Possible Reasons for a Fat Hummingbird
There are a few possible reasons why your hummingbird may appear larger or “fatter” than usual:
It’s Storing Up Fat for Migration
Hummingbirds need to double their weight before migration in order to have enough energy to make the long journey. In the weeks before migration, they enter a phase called hyperphagia where they eat constantly to pack on extra fat. This is normal and necessary.
During this time, the fat stores under their skin and around their organs expand, making their bellies look rounded or even distended. This is especially noticeable in ruby-throated hummingbirds. So if your hummingbird looks big, it could just be bulking up for migration.
It’s a Pregnant Female
Female hummingbirds also need to store up energy in preparation for nesting. A female hummingbird with a rounded belly may be pregnant or getting ready to lay eggs.
Gestation is short, around 16-18 days, but a lot of energy and nutrients are required to produce eggs. So she will eat more leading up to and during the breeding season.
Her belly may look enlarged or swollen as her ovaries fill with yolky eggs and fat deposits build up to fuel her upcoming nesting efforts. Once the eggs have been laid, her belly will go back to normal size.
It Has an Abundant Food Source
Hummingbirds can also look heavier when food is readily available. With a constant surplus of nectar or sugar water, they don’t need to work as hard to meet their high metabolism’s demands.
If your feeder is overflowing with fresh nectar or you have lots of flowering plants, your hummingbird may get the chance to consistently feed and store up some extra fat. This isn’t necessarily bad in moderation.
It’s a Juvenile
Young hummingbirds often appear puffy or round as they grow and develop. Their bodies are still maturing, with extra fat and thicker plumage that can make them look more spherical or pudgy compared to adults.
In particular, the wings of young hummingbirds seem small relative to their bodies. Once they finish growing and reach mature proportions, they’ll look more sleek and slender.
It Has a Health Problem
While less likely, in some cases, an enlarged abdomen or unusual swelling could signal an underlying health issue. Potential causes can include:
- Liver disease – enlarged liver distends abdomen
- Tumor or cyst
- Egg binding – obstruction of egg laying
- Ascites – fluid buildup in the abdomen
If the hummingbird seems lethargic, weak, or unwell, or the swelling has appeared rapidly, it’s best to contact a wildlife rehabilitator for advice. Otherwise, it may be one of the more common explanations above.
How to Tell if Your Hummingbird is Fat
Here are some signs that can help determine if your hummingbird is overweight versus just full or fluffy:
- Rounded belly that appears distended or swollen
- Breast muscles that seem small compared to a large abdomen
- Chest spillage – fat deposits visible protruding on the chest
- Heavy breathing or open mouth panting
- Difficulty or reluctance to fly
- Constant sleepiness and lethargy
- Change in personality – more docile or less aggressive
Subtle fat gain can be hard to detect. But if your hummingbird is displaying multiple signs of obesity, it likely has an unhealthy surplus of fat. Keep reading for tips on preventing excess weight gain.
Is it Bad for Hummingbirds to Get Fat?
Mild fat storage is normal and healthy for hummingbirds. However, excessive fat can cause issues including:
Impaired Flight Ability
Too much weight makes it difficult for hummingbirds to fly efficiently. The extra fat causes their body weight to exceed their wing loading capacity.
Their wings have to work harder to lift the heavier body, so they struggle to take off or can’t sustain flight as long. This leaves them vulnerable to predators.
Overstress of Organ Systems
Abdominal and visceral fat puts pressure on a hummingbird’s digestive organs. This can tax the liver, kidneys, and heart as they work harder to support the increased body weight.
Higher Energy Needs
Excess fat takes more energy to maintain. A hummingbird’s high metabolism has to burn more calories to sustain itself if the bird is overweight. This means they may struggle to balance their energy budget.
Increased Risk of Diseases
Obesity is linked with higher rates of diseases like fatty liver disease and diabetes in hummingbirds, just as in humans. Carrying abundant fat stores tends to put their bodies under increased oxidative stress and inflammation.
Predation and Injury Risk
Fat hummingbirds are less agile and mobile, making them easier targets for predators. Their sluggishness also makes them more prone to collisions and injuries.
So while some fat storage is healthy, too much body fat creates risks for hummingbirds. Moderation is key when it comes to fat reserves.
Tips to Prevent Excess Fat
Here are some tips to keep your hummingbird from becoming overweight:
Avoid Overfilling Feeders
Don’t let feeders become more than halfway empty before refilling. Constant access to abundant, fresh nectar can lead hummingbirds to overeat.
Use Smaller Feeders
Smaller capacity feeders (20-25 oz) help limit gorging and encourage healthy feeding habits. Larger feeders can allow hummingbirds to drink their fill too quickly.
Offer More Feeders
More feeders reduce competition and give all birds adequate access to nectar. With fewer birds per feeder, dominant ones can’t monopolize the food source.
Use Low Concentration Nectar
Dilute nectar to 25% sugar or less to reduce calorie intake. This makes it harder for hummingbirds to pack on excess fat.
Provide Natural Food Sources
Plant native flowers and flowering shrubs to give hummingbirds access to natural nectar sources. This allows them to burn more calories obtaining food.
Change Feeder Locations
Periodically moving feeders forces hummingbirds to expend more energy searching for and accessing food sources. This helps prevent excessive weight gain.
Sample Feeding Schedule to Promote Healthy Weight
Here is an example nectar feeding schedule designed to provide consistent nourishment for hummingbirds while helping prevent obesity:
Time of Day | Feeding Recommendation |
---|---|
Early Morning | Fill feeders with fresh 25% sugar nectar. |
Late Morning | Refill feeders when half empty. |
Early Afternoon | Change location of 1-2 feeders to encourage activity. |
Late Afternoon | Remove any remaining nectar and clean feeders. |
Evening | Do not refill feeders. |
When to Be Concerned About Obesity
In most cases, a fat hummingbird is nothing to be alarmed about, especially during migration or breeding season. However, if you notice the signs of obesity persist for extended periods, it’s worth taking steps to improve the bird’s diet and activity levels.
Contact a wildlife rehabilitator if the hummingbird shows indications of:
- Lethargy, weakness, or loss of mobility due to excess weight
- Overgrown feet caused by lack of perching activity
- Continued weight gain despite diet improvements
- Swelling or distension for more than a few days
These symptoms may suggest an underlying illness is causing the obesity, rather than just overfeeding. A rehabilitator can provide guidance on any necessary medical interventions.
With some adjustments to its care routine, most overweight hummingbirds can get back into healthy body condition. The key is promoting ample exercise along with a balanced, portion-controlled diet.
The Bottom Line
It’s natural for hummingbirds to carry some extra fat at certain times of year, especially before migration or nesting seasons. However, obesity can occur if they have unlimited access to concentrated nectar. Adjust feeder placement, capacity, and sugar content to encourage a healthy energy balance. Seek wildlife rehabilitator advice if you have ongoing concerns about a hummingbird’s weight.