Red-throated Loons (Gavia stellata) are the smallest and most slender of North America’s loons, measuring 21–27 inches in length with a wingspan around 36 inches. They have a thin, slightly upturned bill that they often hold angled upward. In breeding plumage (rarely seen in Arizona), adults display a triangular red throat patch, neat narrow stripes on the neck, and a smooth gray head; in nonbreeding (winter) plumage—what Arizona observers almost exclusively encounter—they appear paler overall, with extensive white on the face and neck, a gray back showing fine white dots at close range, and minimal throat coloration.
Breeding on Arctic tundra lakes, Red-throated Loons migrate along both Atlantic and Pacific flyways, wintering chiefly along coastal waters and on large inland reservoirs. Their diet consists almost entirely of fish, which they pursue with graceful, deep dives. They take off directly from land—unlike other loons—and are powerful, agile flyers, capable of high-speed flight and abrupt maneuvers.
In Arizona, Red-throated Loons are rare but increasingly regular winter visitors to large lakes along the lower Colorado River and, to a lesser extent, other sizable waters. Prior to 2010 there were only three early records, but from 2010 through 2014 the Arizona Bird Committee (ABC) accepted nine new records—including one at Bill Williams River NWR on 30 Jan 2010 and multiple individuals at Lake Havasu between Oct 2011 and Apr 2014—bringing the total to 26 accepted records; the species was removed from the ABC review list at the end of 2014 due to its growing regularity. Sightings generally occur between late October (first recorded 31 Oct 2011) and early April (one lingered until 6 Apr 2014), with most reports in November through January. A subsequent record on Lake Havasu on 7 Dec 2014 further confirmed its status as a winter visitor.
I have not managed to capture a photograph yet.