What is a Brewer's Sparrow? That question was asked many times by NB birders after its presence was announced from Quispamsis about 10 days ago. I can guarantee everyone had to look it up in their favourite bird guides. The Brewer's Sparrow had never been seen in New Brunswick before. No wonder birders were shocked and excited. It became a 'lifer' for almost everyone who saw it.
A small, streaked, faded-looking sparrow appeared at the feeders of a new NB birder in January, 2023. Being a new birder, she called for help. It was quickly identified as a Clay-colored Sparrow until our more expert birders started scrutinizing its appearance. After just 2 or 3 days, and checking with other experts, it was announced that this was indeed a Brewer's Sparrow. Brewer's, Clay-colored and to some extent, Field Sparrows are very similar Spizella sparrows. One needs to look very closely to differentiate a Brewer's from a Clay-colored especially when the bird is out of 'context', i.e., out of its normal range and habitat.
The Brewer's Sparrow (Spizella breweri) is a small-to-medium sized sparrow (13-15 cm long). It is the same size as the Clay-colored but smaller than the Song and Field Sparrows. It is a member of the Passerellidae family. It was discovered in 1850 by John Cassin who named it in honour of the Boston physician and naturalist, Thomas Mayo Brewer. Its original range was thought to be western North America in sagebrush country but in 1925 a montane race was discovered in the Canadian Rocky Mountains. That led to the two distinct races of this species, the sagebrush-dwelling race (breweri) and the montane race (taverneri). This has led to two nominate groups of this species, the Southern race and the Northern or Timberline race. These two groups are sometimes listed as subspecies; Spizella breweri breweri for the sagebrush group and Spizella breweri taverneri as the montane group. Time will tell what the taxonomists will do (if anything) with these two groups.
The Brewer's Sparrow is the drabbest of North American sparrows. I will describe the taverneri race as having broader black streaks on its back, a darker gray breast with more contrast between gray breast and white belly, a slightly longer tail, and a shorter, stubbier bill. For the rest of this description, I will be discussing the breweri race which our visitor represents. The Brewer's Sparrow shows a faded brownish gray overall appearance. It looks small with a long tail and very striped. Its breast is washed all over with a light gray. It has a brown cheek patch which is not heavily outlined, a white line under the cheek patch and a dark malar stripe. The eye has a weak complete white eyering. The crown is brown streaked with a weak central line. The nape is gray streaked. The back is streaked gray brown and there are two weak wing bars. The legs and feet are pale pink. The bill is short and pink with a dark tip.
This species is so similar to the Clay-colored Sparrow that it is no wonder it was mistaken at first. The Clay-colored Sparrow has a white central crown stripe, a gray nape, and distinct dark borders to its cheek patches as well as dark whiskers.
The ranges of the two races of Brewer's Sparrow are different. The winter range of both races overlap in southern Texas, Arizona, New Mexico, California and northern Mexico. The summer ranges are different. The breweri race breeds over most of the western part of the US east of the mountains in sagebrush and scrub habitats. The taverneri race breeds in summers in the north in brushy habitat at treeline in mountains in Canada (Yukon and NW British Columbia) and eastern Alaska. The Brewer's Sparrow does wander sometimes out of its range. According to 'Sparrows & Finches of the Great Lakes Region and Eastern North America', it has been recorded in Minnesota, Illinois and Michigan. It has been accidental to Massachusetts (Bent).
The photo below shows the crown stripe and the weak eyering of the Brewer's Sparrow.
Brewer's Sparrows eat mainly insects and have been shown to be useful controllers of crop pests. Studies have shown that they eat plenty of plant lice, caterpillars, spiders, beetles, ants, and wasps. Their diet includes mainly weed seeds in winter.
Brewer's Sparrows act very secretive around their nests. They will stay on the nest until the last second and then flair up and quickly disappear in the vegetation, often running along the ground. They build their nest very close to the ground (less than 1 metre) but not usually on the ground. The nest is made of dry grass stems and roots and lined with small rootlets, fine grasses and animal hair. It is supported on the loose vegetation around it. The average inside diameter of the nest is 50 mm with a depth of 30 mm. The female lays 3 to 5 bluish glaucous eggs which are speckled and splotched on the large end with dark browns or gray. The female incubates the eggs 11 to 13 days. The young fledge in 8 or 9 days and the young depend on the adults for food and protection for several days. There are often 2 broods per season.
The Brewer's Sparrow is usually quite silent on its wintering grounds except for a tsip call note. On the breeding grounds it is very vocal uttering long series of trills and buzzes. Some notes are high and melodical while others are long and buzzy like its cousin, the Clay-colored Sparrow. They sometimes engage in flock trilling. On listening to its song on my electronic device, I wish we had them here in summer so we could listen to them!
The drab coloration of this species of sparrow and its shy manner account for its not getting much attention. I wonder how well we would know it even if we lived in the west or southwest. However, in migration it does migrate in large flocks. In times past it was regularly seen in flocks of 50 or 100 individuals. It has been seen wintering in Texas accompanied by White-crowned Sparrows, Black-throated Sparrows, Vesper and Savannah Sparrows. At other times these large flocks have been observed to spend a lot of time bathing. Quoting from Bent, p. 1213, these sparrows 'seem to be spending most of the forenoon hours every day in the mesquites along the overflow ditches, thoroughly wetting the plumage in the shallow streamlets and then perching in the green canopied branch-work above to preen at great length. Sometimes such bathing parties would be perfectly quiet save for the sound of fluttering wings. Then again certain individuals would break into prolonged singing...'
The Brewer's Sparrow has declined in some parts of its range due to habitat loss. It is also vulnerable to cowbird predation.
As of today, February 6, our Brewer's Sparrow visitor is doing well, having survived -35ºC temperatures with high winds two days ago.
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