When Do Hummingbirds Fly South? Understanding Their Remarkable Migration

Key Takeaways

• Hummingbird migration is triggered primarily by decreasing daylight hours, not food availability or temperature
• Different species follow distinct migration routes and schedules
• Adult males typically begin migration first, followed by females and then juveniles
• Some species, like the Ruby-throated Hummingbird, can travel over 500 miles non-stop across the Gulf of Mexico
• Not all hummingbird species migrate; some, like the Anna’s Hummingbird, remain year-round residents along the Pacific Coast
• Hummingbirds prepare for migration by entering a state of hyperphagia (feeding frenzy) to nearly double their body weight.

The Timing of Fall Migration: When Hummingbirds Head South

Hummingbirds are among North America’s most fascinating migratory birds, with their fall migration following a complex but predictable pattern. The timing of their southward journey varies by species, location, and environmental factors.

General Migration Timeline

The fall migration for most North American hummingbirds begins as temperatures start to cool and days become shorter. According to research and migration tracking:

• Early Departures (July-August): Adult male hummingbirds are typically the first to depart, with some beginning their southward journey as early as mid-July in northern regions
• Peak Migration (August-September): By August and September, the majority of hummingbirds are actively moving south
• Late Migration (September-October): Most adult females depart during this period
• Final Departures (October-November): Juvenile hummingbirds are usually the last to migrate, with some remaining in southern states until late October or even November.

The fall southern hummingbird migration follows a pattern where birds travel during daylight hours, refuelling their bodies in the early morning, travelling midday, and feeding again in the evening. This allows them to see and stop at food sources along their journey.

Species-Specific Migration Timing

Different hummingbird species follow distinct migration schedules:

Ruby-throated Hummingbird

The most common species in eastern North America, Ruby-throated Hummingbirds (Archilochus colubris) usually start their fall migration between late August and early September. Adult males often begin departing in July, while the last juveniles might not leave until October from the northern parts of their range.

“Ruby-throated Hummingbirds usually start their fall migration in late August or September. From here, they retrace their previous northern routes, and make their exhausting journey back down to Central America.”

Rufous Hummingbird

Known for having the longest migration route of all U.S. hummingbirds, Rufous Hummingbirds (Selasphorus rufus) begin their southward journey relatively early. They typically start moving south through the Rocky Mountains and southwestern states in late July and August, heading to their wintering grounds in Mexico and possibly as far south as Panama.

Allen’s Hummingbird

Some Allen’s Hummingbird populations are migratory, while others are resident. The migratory populations typically begin their southward journey in late summer from the Pacific Northwest and California coast.

Non-migratory Species

Not all hummingbirds migrate. For example, “The Anna’s Hummingbird stays put all year along the Pacific Coast,” making it an exception to the general migration pattern seen in other North American hummingbird species.

What Triggers Hummingbird Migration?

Unlike many other birds whose migration is driven by food availability or temperature changes, hummingbird migration is primarily triggered by other factors:

Primary Migration Triggers

1. Changing Daylight Hours: The most significant trigger for hummingbird migration is the decreasing length of daylight as autumn approaches. As days grow shorter, hormonal changes occur in the hummingbirds’ bodies that prompt them to begin preparation for migration.”Many make this journey during the late summer and fall, spurred not by hunger or falling temperatures but by decreasing daylight hours.”
2. Hormonal Changes: The shortening days trigger chemical and hormonal changes in hummingbirds that lead to two key behaviours:
   • Increased feeding (hyperphagia)
   • Restlessness and the urge to migrate
3. Endogenous Programming: Research suggests hummingbirds have an internal biological clock that helps determine when it’s time to migrate, combined with environmental cues.
4. Secondary Factors: While not primary triggers, these factors can influence migration timing:
   • Decreasing natural food sources
   • Competition for resources
   • Predation pressure.

“The initial urge is triggered by the shortening length of sunlight as autumn approaches, and has nothing to do with temperature or the availability of food.”

How Hummingbirds Prepare for Migration

The preparation for migration is an intensive process that allows these tiny birds to make extraordinary journeys:

Hyperphagia: The Pre-Migration Feeding Frenzy

Before migration, hummingbirds enter a state called hyperphagia – an intense period of feeding that significantly increases their body weight.

“Before migration, hummingbirds feed intensely. Scientists call the pre-migration feeding frenzy hyperphagia. The tiny birds spend more time than usual feeding.”

During this period:

• Hummingbirds can nearly double their body weight
• They focus on high-energy food sources like flower nectar and small insects
• Feeding activity may increase by 25-40% compared to normal periods.

“Hummingbirds will double their weight as they prepare to fly hundreds or even thousands of miles.”

Physiological Changes

Along with increased feeding, hummingbirds undergo several physiological changes:

• Fat Storage: They convert sugar to fat, which provides more energy per gram than carbohydrates
• Muscle Development: Flight muscles may become more efficient for long-distance travel
• Metabolic Adjustments: Their bodies become more efficient at using stored energy.

Migration Routes and Destinations

Hummingbird migration routes vary by species and can be quite complex:

Ruby-throated Hummingbird Routes

Ruby-throated Hummingbirds have two main migration strategies:

1. Gulf Crossing: Many take a direct route across the Gulf of Mexico, flying non-stop for up to 500 miles over open water
2. Coastal Route: Others follow the coastline around the Gulf of Mexico.

Their winter destination is primarily southern Mexico and Central America, with some reaching as far south as Panama.

Rufous Hummingbird Routes

Rufous Hummingbirds have a fascinating migration pattern:

• Spring Migration: They travel up the Pacific Coast
• Fall Migration: They take a different route, travelling south through the Rocky Mountains
• This creates an enormous clockwise loop migration pattern covering thousands of miles.

“Capture data show hummingbirds migrating south through the Rocky Mountains and southwestern states.”

Migration Distances

Migration distances vary greatly by species:

• Ruby-throated: Travel up to 2,000 miles each way
• Rufous: May travel over 3,900 miles one-way, the longest migration relative to body size of any bird
• Allen’s: Travel several hundred miles along the Pacific coast.

Factors That Affect Migration Timing

Several factors can influence exactly when individual hummingbirds begin their southward journey:

Geographic Location

Birds in northern regions generally begin migration earlier than those in southern areas:

• Northern U.S./Canada: Migration may begin in July/August
• Mid-latitudes: Usually September
• Southern U.S.: Often October or even November for some individuals.

Age and Sex

A clear pattern exists regarding which birds migrate first:

1. Adult males (earliest)
2. Adult females
3. Juvenile birds (latest).

“Adult ruby throats migrate south in late summer and early fall before juveniles. Adults start moving south in July from northern states and Canada.”

Weather Conditions

While not the primary trigger, weather can influence departure timing:

• Favourable tailwinds may encourage earlier departure
• Severe storms might delay migration briefly
• Unusually warm or cold seasons can shift timing slightly.

Individual Variation

Individual birds show considerable variation in their exact migration timing based on:

• Previous migration experience
• Overall health and energy reserves
• Individual response to environmental cues.

Common Misconceptions About Hummingbird Migration

Several persistent myths about hummingbird migration should be addressed:

Myth: Leaving Feeders Up Delays Migration

“Hummingbirds migrate in response to hormonal changes, which are triggered by decreasing length of daylight; nothing you can do will make them stay too long.”

Keeping feeders up through fall doesn’t delay migration – it actually helps late migrants gain necessary energy for their journey.

Myth: All Hummingbirds Migrate to South America

While many hummingbirds do migrate to Central America and Mexico, most don’t actually reach South America. Additionally, some species like Anna’s Hummingbird remain year-round residents in certain regions.

“There are currently over 300 recognised hummingbird species, but only 12-15 will regularly migrate into the United States, and even fewer continue all the way north to Canada.”

“Hummingbirds migrate individually. When a late October straggler in the East is a Ruby-throated Hummingbird, it’s usually an immature bird from further north.”

How to Help Migrating Hummingbirds

There are several ways people can assist hummingbirds during their fall migration:

Keep Feeders Available

• Maintain nectar feeders until at least two weeks after you’ve seen the last hummingbird
• Clean feeders regularly to prevent mold and bacteria growth
• Use proper nectar mixture (four parts water to one part white sugar).

Plant Late-Blooming Flowers

Native plants that attract hummingbirds bloom in late summer and early fall provide natural nectar sources:

• Cardinal flower
• Jewelweed
• Fall sage
• Mexican sunflower.

“If possible, have late-blooming flowers in your garden to provide natural nectar sources for the late migrants.”

Provide Safe Habitat

• Reduce pesticide use that might harm hummingbirds or their food sources
• Offer shelter with native shrubs and trees for resting places
• Provide water sources like misters or shallow birdbaths.

Conclusion

The southward migration of hummingbirds is one of nature’s most remarkable phenomena. These tiny birds, weighing only about 3-4 grams, undertake extraordinary journeys spanning thousands of miles. Their migration is primarily triggered by decreasing daylight hours, not food availability or temperature changes as commonly believed.

Different species follow different routes and schedules, but generally, adult males depart first in late July or August, followed by females, with juveniles being the last to leave through September and October. By understanding these patterns, we can better appreciate the incredible journey these birds make each year and take appropriate steps to support them during this critical period.

While there is still much to learn about the specific mechanisms that guide hummingbird migration, ongoing research and citizen science efforts continue to expand our knowledge of these fascinating birds and their remarkable migratory achievements.

Frequently Asked Questions (FAQ)

Q: Do all hummingbird species migrate?

A: No. While most North American hummingbird species do migrate, some like the Anna’s Hummingbird remain year-round residents along the Pacific Coast. Of the more than 300 hummingbird species worldwide, only about 12-15 regularly migrate into the United States.

Q: How far do hummingbirds travel during migration?

A: Migration distances vary by species. Ruby-throated Hummingbirds may travel up to 2,000 miles each way, while Rufous Hummingbirds can travel over 3,900 miles one-way, the longest migration relative to body size of any bird.

Q: Do hummingbirds migrate in flocks?

A: No, hummingbirds migrate individually, not in flocks like many other bird species. Each bird makes the journey on its own.

Q: Will keeping feeders up delay hummingbird migration?

A: No. Hummingbird migration is triggered by changing daylight hours and hormonal changes, not food availability. Keeping feeders up actually helps late migrants gain the necessary energy for their journey.

Q: How do hummingbirds prepare for migration?

A: Hummingbirds enter a state called hyperphagia – an intense feeding period where they nearly double their body weight by consuming extra nectar and insects to store fat for their journey.

Q: How fast do hummingbirds fly during migration?

A: Hummingbirds typically fly at speeds of 25-30 miles per hour during migration, though they can reach up to 60 miles per hour in short bursts.

Q: Do hummingbirds return to the same locations each year?

A: Yes, many hummingbirds are site-faithful, returning to the same breeding and wintering grounds year after year. They often remember specific feeding locations from previous years.

Q: When should I take down my hummingbird feeders in fall?

A: It’s recommended to leave feeders up until at least two weeks after you’ve seen the last hummingbird in your area, which may be as late as November in southern regions.

Q: How do baby hummingbirds know where to migrate?

A: Juvenile hummingbirds have an innate genetic programming that guides their first migration without having learned the route from parents or older birds.

Q: Which hummingbird species has the longest migration?

A: The Rufous Hummingbird has the longest migration route relative to its body size of any bird in the world, travelling up to 3,900 miles one-way from Alaska and Canada to Mexico.

External Sources:

1. American Bird Conservancy: Do Hummingbirds Migrate?
2. Journey North: Hummingbird Migration and Pre-Migration Hyperphagia.