Anna’s hummingbirds (Calypte anna) are small, colorful birds native to the west coast of North America. The males are known for their striking iridescent magenta throat feathers and crown, which they display during courtship rituals to attract females. While the males have very distinctive plumage, the females have more subtle, grayish-green plumage that can make them harder to identify. However, with a little knowledge of Anna’s hummingbird biology and behavior, you can learn to tell males and females apart.
Plumage Differences
The most noticeable difference between male and female Anna’s hummingbirds is the color of their plumage.
Males have:
– Iridescent magenta throat feathers (known as a gorget)
– Iridescent magenta crown
– Green back and tail feathers
– White underparts
Females lack iridescent gorget and crown feathers and instead have:
– Grayish-green back
– Pale gray underparts
– Green tail with white tips on outer tail feathers
The striking magenta and iridescent coloration on the male’s throat and crown feathers is completely absent in females. Females may sometimes have faint reddish spots at the throat but lack the full gorget display. The paler, more muted green and gray plumage provides female Anna’s hummingbirds with camouflage while nesting.
Size and Shape Differences
In addition to coloration, males and females differ slightly in their size and proportions:
| Feature | Male | Female |
|---|---|---|
| Size | 3.5-4 inches long | 3.25-3.75 inches long |
| Weight | 3-4 grams | 3-4.5 grams |
| Beak length | Shorter, straight | Longer, slightly decurved |
As seen in the table, female Anna’s hummingbirds tend to be slightly larger and heavier than males. They also have a longer, more curved beak which is thought to assist with reaching nectar while incubating eggs. The male’s shorter, straighter beak may be better suited to courtship displays. However, these size and structural differences between the sexes are subtle and variable.
Behavioral Differences
In addition to physical features, there are some key behavioral differences between male and female Anna’s hummingbirds:
Male courtship behaviors:
– Display dives – Males climb 30-100 ft then dive down while making loud chirping sounds. This impressive courtship display advertises the male’s strength.
– Aerial displays – Males fly in looping, pendulum patterns while flashing their iridescent throat and crown feathers.
– Vocalizations – Males sing complex, buzzing songs, especially during breeding season.
Female behaviors:
– Nest building – Females alone build a small, compact nest out of plant down, spider webs, and lichens camouflaged on branches.
– Incubation and feeding – Females alone incubate eggs and feed hatchlings. They are very protective of the nest.
– Less vocal – Females may use call notes to communicate with their young but lack complex songs.
– Less aggressive – Females show less aggression and territorial behavior than males who vigorously guard nectar sources.
Observing these courtship rituals and parenting behaviors can help confirm the sex in ambiguous cases based on appearance alone. The fact that only males sing complex songs and perform aerial displays while only females build nests and care for young provides helpful behavioral clues.
Immature and Juvenile Birds
Determining sex can be most challenging with young Anna’s hummingbirds that lack full adult plumage. Immature males resemble adult females until they molt into their adult colors at about one year old. Some tips for aging young birds include:
– Fledglings have short bills and very little throat spotting. Flight feathers are less colorful.
– Juvenile males may show scattered iridescent throat feathers by 5-6 months old. Their voices may crack as they practice songs.
– By one year old, males complete their first molt into full adult plumage.
So while young males may initially resemble females, observing birds over time will reveal their age and sex based on changes in plumage and behavior.
Hybridization with Other Species
In some cases, female Anna’s hummingbirds may hybridize with males of other similar species such as Costa’s and black-chinned hummingbirds. This can result in females with unusual plumage features. Potential hybrids tend to display a mix of characteristics between the two species. Other signs include:
– Males performing courtship displays directed at female of another species
– Hybrid young being cared for by a female Anna’s hummingbird
– Mixed songs containing notes from both parental species
So while hybridization is uncommon, it can occasionally complicate sexing birds in the field based on appearance alone. Looking at multiple characteristics is advised.
Conclusion
While differentiating male and female Anna’s hummingbirds can be tricky at first glance, a combination of factors including plumage color patterns, physical proportions, behaviors, age, and potential hybridization can help determine sex. In most cases, the presence of iridescent magenta throat plumage confirms a male, while its absence indicates a female. Females also tend to be slightly larger with longer curved beaks. But juvenile birds, in particular, may require more careful observation over time to definitively sex as they mature. With practice and attention to detail, anyone can learn to accurately tell males and females of this colorful and charismatic species apart. Proper sex identification is important for understanding hummingbird biology, behavior and evolutionary adaptations.
