MacGillivray’s Warbler

The MacGillivray’s Warbler is a wood Warbler that breeds in low to moderate elevations. Breeding populations found throughout most of the United States are lone or disjunct. These birds are not very gregarious, and they are actually quite secretive and shy. Hence, they’re not easy to sight.

About MacGillivray’s Warblers

As these extremely secretive birds are very difficult to spot, they’re widely sought after by avid birdwatchers. Sighting and identifying them is almost like a trophy for birdwatchers. Although difficult to sight, they are very common in their breeding habitat. They usually inhabit second-growth forests and wet woodlands, which generally consist of willows, shrubs, saplings, and dense thickets.

Interesting facts have recently been discovered about these birds. One of these is that the breeding populations from the Rocky Mountains are genetically distant from the breeding populations in Northeastern Mexico. These populations diverged approximately 1 million years ago, during the Pleistocene glaciation.

MacGillivray’s Warblers and their eastern relatives Mourning Warblers hybridize in the Peace region of British Columbia. In other regions, these birds don’t hybridize due to the difference in their song types. Although this factor has failed to prevent hybridization in this region.

Ornithologists are also intrigued by the migratory behaviors of MacGillivray’s Warblers. These birds only migrate over land, and their route never overlaps with Mourning Warblers. These species that are so closely related never overlap throughout their annual cycles, except for their contact in British Columbia.

As MacGillivray’s Warblers are completely dependant on riparian habitats during breeding and migration, as a result of which they have become an interesting subject to study for researches regarding the management and conservation of this ecosystem. These studies are generally regarding the western portion of the U.S.

One very interesting fact about these birds is that they were previously called Tolmie’s Warblers named after William Fraser Tolmie, an honored surgeon, by esteemed ornithologist John Kirk Townsend. Later, they were renamed as MacGillivray’s Warblers by John James Audubon, after Dr. W. MacGillivray, a Scottish ornithologist who was a close friend of Audubon. A number of birdwatchers and ornithologists are not too happy with the blatant disregard for Townsend by John James Audubon.

MacGillivray’s Warblers are a species of Least Concern, which is also protected under the U.S. Migratory Bird Act Treaty. It’s suggested that populations of these birds are actually expanding due to deforestation. This might be temporary, and the long-term consequences of deforestation won’t be pleasant for these birds.

● MacGillivray’s Warblers Photos, Color Pattern, Song
● MacGillivray’s Warblers Size, Eating behavior, Habitat
● MacGillivray’s Warblers Range and Migration, Nesting

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MacGillivray’s Warbler Color Pattern

MacGillivray’s Warblers are vibrant warblers. Their head and nape are neutral gray, and their lores are an olive green or brown. Their eye-line is dark gray or black, and their eyes have several bold white crescents. There isn’t much individual variation in the number and location of these white crescents.

Their upper tail coverts, rump, and back is yellowish olive-green. Most of the feathers on their wing are brown, and they have olive-green tips. The underparts such as the upper breast and throat are neutral gray, and the lower breasts have black spots on them.

The rest of their underparts are yellow, and the flanks are yellowish olive-green. Females are quite similar to males, but their heads are significantly paler. Their crowns are grayish olive, and their eyelines are not distinctly darker than the rest of their head. White crescents are present near the eyes, but they are not as bold. Their lower breast also lacks
the blackish feathers.

Juveniles look similar to adults, but most of their body is paler or duller in comparison. MacGillivray’s Warblers have a plumage that is very similar to the plumage of Mourning Warblers.

Description and Identification

These yellow and green birds are a beautiful sight to behold. These vibrantly plumaged wood Warblers are commonly found in large and dense tracts of forests. These birds look quite similar to Mourning Warblers. If birdwatchers have a chance to closely observe these birds, then they can identify MacGillivray’s Warblers by the distinct bold white crescents around their eyes, which are not present in Mourning Warblers. The concentration of black feathers around the throat of Mourning Warblers is also significantly lesser.

Very few Mourning Warblers can have physical characteristics extremely similar to those of MacGillivray’s Warblers. Females are also mostly distinguished by the absence or presence of eye crescents, but some female Mourning Warblers might also have eye crescents. If this is the case, observe the grayish-brown wash across the breast on
MacGillivray’s Warblers. As the plumages of these birds could almost be the same, it is suggested that measurements of these birds are observed.

MacGillivray’s Warblers can be differentiated from Connecticut Warblers through their smaller size and shorter legs. Their appearance is also similar to the appearance of Common Yellowthroats.

MacGillivray’s Warbler Song

MacGillivray’s Warblers have a primary, flight song, and 2 call notes. Females use the same call notes, and fledglings make begging calls while foraging. Most primary songs contain 6-8 syllables like “churry churry churry cheery cheery cheery”. The first portion of the song might just be a repetition of the syllable “churry”. The second portion has the cheery syllable vocalized 2-3 times. Rarely, some males sing three-syllable songs, in which the third syllable is used twice at the end.

MacGillivray’s Warblers are often distinguished from Mourning Warblers by observing the primary song. The primary song of MacGillivray’s Warblers is much more complex, longer, and has more syllables per song. The frequency of their song is also higher.

These syllables are also more complex, they might contain more notes, and the shape and structure observed on a sonograph are different. Considerable variation in song or call notes can be observed among individuals.

Male MacGillivray’s Warblers mostly sing the flight song. This song is quite similar to the flight song that Mourning Warblers sing. This song is preceded by harsh chipping notes, and it often also ends with chip notes as the birds descend back to the ground.

Two characteristic calls are vocalized by both the sexes. Males produce a harsh chip note when they are in territorial conflict. Females also use this call when they are scolding intruders that are approaching their fledglings or nests.

The other distinct call note is a high-frequency “chip”. Due to its high frequency, it isn’t easy to understand which bird is vocalizing it, but it serves the function of silencing younglings and stopping the movements of intruders. They are capable of recognizing alarm calls made by other species.

MacGillivray’s Warbler Size

MacGillivray’s Warblers are one of the smaller wood Warblers. They are 3.9-5.9 inches long, with an approximate wingspan of 7.5 inches. They weigh between 0.3-0.5 ounces.

MacGillivray’s Warbler Behavior

MacGillivray’s Warblers are foliage gleaners. Males sing a delightful song when they return to the breeding grounds. These songs serve the purpose of claiming territories and advertising their presence to potential females.

Females arrive at the breeding areas slightly before the males. While females focus on protecting their nests, males defend their breeding territories by chasing away male opponents. Most males defend a territory of 2-4 acres, but some males might choose to defend larger territories. Females construct nests, and both sexes share the responsibility of incubating eggs and raising their nestlings.

MacGillivray’s Warbler Diet

MacGillivray’s Warblers are foliage gleaners which pick at insects and arthropods from branches and foliage in their dense habitats. Sometimes, these birds hunt their prey from the ground.

MacGillivray’s Warblers prefer to forage close to the ground, and they mostly don’t forage from elevations higher than 6 feet. Their diet consists of butterflies, larvae, bees, wasps, weevils, beetles, leafhoppers, and bugs.

MacGillivray’s Warbler Habitat

MacGillivray’s Warblers choose moderate elevations to breed in. Very rarely do they nest in elevations higher than 10,000 feet. These birds generally inhabit riparian corridors and second-growth forests. In the northern portion of their range, they commonly inhabit deciduous forests, and sometimes they breed in chaparral.

While migrating, these birds reside in dense shrubbery found in mountain ranges. Their wintering habitats are not very different from their breeding habitats.

Range and Migration

MacGillivray’s Warblers breed in Western North America. The northernmost portion of their range is in southeastern Alaska, and the southernmost portion of their range is in Central Arizona. They also breed in certain parts of southern California.

Some populations nest in the Cypress Hills of South Dakota, but a larger majority of their population is in the Rocky Mountains, and the area west of the Pacific Ocean.

The winter grounds of MacGillivray’s Warblers are in the Pacific slope of Central America. This range extends from northern Mexico to Panama, and sometimes as far as Columbia. Rarely, MacGillivray’s Warblers winter in southern California.

MacGillivray’s Warbler Lifecycle

MacGillivray’s Warblers begin courtship actives as soon as both sexes arrive on the breeding grounds. This may happen between late May and early June. These birds raise only one brood per breeding season. The eggs laid by the females are short and ovate in shape. These eggs are creamy-white with some brown spotting, and speckling. The texture of the eggs is smooth.

Females lay between 2-6 eggs per clutch. Females solely incubate the eggs. Nestlings are born with closed eyes. Down feathers begin to appear 2 days after the nestlings hatch. 8-9 days after hatching, the younglings leave the nest.

The oldest living MacGillivray’s Warbler was 4 years and 1 month old. In contrast, the oldest recorded Mourning Warbler lived past the age of 7. MacGillivray’s Warblers are susceptible to brood parasitism by cowbirds. This is especially a cause of concern for the MacGillivray’s Warblers that live in the interior regions of British
Columbia.

Nesting

They construct their nests at lower elevations, mostly in shrubs. Females construct the nest by gathering leaves, straw, grasses, and bark. They line their nests with hair, root fibers, and grasses. On average, nests are 1.6 inches deep and are 5 inches in diameter.

Anatomy of a MacGillivray’s Warbler

MacGillivray’s Warblers are small warblers with long and lean legs. They have an average-size pointed bill and a long tarsi.

Final Thoughts

MacGillivray’s Warblers are beautiful Warblers who are not very sociable. Although these birds have some coinciding characteristics with other Warblers, they’re quite unique. Most birdwatchers would love to sight this skulking bird. This task would be as rewarding as it is difficult.

Ornithology

Bird Watching Academy & Camp Subscription Boxes

At the Bird Watching Academy & Camp we help kids, youth, and adults get excited and involved in bird watching. We have several monthly subscription boxes that you can subscribe to. Our monthly subscription boxes help kids, youth, and adults learn about birds, bird watching, and bird conservation.

Bird Watching Binoculars for IdentifyingMacGillivray’s Warblers

The most common types of bird watching binoculars for viewing MacGillivray’s Warblers are 8×21 binoculars and 10×42 binoculars. Bird Watching Academy & Camp sells really nice 8×21 binoculars and 10×42 binoculars. You can view and purchase them here.

MacGillivray’s Warbler Stickers

Stickers are a great way for you to display your love for bird watching and the MacGillivray’s Warbler. We sell a monthly subscription sticker pack. The sticker packs have 12 bird stickers. These sticker packs will help your kids learn new birds every month.

Bird Feeders ForMacGillivray’s Warblers

There are many types of bird feeders. Bird feeders are a great addition to your backyard. Bird feeders will increase the chances of attracting birds drastically. Both kids and adults will have a great time watching birds eat at these bird feeders. There are a wide variety of bird feeders on the market and it is important to find the best fit for you and your backyard.

Bird HousesForMacGillivray’s Warblers

There are many types of bird houses. Building a bird house is always fun but can be frustrating. Getting a bird house for kids to watch birds grow is always fun. If you spend a little extra money on bird houses, it will be well worth every penny and they’ll look great.