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I just spoke with a park ranger at Lassen Volcanic National Park. I was told that the huge group of California Tortoiseshell butterflies, Nymphalis californica, spend time at the summit pretty much every year, including this one, so it is considered an annual occurrence, although the numbers vary. Unfortunately, you just missed them. They arrived in Mid-July ...


8

Almost all North American sandpipers nest far up north (from the northern Great Plains to the shores of the Arctic Ocean). They winter in moderate numbers along the coasts, and very large numbers of migrants come through in waves along the coasts in the spring (March-May, mostly). The numbers in southbound migration (August-October, mostly) are somewhat ...


8

This page makes it seem like they do not migrate. Most other plant eaters, like deer and elk, vacate deep snowy areas and migrate to the lowlands, river bottoms, or south-facing slopes that are relatively snow free. Movement through snow, of course, is not nearly so energetically costly to hares as it is to large ungulates, and hares are able to remain in ...


7

TLDR: Its when a massive amount of birds suddenly migrate all at once to a area they aren't usually found in. An irruption is a dramatic, irregular migration of large numbers of birds to areas where they aren’t typically found, possibly at a great distance from their normal ranges. This type of population shift can also be called Malthusian growth, ...


5

My experience relates to Common Dolphin, but likely applies to dolphins of other species, too. Although dolphin may be seen at any time, you are most likely to see them in proximity to food. So if their prey is migratory, they may follow the prey to some extent; they may also change prey as different fish are available at different times of year. Here in ...


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