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Gearing Up for Fall Migration: Part 1

Updated: Mar 18, 2022

Although we are still in the middle of summer, many bird species are already gearing up or even heading towards their wintering grounds along the Pacific Flyway (PF). The Pacific Flyway is one of four major migratory flyways in North America that at least one billion birds and over 325 bird species use to traverse to and from their non-breeding (winter) and breeding (spring/summer) grounds from Alaska to Patagonia. The PF is 4,000 miles long and 1,000 miles wide with a portion of the flyway in Canada and the rest in the US includes Alaska, Arizona, California, Colorado, Idaho, New Mexico, Nevada, Montana, Oregon, Utah, Washington, and Wyoming. The PF has many important layover areas that birds rely on for a short layover (just a few days) to refuel and rest or stay the rest of the season.

Pacific Flyway Routes. Photo by Alexandra (Allie) M. Weill

Let’s first be clear that not all birds migrate, those that stay in one location year-round are called permanent residents. Those that do migrate are generally moving from low or decreasing resources to areas with more abundant resources and are also searching for nesting locations. Other driving forces may be warmer climates, avoidance of predators, and historic and genetic cues that drive their migratory urges.

Of the migrating birds, there can be short, medium, or long-distance migrants. Generally, birds fly south for the winter (non-breeding) and north for the spring/summer (breeding). The migratory period for the spring ranges from February through April and for Fall, September through December. With weather patterns changing, studies are showing some migratory patterns are changing with species leaving earlier or later than recorded in the past from both wintering and breeding grounds. The length of day is believed to be the primary trigger or cue for migration to begin. The migratory routes are not often a straight line but can alter course during both north and south routes. Some species may also take one route to their breeding grounds and another to their non-breeding grounds, possibly following more abundant resources along the way to ensure their needs are adequately met.

There are so many unique and interesting details of each species but, in this series, we will highlight a few of our locals that are in Orange County over the coming weeks.

A Sanderling waiting for the waves to recede in search of food. Photo by Bill Halladay

The Sanderling, Calidris alba, travel between 1,800 and 6,000 miles each year traveling north to Alaska for breeding and back to Orange County in winter. This little shorebird darling is small enough to fit in the palm of your hand and will generally only be seen in Orange County in the winter months. In the winter, it tends toward a whiter hue with light gray accents, often getting mistaken for our listed Western Snowy Plover. It does have a distinctive shoulder patch that sets it apart from its look-alike friends. During the breeding season, like many bird species, Sanderlings get colorful by adding browns, blacks, and even a hint of yellow with stronger mottling on their back and wings. Their feeding habits are to eat invertebrates just below the surface of the sand and will chase the waves all day in search of a meal.

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