Cassin's Auklet vs Ancient Murrelet

Cassin's Auklet

Ptychoramphus aleuticus

How to recognise a cassin's auklet?

General appearance

The Cassin's Auklet is a small, plump bird with a length ranging from 19 to 25 cm. This seabird exhibits a stocky build and short wings. Its plumage is predominantly gray with a darker tone on the upper side, while the underparts are lighter gray. The face is marked by a small white crescent above the eye, and the cheeks bear a slightly lighter patch. Its bill is short and stout, appearing black, and its legs and feet tend to exhibit a bluish-gray tone.

Male vs female

Cassin's Auklets show very little sexual dimorphism, meaning males and females look very similar. Both sexes sport identical coloration and size, which makes it challenging to differentiate them in the field. Observation of breeding behavior is generally necessary for accurate identification between males and females.

Juvenile

Juvenile Cassin's Auklets resemble adults but display a few key differences. Their plumage is slightly duller with a more uniform gray tone, lacking some of the sharp contrast seen in adults. The white crescent above the eye may not be as pronounced, and the bill is smaller and less robust, appearing paler in hue. As juveniles mature, they gradually acquire the definitive adult plumage.

Size

9.8 in/5.6 - 7.1 oz

Habitat

Primary Habitat

Cassin's Auklet primarily inhabits the cool, coastal waters off the Pacific coast of North America, ranging from Alaska to Baja California. It prefers open seas and offshore islands, nesting in burrows dug into grassy slopes or sandy soil near the shore. The bird thrives in cold water climates, often dependent on upwelling zones rich in marine food resources.

Additional Range

While less common, the bird occasionally enters more temperate waters further offshore during non-breeding seasons. It also exhibits a degree of adaptability by nesting on islands with varying vegetative cover, demonstrating its flexibility to thrive in diverse environmental conditions.

Range Map

What do cassin's auklets like to eat?

Natural Diet

Cassin's Auklet, scientifically recognized as Ptychoramphus aleuticus, has a diet that predominantly consists of small marine creatures. These adept seabirds primarily feast on zooplankton, including copepods, krill, and small fish. Their feeding patterns may demonstrate seasonal variation, with krill becoming more significant in their diet during periods of abundance, typically in spring and early summer. These seabirds rely on dense swarms of these small sea creatures that occur due to ocean currents and upwellings. During winter months, when food availability decreases, Cassin's Auklets may extend their range in search of sufficient nourishment.

Bird Feeders

Cassin's Auklets are not commonly seen at bird feeders and typically do not consume standard feeder offerings. These seabirds are highly adapted to their marine environment and their diet consists mainly of natural resources found in oceanic habitats. Thus, they do not show interest in foods such as seed mixes, suet, or fruits that are often provided by backyard bird feeders. As these birds are primarily pelagic, they rarely come into contact with typical feeder setups found on land. Encouraging the presence of Cassin’s Auklets is best achieved through conservation of their natural marine habitats rather than offering supplemental feeder food.

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Ancient Murrelet

Synthliboramphus antiquus

How to recognise an ancient murrelet?

Ancient Murrelet Characteristics

General appearance: The Ancient Murrelet is a small seabird with a distinctive appearance. Adults are characterized by a striking dark gray body contrasted by their white face and throat. Their wings and back are a deeper slate gray, while their underparts remain lighter. They have slim, short tails and relatively long wings. The bill is small, yellow, and sharply pointed. Male vs Female: In the Ancient Murrelet, there are minimal differences between males and females, both possessing similar coloration and size. This similarity makes it challenging to differentiate between the sexes in the wild without a closer inspection. Juvenile: Juveniles differ from adults in their overall duller appearance, lacking the defined white facial markings seen in adults. Their plumage tends to be more mottled and mixed with browns and grays, which provides better camouflage. As they mature, they gradually acquire the distinct coloration of the adult birds. Juveniles might also have slightly shorter and duller yellow bills compared to adults. In the wild, Ancient Murrelets can often be recognized by their rapid, fluttering flight near ocean waters along rocky coastlines. Seasonally, they might appear slightly heavier before breeding or maintain molted plumage during post-breeding.

Size

9.4 - 9.8 in/6.3 - 9.5 oz

Habitat

Primary habitat

Ancient Murrelets primarily inhabit rocky coastal regions across the North Pacific from the coasts of Alaska to the Sea of Japan. They are typically found in cold, temperate marine environments where they nest in underground burrows on forested islands. The murrelets are known for their tendency to nest in dense colonies in these secluded coastal areas.

Additional range

These birds occasionally adapt to localized conditions beyond typical confines, appearing further south as occasional visitors along North American and Asian Pacific coastlines. Unexpectedly, they may venture into more human-disturbed areas if nesting conditions are suitable. Increased transport and climate shifts occasionally influence their range expansion.

Range Map

What do ancient murrelets like to eat?

Natural diet

In their natural habitat, Ancient Murrelets primarily feed on small fish, plankton, and various crustaceans. These seabirds hunt close to the surface, diving into the ocean to catch prey like capelin, Pacific sand lance, and krill. They often forage in coastal waters and are known to travel long distances following food availability. Feeding habits vary seasonally. During spring, they rely heavily on abundant krill and copepods. In summer, the diet remains diverse with a focus on juvenile fish that are abundant in these months. This helps them efficiently meet the energy requirements for breeding and chick-rearing.

Bird feeders

Ancient Murrelets are not typically attracted to traditional backyard bird feeders, as their diet primarily consists of marine life. However, while they might not frequent feeders, they can occasionally be found in coastal areas where people provide food scraps or fish bits. Since these birds feed at sea, customization of bird offerings would not significantly impact their feeding patterns. For those interested in observing Ancient Murrelets up close, providing access to clean water or ensuring a healthy marine environment nearby is more beneficial than standard backyard bird feeders. Overall, they are best observed in their natural maritime settings rather than seeking alternative foods from terrestrial sources.

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Cassin's Auklet

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Ancient Murrelet

Cassin's Auklet

Ptychoramphus aleuticus

General appearance

The Cassin's Auklet is a small, plump bird with a length ranging from 19 to 25 cm. This seabird exhibits a stocky build and short wings. Its plumage is predominantly gray with a darker tone on the upper side, while the underparts are lighter gray. The face is marked by a small white crescent above the eye, and the cheeks bear a slightly lighter patch. Its bill is short and stout, appearing black, and its legs and feet tend to exhibit a bluish-gray tone.

Male vs female

Cassin's Auklets show very little sexual dimorphism, meaning males and females look very similar. Both sexes sport identical coloration and size, which makes it challenging to differentiate them in the field. Observation of breeding behavior is generally necessary for accurate identification between males and females.

Juvenile

Juvenile Cassin's Auklets resemble adults but display a few key differences. Their plumage is slightly duller with a more uniform gray tone, lacking some of the sharp contrast seen in adults. The white crescent above the eye may not be as pronounced, and the bill is smaller and less robust, appearing paler in hue. As juveniles mature, they gradually acquire the definitive adult plumage.

Size

9.8 in/5.6 - 7.1 oz

There's more to learn about Cassin's Auklet

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Ancient Murrelet

Synthliboramphus antiquus

Ancient Murrelet Characteristics

General appearance: The Ancient Murrelet is a small seabird with a distinctive appearance. Adults are characterized by a striking dark gray body contrasted by their white face and throat. Their wings and back are a deeper slate gray, while their underparts remain lighter. They have slim, short tails and relatively long wings. The bill is small, yellow, and sharply pointed. Male vs Female: In the Ancient Murrelet, there are minimal differences between males and females, both possessing similar coloration and size. This similarity makes it challenging to differentiate between the sexes in the wild without a closer inspection. Juvenile: Juveniles differ from adults in their overall duller appearance, lacking the defined white facial markings seen in adults. Their plumage tends to be more mottled and mixed with browns and grays, which provides better camouflage. As they mature, they gradually acquire the distinct coloration of the adult birds. Juveniles might also have slightly shorter and duller yellow bills compared to adults. In the wild, Ancient Murrelets can often be recognized by their rapid, fluttering flight near ocean waters along rocky coastlines. Seasonally, they might appear slightly heavier before breeding or maintain molted plumage during post-breeding.

Size

9.4 - 9.8 in/6.3 - 9.5 oz

There's more to learn about Ancient Murrelet

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How to tell the Cassin's Auklet from the Ancient Murrelet

Visual differences

Cassin's Auklet and Ancient Murrelet differ primarily in visual traits: - **Size**: Cassin's Auklet is 7.5 to 9.8 inches long, while Ancient Murrelet measures about 9.4 to 9.8 inches. - **Plumage**: Cassin's Auklet has uniformly gray plumage with a white crescent above the eye, whereas Ancient Murrelet displays contrasting black and white, with a distinctive "tuxedo" look. - **Beak**: Cassin's Auklet has a short, stout black beak, while Ancient Murrelet has a more slender, yellowish beak. - **Distinctive Features**: Cassin's has bluish-gray legs and feet; Ancient Murrelet has a darker crown and nape.

Key differences and behavior

Cassin's Auklet and Ancient Murrelet are distinct seabirds with differing behaviors and habitats. Cassin's Auklet thrives in the cold coastal waters of the Pacific, nesting in burrows on coastal islands, often in grassy slopes, and feeds mainly on zooplankton like krill, a diet that even makes their feces glow. In contrast, the Ancient Murrelet inhabits rocky coastal regions from Alaska to Japan, nesting in forested island burrows and feeding on small fish and crustaceans. While both species are monogamous, Cassin's Auklets employ elaborate courtship displays and lay one or two eggs with a longer incubation of 40 days, whereas Ancient Murrelets hatch precocial chicks from two eggs after 30 days, who quickly venture out to sea. Both are adapted to marine life but in contrasting ecological niches.