White-throated Sparrow (Zonotrichia albicollis) by Kim Ehn
By Kim Ehn
“From my upstairs window, I watch a bunch of dead leaves blow into the yard on a gust of wind. They settle, brown and rumpled, among the gathering autumn leaves beneath the bird feeders. Nothing much to attract attention.” – Diane Porter, (birdwatching.com)
Walking a trail edged with color-changing chokeberry shrubs, I was distracted by the soft sounds of rustling on the ground where a spring burn had been. Using a hop and a back step for its dance, the little sparrow with tan and brown head stripes was looking for grubs to refuel. I stopped.
I noticed the whitish throat, the yellow feathers above the lores, and two whitish wings bars. The White-throated Sparrow. Dark bill, not pink like the White-crowned Sparrow. Looking around the underbrush nearby, I spotted its avian counterpart: a white and black head-striped bird picking up a beetle.
Due to a chromosomal inversion, the genetic “polymorphic” difference between black and white-striped birds and tan and brown-striped birds is exhibited by a couple of behavioral differences. The tan-striped males are less aggressive and tan-striped females usually are reluctant to sing. This contrasts with the aggressive nature of the white-striped birds which also show reluctant parenting participation.
These behavior tactics provide alternative life strategies as the pairing of the White-throated sparrows is the attraction of the opposites. Laura Erickson (Cornell Laboratory of Ornithology) reported lab tests where birds were separated by a glass partition and females of both color forms preferred tan-striped males. Males of both color forms preferred the white-striped females. When white-striped females started to sing, white-striped males attacked them so all pairs are one of each color morph. White-striped males mate with tan-striped females and tan-striped males mate with white-striped females.
83% of the North American White-throated Sparrows nest in the Boreal Forests of Canada and Alaska. They often join and can be seen within a flock of Dark-eyed Juncos. Truly a North American bird with only wind-driven records in Northern Europe, many end up in southeastern states for the winter. In Indiana, they arrive earlier in September than other migrating sparrows, and leave by the end of May to journey north again. Widespread throughout the state, the locations are limited only by reports of birders’ observations.
On Cornell Laboratory’s online eBird site (eBird.org), you can track the southward migration by the recent sightings indicated by red location arrows. On May 3, 2019, Lindsay Grossman reported on eBird an “underestimation” of 400 White-throated Sparrows in the Indiana Dunes State Park that “carpeted the ground”.
I hope you have an opportunity to visit a nearby birding location and see a White-throated Sparrow this month.
