― Fitz-James O'Brien
A few nights ago while most of us were sound to sleep, White-crowned Sparrows (Zonotrichia leucophrys) took to the skies by the tens of thousands beneath the Moon and stars. As many readers here know, birds use multiple sources of compass information for orientation during migration, including the geomagnetic field, skylight polarization, the Sun, as well as other celestial cues like the Moon and stars.
Zugunruhe is the physiological restlessness that prompts seasonal migratory departure from breeding grounds, but suitable weather is the primary cue for initiating nightly migration. This means that restlessness doesn't increase gradually during migration, but correlates with weather; birds on the go become more restless with good flying conditions.
Perhaps the mere appearance of the Moon prompts birds for a night of migration. What do they sense upon seeing the great orb of reflected light in the sky? After years of observing birds and bird behavior, I still find nocturnal bird migration to be one of the most amazing feats that any creature partakes in the natural realm.
In the morning the sparrows were just everywhere, feeding on seeds, collecting grit, preening, or just perched together having a look around the prairie-scape. After a six-hour flight, the birds are hungry. Replenishing fat stores takes priority and I find that the sparrows are more approachable for photography.
Naturally, the White-crowned Sparrow isn't the only Zono (short for "Zonotrichia Sparrow") at the prairie right now, there are plenty of White-throated Sparrows with them. I was hoping to encounter Zonotrichia querula (Harris's Sparrow) during this outing, but I've found them late October and even early November during past fall migrations.
What was that!?
Caught preening.
This was certainly the largest influx of White-crowned Sparrows at the conservancy I've observed so far this fall. Was it the peak that corresponds with Harris's Sparrow arrival? I'm not sure. Time and investigation will tell. Yesterday it was a too windy for birding, and it was raining this morning. Hopefully tomorrow I'll have an opportunity to take another Zono reading!
Immature White-crowned Sparrow
Blowing in the wind.
Pheasant Branch, Dane, Wisconsin, US
Oct 9, 2017 6:45 AM - 8:15 AM
43 species
Cackling Goose
Canada Goose
Wood Duck
Mallard
Ring-necked Pheasant
Red-tailed Hawk
Sandhill Crane
Killdeer
Mourning Dove
Red-bellied Woodpecker
Downy Woodpecker
Northern Flicker
Pileated Woodpecker
Eastern Phoebe
Blue Jay
American Crow
Horned Lark
Black-capped Chickadee
House Wren
Golden-crowned Kinglet
Eastern Bluebird
American Robin
Cedar Waxwing
Common Yellowthroat
Palm Warbler
Yellow-rumped Warbler
Chipping Sparrow
Field Sparrow
Dark-eyed Junco
White-crowned Sparrow
White-throated Sparrow
Song Sparrow
Lincoln's Sparrow
Swamp Sparrow
Eastern Towhee
Northern Cardinal
Indigo Bunting
Red-winged Blackbird
Common Grackle
House Finch
Pine Siskin
American Goldfinch
House Sparrow
All images © 2017 Mike McDowell