Swinhoe's Storm-Petrel vs Bulwer's Petrel

In short

Swinhoe's Storm-Petrel and Bulwer's Petrel are both small, dark seabirds, but they differ in structure and behavior. Swinhoe's Storm-Petrel is a Northern Storm-Petrel with a more fluttering flight, while Bulwer's Petrel is a larger Procellariid with a more gliding flight pattern. Spotting them requires attention to their flight style and subtle plumage differences.

Identification tips

1. Flight style: Look for the fluttering flight of Swinhoe's Storm-Petrel versus the gliding flight of Bulwer's Petrel. 2. Size and shape: Note the larger size and more elongated body of Bulwer's Petrel. 3. Plumage: Check for a paler rump in Swinhoe's Storm-Petrel, which Bulwer's Petrel lacks. 4. Location: Consider the geographic range; Swinhoe's is more northern Pacific, while Bulwer's is broader.

Size

Bulwer's Petrel is larger and more elongated than Swinhoe's Storm-Petrel.

Plumage

Both species are predominantly dark, but Swinhoe's Storm-Petrel often shows a paler rump patch, which Bulwer's Petrel lacks. Bulwer's Petrel has a more uniform dark brown coloration.

Behaviour

Swinhoe's Storm-Petrel has a fluttering, erratic flight, typical of storm-petrels, while Bulwer's Petrel exhibits a more graceful, gliding flight pattern.

Habitat

Both species are pelagic and spend most of their time at sea. Swinhoe's Storm-Petrel is typically found in the northern Pacific, while Bulwer's Petrel has a wider range, including both the Atlantic and Pacific Oceans.

Voice

Vocalizations are rarely heard at sea, and both species are generally silent away from breeding colonies.