Local nesting Song Sparrow, Melospiza melodia morphna - Photo by Bob Boekelheide

The Ever-Present Song Sparrow

by Bob Boekelheide

One hundred years ago, there was no such thing as “citizen science.” Despite that, from 1929 to 1936 a brilliant woman named Margaret Morse Nice carried out one of the most detailed and insightful studies into the breeding biology and behavior of birds, by studying Song Sparrows in her backyard, home, and nearby habitats. At a time when women were barely allowed in academia, she helped revolutionize American ornithology doing her own creative research with the birds she watched every day. Married to a biology professor at Ohio State University and raising a family at the same time, “Mrs. Nice” used her own funds to do research with known-individual banded Song Sparrows that she followed over several nesting seasons. She then wrote about them in her seminal work, “Studies in the Life History of the Song Sparrow,” published over two volumes in 1937 and 1943. Before Margaret Morse Nice, American ornithology was mostly shooting specimens and collecting eggs for museum collections, keeping bird records, and “pretty pictures,” as described by Ernst Mayr, the famous biologist. Margaret Morse Nice’s work with Song Sparrows is justifiably considered a classic of the ornithological literature.

Margaret Morse Nice is one of my heroes, and the Song Sparrow is one of my favorite birds. Here on the north Olympic Peninsula, finding a Song Sparrow is easy, as they are common birds in backyards and brushy forests. They are particularly abundant in riparian forests along rivers and streams. They seem to reach their peak abundance along the lower river drainages, such as the lower Dungeness River, where it’s not hard to see and particularly hear large numbers in a short distance. They are so ubiquitous that they are taken for granted.

One particularly noteworthy thing about Song Sparrows is that they are the only species observed on all 1,220 Wednesday morning bird walks in Railroad Bridge Park, since the walks began in September 2001. Every other species, including resident birds like towhees, Steller’s Jays, and chickadees, misses a week every so often, but we always find Song Sparrows. We find them when there is a foot of snow on the ground and we find them during summer heat waves. Why are they so reliable?

For one thing, our local nesting Song Sparrows do not migrate. It’s tempting to say they stay on their nesting territories all year, but we have no direct proof of that at Railroad Bridge Park, because we do not have marked birds. Other studies with non-migratory Song Sparrows in the Pacific Northwest show that established breeders remain near their territories year-round. Studies also show that Song Sparrows with the strongest territorial response have the highest reproductive success, so there’s an advantage to knowing and defending their territories. A look at their annual cycle in Railroad Bridge Park shows that their numbers are very consistent all year, with the exception of a small but noticeable dip in August (Figure 1).

Figure 1 – Average monthly counts of Song Sparrows on Wed am bird walks

What happens in August? August is the end of the nesting season, when adults are quiet, fledglings have dispersed, and territorial boundaries break down a little. It’s also the time of year when adults do their annual molt, so they become more secretive, make fewer sounds, and try not to be discovered by predators. Many other species, such as warblers, completely leave the lower Dungeness riparian forest before molting, but Song Sparrows stick around, even though they do become harder to find. Then, in September and October, a period called the “Fall Settlement,” they begin to intensely defend their territories once again.

How is the local Song Sparrow population doing? Based on data from Wednesday morning birds walks at Railroad Bridge Park, their population seems quite stable (Figure 2). Over the last 23 years, the number of Song Sparrows recorded on these walks was fairly consistent, averaging about 15 Song Sparrows per two-hour walk (Figure 2). A regression line through these 23-years of data points shows essentially a horizontal line with maybe a very slight increase over time.

Yearly changes in the number of Song Sparrows counted on Wed am bird walks

A closer look at Figure 2, however, shows that their abundance actually waxes and wanes a little around the average, in curiously distinct periods. Every year between 2005 and 2011 their numbers were below average, then every year between 2014 and 2018 their numbers scored above average. Since 2021 they’ve passed through another below-average period. It’s tempting to suggest environmental factors might cause the Song Sparrow population to rise and fall over a period of years, such as food availability, predation pressure, or winter survival, but in reality, we don’t know.

How about Song Sparrows numbers during the Sequim-Dungeness Christmas Bird Count (Figure 3)? Over the last 30 years, SDCBC Song Sparrow data are very zig-zaggy, but still show a fairly stable average of about 3.5 sparrows observed per party-hour. This average is higher than nearly all other CBCs in the Pacific Northwest, suggesting the area around Sequim provides very good habitat for Song Sparrows. Their numbers vary a lot between years, though, sometimes rising or falling two- or three-times between adjacent years. This might have to do with weather or viewing conditions, but maybe there’s more going on behind the scenes.

Number of Song Sparrows counted per Party-Hour on SDCBC

There are two obvious peaks on the SDCBC graph, in 2008 and 2015 (Figure 3). 2008 was one of the most difficult years for the SDCBC, with below freezing temperatures and strong winds for much of the day. 2015 was beautiful, with partly cloudy skies and light winds, although it followed three weeks of strong Pacific storms. The lowest year on the graph, 2007, had relatively warm temperatures and passing showers. It suggests that viewing conditions might not be the whole story.

My account about the 2015 SDCBC, written for the January 2016 Harlequin Happenings, provides an interesting description of Song Sparrows that year:

“Sparrows as a group were extraordinarily abundant this year, particularly Song Sparrows. Several parties commented about the extraordinary number of Song Sparrows. In some brushy areas there were sizable roving flocks of just Song Sparrows, very different from how we normally encounter this species. Nearly all looked like our typical Pacific NW coastal Song Sparrows.”

It makes you wonder: Could there be winters when local Song Sparrows leave their territories and form flocks, similar to what migratory sparrows like Golden-crowned Sparrows do every year? This seems most likely if food availability declines and individuals become more efficient finding food by forming a group. Or could it be the result of other birds moving here from somewhere else, like if birds nesting in the Olympic foothills get pushed downslope by snowfall? Conversely, in abundant years like 2008 and 2015, maybe nesting success and winter survival are so high that large numbers of young, unattached birds are here for the CBC? Unfortunately, we’ll never know.

Song Sparrows are very widespread in North America, from the Aleutian Islands to Newfoundland, and from central Canada to central Mexico. Depending on the source, there are at least 24 subspecies of Song Sparrows in North America, maybe as many as 38. From big dark Song Sparrows in Alaska to small grayish Song Sparrows in Mexican deserts, it is one of the most variable bird species in the world. Our local subspecies, Melospiza melodia morphna, is one of the darker ones with rich reddish-brown plumage, found along the Pacific Coast from central B.C. to northern Oregon. Birders who come here from east of the Rocky Mountains sometimes don’t even recognize our local Song Sparrows because they are so dark.

The local nesting Song Sparrow, *Melospiza melodia morphna* - Photo by Bob Boekelheide

Male and female Song Sparrows look alike, but they still have fairly rigid sex roles during nesting. They are typically monogamous, but might be polygynous if there is a surplus of breeding females. The male takes more of the role defending their nesting territory, as well as helping the female select the nest site, at least for the first brood attempt. Like most sparrows, the female builds the nest, usually in a clump of grass on the ground, and does all the incubation, which typically takes 12 to 14 days. Clutch sizes in many studies usually range from 3 to 5 eggs, averaging about 4 eggs per clutch. Male and female share equally in feeding young chicks, but when the chicks begin to fledge the male continues feeding the chicks out of the nest while the female builds a new nest and begins laying the next clutch.

Like most songbirds, Song Sparrow chicks grow very fast. At hatching, the altricial chicks weigh only about 2 g, or less than one penny. When they fledge, at only 10 or 11 days old, they weigh about 19 g on average and are mostly feathered. This means they have grown about ten times larger in only 10 days, supported by hundreds of caterpillars, worms, and other invertebrates. Song Sparrows clearly want their chicks out of the nest as quickly as possible, to avoid predation and other calamities. The chicks continue growing after leaving the nest, reaching full adult mass of about 25 g within the first two months.

Song Sparrows are renowned for producing multiple clutches if conditions permit, often two to three clutches in a nesting season. Including lost clutches, some females have been recorded laying up to seven clutches in a season. Older females usually begin laying earlier, whereas two to three-year-old females have the most clutch attempts. They begin nesting when they’re only one year old.

Around here, the first Song Sparrow nests with eggs are usually reported in early to mid-March. In a perfect world, a pair starting their first clutch in mid-March could fledge four clutches by mid-July, when most birds finish nesting around here. It’s likely that most only produce two or three clutches. We occasionally see Song Sparrow fledglings in Railroad Bridge Park in August, possibly the result of late replacement clutches or final clutch attempts.

Singing Song Sparrow in Nova Scotia, the *Melospiza melodia melodia* subspecies - Photo by Bob Boekelheide

Nest predation, cowbird parasitism, desertion, and misfortune combine to limit the number of fledglings each year. Despite all those clutch attempts, and all those eggs laid, the average Song Sparrow pair is lucky to fledge four or five chicks in an entire nesting season. Of those, only one bird on average eventually returns to become a breeding adult one year later. For most pairs, the number of returning offspring is likely zero.

The song of Song Sparrows is one of the most distinctive sounds of our local woods. The song typically starts out with repeated clear notes on the same pitch, then a rising note followed by a variety of buzzes and quick warbles. We hear them singing year-round, but the rate and persistence of the songs definitely increases during the nesting season. Their equally distinctive call notes of repeated chirps are also easy to recognize. Both the song and call of Song Sparrows are must-learn sounds for beginning birders.

A Song Sparrow’s life is quick and short. Studies show that only about 39 to 64 percent of adult sparrows survive each year, so for every 100 Song Sparrows that reach adulthood less then 10 will be alive within three to five years. The oldest banded Song Sparrows in Margaret Morse Nice’s studies reached only eight and nine years old.

The Song Sparrow nesting season starts right now. You must get outside to hear their magical songs and witness their rush to produce chicks. Take time to sit down and watch them closely as they carry out their lives, maybe even observe a nest and the adults feeding their chicks. It will be worth your time.

Local Sequim Song Sparrow - Photo by Dow Lambert

Many of the interesting facts about Song Sparrows contained in this story came from Birds of the World, an on-line resource available through Cornell Lab of Ornithology. I highly recommend that all bird aficionados subscribe to Birds of the World, both for the information and to support the Lab of Ornithology.