The violet sabrewing (Campylopterus hemileucurus) is a medium-sized hummingbird found in Costa Rica, Panama, Colombia, Ecuador, Peru, Bolivia and Venezuela. Sabrewings get their name from their unusually large and curved bill, which resembles a sabre. There are seven species of sabrewing, and they are all found in Central and South America. The violet sabrewing is distinguished by its mostly violet-blue plumage and white ventral feathers. Like all hummingbirds, the violet sabrewing has unique dietary requirements and feeding behaviors. In this article, we will explore the diet of the violet sabrewing in detail.
Nectar
The violet sabrewing, like all hummingbirds, relies primarily on nectar as an energy source. Nectar is essentially sugar-water produced by plants to attract pollinators. The curved bill of the violet sabrewing allows it to access nectar from specialized tubular flowers. Some favorite nectar sources include plants from the following families:
- Bromeliaceae – Bromeliads like guzmanias and tillandsias
- Ericaceae – Blueberry, cranberry and mountain laurel
- Gesneriaceae – African violets and gloxinias
- Heliconiaceae – Lobster-claws and heliconias
- Lamiaceae – Sages and mints
- Passifloraceae – Passion flowers
The composition of nectar varies between plant species and even individual flowers. On average, hummingbird-pollinated flowers produce nectars that are 25% sugar, mostly in the form of sucrose, glucose and fructose. This provides an efficient energy source for the hummingbird. The violet sabrewing likely seeks out flowers with higher sugar concentrations when possible.
Nectar Feeding
To feed on nectar, the violet sabrewing hovers in front of the flower and extends its tongue deep inside the corolla. Their long, tubular tongue acts like a tiny straw, lapping up the nectar. The tongue tip is forked which helps collect more nectar with each lick. While feeding, the wings beat on average 55 times per second, expending immense amounts of energy. This requires the sabrewing to feed almost continuously during daylight hours. Violet sabrewings move swiftly from flower to flower, not lingering long at each one. They aggressively defend rich sources of nectar, chasing away other hummingbirds or insects.
Insects
While nectar provides the bulk of calories, the violet sabrewing also consumes small insects to obtain key nutrients like protein, vitamins and minerals. Preferred insects include:
- Flies
- Beetles
- Aphids
- Mosquitoes
- Spiders
- Caterpillars
These small prey items are typically caught on the wing. The violet sabrewing perches and makes short sallies out to snatch passing insects. It may also glean insects from leaves and branches. Catching insects takes greater energy expenditure compared to nectar feeding. However, the payoff in nutrients is well worth the effort.
Feeding Behavior
Violet sabrewings exhibit some interesting behaviors related to insect feeding:
- They typically hunt for insects in forest openings or habitat edges where prey availability is higher.
- Males establish insect feeding territories which they aggressively defend from other males.
- They often catch insects stirred up by army ant swarms.
- In the late afternoon, many violet sabrewings congregate at favored insect feeding spots.
So while nectar may fuel a sabrewing’s engine, a bit of protein from insects provides essential nutrition for an active lifestyle. The violet sabrewing strategically balanced both food resources.
Habitat
The food resources available to the violet sabrewing depend largely on its habitat. This species primarily resides in:
- Tropical lowland rainforests
- Subtropical montane forests
- Cloud forests
Within these habitats it prefers forest edges, natural openings, second growth and semi-open areas. The abundance of flowers and insects in these locations allow the sabrewing reliable access to food. Interestingly, violet sabrewings in the northern Andes sometimes migrate to lower elevations in winter where flowering and insects remain more plentiful compared to the frost-covered higher elevation forests.
Elevation
The elevation range of the violet sabrewing extends from near sea level up to 2600 m in the Andes mountains. Across this gradient, the availability of food changes significantly:
| Elevation | Food Resources |
|---|---|
| Lowlands | Greatest diversity of flowers and insects year-round |
| Mid-elevations | Moderate floral and insect diversity. Seasonal shifts in resources |
| Highlands | Lowest diversity. Resources dramatically reduced in winter |
As elevation increases, the violet sabrewing must adapt to harsher conditions and lower food availability in the mountain forests.
Territory and Foraging Range
Violet sabrewings are not particularly territorial birds. They do not maintain long-term feeding territories as some other hummingbird species do. However, males may temporally establish insect feeding territories as mentioned earlier.
Both males and females traverse relatively large foraging areas each day in search of food. Their foraging range depends somewhat on the distribution of resources within their home range. In lowland Panama, the average foraging range of violet sabrewings was estimated at 1-2 hectares. At higher densities, the foraging range may be smaller. In depleted habitats, violet sabrewings may travel farther between suitable flowers and insect sites.
On a daily basis, a violet sabrewing may visit hundreds of individual flowers and cover several kilometers in the process. They also perform altitudinal migrations tracking the seasonal blooming of preferred flowers. Overall, the violet sabrewing is not very territorial but instead covers wide-ranging areas to seek out food.
Competition
With up to a couple hundred hummingbird species living in the Neotropics, there is immense competition for food resources. In any given habitat, numerous hummingbird species coexist by partitioning flower resources based on differences in bill shape, body size and agility. Violet sabrewings use their curved bills to access tubular flowers and blossoms with recessed nectaries. Their medium size allows them to feed on a wide range of flower sizes and shapes.
Here are some other hummingbirds that may compete with the violet sabrewing for food resources:
| Species | Food Competition |
|---|---|
| Green hermit | High – similar bill shape |
| Brown violetear | Moderate – broader bill |
| White-necked Jacobin | Low – much larger size |
| Purple-crowned fairy | Low – smaller size |
When preferred flowers are scarce, competition grows more intense leading to displacement of less dominant species. The violet sabrewing is typically able to maintain access to sufficient food resources. But habitat degradation and loss of flowers poses a greater threat to this and other tropical hummingbirds.
Diet by Season
The diet of the violet sabrewing changes across seasons in correlation with food availability:
Dry Season
In the drier months of winter, many flowers cease blooming leading to a decline in nectar resources. Violet sabrewings become more reliant on insects during this period to compensate. They may also increase visits to any remaining nectar sources, like heliconias, and aggressively defend them.
Wet Season
The rainy summer months see a surge in flowering across the forest. Violet sabrewings shift to feed primarily on readily available nectar. With ample flowers present, they do not need to aggressively guard individual sources. Insect consumption decreases but remains important for micronutrients.
Transitional Periods
During transitions between wet and dry seasons, the violet sabrewing’s diet likely consists of a more balanced mix of insects and nectar. They track the flowering progression up and down mountain slopes at this time.
Overall, the proportion of insects versus nectar in the violet sabrewing’s diet changes in response to seasonal conditions. This adaptability allows the species to persist year-round even as resources fluctuate.
Daily Feeding Pattern
The daily activity pattern of violet sabrewings revolves around seeking food. Here is the typical feeding schedule:
- Dawn – Consume nectar to replenish energy after an overnight fast
- Morning – Focus on nectar; consumes over half its daily nectar intake before noon
- Midday – Shift to more insects to meet protein needs
- Afternoon – Balance of insects and nectar
- Dusk – Final nectar feeding burst to fuel overnight
This pattern provides an optimal energy supply and nutrient intake over the course of the day. Interestingly, male and female violet sabrewings follow somewhat different daily rhythms based on their energetic needs. Males spend more time insect hunting to meet higher protein requirements related to aerial displays and defending territories. Meanwhile, females rely more consistently on nectar to fuel egg production and nesting activities.
Diet Differences by Sex and Age
Beyond the daily rhythms mentioned above, the diet of violet sabrewings also varies by sex and life stage:
Females
– Higher nectar consumption provides energy for egg production
– Lower insect intake except during breeding season when more protein is required
– May eat grit and minerals to meet calcium needs prior to laying eggs
Males
– More insects in the diet to build muscle mass for aerial displays
– Greater nectar intake in preparation for breeding season
– Less nectar consumption in non-breeding months
Juveniles
– Fed mostly insects by parents after hatching
– Gradually switch to more nectar as flying skills develop
– Parents continue supplementing with some insects while young perfect foraging abilities
Meeting the needs of each stage and sex requires dietary flexibility. Violet sabrewings accomplish this through selective foraging and seasonal adjustments in food resources.
Digestive Adaptations
To make the most of its diet, the violet sabrewing has evolved some unique digestive adaptations:
- Rapid digestion – Food passes swiftly through short digestive tract, ensuring rapid energy delivery. Nectar can move through in as little as 20 minutes.
- Food storage – Esophagus expands to store up to 2mL of nectar when gorging, providing a buffer of energy.
- High metabolism – Extremely fast metabolic rate(100 beats/minute) powers energy-expensive hovering flight.
- Glucose absorption – Small intestine rapidly absorbs glucose from nectar to power flight muscles.
- Low kidney function – To eliminate excess water from nectar, sabrewings excrete nearly pure urine. Low renal function reduces energy expenditure.
Additionally, the violet sabrewing has lower dietary protein requirements compared to similar sized birds, probably an adaptation to reduce renal demands. Together, these specializations optimize the digestion and utilization of the sugary nectar diet.
Conservation
The tropical forests the violet sabrewing inhabits are increasingly threatened by deforestation, agriculture and development. Habitat loss not only reduces food plants but may also disrupt the seasonal movements the sabrewing relies on to track blooms.
Specific conservation actions to protect the violet sabrewing include:
- Preserving intact rainforest corridors to provide habitat connectivity
- Mitigating climate change which may desynchronize fruiting and flowering cycles
- Promoting agroforestry systems that provide nectar resources at forest edges
- Educating public on importance of tropical pollinators like hummingbirds
As sensitive indicators of ecosystem health, hummingbirds like the violet sabrewing serve as focal species well-representing broader conservation values. By protecting habitats for this unique pollinator, myriad other species benefit as well. Going forward, balancing forest conservation and human use will be key to the survival of Central and South America’s amazing hummingbirds.
Conclusion
The violet sabrewing survives and thrives in tropical forests by relying on two essential food resources – nectar and insects. It employs a suite of behavioral, morphological and physiological adaptations to obtain sufficient nutrition from both sugary nectar and protein-rich insects. While the proportion of these food sources varies seasonally, daily and by sex, both remain critical components of the violet sabrewing’s diet. This species’ remarkable flexibility in seeking food across a diversity of tropical habitats is a testament to the incredible adaptations of hummingbirds. Ensuring healthy ecosystems with abundant flowers and insects will be vital to protect these unique pollinators into the future.
