Something Different: Don't Try This at Home

Part of the endless fascination of birds is their behavior. The  Gulls that forage at the Great Salt Lake have developed a pretty amazing technique for snacking on brine flies, whenever the flies are around and the gulls are feeling peckish.

First, a word about brine flies. Most of the Great Salt Lake is hypersaline, much too salty to support most forms of life. But the brine flies thrive in the extremely salty water. The brine flies have an estimated population of over 100 billion, and when the pupae hatch the numbers of flies is mind-boggling. WC was there well after the peak of the hatch. Mounds of pupa casings littered the shoreline.

So we start with a peckish California Gull with a taste for brine flies.

California Gull, non-breeding plumage, Great Salt Lake

The brown piles in the foreground are pupa casings from hatched flies; the thinner layer of brown along the waterline is a mat of brine flies.

Foraging for Brine Flies: Step 1

If you are a Great Salt Lake California Gull, you know to start to run along the shoreline, and spread your wings. The vibration from your running and the opening wings put up a cloud of flies.

Foraging for Brine Flies, Step 2

You hold your wings in a forward scoop-like shape – a fairly unnatural position for a bird – and run along the beach. The wings force the brine flies ahead of you and down. Then you lower your head to the area where the flies are densest.

Foraging for Brine Flies, Step 3

And when you have a decent cloud of flies in front of you, you just open your mouth, like this, and run until your mouth is filled.

This is a learned behavior. Gulls have no instinct for this harvesting technique. It’s really a remarkable example of an adaptive learned behavior. It’s not a way that WC would choose to forage. Brine flies are not on WC’s menu. If you’ve ever had one insect in your mouth, you know why. The gulls likely have hundreds of little bugs crawling around in their mouths. Yum.

Which is why WC suggests you not try this at home. But it was amazing to watch.

Updated: Corrected species ID. H/T to Mia McPherson.

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