There's a reason why many wildlife rescue teams sent to the aid of great blue herons have to don motorcycle helmets to get the job done safely: Joffrey Lannister aside, few can match the birds' talents for spiking heads. Basically, great blue herons are spear-hunting machines – and over in California, they're hunting sharks.
Image: Wray Gabel/SFBBO
For the past 34 years, the biologists at San Francisco Bay Bird Observatory (SFBBO) have monitored great blue heron populations in northern California. Keeping watch over nesting colonies means the team is privy to many unique behaviours, but this was a surprise even for experienced eyes.

"It was definitely a cool sighting," says programme director Max Tarjan. "Great blue herons are generalist predators, meaning they eat a large variety of prey. They have been known to capture amphibians, reptiles, fish and mammals."

We've even seen the occasional case of "little bunny foo food", and in San Francisco's Golden Gate Park, the herons have been filmed plucking pop-up gophers as if they're playing some R-rated, natural-world version of Whack-A-Mole:
But despite such hunting prowess, Tarjan says the shark catch raised some eyebrows. "Seeing a heron with a leopard shark is a rare sight," he says. "And the biologists were excited that intern Wray Gabel was able to snap a few photos through her spotting scope."
Images: Max Tarjan, Wray Gabel/SFBBO
Unlike their top-predator kin, leopard sharks are bottom feeders. A taste for small prey like crabs, clams and worms keeps the silvery-bronze fish cruising coastal shallows, but that shoreline habitat also makes them easy targets for other animals. One creature with a taste for leopard shark is the sea lion, but herons take a particularly tactical approach.

In one of the few published observations of the behaviour, scientists witnessed a heron killing a shark with a swift sequence of precise jabs to the head and gills. (When you're planning to eat a long, wriggling fish, your best bet for a successful swallow is to immobilise it first.) 

Many an avian impaler opts for some version of that MO. Case in point: the butcherbirds. These master kebabers (genus Craticus) strike the head of their prey, then keep it still by spiking it on thorns and branches. 
Image: WIRED/YouTube
It's unclear just how often leopard sharks are gobbled up by herons. Many such interactions probably go unnoticed, but the rarity of sightings suggests the fish are not an ideal snack choice. Great blue herons sometimes overestimate their abilities to swallow long prey, and can choke and die as a result

The SFBBO team will continue its observations while working to restore precious salt pond habitat in the area, and there are plans to publish the findings later this year. 

Top header image:jlst2i/Flickr