Here are a pair of White-Necked Jacobin hummingbirds that I spotted at a butterfly and hummingbird farm in Mindo, Ecuador, where I enjoyed the company of countless butterflies and at least a few dozen different birds, mostly hummers, on a pleasantly meandering stroll. Above and immediately below is a male and further down, a few shots of a female.

They’re common throughout South and Central America and north to Mexico and the male, according to Wikipedia, considered to be “unmistakable with its dark blue head and chest and white belly and tail”. Females, as seen below, are more muted with lots of green, but colors can vary, all the way to the striking blues worn by adult males. One 2022 study by researchers at the University of Washington, Cornell and Columbia suggest that females are evolving to resemble males to avoid agression through what they call deceptive mimicry.

From a summary of the study:

In research published Sept. 7 [2022] in the Proceedings of the Royal Society B, [Jay] Falk and co-authors at the UW, Cornell University and Columbia University report that adult female white-necked jacobins with male-like plumage are mimicking male appearance — but not male behavior. In addition, their strength and body size are similar not to males, but to fellow females with muted plumage.

The study shows that the 1 in 5 adult females with male-like plumage are engaging in “deceptive mimicry”: They are essentially trying to pass themselves off as males, without acting like them. In the process they receive quite a benefit. As Falk and his colleagues reported in a paper published last year in Current Biology, females with male-like plumage suffer less aggression from males compared to females with the more typical muted plumage, and can hang out longer at feeders.

Nature also has a paywalled report on the study.

Below, five shots of the very greenish female.

White-Necked Jacobin (Florisuga mellivora) in brief (with assist from WordPress AI but double-checked by me at Birds of the World and Wikipedia):

• Size: Length: 9.5–11 cm (3.7–4.3 in); Wingspan: Approx. 15 cm (5.9 in)
• Diet: Primarily nectarivorous, feeding on the nectar of various flowers. Also consumes small insects and spiders for protein
• Habitat: Prefers humid tropical forests, often near water sources. Commonly found in understory and edges of forests
• Physical Description: Males: Striking emerald green body with distinctive white neck. Females: More subdued coloration, generally brownish with greenish hues. Both sexes have a long, forked tail
• Breeding: Nesting occurs mainly in wet seasons. Nests are small, cup-shaped structures built in bushes or trees. Clutch size typically consists of 2 eggs, which are incubated for about 14-17 days
• Conservation Status: Listed as Least Concern by the IUCN. Populations are stable, but habitat loss remains a potential threat
• Unique Behaviors: Known for its agile flying and acrobatic displays during courtship; aggressively defends feeding territories
• Range and Migration: Found in parts of Central and South America, including areas from Costa Rica to Colombia and Venezuela. Generally non-migratory, but may relocate seasonally in response to food availability

Links for further reference:

• White-Necked Jacobin at Birds of the World
• White-Necked Jacobin at BirdLife DataZone
• White-Necked Jacobin at eBird
• White-Necked Jacobin at Avibase
• White-Necked Jacobin at Wikipedia
• White-Necked Jacobin at Oiseaux.net
• White-Necked Jacobin at iNaturalist

Note 1: all photos snapped in Mindo, Ecuador, on 28 May 2013.

Note 2: This post first appeared on my blog Piran Café, which is no longer being updated, and moved here, with newly processed, on 18 April 2026.