Common Murres (Uria aalge) are recognizable by their black and white, penguin-like appearance and their hilarious calls. They also have one other distinctive trait that needs to be explored further, their diving abilities!

This Common Murre looks ready for takeoff… but is it going to go skyward or underwater? Photo by Alex McDonald, Property of Stubbs Island Whale Watching

Murres diving just under the surface. Photo by Paul Nicklen/National Geographic Creative

When you think of diving birds, your mind goes to penguins. Of all the diving birds, the penguins can reach the deepest depths (Piatt and Nettleship, 1984). Common Murres fill the same ecological niche of penguins in the Northern Hemisphere. They can dive from 170-230 m deep while foraging, exploiting similar prey sources such as fish, squid and marine invertebrates (Piatt and Nettleship, 1984). They both pursue their prey underwater and have numerous adaptations for underwater “flight” and feeding such as increased body size to facilitate deeper dives.

A Humpback Whale comes in and scoops up all the fish that the Common Murres and gulls worked so hard to round up into a tasty bait ball. Photo by Alex McDonald, Property of Stubbs Island Whale Watching

Common Murres are visual foragers, diving after prey from the surface all the way down to depths your average scuba diver can’t fathom reaching (Cairns et al., 1986). They are often found in multi-species groups, foraging on bait balls. They work in conjunction with other diving birds as well as surface birds like gulls and eagles to corral fish into tight balls, making it easier to catch them. These bait balls also attract other marine predators such as whales, dolphins, seals and sea lions, hoping to catch an easy meal.

Success! This Common Murre holds its prize, a cuttlefish. Photo by BSIP/UIG via Getty Images

However, it’s not always about an easy meal. They also take a lot of long, deep dives while foraging, often more than 50 m deep (Hedd et al., 2009). If you’re a scuba diver, you know that it’s not easy to propel yourself down to that depth at any great speed. For the Common Murre though, that’s no problem!

The deep dives they perform are costly, often in cold northern waters that can reach sub-zero temperatures. There are two main parameters that need to be considered when studying diving abilities: swimming speed and diving time (in regards to oxygen storage and metabolism) (Croll and Maclaren, 1993). Common Murres can swim at approximately 1.5-2 m/s and stay under water for almost 3 minutes (Hedd et al., 2009). On average they dive for about 67 seconds (Croll and McLaren, 1993). They have narrow hips and cylindrical bodies to streamline their dives, with their legs functioning as rudders to steer. They have small wings, useful for propelling themselves underwater in a flight-like motion but still functional for flight above water as well. Check out how they “fly” underwater using their wings in this short clip:

Metabolic rates decrease as they reach deeper depths with higher pressure and lower temperatures. Common Murres are relatively small for diving birds and face the challenge of staying warm enough, relying on burning food stores and vigorous diving to maintain their metabolic rates (Hedd et al., 2009). They also have relatively dense plumage, preventing water from penetrating to the skin. Their contour feathers are long and dense, trapping a thick layer of air for insulation (Croll and McLaren, 1993). This trapped air serves another function as well. When they descend to deep depths, that trapped air compresses against their bodies. When ascending again, the trapped air expands and propels them like a rocket back to the surface! The thick-billed murre, their closest relative (Common Murres are also known as thin-billed murres) dives in a similar fashion in even colder waters. This video highlights how they use trapped air to shoot back up to the surface in a trail of bubbles:

Common Murres, like the thick-billed murres in the video utilize both flying and diving, however being able to use both forms of locomotion takes its toll. As you may have noticed above, they are not the most graceful above-water fliers.  They need to take a long run at getting off the water, flapping their wings frantically in search of liftoff. Their landings are equally clumsy, often more crash and less landing.  It seems that as they transition to even more efficient underwater fliers, their above-water flight is going to be impacted. There are already multiple close similarities between murres and their Southern Hemisphere counterparts, the penguins. Loss of flight to increase diving efficiency seems a logical next step for these birds to exploit this cold underwater niche (Piatt and Nettleship, 1984).

This Northern Resident Killer Whale photo bombs an adult and juvenile Common Murre, perhaps offering some fishing tips? Photo by Alex McDonald, Property of Stubbs Island Whale Watching

References

Cairns, D.K., et al., 1986. Activity budgets and foraging ranges of breeding common murres. The Auk. 104, pp. 218-224. Retrieved from http://tinyurl.com/ychshkpg

Croll, D.A., McLaren, E., 1992. Diving metabolism and thermoregulation in common and thick-billed murres. Journal of Comparative Physiology B. 163, pp. 160-166. Retrieved from http://bio.research.ucsc.edu/people/croll/pdf/Croll_1993.pdf

Hedd, A. et al., 2009. Going deep: common murres dive into frigid water for aggregated, persistent and slow-moving capelin. Marine Biology, 156(4), pp. 741-751. Retrieved from http://tinyurl.com/yby32eeq

Piatt, J.F., Nettleship, D.N., 1984. Diving depths of four alcids. The Auk, 102, pp. 293-297. Retrieved from https://alaska.usgs.gov/science/biology/seabirds_foragefish/products/publications/Piatt_Nettleship_%2085.pdf