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MacGillivray’s Warbler (Geothlypis tolmiei) is a species of New World warbler that is best known for its unique call and breeding pattern. Native to the western United States, Mexico, and Canada, this small songbird typically nests in coniferous forests along mountain slopes or streams.

It has recently been listed as Near Threatened by the IUCN due to habitat destruction and fragmentation caused by human activities such as logging and development. This article discusses MacGillivray’s Warbler biology, distribution, migration patterns, conservation status, and management recommendations.

The distinctive white-striped head of the male MacGillivray’s Warbler makes it easily identifiable among other bird species of similar size. Its diet consists largely of insects found on trees, shrubs, bushes and grasses; however it also eats some fruits during the winter months when insect availability decreases.

During breeding season these birds nest in dense thickets that provide protection from predators while they raise their young. They tend to choose nesting sites near water sources such as rivers, creeks or springs which provides easy access to food.

MacGillivray’s Warblers are migratory birds with most individuals migrating south in late summer/early autumn into southern Texas and northern Mexico before moving further south into Central America during the winter months.

Due to its wide range across multiple countries there are many different threats faced by this species including deforestation, urbanisation and agricultural intensification leading to decreased suitable habitat for both nesting and overwintering grounds. As a result populations have declined significantly since 1970 making it an important target for conservation efforts in order to protect this species from extinction.

macgillivrays warbler

Species Overview

The MacGillivray’s Warbler (Geothlypis tolmiei) is a small species of New World warbler. It is found in western North America, where it breeds from May through August and migrates southwards during the winter months.

This species has distinctive yellowish-olive upperparts with white underparts, a dark gray cap on its head, and black lores. Its primary call is described as a loud chip note and its song consists of two distinct phrases that are repeated multiple times.

MacGillivray’s Warblers breed mainly in coniferous or mixed woodlands, such as Douglas fir forests, scrub oak woodlands, riparian areas near streams, meadows with shrubs or trees for cover or open forested hillsides.

The majority of their migration takes place along the Pacific Coast and Rocky Mountain regions between Alaska and Mexico. During this time they feed primarily on insects which they glean from foliage or catch in midair while flying close to the ground.

Due to population declines seen over recent years, MacGillivray’s Warbler was listed as an endangered species by the U.S Fish & Wildlife Service in 1991. Conservation efforts have since been put into place to help increase breeding success rates and improve habitats throughout its range countries including Canada, United States and Mexico. Despite these efforts however populations remain low due to habitat loss caused by human activities such as timber harvesting, grazing and urbanization.

Distribution And Habitat

MacGillivray’s Warbler is a migratory songbird with an expansive range that traverses the Americas. Its distribution ranges from Alaska to Mexico, and its habitat includes both coniferous and deciduous forests as well as brushy scrublands. The species typically breeds in boreal forest habitats of North America and winters in central Mexico or along the Gulf Coast states and northern South American countries.

Migratory routes vary slightly between individuals and populations but generally follow the Rocky Mountain Chain up through Canada into western United States until reaching their breeding grounds.

During migration MacGillivray’s Warblers can be found within wooded riparian corridors such as oak woodlands near rivers or streams, although they are thought to migrate at higher altitudes than many other warbler species. Upon arriving on their wintering grounds, these birds tend to occupy evergreen woodland areas where food sources remain available year-round.

The MacGillivray’s Warbler population appears widely distributed throughout its range; however exact numbers of this species have not been determined due to difficulties distinguishing it from similar looking yellow-rumped warblers during migration periods when identification becomes difficult without vocalization clues.

Despite this fact, some evidence indicates that certain subspecies may face localized declines as a result of land use changes affecting suitable habitat for this species. As such, conservation efforts should focus on protecting remaining grassland/scrubland habitats while further research is conducted to determine any potential impacts of human activity on MacGillivray’s Warbler populations across its entire range.

Physical Characteristics

The MacGillivray’s Warbler is a small warbler species, ranging in size from 10-11 cm and weighing only 7-12 grams. It is olive-green above with yellowish underparts, white wing bars, and an unmarked grey head. The tail feathers are squarish at the tips. Females tend to have less distinct facial markings than males.

When it comes to plumage pattern, the MacGillivray’s Warbler exhibits strong sexual dimorphism; male birds show much brighter coloration than females. During breeding season, adult males sport bright yellow throat patches and black eyestrips which helps them attract mates.

One of the more notable physical features of this species is its bill shape – slender and pointed – allowing it to probe deeply into bark crevices in search of insect prey.

Additionally, they possess well developed vocal cords that enable them to produce loud songs consisting of short phrases made up of various notes including chirps, trills, whistles and buzzes. These help identify their presence during mating season as well as for territorial defense throughout the year.

MacGillivray’s Warblers inhabit broadleaf forests across North America’s western coastal regions from Alaska down through Oregon and California. They can also be found in parts of Mexico and Central America where conditions suitable for nesting exist – areas with dense shrubbery close to open woodlands or moist meadows near lakes or streams provide ideal habitat for these birds.

Breeding Behaviour

MacGillivray’s Warbler exhibits a wide variety of breeding behaviors, including pair bonding and mating rituals. During the breeding season, the warblers form monogamous pairs which usually last for about one year. Both males and females participate in nest-building activities such as selecting nesting sites and constructing nests from grasses and plant materials. The male will often guard the female while she is building the nest to protect her from predators.

Mating rituals consist of males singing courtship songs to attract potential mates. Males may also perform display flights or hover in front of females during these song displays. Once paired, they commonly engage in preening behavior with each other, which strengthens their bond and helps them prepare for egg laying.

The MacGillivray’s Warbler lays eggs between April and July depending on location. Clutches typically contain two to five eggs that are incubated by both parents but primarily by the female. After hatching, both parents feed and care for young until they fledge at around 14 days old.

macgillivrays warbler

Diet And Feeding Habits

Macgillivray’s Warbler is an insect-eating species. The warbler feeds mainly on small insects and spiders, but also consumes fruits such as berries and cherries during the breeding season when they are available. It has been observed feeding on a variety of other food sources including:

  • Caterpillars
  • Beetles
  • Ants
  • Aphids
  • Grasshoppers
  • Sawflies
  • Beeswax moths

Macgillivray’s Warblers forage by gleaning from foliage or hover-catching from perches. They may also flycatch arthropods in open air or pursue them along branches. During summer months, this species can be found snatching flying prey within the canopy of trees.

Additionally, it has been known to feed at sap wells created by Yellow-bellied Sapsuckers (Sphyrapicus varius). Invertebrates make up most of their diet year round; however, fruit consumption increases significantly after hatching fledglings due to their higher energy requirements.

This species is one of few North American passerines that will eat monarch butterfly eggs and caterpillars as well as grasshopper eggs. Some studies have even shown that they prefer these larger more energetic items over smaller less nutrient rich ones like aphids and beetles.

These findings suggest that macgillivray’s warblers supplement their diets with high caloric foods while raising young which helps increase fledgling survival rates. All in all, the macgillivray’s warbler’s diet comprises mostly small invertebrate animals supplemented by some fruit depending on availability throughout different seasons.

Conservation Status

The conservation status of the MacGillivray’s Warbler is a matter of concern for avian wildlife organizations. It is currently listed as endangered under the Endangered Species Act, due to its severely restricted range and population size. A variety of conservation efforts have been undertaken in an effort to protect this species from extinction including habitat protection, reintroduction programs, and research initiatives.

Habitat conservation is considered one of the most important strategies for preserving the MacGillivray’s Warbler. This includes restoring or maintaining areas with suitable nesting habitats such as riparian corridors, shrublands, and woodlands that provide food sources and cover.

Research into potential threats facing this species has also revealed additional threats such as predation by invasive species and disease outbreaks which must be addressed through further mitigation measures.

Conservation organizations continue to strive towards increasing public awareness about the importance of protecting these birds and their habitats so they can thrive once again in their native ranges. Various projects are underway to better understand how best to conserve this species while minimizing any potential impacts on other species or human activities.

With continued support from all stakeholders involved, it is possible that future generations will enjoy seeing a healthy population of MacGillivray’s Warblers thriving in its natural environment.

Interesting Facts

The MacGillivray’s Warbler is a small, colorful songbird that belongs to the wood-warbler family. It has a grayish green back, yellow throat and belly, white eye ring and a pointed crest on its head. This species of warbler is particularly interesting due to some unique facts about it.

First off, the MacGillivray’s Warbler is an extremely rare bird in North America; it only breeds in certain areas of Idaho, Montana and Wyoming. There are also nonbreeding populations in British Columbia, Canada during summer months as well as Mexico for wintering grounds.

Due to its rarity, the International Union for Conservation of Nature listed this species as Near Threatened – meaning that their population is decreasing but still not critically endangered.

In terms of behavior, these warblers are quite active birds with quick wing beats when they fly short distances looking for food or nesting materials. They primarily feed on insects such as caterpillars, beetles and spiders which can be found among coniferous trees and shrubs where they build nests made from mosses and lichens lined with feathers or fur.

These warblers have also been known to eat flower petals while visiting gardens near forested areas making them popular amongst birdwatchers.

Overall, the MacGillivray’s Warbler is truly an amazing species because of their striking features and behaviors that make them stand out from other tiny songbirds native to North America. Although their conservation status continues to fluctuate based on habitat destruction and climate change, there is still hope for preserving this remarkable species in our forests today.


The MacGillivray’s Warbler is a species of New World warbler that is found throughout much of the western United States and parts of northern Mexico. This species inhabits semi-open woodlands, montane forests, and coastal scrub habitats.

It has an olive green to yellowish back with a white belly, two light wing bars and a distinct eye ring. Breeding males have bright orange throats and cheeks and are easy to identify in their breeding grounds.

MacGillivray’s Warblers feed on insects such as beetles, butterflies, moths, spiders, ants, grasshoppers and caterpillars which they glean from foliage or catch while hawking in flight. They also eat fruits and berries when available during winter months. The current population trends of this species remain unknown due to lack of data; however it appears to be stable across its range given no significant threats at present time.

MacGillivray’s Warbler is an interesting bird worthy of further study and observation by wildlife enthusiasts all over the world. Its unique plumage allows for easy identification in its habitat where it can be seen flitting through the undergrowth searching for food or singing away atop high tree branches proclaiming its presence within its territory. With increased research efforts we may one day better understand the ecology of this enigmatic little warbler.