Ducks and Bread

I am sure many of you have already heard that it is not recommended to feed bread to birds. Upon hearing this statement I find people have two reactions:

  1. “oh my… I feel terrible. I’ve feeding the ducks every Saturday and now I realise I’ve been making them sick. I wish I had learnt this sooner.”
  2. “but I’ve been feeding the ducks every Saturday and they seem fine. You scientists are just being ridiculous. My grandfather used to take me to feed the ducks and I’m not about to stop now.”
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Feeding the Ducks

Feeding ducks is a tradition, albeit an informal one, that people have strong sentimental attachment to and understandably so. However, the evidence shows that feeding bread to ducks probably isn’t the best thing to be doing. I thought we should take a good look at why this is and what we can feed the ducks instead.

What is on a duck’s menu?

First let’s look at what ducks feed on when humans are not proffering bread. A duck’s diet is dependant on what species they are so what ducks are we feeding bread to? On the east coast of Australia we most frequently see: wood ducks, pacific black ducks, grey teals, mallards, pink-eared ducks, magpie geese, black swans, plumed whistling ducks and domesticated duck and geese released into the wild.

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Variety of species on the lake

If you want to know specifics on these species take a look at the information provided by Birdlife (http://birdlife.org.au/all-about-birds/australias-birds/find-a-bird/). The birds that are the most commonly fed are: pacific black ducks, black swans, domesticated duck breeds, and wood ducks. The Pacific black duck’s diet consists mainly of the seeds of aquatic plants but they also eat crustaceans, molluscs and aquatic insects. Black swans eat algae and weeds. Wood ducks mostly eat: grasses, clover and native herbs but also predate insects. Domesticated duck breeds will eat practically anything but what they should be eating is duck pellets, grasses and grains. The natural diets of these birds are for the most part vegetarian.

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Pink-eared ducks also frequent lakes. They will not eat bread that you offer and rely on the algal blooms for food. If the populations of other species are bolstered by bread then they will out compete the Pink-eared ducks who will have to find food elsewhere

If an animal eats something outside of its natural diet the result is often a bellyache because their digestive system is not capable of breaking that food down. If the digestive system can’t break down the food, then the animal is also not getting any of the resultant nutrients from that particular food item. For instance, a polar bear is a carnivore but if for some reason it ate grass, that grass would go straight through its system. This is because grass requires a specialised digestive tract in order for it to be digested. The same goes for any organism really. Humans for example are quite capable of eating a dictionary but they are going to find nearly zero nutritional value and most likely make themselves slightly sick. Whereas if a bookworm ate a dictionary, it would be rather full and quite content with its accomplishment.

WARNING! science approaches…

There are often signs at ponds and lakes politely thanking people for not feeding bread to ducks. Many science based and journalistic publications have also written articles asking people to not feed bread to ducks. We hear it constantly but why? Why is it that bread is so bad for ducks? The simple answer is that it is not in their natural diet. The long answer requires us to take a look at their digestive tract. Don’t worry I won’t make you look at photos of a dissected bird.

In vertebrates it is a reasonable assumption that the digestive process begins with the mouth parts. In the case of the cow, digestion begins with the tongue. In sheep, teeth begin digestion and in ducks it is their bill.

We have a duck. This ducks wants to eat some grass. So it bends down and nibbles at the

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a duck

grass using its bill. The bill is actually just the maxilla (top jaw bone) and mandible (lower jaw bone). Ducks do not have teeth but a specially designed palate for grinding down the grass. Birds lack a soft palate and instead have only a hard palate. There is a narrow groove down the centre of the hard palate which is why birds can not swallow water like we do but instead have to scoop the water with their beak and allow the water to dribble down to the oesophagus by utilising the effects of gravity.

Salivary glands protrude through the hard palate. A very generalised rule is that the drier the content of the diet, the greater the development and density of these glands. Granivores (seed eaters) generally have very well developed and plentiful salivary glands whereas a pelican that eats fish and similarly moisture rich food, has less developed and fewer salivary glands. The saliva coats the food to aid in swallowing. Saliva also contains enzymes (e.g. amylase) which begin to break down the chemical bonds of the food. Saliva also protects the oesophagus from gastric juice in the instance of gastric reflux (heartburn). Before the grass can leave the mouth it forms a bolus. This is a clump of food that is coated in saliva. This is nature’s way of packaging a gift for the stomach.

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Mallard and the interior surface of its maxilla (inside its mouth)

Now that the grass has formed a bolus it can move to the oesophagus (throat). The oesophagus is a muscular tube with sphincters (a ring of muscle like an o-ring) at either end that joins the mouth to the stomach. The oesophagus in ducks is elongated because they have relatively long necks compared to their head and body size. Food can not simply fall down the oesophagus instead it needs to be pushed down. This is when packaging the food into sphere like boluses comes in handy. The oesophagus contracts behind the bolus and then relaxes. This is a radial peristaltic contraction (muscle contracting around the diameter of the oesophagus) and creates a wave which stops the bolus from moving backwards despite the actions of the body. This means that the bolus can not travel back up the oesophagus even if the head were below the body (i.e. upside down). The longitudinal peristaltic contraction (contraction going up and down the oesophagus) moves the bolus down the oesophagus.

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Gastroesophageal sphincter’s job is to yell “you shall not pass” to gastric juices

The gastroesophageal sphincter (ring of muscle at the base of the oesophagus that shouts “you shall not pass!” to the gastric juices of the stomach so you don’t get reflux) is permanently contracted except during peristalsis (swallowing). When the peristaltic wave hits the gastroesophageal sphincter it temporarily relaxes to allow the bolus to pass. This means that when it is working properly the gastroesophageal sphincter is essentially a one-way valve.

In birds there is a modified section of the oesophagus known as the crop. In humans the bolus goes from the mouth (A) to the stomach (B) via the oesophagus (much like if you want to travel from Toowoomba to Brisbane you would go via the Warrego highway). In birds however, the bolus sometimes takes a detour to the crop (C) before its final destination of the stomach (B). This short stopover is for temporary storage. This storage facility allows birds to stock up on food while it is plentiful and then allow them to find a nice quiet place to sit and digest at their discretion. This means they are not constantly in the open where they can easily be picked off by a predator.

Just to confuse everyone further birds do not have a true stomach as such. Instead they have modified organ divided into the proventriculous and the gizzard/ventriculous. The colloquial term (what everyone who isn’t a vet calls it) for these sections is the stomach but if we’re going to nit pick it really isn’t a stomach but together they do a very similar job. The proventriculous is the glandular stomach and the gizzard is the muscular stomach. I like to think of the proventricilous as the brains and the gizzard as the brawn. This is because the proventriculous stores the ingesta (the stuff that has come from the previous section of the digestive tract) and sends it to the gizzard along with digestive secretions (e.g. hydrochloric acid and pepsin). The gizzard then has to do the hard work of macerating and grinding the ingesta. The gizzard of the ruffled grouse has a large concentration of muscle fibres and by contracting these fibres it is capable

of cracking the shell of an acorn. The walls of the gizzard essentially act as teeth. Birds eat stones which help the gizzard to grind down its contents. The gizzard also has the capability to change size to cope with the challenges of a specific diet. This is like a bicep increasing in size because the body is lifting weight regularly but decreases in size when weight lifting ceases. The gizzard is also sort of like a cement mixer making sure that the ingesta is being thoroughly mixed with the digestive juices. The ingesta now has a very low pH (highly acidic) due to the addition of the hydrochloric acid.

The following sections of small intestine (the jejunum and the ileum) are primarily involved in absorption of nutrients. The breaking down of the products has bee

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This chick will be aided by the Meckel’s Diverticulum in sustaining itself until it can forage successfully

n largely accomplished by the proventriculous, gizzard and the duodenum. Between the jejunum and the ileum is a small protuberance (sticky out bit) known as the Meckel’s diverticulum. The Meckel’s diverticulum is a vestige of the yolk sac and helps to feed the chick days after it has hatched. The ileum then opens into the large intestine and the caece.

The caece consists of two pouches individually referred to as caecum. Water is reabsorbed here and fermentation of coarse matter also occurs. The fermentation of these coarse materials produces several fatty acids and eight different vitamin Bs. The caece empty two to three times per day producing paste like droppings with a foul smell.

Material in the large intestine is referred to as faecal matter. The large intestine then reabsorbs the remaining moisture as well as minimal nutrient absorption. The faecal material then moves to the cloaca. In the cloaca, white uric acid crystals are added from the kidney (birds don’t excrete urine like humans). The colour and texture of the faecal material is indicative of the health status of the digestive tract.

The digestive system is designed to remove every possible nutrient from food that it can. This is the case for every digestive system. If an organism goes through the effort of finding food which, is often a dangerous task in the wild, it needs to make sure it is a very worthwhile venture. When we eat our body is searching for every morsel of energy, mineral and vitamin that it can extract. The body invests energy into this process in the hope of having a greater return.

What is bread even?

To know why bread causes such a big problem to ducks we also need

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Bread

to look at exactly what bread is. Bread is tasty and extremely versatile food stuff. In the western world we tend to eat a lot of it and probably in fact a little too much. It ha
s a very important place in many cultures and in fact, ‘bread’ and ‘dough’ are often synonymous with money (i.e. ‘breadwinner). It is one of the oldest artificially processed (doesn’t grow on a tree) foods in the world.

Bread is amazing but what exactly is it? It is a carbohydrate with very little nutritional value. It is low in fibre, lacking minerals (other than salt) and high sugar levels. In Australia, the salt in bread is not even legally required to be iodised. A simple white loaf is formed from heavily processed ingredients. The husks of the grains and other fibrous bodies have been removed or ground down to insignificance. This basically means that the factory has already done much of the breaking down of the fibre and other structural components leaving less work for your digestive system (less energy required to access the energy your food provides your body). A lack of fibre in food increases the likelihood the food will be receive a high ranking on the glycemic index (high GI). Food that is high GI releases its energy in a large burst. The body gets a huge rush of energy from high GI foods which, throws the body’s equilibrium out temporarily. The energy burst is large but short lived. This is actually a bit of an issue for the body. In humans, and lab rats, low fibre diets have now been linked to an increased probability of developing adult-onset diabetes.

Analogy: you are steam train driver. You need to keep the train moving down the tracks. Do you shovel small amounts of coal continuously into the furnace? Or do you throw in a bomb with the equivalent amount of energy that the coal would provide over a day? Hopefully you would go for the first option…. The bomb would just release all of the energy in one burst probably resulting in the death of everyone on the train. So I think it’s probably best just to deliver the coal to the furnace when the train needs it. This is loosely the equivalent of eating high GI foods. You should feed your body food that will release its energy slowly over the course of a day rather than in one huge bomb that destroys your pancreas (the squishy thing inside you that makes helps control your sugar levels).

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Shovelling coal into a the furnace of a steam train

I’m not saying bread is evil cut bread out of your diet no one should eat gluten. Just like everything eat it in moderation and don’t gorge yourself on it 24 hours a day 7 days a week. It is a fact that bread is not the healthiest food in the world but it’s ultimately fine as long as it’s in moderation and you’re not coeliac. Anyway I digress because I’m meant to be talking about ducks….

What all of that complicated jargon means

Bread causes issues at multiple junctures of the duck’s digestive system. The simplest answer to why is, “it’s not in their natural diet”. A more complex answer includes:

  • ducks are probably most commonly fed low fibre, high GI white bread
    • high GI means they have access to a lot of energy virtually instantly
    • In humans and lab rats high GI, low fibre diets have been linked to an increased probability of developing adult on-set diabetes
  • the ducks eat and eat and eat the available bread, filling not only their stomachs but their crops
    • this means that the ducks are overeating on a food supply, storing it in their crops and do not have to go find food other than bread to satisfy their hunger
    • not exhibiting natural behaviours such as searching for food
    • if the ducks have plentiful food in an area then they do not need to migrate to a new area
      • this has implications for:
        • disease
        • gene pools are not mixing (inbreeding might occur)
  • The gizzard is a muscle that can increase in size depending o
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    Pacific Black Ducks

    n its workload. If the main component of a duck’s diet is bread then the gizzard does not need to work hard at all. This is because, in general, bread is soft, fluffy and lacks fibre. If the gizzard has diminished in size due to lack of need what happens to the duck when its diet is changed to something far tougher? To be honest this is an educated guess but I daresay the duck would have trouble processing foodstuffs less digestible than bread. If bread were not available then the duck may not be able to extract adequate nutrients from its food until its gizzard has readjusted. For example, you lift weights regularly. Your personal best is 1000kg (you’re secretly Mr Incredible). You stop lifting weights for a period of time which means your biceps will diminish in size. This is because it takes a lot of energy to maintain muscle so the body let’s it shrivel away. If you try to lift 1000kg during this period of inactivity and decreased muscle mass, you will not be capable because the muscle is just not there to cope with the task. This is a similar principle for a duck’s gizzard that is used to processing bread and has to suddenly switch to grasses and grains.

  • The caece have no coarse products to ferment and absorb the resultant nutrients
  • the faecal material (poo) may not have the correct consistency due to the improper diet
    • duck may become constipated
    • duck may experience diarrhoea
      • particular problem for egg laying. Duck’s have a specially designed system to stop faecal matter touching the eggs but diarrhoea gets everywhere and will end up on eggs
  • if the diet does not contain proper calcium for egg laying the duck will need to draw calcium supplies from her own bones to form the egg shells
    • duck will suffer from brittle bone syndrome
    • eggs may not have hard enough shells to survive until hatching

Certain animals are just not designed to eat certain things. Ducks are not designed for eating bread especially in the quantities that they do.

Wings of the heavenly messengers

One of the most notable signs of why feeding bread to ducks is bad is a syndrome known as ‘angel wing’. The term angel wing is a rather romanticised version of the reality of the condition. The clinical term is carpal valgus which means a deformed carpal joint resulting in alignment being displaced from the mid-line of the body (i.e. not everything is where it should be). It is induced by a high calorie diet deficient in low vitamin D and E.

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Muscovy duck with angel wing/ carpal valgus

Birds with angel wing can not fly unless the case is particularly mild. It is most commonly observed in male birds and the left wing is more predisposed to the syndrome than the right. Some species are have a higher chance of developing the syndrome (muscovy ducks). There is no treatment for adult birds other than analgesics for pain and trimming feathers for appearances sake or euthanasia. In young birds a change in diet and splinting can help correct the issue. In wild birds angel wing is often a result of the birds being fed bread. The birds fill themselves on the bread which has very little nutritional value and they become vitamin deficient and develop angel wing.

Why haven’t ducks gone the way of the dodo if feeding bread is so bad?

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Did Donald Duck eat bread and go the way of the dodo?

Now if bread is as bad as all of that then why are there still ducks to feed every Saturday morning? Why hasn’t the bread killed them off because my Grandfather would feed the ducks with me and his grandfather took him to feed the ducks? Well…. simply put, nature is not so simple. Ecology is not black and white but an interweb of thousands upon thousands of possibilities most of which humans do not understand or as yet even aware of. In this case however, in my mind the most probable reason is that while some people gorge themselves solely on fast food day and night they may feel disgusting, have a multitude of health complications (e.g. their heart wants to explode, clogged arteries and vitamin deficient) and they’re going to die an early death but they can still technically breed. A duck that eats bread is unlikely to only live off bread but for argument’s sake let’s pretend it has. This duck will feel disgusting and will probably never reach old age. All of the other ducks around it feel the same way and they have all felt this way their entire lives. However, they still have it within themselves to breed just enough that their populations do not diminish. If pond ducks were heavily predated or if their habitat (the pond) was removed then their population would undoubtedly die out because they are not breeding enough to compensate.

Daffy Duck overate

Another question I’ve been asked about a wide variety of animals and humans feeding them the wrong foods is, “but if it’s so bad for them then why do they eat it?”. Simple, you see those golden arches over there? That American Colonel from the south and his fried birds? The male chicken that is for some reason pigmented at the 564–580nm range (red)? We are twice guilty because unlike the ducks we know that fast food is bad for us. It is tasty and convenient so we eat it.

Feeding ducks bread may mean more rats which means snakes

There are a lot of accessory problems to feeding ducks such as:

  • the particular species of bird being fed may overpopulate the area forcing other species from the area
  • overpopulation resulting in spread of disease
  • the ducks will remain in the vicinity at which they are regularly fed causing a build up of faeces in that area. Not only does it not duck poo smell rath
    er gross it also promotes the spread of disease
  • bread not eaten by the birds sits in the environment causing a build up of pathogenic bacteria and mould
  • if the ducks do not eat the bread then pests such as the black european rat or the house mouse will eat it instead. If rodents are getting fed then t
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    Surface of a pond frequented by waterfowl

    hey will colonise the area and the following will happen:

    • they will eat baby birds
    • their predators, such as snakes, will follow them into the area
    • heightened spread of disease
    • they will take away resources from native animals (e.g. reeds, shelter and food)
  • birds are extremely sensitive to mould to the point if they consume specific mould they will die
  • birds lose their fear of humans and can become aggressive. To a healthy, adult human this is not a problem but to a toddler or an adult with mobility issues this is a big problem. Often it is the case that the animal is then blamed for this behaviour resulting in its removal
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Swan being too familiar with a human

What not to feed:

  1. bread
  2. crackers
  3. chips (hot chips and crisps)
  4. sweet foods (i.e. lollies
  5. chocolate
  6. basically anything manufactured (i.e. bread, cake, sausages, biscuits…)
  7. mouldy bread is the exact opposite of what you should feed a duck

What you can feed ducks:

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Keep your frogs happy with the occasional meal worm
  • wild bird seed
  • corn
  • defrosted frozen vegetables (excellent way to get rid of frozenpeas because does anyone actually like frozen peas?)
  • rice (cooked or uncooked)
  • mealworms (you can keep a mealworm farm and feed other animals as well such as magpies, kookaburras, tawny frogmouths, egrets, frogs and lizards)
  • duck pellets
  • chopped fruit and vegetables (could even be scraps such as apple peel)

How to get rid of your stale bread

  • croutons
  • French Toast
  • bread and butter pudding
  • unsuspecting house guests
  • breadcrumbs which have a million different uses:
    • cheesecake base
    • Orange Tunisian Cake
    • Mud cake
    • salmon and potato patties
    • rissoles
    • meatloaf
    • base of Italian style bread loaves for extra crispy texture
    • crispen in oven and add to dishes such as pasta
    • chicken schnitzel
    • macaroni and cheese
    • chicken nuggets
    • crumbed fish
    • Bruschetta

A few last tips:

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Jessica Lawrence reminding us that there are things that taste better than skinny feels

Just remember that bread is bad for the wildlife. It is a carbohydrate with very little nutritional value (but it tastes amazing and I for one can’t stop eating it). If you’re not sure if you can feed an animal something it’s best just to avoid it until you know for sure. Even if you do feed animals food that is naturally in their diet that can cause problems (e.g. aggression towards humans, overpopulation…)

 

My advice to anyone who wants to feed wildlife is, just be sensible about it and follow these guidelines:

  • Feed only foods that the wildlife would eat in their natural diet or foods that mimic their natural diet (i.e. feeding ducks oats)
  • Never feed wildlife in a nature reserve (i.e. National Park) or where it is signed explicitly not to. Remember, feeding animals is not a human right.
  • If you want to feed animals in a public place, such as ducks in a park, change where you feed them each time. Don’t worry they’ll find you because ducks have an extra sense for finding free food (much like uni students).
  • Change what you are feeding the wildlife regularly or take a mixture of things (i.e. handful of grain, oats and vegetables)
  • avoid feeding aggressive animals
  • do not throw food into the water
  • if you have left over food supplies then take it home with you or donate to someone else at the park. Do not leave food on the ground for the rats or the ever majestic bin chicken (sometimes called an Australian white ibis).
  • remember that the ducks do not need to eat as much as us so feed a little at a time.
  • let the animals come to you, do not chase them trying to get them to eat
  • if you’re feeding animals at home try not to put out feed daily and only put out small amounts of feed at a time
  • the key is to not let the animals become dependant on you and force them to continue to forage for themselves so mix it up feeding days and times so they do not become reliant.
  • if you want to encourage native birds to visit your yard, try planting native shrubs and plants
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The king parrots love to visit our veranda for wild bird seed. They will squeak for more when it runs out but it is for their own good that you ignore their pleas.
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