BirdWatching USA – September-October 2019

8 BirdWatching

sinceyouasked

(continued on page 10)

Maps show seasonal movements of a sparrow and grebe

eBird is the real-time online checklist operated by the Cornell Lab of Ornithology and Audubon. “On the Move” is written by

eBird’s Garrett MacDonald, Chris Wood, Marshall Iliff, and Brian Sullivan. Submit your sightings at eBird.org.

ON THE MOVE FROM eBIRD

Fox Sparrow

Horned Grebe

Fox Sparrow is one of the most geographically variable bird species in North America. Experts have

identified at least 18 subspecies partitioned into three or four distinct groups that each differ in

breeding habitat, vocalizations, plumage, and behavior. The species breeds in montane forest across

the northern boreal forest of Canada and Alaska and in the western United States, generally

preferring streamside thickets and chaparral. By October, Fox Sparrows have vacated the breeding

range and can be found across most of the lower 48 states in dense thickets, where they commonly

occur with other sparrows seeking similar habitats. During the nonbreeding season in January, the

species is found in the eastern states, especially the Southeast, and along the entire Pacific Coast

from coastal British Columbia to southern California. Listen for the species’ loud smack call, a sure

giveaway that a bird is lurking out of sight in deep brush.

The Horned Grebe is known to most North American birders only from the nonbreeding grounds

and during migration, where it occurs across nearly all of southern Canada and the lower 48 states.

During the breeding season, however, the species is found from central Alaska through most of

western and central Canada and into portions of Montana and North Dakota, where it breeds in

small ponds and lake inlets with emergent vegetation. Horned Grebes nest solitarily or in small

clusters of pairs during the breeding season and can occur in large groups of several hundred

individuals during the nonbreeding season. In October, look for the species on lakes, large ponds,

and reservoirs in inland North America, as well as close to shore along both coasts. During the

nonbreeding season, in January, the bird is found primarily from Texas east to the Mid-Atlantic

region, and along the entire Pacific Coast.

October 2008-

October 2008-

January 2008-

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Q

A

do Burrowing Owls have a nest

burrow, but they usually also

have roosting burrows used for

shelter, especially outside the

breeding season.

What makes a group of

hawks a “kettle?” —

Clair Van Buren,

Bloomington, Indiana

Hawks and other raptors

migrate during the day. As the

sun heats the ground, warm air

rises from the earth. Certain

geographic features, including

natural topography or human-

built areas, can vary the rate

and location of heating, creating

columns of warm, ascending air.

Birds can enter these updrafts,

and by flying or soaring in a cir-

cle within the column, they can

be lifted high into the sky. As

the birds reach a height where

the column dissipates because

it meets increasingly cooler air,

they can simply set their wings

and glide down into another

thermal in the direction they are

headed. Using this method, the

birds can travel quite far while

conserving energy, as it takes

far less effort than constant

flapping.

The sight of a group of

hawks taking advantage of a

thermal, all swirling and spiral-

ing, is reminiscent of objects

being stirred or boiling in a pot

— hence the terms a “kettle of

hawks” or “hawks kettling.”

Thermals do not form until

the sun is sufficiently high in

the sky, usually mid-morning,

so observing kettles of hawks

doesn’t require rising at the

crack of dawn. Nor do thermals

form over water. Notably,

migrating hawks will lose

altitude as they cross a lake or

large river, so sites located near

shorelines are great places to