Where do Lesser Goldfinches winter?

The Lesser Goldfinch (Spinus psaltria) is a small songbird found primarily in the southwestern United States and Mexico. It is a migratory species, breeding in the western U.S. and wintering primarily in Mexico. Understanding where Lesser Goldfinches spend the winter months can provide important information about their full annual cycle and habitat needs.

Overview of Lesser Goldfinch

Lesser Goldfinches are small finches with a total length of about 4-5 inches. They have a short conical bill suited for eating seeds. Their breeding plumage features a bright yellow body, black wings with white markings, and a black cap. Their non-breeding plumage is more dull brownish-olive.

Some key facts about Lesser Goldfinches:

• Scientific name: Spinus psaltria
• Range: Breeds in western North America, winters in western and southern U.S. and Mexico
• Habitat: Open woodlands, chaparral, weedy fields
• Diet: Seeds, buds, insects
• Conservation status: Least concern

Lesser Goldfinches make a pleasant musical warbling call. They are common visitors to bird feeders within their range.

Breeding Range and Habitat

Lesser Goldfinches breed across much of the western United States and southwestern Canada:

• Western Canada from southeastern British Columbia to southwestern Saskatchewan
• Western U.S. from eastern Washington to western Texas
• Isolated populations in western Colorado and northern New Mexico

Their breeding habitat consists of open woodlands, chaparral scrublands, and weedy fields. They particularly favor areas with thistles and other seed-bearing composites.

During the breeding season, Lesser Goldfinches often feed on annual weeds and other herbaceous plants. They build a compact cup-shaped nest out of plant fibers, spider silk, and other materials. It is placed in a shrub, tree, or vine up to 10 feet above ground.

Timing of Breeding Season

Lesser Goldfinches breed between mid-March and early September, with exact timing varying across their range:

• Pacific Northwest: April to August
• California: March to August
• Southwest: May to September

They may raise 2-3 broods per season. The female incubates the eggs for 12-14 days. The nestlings fledge about 2 weeks after hatching.

Wintering Range and Habitat

In the winter months, most Lesser Goldfinches migrate south to the southern U.S. and Mexico. Their winter range includes:

• Southeastern California
• Southern Arizona
• Southern New Mexico and western Texas
• Central Mexico

A smaller number may remain through winter along the Pacific Coast from southern California to Washington.

Their preferred winter habitat includes open woodlands, brushy fields, desert washes, and suburban parks and gardens. Sources of seeds are particularly important.

While some Lesser Goldfinches remain further north, most migrate south to avoid severe winter weather and food shortages. Wintering grounds in Mexico and the southern U.S. offer more abundant sources of seeds and insects.

Timing of Fall and Spring Migration

Lesser Goldfinches begin leaving their breeding grounds for wintering areas in early fall, from August to October. Not all individuals migrate at the same time. The timing of migration depends on factors like weather conditions and food availability.

Here is an overview of when Lesser Goldfinches migrate in fall and spring:

As this table shows, most Lesser Goldfinches leave their breeding grounds by November. Spring migration back north can begin as early as January from southern wintering areas.

Winter Diet and Feeding

The diet of Lesser Goldfinches during the winter consists mainly of seeds and buds from annual weeds, shrubs, and trees. Some favorite winter food sources include:

• Thistle
• Sunflower
• Milkweed
• Elderberry
• Sagebrush

They also supplement their diet with fruit and berries. In suburban areas, Lesser Goldfinches visit bird feeders for offerings like nyjer seed and black oil sunflower.

In winter, Lesser Goldfinches often forage in mixed flocks with other finch species, such as House Finches. Flocking provides more eyes to locate food sources and avoid predators.

Adaptations for Winter Survival

Lesser Goldfinches have a few key adaptations that help them survive cold winters:

• High metabolism – They can raise their metabolism up to 50% in winter to generate more body heat.
• Fluffed feathers – Fluffing out their feathers creates more insulating air pockets.
• Food caching – They cache excess seeds to provide backup food supplies.
• Nightly hypothermia – They lower their body temperature by 10-12°F at night to conserve energy.

Their small size also makes it easier for Lesser Goldfinches to find cover from the elements in winter.

Status and Threats

Lesser Goldfinches have an extensive range and are not considered globally threatened. Their total population is estimated at 19 million birds. Trend data from the North American Breeding Bird Survey indicates Lesser Goldfinch numbers increased between 1966-2015.

However, Lesser Goldfinches do face some localized threats during both their breeding and wintering periods:

• Habitat loss from development, agriculture, etc.
• Climate change altering suitable habitat
• Use of pesticides reducing food supplies
• Collisions with buildings and vehicles

Providing suitable breeding habitat with seed sources, and protecting key wintering grounds in the U.S. and Mexico, are important conservation measures for maintaining Lesser Goldfinch populations. Participating in citizen science projects, like the Christmas Bird Count, can also help monitor wintering numbers.

Research Methods

Biologists use various research methods to study the wintering ecology and behavior of Lesser Goldfinches, including:

Banding and Tracking

Attaching leg bands or radio transmitters allows individual Lesser Goldfinches to be identified and tracked throughout their annual cycle. This provides data on their migratory connections, site fidelity, survival rates, and more.

Winter Population Surveys

Large-scale surveys like the Christmas Bird Count are conducted each winter to monitor populations across the Lesser Goldfinch’s range. Repeated over time, these surveys reveal population trends.

Habitat Analysis

Analyzing the vegetation composition and food availability of different wintering sites can identify high quality habitats. Food supplementation experiments also evaluate habitat quality.

Genetic Studies

Genetic analysis of birds sampled across the wintering range determines the connectivity between breeding and wintering populations. Stable isotope analysis of feathers can reveal links between breeding and wintering grounds.

Feeding Observations

Direct observations of wintering flocks provide details on their feeding behavior, social interactions, flight patterns, vocalizations, and responses to environmental factors.

Conclusion

In conclusion, most Lesser Goldfinches that breed in the western U.S. and southwestern Canada migrate south to winter primarily in Mexico and the southern U.S. Wintering habitat consists mainly of open woodlands and scrublands that provide seeds and buds. Lesser Goldfinches begin heading south in August-October and start northward spring migration as early as January. A variety of research methods help reveal details of their migratory connectivity, population trends, winter ecology, and conservation needs. Maintaining suitable breeding and wintering habitat across their range is key to ensuring healthy Lesser Goldfinch populations into the future.