What kinds of gulls can you find in Colorado?
If you’re like me, you’ll be surprised to find out that there is no specific bird called a “seagull!” Instead, gulls are a diverse family of birds with different habitats, ranges, and color patterns.
I’ve also included terns in the list below, a closely related subgroup of gulls. In general, gulls have hooked beaks while terns’ beaks are straight, and terns have webbed feet while gulls don’t.
Please be aware that today I’m ONLY listing and focusing on the plumage of ADULT gulls. Baby and young gulls’ can look so different that it would be confusing to describe all the variations here. But if you want to dive even deeper into gull identification, check out this field guide, which has photo examples of gulls with different plumage based on their age:
8 COMMON Gulls and Terns In Colorado!
#1. Lesser Black-backed Gull
- Larus fuscus
- Adults measure 20.5 to 25.2 inches in length and have a 53.2 to 59.1-inch wingspan.
- Breeding adult plumage is white below, slate gray above, white head, black wingtips, and in non-breeding plumage, the head and neck are typically spotted brown.
- They have yellow eyes, bright yellow legs, and a yellow bill with a red spot on the lower mandible.
Although they’re native to Europe, Lesser Black-backed Gulls populations are increasing worldwide. They occupy rocky islands, cliffs, and salt marshes. In addition, you can spot these gulls in aquatic habitats such as bays, lakes, rivers, and the open ocean during the winter and migration season.
Lesser Black-backed Gulls adjust their hunting style depending on the prey. They may swoop down to the water’s surface in flight to catch fish, mollusks, insects, crustaceans, marine worms, smaller birds, and eggs, or forage on land for rodents, berries, seaweed, and seed. They’re scavengers and are often seen around fishing boats and landfills. They will even steal food from other birds.
In spring, Lesser Black-backed Gulls return to breeding grounds soon after the ice and snow have melted. You’re likely to see monogamous breeding pairs preening each other’s head and neck feathers. In North America, Lesser Black-backed Gulls sometimes pair with Herring Gulls due to a lack of available mates.
Both the males and females incubate the eggs and aggressively defend their nest. Their protective behavior continues when their chicks hatch. Males will strike imposing postures and call loudly to warn away other males. They may also get into fights with any bird (or human!) that gets too close. Watch below!
#2. Herring Gull
- Larus argentatus
- Adults range from 22.1 to 26.0 inches in length and have a 53.9 to 57.5-inch wingspan.
- Breeding adults have light gray backs, white heads, white undersides, and black wingtips and may have dusky marks on their heads during the winter.
- They have yellow eyes, dull pink legs, hefty bills, and barrel chests.
Herring Gulls are the familiar, quintessential “sea-gull” in Colorado. They occupy farmland, coasts, bays, beaches, lakes, piers, and landfills. They’re most abundant on the coast and surrounding large lakes and river systems.
If you spend time at the beach, you’ve probably noticed Herring Gulls waiting for you to drop your snack! In addition to popcorn and chips from humans, they consume fish, crustaceans, mollusks, sea urchins, marine worms, smaller birds, eggs, carrion, and insects.
Herring Gulls will stop at nothing to get a meal! They’ve been observed preying on fish driven to the surface by feeding whales. They also will take hard-shelled items such as crabs and mollusks high into the air and drop them onto rocks to break them open.
Individuals have even been observed “fishing.” One individual was recorded dropping pieces of bread into a pond and catching the goldfish that came up to feed. It didn’t eat any bread itself, suggesting the gull was using the bread as a lure!
The population of Herring Gulls declined steeply during the 19th century because of over-hunting. While their range and population recovered during the 20th century, overfishing, oil spills, and pesticide contamination have reduced some populations.
#3. Ring-Billed Gull
- Larus delawarensis
- Adults range from 16.9 to 21.3 inches in length and have a wingspan of 41.3 and 46.1 inches.
- Breeding adults are clean gray above with a white head, white body, white tail, and black wingtips spotted with white.
- They have yellow legs, eyes, and bill with a black band.
Look for Ring-Billed Gulls in Colorado near aquatic habitats.
These are the gulls you’re most likely to see in inland locations. Look for them on coasts, piers, large bodies of water, and landfills, since they prefer to nest near freshwater sources. These gulls are adapted to human-disturbed areas and are common around cities, farmlands, docks, and even in parking lots.
Ring-billed Gulls are known for dropping and then re-catching prey. This “game” is a way of honing their hunting skills!
Interestingly, Ring-billed Gulls use a sort of built-in compass to navigate. Scientists found that chicks as young as two days old showed a preference for magnetic bearings that would lead them to their winter habitat. They typically return to their nesting location to breed each year, often within a few meters of old nest sites.
#4. California Gull
- Larus californicus
- Adults are 18.5 to 21.3 inches in length and have a wingspan of about 51.2 inches.
- Breeding adults have a medium gray back and white head and underside.
- They have dark eyes, yellow legs, and a yellow bill with a small black ring and a red spot on the lower mandible that is brighter in breeding individuals.
California Gulls can be found in various habitats in Colorado. For example, you might spot them on coasts, farms, lakes, or urban centers.
They frequently forage at farms and in plowed fields and often follow farming equipment that stirs up insects. During winter, when farming activity slows, they spend more time at coastal locations and breeding islands.
These gulls are opportunistic omnivores, meaning they’ll eat nearly anything they can fit in their mouth!
They feed on fish, small mammals, human refuse, carrion, grasshoppers, mayflies, brine shrimp, earthworms, cherries, grain, bird eggs, and more. Their favorite way to catch a meal is to run through large groups of alkali flies with their bills open, catching them along the way.
#5. Franklin’s Gull
- Leucophaeus pipixcan
- Adults range from 12.6 to 14.2 inches in length and have a 33.5 to 37.4-inch wingspan.
- Breeding adults have black heads with white crests above and below the eye, dark gray upperparts, white underparts, and a black wingtip separated from the gray upper wing by a white crescent.
- The legs and bill are reddish.
Franklin’s Gulls are often spotted inland in agricultural fields, prairies, flooded pastures, marshes, estuaries, and lakes. They’ve been spotted as high as 14,00 feet above sea level in the Rocky Mountains! These gulls prefer to nest in freshwater marshes with abundant vegetation and patches of open water.
Like other gulls in Colorado, they forage by walking, wading, swimming, or flying and catching insects from the air. In agricultural areas, they’ve been known to follow tractors and feed on worms and insects dug up by plowing.
Colonies are very sensitive to disturbance. “Panic flights,” where large numbers of gulls fly off their nest sites and circle in silence for several minutes, occur when humans or predators disturb the colony. Although these terns and gulls aren’t Franklin’s Gulls, this video gives a good idea of what a panic flight looks like!
Populations of Franklin’s Gulls have declined throughout their range. As a result, Partners in Flight have listed them on the Yellow Watch List. They’re threatened by the loss of wetland habitat, environmental pollutants, climate change, and their sensitivity to human disturbance.
#6. Bonaparte’s Gull
- Chroicocephalus philadelphia
- Adults measure 11 to 11.8 inches in length and have a wingspan of 35.4 to 39.4 inches.
- Breeding adults have black heads, gray wings, white undersides, and large white triangles on their wingtips.
- They have red legs, small bodies, and slender bills.
This is the smallest species of gull in Colorado!
Look for Bonaparte’s Gulls on ocean bays, lakes, and swamps. They breed and nest where coniferous trees meet the edges of lakes and bogs.
They visit many aquatic habitats during migration and winter, including lakes, rivers, coastal estuaries and lagoons, and the open sea. In addition, they often congregate around sewage treatment ponds, probably due to the increased insect availability in these areas.
Bonaparte’s Gulls are also known for their “conveyer belt” foraging, which they use in some areas. Large numbers of Bonaparte’s will fly upwind above the water’s surface, dipping down to seize prey such as small fish. Then, when they reach the end of the food patch, they fly upward, and the wind carries them back to the beginning.
#7. Black Tern
- Chlidonias niger
- Adults range from 9.1 to 14.2 inches in length and have a 22.4 to 23.6-inch wingspan.
- Breeding adults are dark gray above with black heads, black undersides, and pale underwings.
- They have dark legs, eyes, and bills.
Black Terns prefer wetlands with extensive vegetation and open water for breeding. They can be spotted in various wetland habitats during migration, including lagoons, river edges, lakes, marshes, sewage lagoons, beaches, and open ocean waters.
They spend their winters in coastal regions of the tropics foraging for small fish in coastal waters. However, they’ll also spend time in lagoons, saltpans, estuaries, shrimp farms, marshes, and farm fields not far from the coast.
Black Terns generally hunt their prey in flight. But, unlike many gulls and terns in Colorado, Black Terns don’t plunge into the water after prey. Instead, they fly low over marsh vegetation and water, swooping low to scoop up prey. They’re agile flyers and will also capture insects out of the air, chasing after them like a swallow.
Black Tern populations have been declining since 1966. Populations frequently move and are difficult to monitor, and the causes of their decline aren’t well understood. However, it’s likely that destruction of wetland habitat, pesticide pollution, and climate change have all contributed.
#8. Forster’s Tern
- Sterna forsteri
- Adults measure from 13 to 14.2 inches in length and have 30.7 to 31.5-inch wingspan.
- Breeding adults are gray above and white below with a black cap.
- They have an orange bill with a black tip, orange legs, and silvery wingtips.
The Forster’s Tern is the most widespread tern in Colorado!
Forster’s Terns spend the breeding season in marshes and wetlands. They winter along the coast and can be spotted in estuaries, inlets, coastal lagoons, and sheltered bays.
Forster’s Terns typically fly along or near shorelines 20 to 25 feet in the air and feed on small fish. They catch prey by diving and plunging into the water, occasionally from as high as 50 feet up. These birds normally make shallow dives but can take prey nearly a foot below the water’s surface.
The populations of Forster’s Tern are difficult to monitor because their colonies shift locations from year to year. However, they’re believed to be stable. Sea-level rise and destruction of wetland habitats may become issues in the future for this species.
Which of these gulls and terns in Colorado have you seen before?
Tell us below in the COMMENTS section!