Hummingbirds are a cherished sight across Montana during the warmer months. These tiny birds, however, are not year-round residents of the state. Their presence is seasonal, marked by a remarkable migratory journey that sees them depart as cooler weather approaches. This annual exodus is a fascinating natural phenomenon, signaling the end of summer for many Montanans.
Typical Departure Schedule
Hummingbirds typically begin their southward migration from Montana in late summer to early fall. While some early migrants, particularly male Rufous hummingbirds, may start their journey as early as July, most common species like the Calliope, Black-chinned, and Broad-tailed hummingbirds will depart during this two-month window. This departure period is not a single, fixed date but rather a gradual process, with different individuals and species leaving at slightly varied times. By late September or mid-October, the vast majority of hummingbirds will have left Montana, although a few may linger if conditions allow.
Males often initiate the migration ahead of females and younger birds, sometimes by as much as two weeks. This staggered departure ensures that males, having completed their breeding duties, can begin building energy reserves for the long flight south. While most are gone by mid-October, any hummingbirds observed in Montana during winter are typically individuals unable to complete the journey due to age, illness, or injury.
Environmental Cues for Migration
The timing of hummingbird departure from Montana is closely linked to several environmental cues. A primary trigger for their migratory instinct is the changing photoperiod, or the shortening of daylight hours as summer transitions to fall. This reduction in daylight signals to the birds that winter is approaching and prompts physiological changes necessary for migration. These cues are deeply ingrained, part of their circannual (yearly internal) rhythm.
Decreasing temperatures also contribute to the migratory urge, working in conjunction with changes in daylight. Even if food sources like nectar-producing flowers and insects are still abundant, these environmental signals override the immediate availability of food. Hummingbirds are driven by an instinctual urge to migrate before conditions become too harsh, ensuring they reach warmer climates with ample resources for the winter. Before embarking on this journey, they will significantly increase their food intake to build up fat reserves, sometimes doubling their body weight.
The Long Journey South
After leaving Montana, hummingbirds embark on an extraordinary journey. Most species found in Montana migrate to Mexico or Central America, with some traveling as far south as Panama. For instance, Ruby-throated hummingbirds, though rare breeders in Montana, commonly winter in Central America. This migration is a solo endeavor; unlike many other bird species, hummingbirds do not travel in flocks.
The distances covered are immense for such small creatures. Hummingbirds from Montana might fly approximately 1,900 miles to reach the Mexican border, a journey that could take around 64 hours of flight time. Those migrating to Panama may travel up to 4,300 miles, requiring about 143 hours of flight. This demanding journey requires constant refueling along the way, as they burn energy at an incredibly fast rate. They face numerous challenges, including adverse weather, predators, and the need to find suitable stopover locations for feeding and resting.