One of the regularly occurring systematic ID biases among birders in Oklahoma (and Texas) during spring is that between Song Sparrows and Lincoln’s Sparrows (and some other sparrow species). This bias has been so persistent as to create false patterns on these species’ migrations involving thousands of eBird observations in these states. So here are some ID tips.
Both Song Sparrows and Lincoln’s Sparrow occur in Oklahoma as migrants and winter residents, although Lincoln’s Sparrow is much less common during winter and is generally absent from northwestern Oklahoma and the Oklahoma Panhandle during winter. However, during spring migration periods in Oklahoma (excluding the Panhandle), Lincoln’s Sparrows are common to abundant from early April to mid-May, while most Song Sparrows have left by late March in southeastern Oklahoma to early April in north-central Oklahoma, only a very few persisting a few weeks longer.
The chart below shows data for a site in Norman, central Oklahoma during 2013 and 2014 where Song Sparrows were common during winter, and Lincoln’s Sparrows much less common. It shows how Song Sparrows decline in March (the top two lines at 15 Mar, and Lincoln’s Sparrows increase in early April to early May (the top two lines for 26 Apr. It also shows some annual variation where 2013 was cold later, delaying departure of Song Sparrows by about a week and arrival of Lincoln’s Sparrows by a week. Song Sparrows were clearly rare to absent after 12 Apr both years, and Lincoln’s Sparrows common by 12 Apr both years. However, many Lincoln’s Sparrows are identified as Song Sparrows even into May, an ID bias.
IDENTIFICATION TIPS. Find illustrations (photos) in field guide or the internet when reading this.
Both Song Sparrows and Lincoln’s Sparrows fall into a group of sparrows with streaked underparts. A common trait used by birders to identify Song Sparrows is the center-spot on chest formed where streaks seem to coalesce. While this character occurs on most Song Sparrows, it is not definitive; many Lincoln’s Sparrows (even some Savannah Sparrows) can show this trait. Thus, it should not be used as a distinctive (unique) Song Sparrow characteristic.
How would one distinguish? In general:
--Song Sparrows have a contrasting face pattern (stronger tone differences between dark and pale facial markings); strong brown streaks of chest occur on a whitish background. Song Sparrows also have a stongly streaked malar (area on sides of throat). See first photo below.
-- Lincoln’s Sparrows, there is low contrast in facial marks (more even-toned), and the streaks on chest are very thin and black and on a buffy background. See second photo below.
--Savannah Sparrows also have a contrasting face pattern (like in Song Sparrow), except that the superciliary (band over eye) is pale tan in Savannah (yellow in breeding individuals) as opposed to gray in Song Sparrows.
There are other features than can be helpful. Lincoln’s Sparrows are more petite compared to Song Sparrows. During April, a streaked sparrow in a treed suburban neighborhood in Oklahoma would almost certainly be a Lincoln’s Sparrow. Song Sparrows in migration are rare in suburban settings and, if they occur in a suburban backyard, would do so during their key migration period in March.
Because a different race of Song Sparrow occurs in the Oklahoma Panhandle, migration patterns are slightly different there; Song Sparrows arrive earlier (mid-late September), and depart later (most by late April, a few in early May). Lincoln’s Sparrows are present as migrants in the Oklahoma Panhandle from mid April to mid May.