Watershed Weekly is a paid commentary written by the Takshanuk Watershed Council.
By Derek Poinsette
The Cambridge English Dictionary defines migration as “the process of animals traveling to a different place, usually when the season changes.”
Biologists use the term specifically for large-scale movements of populations of animals over relatively long distances and between different habitats. For example, a bear moving up onto the mountainside to snooze during the day, and then back down to the river to feed on salmon at night, is not technically a migration. This behavior would instead be called a diel (or daily) activity pattern.
An example of a proper, and quite impressive, migration is the arctic terns that breed here on Glacier Point and then spend our winter months on the ice surrounding Antarctica — an annual round-trip of 50,000 miles, give or take.
Animals are able to expend large amounts of energy migrating because there is a significant benefit for them to do so. In other words, something about that behavior has increased the animal’s chances of survival and reproductive success over time.
Evolutionary biologists call this concept fitness. The migrating animals are able to take on a significant risk in seasonally moving long distances because the grass actually is greener on the other side. In doing so, they are increasing the chances of passing genes to future generations, even while many individual animals do not survive the journey. If this was not the case, if there was not this high-level benefit to the animal and to the species as a whole, they would just stay home.
Down on a more flesh-and-bones level, animals migrate for a few different reasons. Large schools of herring and hooligan start moving into the Upper Lynn Canal from the outer coast in the middle of April to spawn and reproduce. They come here because thousands of years of evolution have indicated that this is a good place to do that, and the chances are good that their offspring will survive and thrive.
Following closely behind these forage fish (herring and hooligan) are sea lions, seals, whales and piscivorous (fish-eating) fish like Chinook salmon and halibut, all of whom are migrating here not to spawn, but to feed. So, although the herring and hooligan are being gobbled up by the millions on the journey to get here, it is still worth their collective effort over a long, multi-generational, time frame. The same cost-benefit equation applies to all migrating animals, including humpback whales that are burning lots of calories and exposing their newly born calves to a gauntlet of predators, in swimming more than 3,000 miles from Hawaii and Mexico.
Tens of thousands of birds also stop here in the spring to take advantage of the hooligan and herring runs, and other resources as well, like mollusks and aquatic invertebrates. Gulls may be the most abundant and noticeable avian migrant, followed by surf scoters. A recent study found that as many as 18% of the entire world’s population of surf scoters could be coming to the Upper Lynn Canal every spring.1 That’s an astounding number, given that surf scoters are relatively common throughout North America, on both the Atlantic and Pacific coasts from arctic Canada down to Florida and Mexico.
For most winged creatures, the Upper Lynn Canal is not their final destination, but is instead a convenient refueling station to propel continued migration to summer breeding grounds farther north. The Chilkat Valley is particularly critical to this phenomenon, as it provides for the migrants an abundance of food and a safe and efficient flyway up and over the ice-covered mountains to the interior. Like the schools of forage fish out in the fjord, the gulls, terns, ducks, geese, shorebirds, cranes, loons, song birds, woodpeckers and hummingbirds are constantly being pursued, and fed upon, by migrating birds of prey: eagles, hawks, falcons, ospreys and owls. The benefits provided to these creatures by the geography and the ecosystems of the Upper Lynn Canal must be great indeed to be worth such a price.
There is a concept of ecology called the ecotone. It occurs where two or more different ecosystems meet and overlap, usually resulting in relatively greater biodiversity. The entire Upper Lynn Canal area could be conceived of as a large ecotone. It is situated at a geographic nexus of geology and biology, where the temperate maritime ecological zones to the south and west meet and are linked via migratory corridors with interior sub-arctic and boreal forest ecozones north and east.
For both birds and terrestrial animals (including humans), a small handful of mountain passes provide connectivity, and allow for relatively quick passage between a number of very different ecosystems and biogeographic regions.
For these reasons, the Upper Lynn Canal is one of the most biologically productive and diverse places in Alaska, and the annual spectacle of spring migration is a direct result of this complex interaction of geography and biology.
From the perspective of the resident organisms, including us, this connectivity and ecological viability is an extremely valuable and precious attribute, as is attested to by the abundance of migrants who fly and swim great distances to visit us each and every spring.
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Spring Migration in the Upper Lynn Canal
Watershed Weekly is a paid commentary written by the Takshanuk Watershed Council.
By Derek Poinsette
The Cambridge English Dictionary defines migration as “the process of animals traveling to a different place, usually when the season changes.”
Biologists use the term specifically for large-scale movements of populations of animals over relatively long distances and between different habitats. For example, a bear moving up onto the mountainside to snooze during the day, and then back down to the river to feed on salmon at night, is not technically a migration. This behavior would instead be called a diel (or daily) activity pattern.
An example of a proper, and quite impressive, migration is the arctic terns that breed here on Glacier Point and then spend our winter months on the ice surrounding Antarctica — an annual round-trip of 50,000 miles, give or take.
Animals are able to expend large amounts of energy migrating because there is a significant benefit for them to do so. In other words, something about that behavior has increased the animal’s chances of survival and reproductive success over time.
Evolutionary biologists call this concept fitness. The migrating animals are able to take on a significant risk in seasonally moving long distances because the grass actually is greener on the other side. In doing so, they are increasing the chances of passing genes to future generations, even while many individual animals do not survive the journey. If this was not the case, if there was not this high-level benefit to the animal and to the species as a whole, they would just stay home.
Down on a more flesh-and-bones level, animals migrate for a few different reasons. Large schools of herring and hooligan start moving into the Upper Lynn Canal from the outer coast in the middle of April to spawn and reproduce. They come here because thousands of years of evolution have indicated that this is a good place to do that, and the chances are good that their offspring will survive and thrive.
Following closely behind these forage fish (herring and hooligan) are sea lions, seals, whales and piscivorous (fish-eating) fish like Chinook salmon and halibut, all of whom are migrating here not to spawn, but to feed. So, although the herring and hooligan are being gobbled up by the millions on the journey to get here, it is still worth their collective effort over a long, multi-generational, time frame. The same cost-benefit equation applies to all migrating animals, including humpback whales that are burning lots of calories and exposing their newly born calves to a gauntlet of predators, in swimming more than 3,000 miles from Hawaii and Mexico.
Tens of thousands of birds also stop here in the spring to take advantage of the hooligan and herring runs, and other resources as well, like mollusks and aquatic invertebrates. Gulls may be the most abundant and noticeable avian migrant, followed by surf scoters. A recent study found that as many as 18% of the entire world’s population of surf scoters could be coming to the Upper Lynn Canal every spring.1 That’s an astounding number, given that surf scoters are relatively common throughout North America, on both the Atlantic and Pacific coasts from arctic Canada down to Florida and Mexico.
For most winged creatures, the Upper Lynn Canal is not their final destination, but is instead a convenient refueling station to propel continued migration to summer breeding grounds farther north. The Chilkat Valley is particularly critical to this phenomenon, as it provides for the migrants an abundance of food and a safe and efficient flyway up and over the ice-covered mountains to the interior. Like the schools of forage fish out in the fjord, the gulls, terns, ducks, geese, shorebirds, cranes, loons, song birds, woodpeckers and hummingbirds are constantly being pursued, and fed upon, by migrating birds of prey: eagles, hawks, falcons, ospreys and owls. The benefits provided to these creatures by the geography and the ecosystems of the Upper Lynn Canal must be great indeed to be worth such a price.
There is a concept of ecology called the ecotone. It occurs where two or more different ecosystems meet and overlap, usually resulting in relatively greater biodiversity. The entire Upper Lynn Canal area could be conceived of as a large ecotone. It is situated at a geographic nexus of geology and biology, where the temperate maritime ecological zones to the south and west meet and are linked via migratory corridors with interior sub-arctic and boreal forest ecozones north and east.
For both birds and terrestrial animals (including humans), a small handful of mountain passes provide connectivity, and allow for relatively quick passage between a number of very different ecosystems and biogeographic regions.
For these reasons, the Upper Lynn Canal is one of the most biologically productive and diverse places in Alaska, and the annual spectacle of spring migration is a direct result of this complex interaction of geography and biology.
From the perspective of the resident organisms, including us, this connectivity and ecological viability is an extremely valuable and precious attribute, as is attested to by the abundance of migrants who fly and swim great distances to visit us each and every spring.