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By Ann Nightingale
One of the great things about being a nature lover is that your powers of observation seem to improve. While others are walking by, oblivious to the activities going on all around them, naturalists notice the creatures and the behaviors, especially if they are out of the ordinary.
Such was the case on March 24, 2012, a sunny Saturday morning, when Ginger Morneau, her husband Ken, and brother Lou Baker were walking along the Ogden Point Breakwater in Victoria, BC. The breakwater is a favourite spot for locals and visitors, reaching out about a half mile from the waterfront south of downtown. The area is also popular with divers as it is a marine park, populated with interesting fish, marine plants and invertebrates. Walkers strolling along the top of the breakwater can often see marine wildlife in the water below.
As the group headed out along the walkway, Ginger noticed a gull acting strangely a short distance ahead of her. The bird was on the inside of the breakwater, where the water is clear and can be quite still. The gull appeared to be feeding on something underwater, but it didn’t raise its head. As they approached, they could see a red-orange shape in the water below the gull. When they got to the spot directly above the gull, they could see that it was an octopus. And Ginger’s camera was in her hand.
The Giant Pacific Octopus can be seen regularly patrolling the shallows of the shorelines around Victoria. They primarily feed on crustaceans, but are known to occasionally take fish and even birds. Octopi are extremely intelligent animals, and great problem solvers. Although they live only about four years, they can grow to have a span of more than 20 feet and to weigh more than 100 pounds. This one wasn’t that large, but it was still an impressive individual. What was even more impressive, though, was that it had one of its tentacles wrapped around the head of the gull, holding it under water.
The first winter Glaucous-winged Gull was struggling, flapping its wings in an attempt to break the octopus’s grip, but without success. The octopus’s eight tentacled arms allowed it to cling firmly to the rocks and simultaneously maintain its grasp on to the gull. Initially, air was bubbling to the surface, but within a minute, the struggle was over. More tentacles came out of the water to grab the body of the gull and pull it completely under. Other gulls flew overhead, noisily checking out the scene as if to see if there were going to be any scraps, but disappeared once the victim had been pulled from the surface.
Ginger described the battle as “primal” and although she wanted to rescue the gull, it wouldn’t have been possible due to the sheer drop from the walkway–not to mention that the writhing tentacles of the octopus were more than a little intimidating. So she snapped a few more pictures, aware that she was witnessing a rarely-seen event. There wasn’t time for more–from her first picture to her last, only 53 seconds had elapsed. A couple of others watched the spectacle, but most people just walked on by, unaware of the struggle just fifteen feet below them.
Gulls will eat octopus, given the opportunity. There’s a decent possibility that the victim in this story might have even been pecking at the octopus before Ginger and her family happened by. We’ll never know who started this battle, even though we definitely know who won! There are other records of octopus catching and eating sea birds, including reports of one with a den near a boat ramp on Whidbey Island that was seen catching both gulls and Pigeon Guillemots. However, Ginger’s are the only photos we’ve found that document this behavior.
To commemorate witnessing and photographing this amazing event, Ginger, Ken and Lou went out for a calamari lunch.
Mather, Jennifer A., Roland C. Anderson and James B. Wood (2010). Octopus: The Ocean's Intelligent Invertebrate (2010).
Sazima, Ivan and Lisandro Bastos de Almeida (2008). The Bird Kraken: Octopus preys on a sea bird at an oceanic island in the tropical West Atlantic. Marine Biodiversity Records, 1 , e47 doi:10.1017/S1755267206005458
In our first investigation of avian flight strategies we explored dynamic soaring and how some birds are able to take advantage of wind gradients (differences in the speed of two air masses) to cover great distances with nary a wingbeat.
In this piece we will explore how soaring birds exploit the temperature differences in neighboring air masses. Vultures, hawks, pelicans and cranes are among the species one most often sees gliding in tight circles and using thermal uplift to gain altitude with very little wing flapping.
Rising columns of warmer air (thermals) are created by the solar heating of the Earth's surface. Areas with the most exposure to the sun warm more rapidly than areas that are shaded, thus the air masses above exposed areas also warm more rapidly.
Since warm air masses are less dense, they rise while the dense cooler air masses descend, in essence adding a push to the already rising columns of warmer air. When a soaring bird encounters these rising air masses it starts circling in an effort to remain within narrow column of rising air, which carries it upward. Other soaring birds or flockmates recognize that they are riding a thermal and join in to form a "kettle." It is not unusual to see multiple species of vultures (Black and Turkey Vultures in North America) and hawks together in a single kettle. When birding in south Texas in Winter one of the best ways to find Zone-tailed Hawks is to look for kettling vultures as they make their mid-morning departures from roost sites. Roost sites are often located along rivers or other bodies of water. The land heats up quickly while the water absorbs most of the insolation rather than reflecting heat back into the atmosphere, presumably creating a significant difference in the temperatures of neighboring air masses (see illustration below).
If one watches long enough, kettling birds will reach the apex of the rising column and start peeling off the top of the thermal in a long gradual straight-line descent until they find another thermal, where the process is repeated. On 16 September 1993, near Danville, Hendricks County, Indiana, I watched as a southbound group of 103 Broad-winged Hawks followed the pattern shown in the graphic above. The birds streamed single-file into a thermal and formed a kettle almost directly overhead. The hawks were perhaps 200 feet up when they entered the thermal. They then spiraled upward several hundred feet before peeling off the top of the updraft single-file. They glided south about a half mile or so, caught another thermal and kettled up again. It was amazing to watch. I envisioned this process being repeated over and over again all the way to their South American wintering grounds. On many other occasions I've observed transient flocks of American White Pelicans and migrant Sandhill Cranes move along from thermal to thermal.
Clearly, there is a significant conservation of energy that comes from utilizing this strategy. According to Knopf and Evans (2004), the weight of most American White Pelicans likely ranges from 5.4 to 9.0 kg (12-20 lbs). Getting that amount of mass airborne and keeping it there would require a lot more energy in the absence of thermal updrafts. Like vultures and many hawks, pelicans have comparatively long, broad wings and relatively short, broad tails. They do most of their commuting and longer flights between mid-morning and mid-afternoon when the most direct sun angles increase surface heating. It is always impressive to watch as these massive birds rise almost out of sight with almost no expenditure of effort.
Knopf, Fritz L. and Roger M. Evans. 2004. American White Pelican (Pelecanus erythrorhynchos), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online; http://bna.birds.cornell.edu/bna/species/057doi:10.2173/bna