Anna’s hummingbird Hummingbird Species

Anna’s Hummingbird (Calypte anna)

Introduction

The Anna’s hummingbird (Calypte anna) is a medium-sized hummingbird native to the west coast of North America. Known for its iridescent emerald-green back and rose-pink throat, it is one of the most striking and recognizable hummingbird species. Anna’s hummingbirds are found year-round along the Pacific Coast from British Columbia to Baja California. They thrive in suburban neighborhoods, parks, and gardens where nectar flowers and feeders abound.

Anna’s hummingbirds display remarkable adaptability, enabling them to survive cold winters and hot summers across their range. This article will provide an overview of Anna’s hummingbird biology, behavior, habitat, diet, conservation status, and unique adaptations that allow them to flourish along the Pacific Coast.

Physical Description

Anna’s hummingbirds exhibit sexual dimorphism, meaning males and females display different plumage. Adult males have glossy, iridescent emerald-green feathers on their back and crown which appear black in some lights. Their throats are brilliant magenta and catch the light to glow reddish-pink. The females lack iridescent throat feathers and are instead light grey underneath with greenish feathers on the back and crown.

Both sexes have slender curved bills well-adapted for accessing nectar from flowers. Their wings beat up to 70 times per second, allowing them to precisely hover in place or dart rapidly between flowers. Anna’s hummingbirds are relatively large, measuring 3.5-4 inches long with a wingspan of 4.5 inches and weight of 3-6 grams.

Range and Habitat

Anna’s hummingbirds are found year-round along nearly the entire Pacific Coast from southern British Columbia to Baja California. Their range extends inland to western Nevada, Arizona, and northwest Mexico. They thrive in suburban neighborhoods, parks, and gardens where flowering plants provide a steady nectar supply.

Along the northern limits of their range, Anna’s hummingbirds congregate in urban areas during winter where feeders and exotic flowering plants provide food when native plants are dormant. As temperatures warm in spring, the hummingbirds disperse to breed across a wider range of habitats including forest edges, scrublands, meadows, and mountainsides.

Anna’s hummingbirds readily adapt to backyard feeders, allowing them to expand their range northward in recent decades as more people have put up feeders that provide a consistent winter food source. They are now one of the most common backyard birds along the Pacific Coast.

Diet and Feeding

Like all hummingbirds, Anna’s hummingbirds have a specialized diet consisting primarily of nectar and small insects and spiders. They use their slender, slightly curved bills to access nectar, lapping it up with their forked tongues up to 13 times per second. Preferred nectar sources include currants, fuchsias, trumpet vines, passionflowers, penstemons, and flowering trees like cypress, eucalyptus, and tulip.

Anna’s hummingbirds also consume small insects and spiders which provide essential amino acids and fat. They may hawk flying insects in midair or glean them from leaves and bark. Spiders are plucked from their webs near nectar plants using the hummingbird’s bill.

At feeders, Anna’s hummingbirds prefer a 20% sugar solution, but they will readily adapt to the concentration provided. They may defend feeders as part of a feeding territory, chasing away other birds that try to poach the nectar reward. Anna’s hummingbirds drink up to half their weight in nectar each day and may visit 1,000 or more flowers daily to meet their energetic needs.

Behavior and Communication

Male Anna’s hummingbirds are highly territorial and establish breeding and feeding territories each spring. They perform dramatic aerial dive displays, climbing up to 100 feet before diving toward the ground with a burst of trills and chirps, advertising their territory. The dive display produces a loud sound from air rushing through the male’s tail feathers.

Females build a small cup-shaped nest high in a protected location, often in trees and shrubs around human habitation. The nest is made of plant down lined with spider silk and lichen flakes, expanding as the female’s two eggs hatch over 2-3 weeks. Once the young fledge after another 3 weeks, the female raises them on her own.

Anna’s hummingbirds are boldly curious and may closely investigate humans that enter their territory. They communicate with chirps and squeaks and defend their territory by aggressive displays and chasing. Males produce a sharp chip note while females use higher-pitched squeaking or ticking sounds.

Seasonal Behaviors and Torpor

Anna’s hummingbirds reside year-round along much of their Pacific Coast range. Their small size and rapid metabolism make them vulnerable in cold climates, but they have adapted remarkable strategies to survive the winter.

As temperatures drop, Anna’s hummingbirds enter a state of torpor at night, lowering their metabolic rate and body temperature to conserve energy. Their heart rate slows from over 1,000 beats per minute to just 50-180 beats per minute. They may also become slightly lethargic during the day.

By entering torpor, Anna’s hummingbirds can reduce their metabolic rate by 50-90%. This enables them to survive temperatures below freezing by using less energy. Access to feeders and winter blooms helps maintain their fat reserves to survive long nights of torpor.

Conservation Status

Anna’s hummingbirds remain widespread and common across their range, propelled by their adaptability to urbanization and backyard bird feeders. However, they do face threats from habitat loss, pesticides, window collisions, and climate change. Their reliance on nectar makes them vulnerable when exotic plants replace native flowers or pesticides reduce insect populations.

Development causes habitat loss while glass windows and buildings poses collision risks, estimated to kill nearly one billion birds per year in North America. Warmer temperatures associated with climate change may impact their range and seasonal behaviors.

Despite these threats, Anna’s hummingbird populations appear stable, supported by artificial feeders and gardens. They are classified as Least Concern by the IUCN Red List due to their large and increasing population size. No special conservation actions are currently needed, but awareness and monitoring help ensure these resilient hummingbirds continue thriving in urban areas and beyond.

Unique Adaptations

Anna’s hummingbirds display a number of unique evolutionary adaptations that aid their survival in varied environments along the Pacific Coast:

– High metabolism – Anna’s hummingbirds have extremely high metabolisms to power their constant hovering and rapid movements. Their heart rate can reach over 1,200 beats per minute and they may breathe 250 times per minute. This energetic lifestyle requires visiting hundreds or thousands of flowers daily to meet their liquid and nutritional demands.

– Torpor – Allowing their body temperature and metabolism to plunge at night helps Anna’s hummingbirds conserve energy when food is scarce. By temporarily entering torpor, they can survive temperatures below freezing.

– Bill shape – Their slender bills are specialized for accessing nectar at the base of tubular flowers. A slight downward curve aids them in licking up small liquid droplets.

– Tongue structure – Their forked tongue has tube-like projections along the tips which soak up and trap nectar. When retracted, the nectar moves through capillary action along the tubes up to the hummingbird’s mouth.

– Leg strength – Anna’s hummingbirds have proportionately small legs but substantial strength for perching without expending extra energy. This aids their hovering ability.

– Flying maneuverability – Their wings have shoulder joints that rotate through almost 360 degrees, enabling swift backward, hovering, and upside-down flight.

– Sugar metabolism – They can rapidly use ingested sugars to fuel their muscles and metabolize fructose, an advantage when eating exotic ornamental plants.

– Cold hardiness – Expanding their winter range into cooler climates has been facilitated by cold hardiness adaptations including increasing fat storage, plumage density, torpor use, and microhabitat selections.

Conclusion

With their glittering green and pink plumage and aerial acrobatics, Anna’s hummingbirds are a favorite Pacific Coast backyard bird. Their adaptability to human habitats and sugar-water feeders have allowed their population to thrive and expand northward in recent decades. Despite threats posed by habitat loss and high-energy lifestyles, Anna’s hummingbirds remain energetic, resilient residents across the west thanks to their remarkable behavioral and physiological adaptations for thriving along the Pacific Coast. Their willingness to visit backyard feeders allows many people a glimpse into the unique and captivating world of hummingbirds.