Bulwer's Petrel vs Ashy Storm-Petrel

Bulwer's Petrel

Bulweria bulwerii

How to recognise a bulwer's petrel?

General appearance

The Bulwer's Petrel is a medium-sized seabird characterized by its sleek, elongated body and narrow wings that enable graceful gliding over the water. Its plumage is primarily a dark chocolate brown, often appearing black in dim lighting. The head, back, and wings possess a slight sheen, adding to its striking appearance. The bird's bill is slender and black, complementing its streamlined body. Legs and feet are also dark, aiding in its inconspicuous presence at sea.

Male vs female

In Bulwer's Petrels, sexual dimorphism is minimal. Both males and females share similar size and coloration, making it difficult for observers to distinguish between the sexes. They are nearly identical in plumage and size, with no discernible differences in markings or color.

Juvenile

Juvenile Bulwer's Petrels closely resemble adults, sharing the same dark plumage. However, younger birds might display slightly more faded or dusky feathering compared to the polished look of mature adults. While the overall structure remains similar, juveniles might appear a bit scruffier as they transition into adults. Over time, their plumage gains the sheen characteristic of adult Bulwer's Petrels, completing their development.

Size

9.8 - 11.0 in/3.0 - 4.8 oz

Habitat

Habitat of the Bulwer's Petrel

Primary habitat: Bulwer's Petrel primarily inhabits subtropical and tropical oceanic waters. They are found across the Atlantic, Pacific, and Indian Oceans. Preferring warmer climates, they nest on remote islands with cliffs or rocky outcrops where vegetation provides adequate cover from predators. Additional range: While their primary range is over open seas, they can sometimes be sighted closer to coastal regions during breeding seasons. Despite their pelagic nature, these birds occasionally venture near islands not commonly used for nesting, demonstrating some level of adaptability to varying maritime environments.

Range Map

What do bulwer's petrels like to eat?

Natural diet

Bulwer's Petrel, a pelagic bird found across the subtropical and tropical oceans, primarily sustains itself on a maritime diet. Its primary food sources include small fish, squid, and crustaceans. Specialized for life at sea, these petrels are adept at catching prey near the water's surface, often during the night when marine life ascends closer to the surface. They take advantage of their excellent low-light vision to forage effectively in the dark. Seasonal shifts impact their diet minimally, as their aquatic prey remains available year-round. However, certain fluctuations in oceanic food availability can influence specific diet composition depending on geographical location.

Bird feeders

As a strictly oceanic bird, Bulwer's Petrel rarely, if ever, frequents traditional land-based bird feeders because they are well-adapted to sourcing food from the open ocean. Unlike many common backyard birds that enjoy a range of seeds, fruits, or suet offered at feeders, the Bulwer's Petrel's diet is specialized for catching marine food items. Human attempts to supplement their diet using bird feeders would unlikely succeed, as the petrels seldom approach terrestrial environments for feeding purposes and are specifically reliant on their natural oceanic habitat to meet their dietary needs.

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Ashy Storm-Petrel

Hydrobates homochroa

How to recognise an ashy storm-petrel?

Ashy Storm-Petrel Recognition Guide

General appearance: The Ashy Storm-Petrel is a small, slate-gray seabird notable for its uniformly ashy coloration without any striking patterns or contrasts. This bird typically measures about 18 to 20 centimeters in length with long, slender wings spanning approximately 43 to 47 centimeters. Its plumage has a soft, sooty color throughout, mirrored by dark brownish hue in its long, slightly forked tail. The bird's head, back, wings, and upper parts are varying shades of ashy gray, lending it camouflage against the ocean's murky horizons. Male vs female: Both the male and female Ashy Storm-Petrels showcase similar morphologies and plumage characteristics. There are no conspicuous differences, and thus, distinguishing the sexes based on appearance alone can be challenging. Both sexes share identical coloration and size, making external identification in the field infeasible without behavioral context or genetic analysis. Juvenile: Juvenile Ashy Storm-Petrels bear a close resemblance to adult birds with only subtle differences in appearance. They generally display slightly paler or duller plumage and may lack the full depth of coloration seen in mature birds. As juveniles age, they gradually acquire the adult's consistent ashy gray tone, completing the transition in several months as they mature in the marine environment.

Size

7.1 - 8.3 in/1.2 - 1.9 oz

Habitat

Primary Habitat

The Ashy Storm-Petrel primarily inhabits the coastal regions of the eastern North Pacific. This small seabird is most commonly found around the Channel Islands of California, preferring the cool, misty environments of rocky ocean islands. Its typical range extends from Northern California to Baja California, Mexico.

Additional Range

Beyond its preferred maritime climate, the Ashy Storm-Petrel has been observed straying into unexpected environments, such as offshore deep waters. During migration or dispersal, they may sporadically appear further inland. However, they remain largely dependent on island or coastal habitats for breeding and roosting.

Range Map

What do ashy storm-petrels like to eat?

Natural Diet

The Ashy Storm-Petrel primarily feeds at sea, where it forages for small fish, squid, and planktonic crustaceans. These birds often capture their prey by skimming near the water's surface, expertly dipping down to snatch meal items with their beaks. They occasionally follow ships to take advantage of fish scraps and other organic matter churned up in the water. There is little variation in their diet by season, as their foraging areas typically remain consistent year-round.

Bird Feeders

Bird feeders do not significantly supplement the diet of the Ashy Storm-Petrel, as its feeding habits are primarily geared towards marine environments. They rarely visit inland feeders, largely because they do not usually inhabit areas where feeders are prevalent. However, should an Ashy Storm-Petrel wander close to coastal feeders, it might show some curiosity towards fish-based suet or other seafood baits. Nevertheless, such occurrences are rare, and they are generally not observed feeding at human-provided feeder sources.

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Bulwer's Petrel

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Ashy Storm-Petrel

Bulwer's Petrel

Bulweria bulwerii

General appearance

The Bulwer's Petrel is a medium-sized seabird characterized by its sleek, elongated body and narrow wings that enable graceful gliding over the water. Its plumage is primarily a dark chocolate brown, often appearing black in dim lighting. The head, back, and wings possess a slight sheen, adding to its striking appearance. The bird's bill is slender and black, complementing its streamlined body. Legs and feet are also dark, aiding in its inconspicuous presence at sea.

Male vs female

In Bulwer's Petrels, sexual dimorphism is minimal. Both males and females share similar size and coloration, making it difficult for observers to distinguish between the sexes. They are nearly identical in plumage and size, with no discernible differences in markings or color.

Juvenile

Juvenile Bulwer's Petrels closely resemble adults, sharing the same dark plumage. However, younger birds might display slightly more faded or dusky feathering compared to the polished look of mature adults. While the overall structure remains similar, juveniles might appear a bit scruffier as they transition into adults. Over time, their plumage gains the sheen characteristic of adult Bulwer's Petrels, completing their development.

Size

9.8 - 11.0 in/3.0 - 4.8 oz

There's more to learn about Bulwer's Petrel

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Ashy Storm-Petrel

Hydrobates homochroa

Ashy Storm-Petrel Recognition Guide

General appearance: The Ashy Storm-Petrel is a small, slate-gray seabird notable for its uniformly ashy coloration without any striking patterns or contrasts. This bird typically measures about 18 to 20 centimeters in length with long, slender wings spanning approximately 43 to 47 centimeters. Its plumage has a soft, sooty color throughout, mirrored by dark brownish hue in its long, slightly forked tail. The bird's head, back, wings, and upper parts are varying shades of ashy gray, lending it camouflage against the ocean's murky horizons. Male vs female: Both the male and female Ashy Storm-Petrels showcase similar morphologies and plumage characteristics. There are no conspicuous differences, and thus, distinguishing the sexes based on appearance alone can be challenging. Both sexes share identical coloration and size, making external identification in the field infeasible without behavioral context or genetic analysis. Juvenile: Juvenile Ashy Storm-Petrels bear a close resemblance to adult birds with only subtle differences in appearance. They generally display slightly paler or duller plumage and may lack the full depth of coloration seen in mature birds. As juveniles age, they gradually acquire the adult's consistent ashy gray tone, completing the transition in several months as they mature in the marine environment.

Size

7.1 - 8.3 in/1.2 - 1.9 oz

There's more to learn about Ashy Storm-Petrel

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How to tell the Bulwer's Petrel from the Ashy Storm-Petrel

Visual differences

Bulwer's Petrel and Ashy Storm-Petrel have notable visual differences. Bulwer's Petrel is larger, weighing 3-4.8 oz and measuring 9.8-11 inches long, with dark chocolate brown plumage and a slender black bill. In contrast, the Ashy Storm-Petrel is smaller, weighing 1.2-1.9 oz and measuring 7.1-8.3 inches, with smoky gray plumage and a shorter, more robust beak. Both have long, narrow wings, but Bulwer's Petrel wings are sleeker, adding to its streamlined silhouette, while the Ashy Storm-Petrel's gray coloring helps it blend with foggy ocean environments.

Key differences and behavior

Bulwer's Petrel and Ashy Storm-Petrel exhibit distinct behavioral differences. Both are nocturnal, but Bulwer's Petrel glides solo over tropical oceans, emitting laughter-like calls, while Ashy Storm-Petrel performs nocturnal dances in flocks along the California coast. Bulwer's Petrel prefers warm, open seas, nesting on undisturbed, isolated islands, whereas Ashy Storm-Petrel inhabits the foggy, rocky shorelines of the eastern North Pacific. Their breeding strategies are similar, with both species forming monogamous pair bonds for a season, but Bulwer's engages in aerial acrobatics, whereas Ashy Storm-Petrel includes distinctive call flights. Both rely on maritime diets, consuming fish, squid, and crustaceans, though Bulwer’s excels at low-light foraging. The Ashy Storm-Petrel occasionally follows ships for food, unlike the strictly pelagic Bulwer's.