to maintain water quality
- Sustainable management of commercial and recreational fisheries
- Population monitoring and modeling to detect declines
- Education and outreach about avoiding disturbance
In California and Mexico, collaboration across agencies, researchers, and stakeholders has improved protection for red legged cormorant breeding habitat. Continued monitoring and adaptive management will be needed to understand how factors like climate change and offshore development may impact populations in the future.
Key facts about red legged cormorant habitat
- Range limited to Pacific coast from Aleutians to Baja California
- Nest on steep cliffs and rocky islands
- Forage in nearshore waters within a few miles of colonies
- Dive to 130 ft depths to catch fish and invertebrates
- Require undisturbed nest sites and healthy fish populations
- Sensitive to human disturbance when nesting
- Conservation requires protection of nesting and foraging areas
Conclusion
In summary, the red legged cormorant is an important marine bird along the Pacific coast that relies on a very specific set of coastal habitats. Steep, predator-free cliffs and islands are required for nesting colonies, while nearby nutrient-rich marine waters provide the food resources needed to raise chicks. Conservation of this species centers on protecting both nesting and foraging areas from human impacts. Maintaining high quality habitat will be key to ensuring the long-term survival of red legged cormorant populations.
