July 2008

For the Birds: Upland Sandpiper and Eastern Meadowlark

This column is the last of three on grassland birds in Maine. In today’s column, we will take a look at Upland Sandpipers and Eastern Meadowlarks, both of which require grasslands for nesting.

Like the American Woodcock, the Upland Sandpiper is a shorebird that has adopted a purely terrestrial lifestyle. Don’t look for Upland Sandpipers foraging on intertidal mudflats with Sanderlings, Semipalmated Sandpipers, Greater Yellowlegs and other members of the sandpiper family. Rather, Upland Sandpipers prefer rather dry habitats with a dearth of trees. Grasslands are their natural breeding areas although lowbush blueberry barrens can serve as nesting sites as well. Grassy areas at airports also provide nesting habitat.

An Upland Sandpiper is a large sandpiper with a long bill. Its neck is markedly thin and its head seems to be too small for its body. The plumage consists of black, brown and tan feathers that make the bird cryptic in the tall-grass habitats it prefers.

The call of the male is a sound that will stick with you. Many people will not recognize the eerie whistle of the male as coming from a bird. Efforts to represent the whistle in human syllables include “whooooleeeeee, wheeelooooo-ooooo”. To some, the call sounds like a “wolf whistle”.

The greatest abundance of nestling Upland Sandpipers is found in the Dakotas, Nebraska and Kansas. Populations can be found westward to the Rocky Mountains and eastward, occurring patchily in New England and some of the Mid-Atlantic States. These birds winter on the pampas and other grassland habitats in South America.

In most nesting areas, Upland Sandpipers have suffered at the hands of humans. First, early European settlers killed them for food as well as collected their eggs. Later, market hunters took even more. But, the most devastating effect caused by humans was the plowing of the tall-grass prairies to plant crops. Breeding Bird Survey data show that numbers of Upland Sandpipers continue to decline over most of its breeding range, North Dakota being the only state where Uppies are holding their own.

The last species we will consider is the Eastern Meadowlark, a species associated with farmlands. Before European settlement, Eastern Meadowlarks were dependent on native grasslands for habitat. Unlike the Upland Sandpiper, meadowlarks have proven to be adaptable, readily nesting in pastures.

Eastern Meadowlarks are found broadly throughout eastern North America. Their northern limit occurs from Minnesota eastward through Ontario and into the Maritime Provinces. Meadowlarks can be found throughout the states south of this line. They even extend discontinuously throughout Central America.

In most of their range, Eastern Meadowlarks are non-migratory. The meadowlarks in New England and other northern states withdraw in late fall to warmer portions of the species’ range. Meadowlarks usually return to Maine in late March to April.

Eastern Meadowlarks are distinctive birds. They have a bright yellow breast with a V-shaped black patch on the upper breast. The description of a yellow V-necked sweater is certainly apt. On the side of the face below the eye, a whitish stripe, the malar stripe, is distinctive. The Western Meadowlark, which overlaps with Eastern Meadowlark in some parts of their ranges, is almost a dead ringer for the Eastern. However, the malar stripe of the Western Meadowlark is mostly yellow.

The upper side of the Eastern Meadowlark is mottled gray, black and brown, allowing the bird to blend in well with its grassland habitat. The outer tail feathers are white, making these feathers a good field mark for a flying meadowlark.

Like other grassland birds, Eastern Meadowlarks will be detected first by their voice. The song of this species is a series of clear, slurred whistles. Some ornithologists have tried to capture the cadence of the song as “song of the earth”.

Despite their use of agricultural fields for nesting, Eastern Meadowlarks are showing alarming declines throughout much of their range. Part of this stems from a reversion of old farms back to forests. Human encroachment to breeding areas also plays a role in the decline of these birds.

As an overview, we have seen that grassland birds are declining through much of their range. While we should be concerned, there is some reason for hope. In recent years, the science of landscape ecology has matured. Landscape ecologists study how variation in habitat at large scales affects the distribution of organisms. Landscape ecologists understand the importance of interconnected reserves, of conserving habitat near already protected habitat and of evaluating the conservation potential of available tracts of land. Active management of grasslands will need to be continued to prevent forests from taking over.

[Published on July 26, 2008]

For the Birds: Grassland Sparrows

This column is the second of three on grassland birds in Maine. In today’s column, we will take a look at three sparrows (Savannah, Vesper and Grasshopper) that require grasslands for nesting. In the next column, I’ll discuss the Upland Sandpiper and Eastern Meadowlark and end with some of the conservation challenges of these habitats.

The three sparrows in today’s column are more often heard then seen so learning to recognize them by song is the best way to find these somewhat shy birds.

The Savannah Sparrow is the most common of the three. Its breeding range covers most of the northern two-thirds of North America, extending into the arctic tundra. It is a migratory breeder in most parts of its range. During the winter, Savannah Sparrows withdraw to the southern tier of the United States and into much of Central America.

The species was named the Savannah Sparrow by Alexander Wilson, a contemporary of Audubon. Wilson collected a specimen in Savannah, Georgia and honored this charming southern city by naming a sparrow after it.

The song of the Savannah Sparrow has a distinctive buzzy quality. The song typically begins with a few short notes, then a buzzy trill and a final note or two of lower pitch. The song carries well, particularly the trill and final notes. A singing male can usually be seen singing from a grass stem or short shrub.

Visual identification of this species is straightforward. A Savannah Sparrow has a streaked breast like a Song Sparrow. The Savannah Sparrow’s streaks are less bold than those of a Song Sparrow and typically do not coalesce into a dot as in most Song Sparrows. The best field mark is the yellow line above the eye that is especially conspicuous in front of the eye.

During the breeding season, Savannah Sparrows mostly feed on insects. Outside of the breeding season, they switch to a diet of seeds they are able to find on the ground.

Like the Bobolinks discussed in the last column, a male Savannah Sparrow may have more than one female partner. The insect abundance in a grassland or meadow is abundant enough to allow a male to help feed two clutches of nestlings.

Vesper Sparrows have a broad distribution in North America, not quite rivaling the broad range of the Savannah Sparrow. Vesper Sparrows nest across the middle third of our continent and winter in the southern tier of states south into Mexico.

The song of the Vesper Sparrow has a distinctive beginning of two to four long clear notes followed by a downslur and then a series of flute-like trills, first rising in pitch and then falling. Vesper Sparrows sing throughout the day but continue to sing in the evening after most birds have ceased to sing. Those evening songs are the reason the bird is called the Vesper Sparrow.

The dependence of Vesper Sparrows on grassland habitats is doubly reflected in its scientific name, Pooecetes gramineus. Pooecetes means “grass dweller” and gramineus means “fond of grass”. In Maine, grasslands and blueberry barrens are the best places to find this sparrow.

The Vesper Sparrow is a rather large sparrow. These sparrows have a streaked breast and distinctive white outer tail feathers. Some of the wing coverts are rufous in color, giving rise to the older common name of Bay-winged Bunting.

We believe that Vesper Sparrows were rare in the east before European settlement. The clearing of forest for pastures allowed Vesper Sparrows to increase in eastern North America. The species is declining in the east now because of the reversion of so many farms to forest.

Grasshopper Sparrows are the least common of the three grassland sparrows. They breed broadly throughout the eastern two-thirds of the United States but are usually found in low numbers. Their populations have declined in many portions of their range because of the destruction of grasslands and prairies these birds require for nesting.

The common name of this species stems from its insect-like songs. Male Grasshopper Sparrows are unusual among sparrows in that they sing two distinctly different songs. Their Primary Song consists of one to three high-pitched notes followed by an insect-like trill. It can be described as tsick, tsick, tsurrrrrrr. This song is used to repel other males from its territory. A second song, the Sustained Song, consists of a more musical series of short buzzy notes given either from a perch or in flight to attract a female.

The pronounced flattened head, the large bill and upper orange breast make the Grasshopper Sparrow easy to identify once sighted.

[First published on June 28, 2008]

For the Birds: Bobolinks

A suite of birds collectively called the grassland birds nest in New England. This group of birds includes the Upland Sandpiper, Savannah Sparrow, Vesper Sparrow, Grasshopper Sparrow, Eastern Meadowlark and Bobolink. Wildlife biologists are concerned about this group of birds because their populations are declining in New England, including our Maine populations.

Grassland habitats are rather limited in New England and have invited development into farms or towns because tree cutting is not required adapt the line for human uses. Fortunately, grassland birds are adaptable and often nest in hayfields or blueberry barrens. However, many hayfields in Maine are no longer maintained and are reverting to forest. We have much more forested land now in Maine than we did in 1900. Thus, the decline of their required habitat helps explain the decline of these grassland birds.

Today’s column is the first of three on the grassland birds of Maine. We’ll start with one of the most beloved birds of Maine, the Bobolink.

With their beautiful plumage (mostly black with white on the back and wings, and a yellow patch on the back of the head and nape), male Bobolinks are strikingly handsome birds. Some waggish authors have described them as having tuxedos on backwards.

The female is nondescript, brown on the uppersides with streaking and yellowish underneath. This plumage makes them nearly impossible to see in a grassy field.

The male’s song is equally distinctive: a long, bubbly series of metallic notes. A student of mine, an obvious Star Wars fan, said the song sounds like the robot R2D2! The Bobolink song has inspired poetry. The American poet, William Cullen Bryant, based his poem “Robert of Lincoln” on the song of the Bobolink.

The breeding range of Bobolinks extends across the northern tier of the United States from Maine to Washington as well as the southern portion of the Canadian provinces.

Bobolinks winter south of the equator in South America, The wintering habitat is the grasslands known as the pampas in southwestern Brazil and Argentina. Each year, a Bobolink makes a round-trip of 12,000 miles. We know of one banded female that lived to be nine years old. Presuming she made the trip every year, she traveled the equivalent of circling the globe at the equator four times.

Orientation and navigation have been fairly well studied for Bobolinks. Researchers have found that the primary cue for navigation in Bobolinks is the earth’s magnetic field.

Bobolinks arrive in central Maine by the second week of May. Males are conspicuous as they stake out territories and await the arrival of the females. When a female passes overhead, a male will perform an aerial song display to attract the female’s attention. If the female lands, the male will go through a series of courtship behaviors to court the female. These behaviors include a low circle flight on stiffly held wings and an abrupt drop to a low perch or the ground. When the male drops, he holds his wings in a shallow V (like the gliding silhouette of a Turkey Vulture) and gives a few buzzy notes, dangling his legs on the descent. When he touches the ground, he may hold his wings in the shallow V for several seconds.

A female is slow to choose a mate. A male may have to perform this elaborate courtship sequence five times a minute for a half-hour or more. A pair bond is formed when the female leads the male on a long chase, flying for up to six minutes.

Bobolinks are examples of polygynous birds; a male may have more than one female on his territory. The frequency of polygyny seems to be related to habitat quality. In high quality habitats where food is easier to find, a male frequently has two or more mates. In lower quality habitats, single females are typically found with the males. In Wisconsin, over half a population of males had at least two mates and one male had four mates. On the other hand in New York, fewer than 15% of the males had more than one mate.

Nests are always made on the ground in dense vegetation. The nest is usually located at the base of herbaceous, non-grassy vegetation like goldenrods or clover. The female chooses the nest location and builds the nest in one or two days.

A female typically lays five eggs although as many as seven can be laid by some females. Both the female and the male feed the young. Even a male with multiple mates participates in feeding although most assistance may be given to his primary mate.

[First published on June 14, 2008]

For the Birds: Red-eyed and Philadelphia Vireos

Red-eyed Vireos have returned from their South American wintering grounds. One of the most common songbirds in North America, the Red-eyed Vireo’s song is a distinctive but somewhat plain series of two- and three-note phrases. Some authors render the song in human terms as “here-I-am, where-are-you, over-here, in-the-tree” that will resonate with anyone who has heard a Red-eyed Vireo singing. Red-eyed Vireos are energetic songsters, singing throughout most of day with rates as high as 85 phrases/minute.

The Philadelphia Vireo occurs in northern New England and much of southern Canada. This vireo closely resembles the Red-eyed Vireo but has a less distinct line above the eye and has a yellow wash on the underparts. The Philadelphia Vireo is also smaller, averaging 12 grams in weight to the 17-gram weight of a typical Red-eyed Vireo. Both species can be found in the same deciduous woodlands.

Most nesting male songbirds defend their territories against other males of its species. If you play a recording of a Yellow Warbler in the territory of a Yellow Warbler, the male will quickly come toward the source of the sound and look to chase off the unwelcome intruder. However, playing a tape of the song of a Black-throated Blue Warbler or a Chestnut-sided Warbler will produce no reaction by the Yellow Warbler. In general, male songbirds defend their territories against members of their own species but not against members of other species.

The two vireo species above provide an exception to this rule. Red-eyed Vireos and Philadelphia Vireos defend their territories against their own species and against the other species. In other words, both vireos show interspecific (between-species) and intraspecific (within-species) territoriality.

The song of the Philadelphia Vireo is very similar to the singsong phrases of the Red-eyed Vireo song. Even highly experienced birders pass off singing Philadelphia Vireos as the more common Red-eyed Vireos. The reason for the similarity will soon be apparent.

In northern New England forests, insect prey may become quite hard to find during the breeding season. Because both vireos eat largely the same species of insects, there is an advantage for a territorial vireo to keep a member of its own species and members of the other vireo species away from its food sources.

In most cases, the vireos avoid direct confrontations over the boundaries of a territory. Instead, a territorial bird proclaims his ownership of a territory by singing from perches throughout his territory. Similarly adjacent territory owners sing throughout their territory. The neighboring birds recognize unseen but real boundaries, avoiding physical interactions.

In the case of actual fighting between the two vireo species, the smaller Philadelphia Vireo usually comes out on the short end. One observed fight involved three minutes of violent contact, wing beating and pecking, with the larger Red-eyed Vireo winning the battle.

The problem the Philadelphia Vireo has is how to maintain exclusive ownership of a territory, defending against a larger and stronger Red-eyed Vireos that may be trying to expand his territory to find scarce food. Philadelphia Vireos have solved the problem by becoming a social mimic. These birds mimic the song of the Red-eyed Vireo.

Play-back experiments have shown that Red-eyed Vireos cannot tell the difference between a Red-eyed Vireo song and a Philadelphia song. No wonder birders have trouble telling the two species apart by song! On the other hand, Philadelphia Vireos can distinguish between a Philadelphia Vireo song and a Red-eyed Vireo song.

Red-eyed Vireos assume that a neighboring Philadelphia Vireo is a Red-eyed Vireo and accept it grudgingly as a neighbor. If the Red-eyed Vireo only knew its neighbor was the meek Philadelphia Vireo, the latter could be evicted. Philadelphia Vireos mimic the song of the Red-eyed Vireo to level the playing field; it’s a case of brains over brawn.

Computer analysis of the songs of these two species reveals that Red-eyed Vireos never sing the same phrase twice in succession. Philadelphia Vireos, occurring in the absence of Red-eyed Vireos, may sing the same phrase twice before a new song is sung. However, in the presence of a Red-eyed Vireo, the Philadelphia Vireo never gives identical consecutive phrases, indicating that the species actively mimics the Red-eyed Vireos. Pretty clever birds!

[First published on May 31, 2008]