By Dr. David Wartinbee, for the Redoubt Reporter
Photo courtesy of Dr. David Wartinbee. A common loon paddles on Hidden Lake recently. Loons are claiming territory now in preparation for mating season.
As soon as the ice cover melts on Hidden Lake, it’s time to get the boat out for the first run of the season. Besides the lake trout fishing, I also enjoy these early season forays because one can see waterfowl, like common loons, mergansers, golden-eye ducks, grebes and scoters. Whether feeding, courting or establishing territories for future breeding, they have their brightest plumage this time of year.
My favorite birds on the lake have to be the common loons. Perhaps this fondness comes because of their bold, black-and-white coloration. Maybe it comes from their haunting calls and yodeling that seems to be a sign of wilderness. Either way, I love seeing these birds and watching their antics during breeding or territory defense. There are a couple other species of loons found in Alaska, but today I will concentrate on the common loon, Gavia immer.
Just about any lake with a native fish population will attract these 7- to 12-pound birds since fish are their primary food source. Most all of their fish are caught while swimming underwater. Smaller fish are usually swallowed underwater but loons will come to the surface to wrestle with larger fish. I have watched a loon struggle with, and finally swallow, a 10-inch rainbow trout. While fish are their preferred diet, they are also known to feed on various invertebrates, like mollusks, leeches and aquatic insects.
Capturing fish underwater may seem daunting to us but it is all in a day’s work for loons. They have powerful webbed feet situated at the very back of the body so they are fast and agile swimmers. Interestingly, this body that is so well adapted for swimming means they are clumsy when out of the water. While most birds have hollow bones to conserve weight for flight, loons have relatively solid bones. Their heavy weight and streamlined body shape enables them to act like a submarine and slowly sink underwater or dive out of sight.
As all pilots know, extra weight means the necessity of going faster before being able to fly. Heavy loons have to flap their wings while running across the water for 75 to 100 yards before being able to get airborne. So don’t look for loons on small ponds, since they would not be able to get back into the air.
Some lakes may seem to have the same pair of loons nesting there for years on end. Recent research and more than 18 years of marking adult birds has revealed some new twists on old ideas about loons. One of the most startling is that the males get chased off prime nesting territories with surprising regularity. This also means that loons do not mate for life, as popular stories might indicate.
When young loons become sexually mature and are only a couple years old, they are lighter in weight than older males and they cannot compete for prime territory. In order to breed at a younger age, these males will be forced to seek out lower-quality lakes and try to attract a female willing to try rearing a family. When they reach the age of 5 to 7 years, they become larger in size and may try challenging an older male in an established territory.
If the intruder, or “floater,” is unable to chase a resident male from a prime territory, it will have to leave and challenge a less-aggressive male somewhere else. Much of the haunting tremulo calls we hear around lakes are males calling out to intruder males or those flying overhead. As long as a male can defend a territory from other intruders, he will choose the best nesting site around the lake.
When males get to be more than 10 years old, they lose body mass and are in danger of being chased out of their prime territory. So, while there may have been loons breeding in a location for many years, the individual male or female birds have probably changed at regular intervals.
If a male has successfully raised a brood on a lake the previous year, that habitat becomes very attractive to other males and the number of challenges by subordinate males increases substantially. In order to defend the territory, the resident male and its mate use a series of swimming approaches while the male yodels to indicate a readiness to defend the territory.
When really agitated, the male will rise up out of the water, assuming a position that can be described as looking like a penguin on the water surface. The visual display and audible calls only take a few minutes and the intruder usually departs. However, when the resident male is older and with declining body mass, there can be serious fighting.
Combatant males can lose patches of feathers and, more often than one might think, the resident male is driven out. In some cases, the resident male can be killed. A surviving, deposed male then has to settle for trying to attract a female in less-promising territory.
Loon nests are vulnerable to land-based predators, like foxes and coyotes. Because of this, nests are often placed on floating masses of reeds or on small islands. Because loons are unable to walk with any agility, they place their nests right next to the water’s edge and prefer to have deep water nearby. Deeper water enables them to approach or escape quickly without being seen by predators.
After incubation of the brown, speckled eggs for 25 to 28 days, the chicks hatch. While they can swim immediately, parents usually feed them onshore for a couple of days. Then the parents take them out on foraging trips with the chicks swimming or riding on the back of one of the parents. Within a week the chicks will try to capture insects and minnows, but they must rely on the parents for quite awhile. By 8 weeks old, loon chicks are able to catch about half their food. By 11 to 12 weeks old, the young are mostly feeding themselves, although they will hang out with the parents until it’s time to start migrating.
These beautiful, black-and-white birds are just starting to form pair bonds and establish territories. In a few weeks they will be nesting and the females will be sitting on the usual clutch of two eggs. When you are out visiting our lakes this spring, be aware that loons are nesting and give them a little space so they can rear their young. If you sit quietly and pay attention, you can observe the parents carrying and feeding their young chicks.
David Wartinbee, Ph.D, J.D., is a biology professor at Kenai Peninsula College’s Kenai River Campus. He is writing a series of columns on the ecology of the Kenai River and Cook Inlet watershed.
