The United States plays host to two kinds of native pelican: the brown and the American white. Both are web-footed, giant-beaked, throat-pouched and fish-loving – but, otherwise, distinct as can be. The brown pelican is a graceful pterodactyl-esque seabird that hugs cresting waves and performs steep, extravagant plunge-dives after fish:

The American white pelican, a snowy-feathered giant which may be more than twice the brown's size, is as much a bird of inland freshwater as the seashore. Ponderous on the wing, it employs a laidback fishing method instead of aerial acrobatics, paddling and dabbling with its bill and sometimes whole head submerged. The birds often fish communally, trawling bunched together in unison and also cooperating to herd fish into shallows:

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All together now... Image: Richard Stamats/YouTube

White and brown pelicans overlap in range, especially this time of year, when the cousins may share wintering bays and seashores on the US Gulf Coast, Mexico and Central America. And recently, on the western coast of Florida, an unusually intense encounter between the two played out in a harbour.

Amanda Hipps, a graduate student at Florida Atlantic University who studies the gopher tortoise, photographed the interspecies interaction, which she watched from a boat in the fishing village of Cortez south of Tampa Bay. She told me she noticed four white pelicans initially in the vicinity of the brown, and began taking pictures since the proximity allowed for an interesting size comparison. (Brown pelicans are plenty big birds, mind you, but the American white pelican – sometimes weighing more than nine kilograms [20 lbs.] and spreading black-rimmed wings that may be three metres [ten feet] across – ranks among the very largest birds in North America.)

Image: Amanda Hipps/used with permission 

As Hipps watched, more white pelicans arrived on the scene, and they began acting aggressively towards their smaller relative. Ultimately, a total of ten ganged up on the brown, physically bullying it.

"They appeared to be going after the head/beak," Hipps said, "and in some moments, there would be a white pelican directly on top of the brown so it was fully submerged under water."

Hipps watched the drama for about four minutes before the boat she was aboard had to depart on account of shallow water. "By the time we left, all ten white pelicans were still surrounding it, but the brown appeared tired and may have given up," she said. The ultimate outcome is a mystery: Hipps doesn't know whether the besieged bird drowned, or managed to shed its attackers.

Image: Amanda Hipps/used with permission 
Image: Amanda Hipps/used with permission 

Later study of her photos revealed something Hipps hadn't initially noticed: the brown pelican had at least one fish in is beak. So the assault by the white pelicans appeared to be a case of attempted piracy: kleptoparasitism, technically speaking, something the species is well known for.

White pelicans will zero in on other birds that are actively fishing and attempt to steal their catch. One study at Grand Rapids, Manitoba documented white pelicans robbing (or trying to rob) herring gulls, double-crested cormorants and even an osprey, which a pair of pelicans chased in flight so that the raptor ended up dropping its freshly plucked fish (which was then gobbled up by one of the pursuers).

Pelicans also attempted to pilfer from one other, and these attempts could be "violently aggressive" (á la Hipps's observation), as was one assault on a cormorant: "In only two of eight recorded cases when a cormorant surfaced with a fish in its bill was a pelican able to steal the fish," the researchers wrote. "One of these thefts was extremely violent; the pelican grasped the cormorant's neck in its bill, shook it, and held it under the water. A second pelican then stole the fish that was released."

Dr David Bird, emeritus professor of Wildlife Biology at McGill University in Montreal, told me he wasn't aware of a previous record of white-pelican kleptoparasitism on brown pelicans in the scientific literature. But given both pelicans' habit of pilfering fish and  the birds' overlapping distribution, as well as the white pelican's significant advantages – in terms of size and cooperative foraging – he wasn't surprised.

You might think the highly conspicuous predatory dives of brown pelicans would make them more vulnerable to kleptoparasitism by sharp-eyed white pelicans, but Bird doesn't suspect this is a common interaction. "I doubt that the white pelicans are keying in on the splashes of the diving brown pelicans," he said. "I think that this particular bird was just unlucky enough to be in the wrong place at the wrong time."

The violence of this encounter, he suggests, could potentially have escalated because of aggressive resistance by the brown pelican. "Brown pelicans are often parasitised by gulls and terns, which sometimes perch on their heads," he explained. "To avoid this, the brown pelicans can use evasive manoeuvres or open their beaks at the smaller thieves, sometimes even seizing them in their beaks. But that certainly would not be effective against a bunch of much larger white pelicans."

The brown pelican may have been the mugging victim in this case, but Bird emphasises the species doesn't have any sort of squeaky-clean rap sheet in this regard: it's an enthusiastic kleptoparasite that'll steal from herons, wood storks and other birds, and it'll sometimes even kill nestlings.



ht: David Steen

Top header image: Pixabay