Given that birds consume an awful lot of fat and carbs in their lives, it’s natural to wonder if there is such thing as fat birds.

‍They are exceptionally active creatures, true, with bodies designed to be as efficient as possible in terms of breathing, movement and breeding. But even birds stop moving at some point, so there potentially must be times when they can eat more than they can burn off.

Observing that some birds have a seemingly endless all-you-can-eat buffet but never showing any signs of weight gain led one environmental biologist to wonder whether birds can in fact regulate the energy they use regardless of their intake.

Acknowledging that there is always the possibility that we don’t see fat birds because they are easily caught by predators, Lewis Halsey aims to understand more about how birds may be able to control their energy budgets, with a view to enabling us to re-evaluate our approach to fat and health issues, which is often one of reducing what we eat in order to lose weight.

Birds may in fact employ a number of behavioural and physiological strategies that don’t involve staying away from carbs, such as fidgeting, adjusting posture, changing wingbeat speed, or environmental considerations such as anticipating bad weather or probable predation, where they know to stock up in advance as it will be some time before the next meal. Research is ongoing, and I for one am looking forward to the results.

Another method of avoiding fat birds is self-control. Self-control is defined as the conscious effort to limit your desire to do something, especially during stressful situations, like drink or eat a lot when bad news has come.

Birds lead extremely stressful lives: they are constantly on the lookout for food, predators, another bird to breed with, bad weather, nesting sites, competition with other birds for territory, and so on. It ain’t easy being a bird and it would be even harder for fat birds.

‍Given this life, it’s kind of a wonder that some don’t just choose to sit around all day crunching though tiny buckets of popcorn and hiding from the world.

Ground control

Studies have shown that in humans, learning self-control and avoiding impulsive behaviour from childhood leads to greater physical health, a lack or absence of reliance on substances, healthier personal finances, and reduced criminal offending.

Signs of self-control have only really been observed in other species with brains larger than birds who display cognitively advanced behaviours, like the chimpanzee. However, a study in 2018 showed that some birds display strikingly similar abilities.

The European great tit, from the same family as the chickadee in the US, has been observed to make choices that were not impulse-driven. By placing food in a translucent tube with a small opening at the top, researchers at Lund University in Sweden found that in 80% of the time, instead of pecking mindlessly at the wall of the tube where the food was visible, an impulsive act, the great tits would instead delicately seek to extract it through the small opening: an act of measured control.

‍Also, unlike their cousins the marsh and willow tits, great tits don’t cache food for the winter; instead, they keep tabs on other birds who do, and when alone and unobserved, will raid that stash. This possibly “underhand” behaviour may not sound like self-control, but in the science world it is considered to be an admirable trait of restraint and planning.

Humongous hummingbird

Hummingbirds eat a lot of sweet stuff, but most don’t get fat at all; their hearts can get to a rate of 1,260 beats per minute, and whilst does nectar account for around 90% of their diet, their bodies are specifically designed for digesting sucrose.

The majority of hummingbirds run very little risk of gorging themselves and piling on the pounds – there has been some concern in the past over sugar feeders causing liver disease, but this has actually only ever been observed in captive hummers, and never in the wild.

Of the 300 or so species, around 12-15 migrate, like the Rufous and Ruby-throated species. These hummingbirds put on a heck of a lot of weight, but not for very long. Travelling from the Yucatan to the Gulf Coast of the United States, a distance anywhere between 450 and 600 miles, these migratory hummers need to really fatten up to survive that journey.

As with all migratory species, daylight and temperature changes trigger a feeding response, and when that happens, they embark on a veritable frenzy known as hyperphagia; towards the end of summer, they spend almost every waking second eating.

As the bird eats more than it can burn off, the excess is stored as yellow fat around the internal organs and body cavity. Yellow fat can produce twice as much water during processing then protein or carbohydrates, which means the birds don’t dehydrate on their journey.

An extra two grams of fat, 60% of its usual body weight, is enough to power it across the vast expanse of the Gulf of Mexico at a rate of around 35 miles per hour. You can often tell when a hummer is ready to go – their tiny heads perch atop a round fluffy barrel.

‍Adding 50% or more to its lean body weight causes fat to bulge almost everywhere, and those who study them can gently blow their breast feathers apart to see it around the hollow of the throat, under the wings, and in the abdomen.

This is a welcome sight for many, as it means they have found enough food to make that arduous journey and continue the family line. Once the destination is reached, they resume their normal pace of eating and activity, and are back to their slender selves again in no time.Remember, all those miracle diets out there have one thing in common: not to eat the bad stuff.

Perhaps Halsey’s and other research will shine a light on new ways to regulate our own energy expenditure, and who knows – maybe one day we can still have our cake and eat it.