Rivoli's Hummingbird: The Mountain Giant of the Arizona Sky Islands

Male Appearance

The male Rivoli's is one of the most dramatic hummingbirds anywhere in North America. The crown is rich iridescent purple --- a deep, saturated violet that shifts toward blue or magenta depending on lighting angle. The gorget is an equally brilliant emerald green, separated from the purple crown by a narrow dark line. The rest of the body --- back, breast, belly, flanks --- is a deep blackish-green that appears simply dark in poor light but shows complex green iridescence in direct sun. The undertail coverts are white, a useful mark visible in flight. The bill is long, straight, and black. In silhouette, the Rivoli's is noticeably larger than any other Arizona hummingbird except the Blue-throated Mountain-Gem --- this size difference, combined with the slower wingbeat, makes the bird identifiable by manner of flight alone with practice.

Female Appearance

The female Rivoli's is one of the more subtly beautiful female hummingbirds. She is dark brownish-green above, with underparts that are heavily spotted and streaked with dusky and greenish tones --- not the clean gray-white of a female Broad-billed or the buffy warmth of a Buff-bellied. A clear white postocular stripe (white stripe behind the eye) is the most useful field mark, set against the darker face. The bill is long and straight (longer than most female hummingbirds), and the overall impression is of a large, dark, somewhat nondescript bird that rewards patient observation to appreciate fully. Undertail coverts show white tips.

Similar Species & How to Tell Them Apart

• Blue-throated Mountain-Gem --- The only US hummingbird larger than Rivoli's; the male has a distinctly blue throat (not iridescent --- genuinely blue) and bold white tail corners. The female Blue-throated is gray, not streaked.

• Broad-billed Hummingbird --- Much smaller; male is all blue-green with a red bill; no purple crown.

• Anna's Hummingbird --- Much smaller; rose-red gorget, not green; shorter bill.

• Female Rivoli's vs. female Blue-throated: The female Blue-throated has more prominent white facial stripes and very large white tail corners; the female Rivoli's has a spotted/streaked breast rather than the Blue-throated's plain gray underparts.

Size alone eliminates most confusion --- a Rivoli's alongside other Arizona hummingbirds looks like a different category of bird.

• April: First Rivoli's arrive at Arizona sky-island mountain sites, typically in early to mid-April. Earliest arrivals are usually recorded at lower-elevation canyon feeder stations.

• May--June: Breeding season; males display and hold territories in pine-oak woodland.

• July--August: Monsoon season brings peak flower productivity; Rivoli's trap-line behavior becomes most visible as birds move between flowering agaves, penstemon, and cardinal flowers along canyon margins.

• September--October: Departure; most birds leave by late September, though an occasional individual may linger into October or, rarely, attempt to winter at well-stocked feeders.

Best months: June through August at Huachuca Mountain sites. The combination of active breeding, monsoon flower abundance, and accessible feeder stations makes this the most productive window.

The Rivoli's large size and trap-lining behavior call for a slightly different approach than with smaller territorial hummingbirds:

• Large-capacity feeders: The Rivoli's large bill and body handle standard feeder ports comfortably. Large saucer-style feeders with wide rims allow comfortable perching for this larger bird.

• Multiple feeders spread across the yard: Since Rivoli's trap-line, placing feeders at multiple points around a high-elevation property (5,000+ feet, pine-oak setting) increases the chance of attracting a bird on its regular circuit.

• Height: Rivoli's often approach from the tree canopy; feeders hung at 6--10 feet or at canopy edge may be visited more readily than low placements.

• Patience: Unlike territorial hummingbirds that guard a feeder continuously, a Rivoli's may visit once every 20--90 minutes depending on the length of its trap-line circuit. Do not be discouraged by long gaps between visits.

• Nectar quality: Always use dye-free 1:4 sugar-water. In high-elevation pine forest temperatures can drop rapidly at night; check that feeders do not freeze on cold nights.

Rivoli's Hummingbirds breed in the United States, nesting in pine-oak woodland in the Huachuca, Chiricahua, Santa Rita, and Pinaleno mountain ranges of Arizona, and in comparable habitat in the Mogollon Highlands of New Mexico.

Females build the nest entirely alone --- a bulky, deep cup of plant fibers and spider silk, often larger than nests of smaller species, typically placed on a horizontal branch of an oak or pine at moderate height (8--25 feet). Females alone incubate two white eggs for approximately 15--19 days. The nestling period is longer than in smaller species, reflecting the Rivoli's larger body size; young fledge at roughly 24--28 days. Males play no role in nest building or chick rearing.

Breeding documentation in the US is not uncommon for those actively searching at appropriate elevation sites, particularly along the trails and roads in the upper Huachuca and Chiricahua ranges.

Rivoli's Hummingbird is Least Concern (IUCN). It is widespread in the mountain ranges of Mexico and Central America from Sonora south to Nicaragua. The US breeding population represents a tiny fraction of the global total but holds significant scientific and conservation interest as one of the northernmost populations of a high-elevation forest specialist.

The primary threats to US-breeding Rivoli's are the same factors affecting all sky-island mountain species: climate-driven changes in pine-oak forest composition, drought stress on mountain springs and streams, and the long-term impacts of altered fire regimes. Sky Island Alliance and similar organizations working to maintain ecological connectivity and water availability in the southeastern Arizona mountain ranges are the most critical conservation partners for this species in the US context.