Mourning Warbler

The Mourning Warbler is a common breeder residing in disturbed habitats within the boreal forests of North America. These birds greatly benefit from human interference or natural disturbances in forest areas. Forest clearings are ideal nesting spots for these birds. There is not enough information about the migration and wintering habitats of Mourning Warblers as these birds are quite secretive in nature. Although there is a scarcity of research about them, new research is being conducted.

About Mourning Warblers

Mourning Warblers present in the southeastern portion of their breeding range winter in Venezuela. New information has also been obtained about the reasons for mortality when these birds are migrating. Dangerous weather and collisions are two of the major causes of the mortality of these birds.

For a long period of time Mourning Warblers were incorrectly considered as 1 of the 4 species from the genus Oporornis, but recently researchers have realized that they belong to the genus Geothlypis. Throughout their range, Mourning Warblers come into contact with all other species of birds from their genus.

In appearance, and in behavior Mourning Warblers are very similar to their western relatives, MacGillivray’s Warblers. Ornithologists gave been intrigued by the species status of these birds for a number of years. They were considered subspecies by some, but there is enough evidence to classify them as two different species.

There are distinct differences between the skeletal dimension, songs, and patterns of geographic variations in their songs. On top of this, these birds are also quite intolerant of each other.

Some confusion had arisen in the past, possibly due to the convergence of the songs of these birds in certain regions. The reason for this was probably the characteristic of the males to learn and use attributes of songs of different species into their song.

Mourning Warblers quickly colonize clearings 1-2 years after their harvest. Human exploitation of natural forests in the form of oil exploration, mining, burning, and logging is very beneficial to Mourning Warblers. 7-10 years after colonizing a forest clearing, the numbers of Mourning Warblers begin to steadily decline.

● Mourning Warblers Photos, Color Pattern, Song
● Mourning Warblers Size, Eating behavior, Habitat
● Mourning Warblers Range and Migration, Nesting

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Mourning Warbler Color Pattern

Mourning Warblers have a gray chest, neck, and head. Their back and wings are olive-green and their underparts are yellow. These birds undergo molting during spring and fall.

During the breeding season, adult males have a gray head and neck which becomes grayish-black as it extends down to their pileum, chin, nape, and throat. Their lower bodies are yellow, and their chest is black. The bright yellow of their underparts turns to olive green as it extends to the flanks and sides. The rest of the upper parts are mostly olive-green with white edges.

Females during breeding season look similar to the males, but they lack the black coloration on their chest, throat, and chin. Instead, these parts are brownish-white or light gray in color. The colors of their nape and pileum are also duller. The underparts of females are not as bright as the underparts of males.

During winters, male Mourning Warblers undergo slight changes in their plumage. They gain a white-eye ring that is broken. Gray tips can be observed on the feathers of their chest and throat.

Juveniles look quite different from males. The upper portion of their body is olive-brown, and their breast and sides are yellowish-brown. Their belly is much duller than the bright yellow belly of the adult.

Description and Identification

Mourning Warblers are beautiful birds that have a pretty unique coloration. The only other two species of birds they can be confused with are Connecticut Warblers and MacGillivray’s Warblers. Adult males very closely resemble MacGillivray’s Warblers. The eye-arcs of Mourning Warblers are thinner and longer than those of MacGillivray’s Warblers. Another distinguishing factor is that Mourning Warblers have wings that are relatively larger than their tail length. Songs and calls are a good way of distinguishing between these two species.

Mourning Warbler Song

Only male Mourning Warblers sing the primary song of these birds. It is assumed that the purpose of the song is to establish territories and advertise their sexual status. Males might sing this song while sitting on the ground, or while being perched atop a branch up to 65 feet up in the air.

The primary song contains the rhythm and complexity lacked by the individual call notes vocalized by Mourning Warblers. This song consists of a series of syllables that are commonly changing, “chorry chorry chorry churry churry churry”.

On average their song contains 5.68 syllables. This song might vary due to the difference in regional dialects. Mourning Warblers broadly inhabiting the same range will have a single song type. This song type can be the same for hundreds of miles. The breeding song of these birds is most commonly heard during the breeding season, and less frequently while they are migrating.

The song of these birds is also often confused with the songs of MacGillivray’s Warblers. One needs to be well informed to know the differences between their songs. Sometimes, even enough information about their songs might not help because some of these birds have a tendency to learn the characteristics of each other’s songs.

Flight songs are also mostly sung by males. These songs are primarily sung in their breeding range when these birds are in the latter stages of nesting. Before beginning the flight song, the male vocalizes some chip notes and ascends into the sky. He begins singing this song and descends extremely rapidly. Sometimes chip notes are also included during the descent. Males and females also use harsh chip notes in alarm, or while defending their territories.

Mourning Warbler Size

Mourning Warblers are average-sized wood Warblers. Compared to other songbirds, they are small in size. Their length ranges from 3.9-5.9 inches, and their wingspan is approximately 7.1 inches. They weigh between 0.4-0.5 ounces.

Peculiarly, the size of Mourning Warblers increases from north to south. This is strange because most birds or animals are larger in colder portions of their range.

Mourning Warbler Behavior

Mourning Warblers are ground foragers which usually stay close to the ground. As these birds are mostly roaming around in deep thickets and dense vegetation, they are generally hard to sight.

After arriving in a suitable breeding territory, males begin singing and using calls to establish and protect their territory. If this isn’t enough to drive away their opponents, they attempt to chase them away. These birds are swift and agile in flight.

Mourning Warblers can be monogamous or polygynous in nature. Females preen during incubation, and if it’s hot, they may pant.

Female Mourning Warblers are very rarely a part of territorial encounters. Males are more proactive when it comes to defending their territories. Other than the songs and call notes mentioned before, males might use tail-flipping and wing-flipping displays to intimidate their rivals. Some non-territorial encounters have been noticed between male Mourning Warblers and other species of birds.

Mourning Warblers are mostly reclusive on the wintering grounds. These birds are most commonly predated at their nests. The most common predators of their eggs are eastern chipmunks, ground squirrels, raccoons, least chipmunks, eastern chipmunks.

When a predator approaches the nest, the female usually remains tightly anchored to the nest. In some cases, fledglings and parents use broken-wing displays to indicate the arrival of a predator. Females might try to distract the predator by rapidly scurrying to the ground. Nervous Mourning Warblers scold intruders that enter the boundaries of their nesting territories while rapidly flipping their tails.

Mourning Warbler Diet

Insects make up the largest portion of their diet. When these birds are on the breeding grounds, they are mostly insectivorous. Other food items consumed by them are spiders, beetles, and larvae.

In winter, or during fall migration, these birds add plant matter into their diet. Even during this period, Mourning Warblers mostly consume insects. Mourning Warblers mostly forage during the day in layers of herbs and shrubs. Big
tooth aspens, sugar maples, red maples, paper birches, quaking aspens are some examples of these.

There isn’t a lot of information about the diet of these birds because they are quite secretive in nature. From the limited information available, it can be observed that the dominant foods can differ according to the geographical range of these birds.

Mourning Warbler Habitat

Mourning Warblers mostly inhabit clearings in boreal forests. When these areas regrow, they might become uninhabitable for these birds. Perhaps, this is the reason why populations of Mourning Warblers don’t inhabit the same regions for more than 10 years.

Human activities, fires, storms, and insect outbreaks can help provide these birds with suitable habitats. The dominant trees that are present in the main habitats are in the northern portion of their range such as hemlocks, spruces, pines, balsam firs, birches, and aspens.

Some Mourning Warblers also inhabit areas in higher elevations in the Appalachian Mountains. Beeches, oaks, maples, and ashes are more commonly found in trees in this area. If trees are destroyed as a result of fire or other unfortunate events, saplings and shrubs immediately begin growing in this area.

In these disturbed areas blueberries, hollies, hazels, chokecherries, raspberries, wild roses, alders, wild cherries, and cranberries grow. While migrating, Mourning Warblers choose similar habitats if they are available.

Once the former breeding habitat of Mourning Warblers is unusable due to trees dominating shrubs, these birds need to find other habitats that are suitable. So, sometimes while returning from their wintering habitats, they might have to reside in marginal habitats before finding another permanent breeding habitat.

Range and Migration

During the breeding season, these birds are found in a belt that stretches east from North Alaska to all the Canadian provinces. The habitats of these birds are well protected in this range.

In winter, these birds can be sighted in the mangroves of South and Central America. These birds are nocturnal migrants that cover large distances. While migrating, these birds need to make stopovers to feed themselves. These stopovers might last for 4-7 days.

Mourning Warbler Lifecycle

They raise only one brood annually. Mourning Warblers begin courtship once both males and females have reached the breeding grounds. The breeding period for these birds is generally between late May to early June.

Females lay between 2-5 short and ovate eggs. These eggs are creamy white, have specks of black that are mostly near the top part of the eggs. They usually lay eggs 3 hours before sunrise. The incubation period takes up to 12 days in total.

Nesting

Mourning Warbler nests are placed on the ground, or in very close vicinity to the ground. Their nests aren’t usually higher than 3 feet from the ground. These nests are set in dense shrubbery, or among other vegetation.

It can be assumed that females do most of the nest construction. Materials such as leaves, bark, weeds, sedges, and grasses are used to make a large nest. It is then lined with rootlets, hair, and fine grasses. The nest is 3.4 inches tall and has a diameter of 6.3 inches. It is usually about 1.9 inches deep.

Anatomy of a Mourning Warbler

Mourning Warblers are slightly stocky birds with thin and pointy bills. Their legs and tarsus are average-sized.

Final Thoughts

Mourning Warblers are gorgeous birds that are not easy to spot. Their name is particularly interesting. They have earned this name due to the black throat patch of the males which makes it look like these birds are always dressed in mourning. Not many other birds have such extensively colored throats. Sighting a Mourning Warbler should be an especially rewarding experience for an enthusiastic birdwatcher.

Ornithology

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Bird Watching Binoculars for IdentifyingMourning Warblers

The most common types of bird watching binoculars for viewing Mourning 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.

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Stickers are a great way for you to display your love for bird watching and the Mourning 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 ForMourning Warblers

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Bird HousesForMourning Warblers

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