Autumn will soon be upon us, and if you’re bird watcher, people will commonly ask you, “Why do
birds fly south for the winter?” My stock answer is usually, “Because it’s too far to walk!” But the correct answer is, “It depends.” It also bears pointing out that not all birds migrate. Here in the mountains of southern California, we have a number of species that are year-round residents. Steller’s jay, mountain chickadee, common raven, western bluebird, and robin are a few examples.
The migratory birds we see in this region fall typically into two categories: breeding migrants and winter residents. However, we also have a few migratory birds that can be considered “pass-through” species, or transients.
Our breeding migrants include perennial favorites such as the black-headed grosbeak and the western tanager. Both species undertake a relatively short fall migration to Mexico, although some western tanagers go as far south as northern Panama. The award for longest distance flown by one of our breeding migrant goes to the cliff swallow. A colony of these birds build their mud nests on the water tower that sits near the northeast corner of Lake Arrowhead. These birds arrive here in March and the nesting season is in full swing by mid-April. They feast
on the abundant flying insects over the lake until early October, when they begin their journey to South America that may cover more than 4,000 miles.
Our migratory winter residents are mostly waterfowl, along with a few species of grebes and song birds. Mallards are one of the few ducks we commonly see year-round, although red-heads and gadwall might be spotted now and then on one of our local lakes throughout the year. During the winter, our local lakes are home to at least 12 additional species of ducks. These include American wigeon, canvasback, ring-necked, lesser scaup, bufflehead, common goldeneye, ruddy duck, and my favorite, hooded merganser. These are some of the handsomest birds of the mountains and they make birdwatching worth the effort, even on the coldest of mornings.
Our transient migrants spend a (usually brief) portion of their migration journey here in the mountains to rest and refuel on their way north in the spring and on their way south in the fall. Examples of these include Wilson’s warbler (although a small number actually breed here in the mountains) and the red-necked phalarope.
Phalaropes are especially interesting birds. These sandpipers breed in the Alaska and Canadian tundra and undertake a migration of more than 6,000 miles to the South Pacific Ocean off the coast of South America. I’ve seen them stopping on Lake Arrowhead in September on their way south. But don’t look for them on shore. Unlike other sandpipers, these birds swim in open water searching for small invertebrates to eat. And the way they find food is fascinating. They rapidly spin in circles creating a small upwelling of water under their legs. This draws water up from below, carrying small aquatic organisms that serve as their main food source. Because of their long journey, red-necked phalaropes are here for a brief time; maybe a week or two in late September.
As to our original question about the reason birds fly south for the winter, stay tuned for my next blog for the answer!
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