The blue grosbeak is a medium-sized songbird that breeds in the central and eastern United States and Mexico. However, when winter approaches, blue grosbeaks migrate south to spend the colder months in Mexico, Central America, and northern South America.
Here are some key questions answered about where blue grosbeaks go in winter:
What are the wintering grounds of blue grosbeaks?
The core wintering grounds of blue grosbeaks extend from southern Mexico through Central America to Panama. Some individuals may wander as far south as northern Colombia and Venezuela in South America. However, most blue grosbeaks winter from the Yucatan Peninsula through Nicaragua.
Within their wintering range, blue grosbeaks occupy open and second growth habitats. They particularly favor forest edges, overgrown fields, pastures with scattered shrubs and trees, and other open areas with dense, low vegetation.
Mexico
In Mexico, blue grosbeaks winter primarily along both coasts. On the Pacific coast, they occur from southern Sonora to Chiapas. On the Gulf coast, they range from Tamaulipas through Veracruz and Oaxaca.
Some inland wintering also occurs in Mexico, especially in the Balsas River valley of southwestern Mexico. But the majority of the wintering population remains along the coasts.
Central America
Central America hosts the core of the wintering population of blue grosbeaks. They occur along both the Caribbean and Pacific slopes from Guatemala through Panama.
Along the Caribbean slope, blue grosbeaks inhabit coastal scrub, agricultural areas, and clearings in humid broadleaf forests. On the Pacific slope, they occur in arid scrub habitats and deciduous forest edge.
Northern South America
A smaller number of blue grosbeaks expand into northern Colombia and Venezuela in winter. They are most common in drier habitats along the Caribbean coast.
The Guajira Peninsula of Colombia and Venezuela marks the southern limit of the winter range for blue grosbeaks. Only occasional vagrants are reported further south than this point.
What specific areas and habitats are used?
During the winter, blue grosbeaks utilize a variety of open and semi-open habitats throughout their range in Mexico, Central America, and northern South America.
Coastal Regions
Coastal scrub along both the Gulf of Mexico and Pacific Ocean coasts provides important wintering habitat. Blue grosbeaks inhabit thickets of shrubs and small trees in these coastal areas.
Other coastal habitats used include weedy fields, forest edges, pastures, and mangroves. The birds feed on seeds and insects in these locations.
Agricultural Areas
Blue grosbeaks commonly winter in agricultural areas, including crop fields, fallow fields, and cattle pastures. They often forage along fences, hedgerows, and roadsides.
Some specific agricultural crops used by wintering blue grosbeaks include rice, sorghum, corn, sugar cane, and coffee plantations. These provide good foraging habitat as well as cover.
Secondary Forest
Second growth scrub and open forests are also inhabited. The birds occur along forest edges, in canopy gaps, and in early successional growth.
Blue grosbeaks frequently utilize fence rows, living fences, and other strip habitats that provide cover adjacent to open areas for feeding.
Urban Areas
Some blue grosbeaks overwinter near human settlements. They visit gardens, backyards, parks, and other urban green spaces.
Weedy vacant lots, scrubby field edges, and areas of secondary growth within cities can hold wintering blue grosbeaks.
What is their elevation range in winter?
Blue grosbeaks occur from sea level up to around 1,600 meters (5,250 feet) in elevation during winter. However, most remain below 1,000 meters (3,300 feet).
In Mexico, they primarily winter at low elevations along the coasts. Some occur inland at higher elevations in the Balsas River basin.
Elevations used are higher on the Pacific slope of Central America than on the Caribbean slope. Blue grosbeaks reach 1,600 meters in the highlands of Costa Rica and western Panama.
Caribbean Slope
On the Caribbean slope of Central America, blue grosbeaks are mostly found below 500 meters (1,650 feet) in elevation. The highest densities occur in lowland areas closer to the coast.
Pacific Slope
On the drier Pacific slope, blue grosbeaks winter up to 1,600 meters (5,250 feet) elevation. This higher elevation range is used especially in Costa Rica and western Panama.
Northern South America
In northern Colombia and Venezuela, blue grosbeaks are rare above 1,000 meters (3,300 feet) elevation. Most remain in lowland habitats near the coast.
When do they arrive on the wintering grounds?
Most blue grosbeaks start arriving on their core wintering grounds in Mexico and Central America in September. However, the timing of arrival depends on location:
- Mexico – begin arriving early September
- Guatemala – arrive mid to late September
- El Salvador – arrive late September
- Nicaragua – begin arriving late September
- Costa Rica and Panama – arrive early October
The birds arrive slightly later farther south. In northern Colombia and Venezuela, the first returning blue grosbeaks usually appear in early to mid-October.
Males tend to precede females on both fall and spring migration. Immature birds also often migrate later than adults.
Weather Influences Arrival
Weather conditions can influence the exact timing of arrival. Blue grosbeaks may show up earlier following favorable winds or other beneficial migratory conditions.
But most birds arrive on the wintering grounds within a few weeks of the typical schedule each year.
When do they depart the wintering grounds?
Most blue grosbeaks vacate their wintering grounds and begin spring migration in April and May. However, departure dates vary across the winter range:
- Mexico – majority leave by late April
- Central America – most depart late April through May
- Venezuela and Colombia – leave late April to mid May
As with fall arrival, males usually depart a few days ahead of females in spring. Immatures also tend to migrate later than adults.
Weather Influences Departure
Local weather patterns help trigger the initiation of spring migration. Favorable winds or temperatures can cause earlier departure some years.
But most birds stick fairly close to the typical spring departure schedule across their winter range.
How long do they stay on the wintering grounds?
On average, blue grosbeaks spend around 7 months on their wintering grounds each year. However, the exact duration depends on location:
Region | Approx. Duration of Stay |
---|---|
Mexico | 5-6 months |
Central America | 6-7 months |
Venezuela/Colombia | 7-8 months |
Farther south, the duration of stay increases. Birds wintering in Panama remain about a month longer than those in Mexico before heading north.
Duration Varies Between Individuals
The exact duration spent on the wintering grounds can vary substantially between individual blue grosbeaks. Some may linger longer while others depart earlier.
But most follow the general pattern of arriving in fall and departing in spring within the typical timeframe for the given region.
What are the migration routes and stopover sites?
On migration between their breeding and wintering grounds, blue grosbeaks follow inland routes across North America. Their migrations include long non-stop flights as well as periods of stopover to rest and refuel.
Fall Migration Routes
In fall, blue grosbeaks migrate southwest from breeding areas to Mexico and Central America. Some key migration corridors used include:
- Mississippi River valley through Texas to Mexico
- Along the Front Range from Colorado through New Mexico into Mexico
- Great Plains corridor south through Texas
These broad fronts bring the majority of birds from the U.S. and Canada through central Mexico and towards southern Mexico and Central America.
Spring Migration Routes
On spring migration, blue grosbeaks follow a loop route first northeastward, then curving northwest back to breeding areas. Major spring routes include:
- Across Gulf coastal regions into southern Texas
- Through Central U.S. into the Great Plains
- Via inland routes through Texas into the Great Plains
These pathways bring birds north through the central U.S. towards breeding grounds in the Midwest, Great Plains, and eastern regions.
Stopover Sites
Blue grosbeaks use a variety of stopover habitats along migration routes to rest and refuel between long non-stop flights. Important stopovers include:
- Riparian woodlands along major river corridors
- Forest edges and openings providing fruiting shrubs/trees
- Early successional and scrub habitats
- Coastal thickets along the Gulf of Mexico
Quality stopover habitat helps migrating blue grosbeaks successfully complete their long journeys between breeding and wintering areas.
How do they navigate their migrations?
Blue grosbeaks utilize a combination of innate abilities and learned behaviors to successfully navigate migration between breeding and wintering grounds. These include:
Orientation and Navigation
- Innate sense of direction using the sun and stars
- Ability to orient using the earth’s magnetic field
- Sophisticated spatial map and compass mechanisms
Environmental Cues
- Terrestrial landmarks for navigation
- Weather and wind patterns
- Celestial cues from sun, moon, stars
Learned Behaviors
- Following experienced individuals
- Memory of flyways, stopovers used in previous migrations
Blue grosbeaks begin learning migration routes and behaviors from the time they hatch. This allows them to successfully migrate long distances over many years.
Do they return to the same winter sites each year?
In many cases, individual blue grosbeaks show high winter site fidelity. They return to the same regions, and sometimes even specific locations, year after year. However, fidelity varies between populations:
Strong Fidelity in U.S. Breeding Populations
Blue grosbeaks that breed in the U.S. exhibit strong winter site fidelity. Studies of banded birds reveal many return to within a few miles of previous winter territories.
Lower Fidelity in Neotropical Migrants
For birds breeding in Mexico, Central America, and South America then migrating shorter distances, winter site fidelity is weaker. These populations tend to wander more during the non-breeding season.
Benefits of Site Fidelity
Returning to familiar wintering areas each year provides benefits like:
- Knowledge of reliable food sources
- Awareness of hazards, predators, and competition
- Saved energy compared to locating new sites
These advantages likely drive the evolution of site fidelity, especially in long-distance migratory populations.
Do they migrate individually or in flocks?
Blue grosbeaks migrate using a mix of individual and group movements:
- Mostly migrate individually or in small loose groups
- Larger flocks form where birds converge at geographic bottlenecks
- Flocks provide safety through predator detection and avoidance
Some patterns of blue grosbeak migratory behavior include:
Fall Migration
- Juveniles tend to migrate in larger flocks than adults
- Adults more often migrate solo or in small groups
- Large aggregations may form at barrier sites like the Gulf of Mexico
Spring Migration
- Larger flocks form early in migration further south
- Groups get smaller as migration proceeds north
- Flocks may facilitate navigation back to breeding areas
So while blue grosbeaks aren’t obligate flock migrants, loose aggregations can facilitate their long journeys between seasonal ranges.
Conclusion
In summary, blue grosbeaks undertake a remarkable annual odyssey spanning thousands of miles between breeding and wintering grounds. Their migration is guided by innate abilities honed by learning and experience. Flexibility in routes and timing aid the birds in completing these epic journeys.
Understanding where blue grosbeaks go and how they get there provides insight into the behavioral adaptations that allow songbird migration to persist in the face of habitat loss and other modern threats.