California hosts a vibrant array of hummingbirds, leading many to wonder if these birds remain year-round or depart for warmer climates. The answer depends entirely on the specific species. California’s unique geography and climate support both species that undertake seasonal journeys and others that have adapted to permanent residency.
Resident Versus Migratory Species
The hummingbirds found in California can be separated into two main groups: the year-round residents and the seasonal migrants. The Anna’s Hummingbird is the most common and widespread permanent resident, found along the Pacific coast and in the southern half of the state throughout the entire year. The ability of the Anna’s to breed and survive the milder California winters distinguishes it from its relatives.
Other species also exhibit year-round residency in specific areas. The Costa’s Hummingbird is a permanent resident primarily in the hot, arid desert regions of Southern California. A non-migratory subspecies of the Allen’s Hummingbird has also established a year-round presence near Los Angeles and on the Channel Islands.
California serves as a crucial stopover or summer breeding ground for several migratory species. The Rufous Hummingbird is a prominent migrant, passing through California to reach breeding grounds in the Pacific Northwest and Alaska. Other seasonal visitors include the majority of the Allen’s Hummingbird population, the Black-chinned Hummingbird, and the tiny Calliope Hummingbird. These species rely on California for refueling before continuing their long journeys.
The Journey: Timing and Routes
The migratory species, particularly the Rufous and Allen’s Hummingbirds, follow predictable, demanding routes that make California a seasonal highway. Rufous Hummingbirds begin their northbound spring migration, leaving their wintering grounds in Mexico as early as January or February. They follow the Pacific Coast, using the “Pacific Flyway” to reach breeding areas up to 4,000 miles away in the Northwest and Alaska.
Their return journey in late summer, often starting as early as July, shifts inland. Instead of retracing the coast, the Rufous typically travels south through mountain ranges, including the Sierra Nevada and Rocky Mountains. They use high-elevation meadows where flowers bloom later in the season. This clockwise loop across the western continent is a feat of endurance.
Allen’s Hummingbirds also arrive early in spring, often reaching California’s coastal breeding areas in February. Most populations migrate south to winter in central Mexico, with the fall migration peaking relatively early in July. To power these long-distance flights, all migratory hummingbirds must engage in hyperphagia, or excessive feeding, to double their body mass with stored fat reserves. These fat reserves provide the concentrated energy needed to complete non-stop segments of their journey.
Adaptations for Year-Round Residency
The Anna’s Hummingbird thrives as a permanent resident due to behavioral and physiological adaptations that align with California’s environment. The mild, temperate climate along the coast prevents hard freezes that would eliminate winter nectar sources in other regions of North America. This consistent weather allows for a year-round breeding cycle, which is unusual for a North American hummingbird species.
The birds utilize a variety of food sources beyond native flowers. Non-native ornamental plants, such as eucalyptus trees, provide winter-blooming nectar sources that were historically unavailable. Anna’s Hummingbirds also rely more heavily on insects and spiders for protein than many other species, a food source available even when nectar is temporarily scarce.
To survive cold nights, the Anna’s Hummingbird employs a physiological state called torpor. During torpor, the bird lowers its metabolic rate and body temperature, conserving up to 50 times the energy it would use while awake. This temporary, regulated hypothermia is an adaptation that allows the birds to endure periods of food shortage or overnight cold.