Birds, like humans, are endothermic (warm-blooded) animals. Like us, their body heat is generated from within and must be kept within a certain range for survival. However, because most birds are fairly small, they have a larger body surface relative to their size, meaning they lose heat faster than we do. So how do they keep warm?

Photo by Blalonde (via Wikimedia Commons). Licensed under the Creative Commons Attribution-Share Alike 4.0 International licence.

As the seasons turn and the temperatures drop, we’re able to wrap up warm in thick knits or stay indoors with the benefit of central heating to keep us cosy. But wild birds, who live their entire lives outside, have no such luxuries.

Some UK birds, unwilling to tolerate the cold, simply migrate to warmer regions of the planet until spring rolls back around. But many others—including finches, robins and sparrows—stay here and stick it out. In fact, due to climate change, some wild birds that used to migrate to the southern hemisphere every year (such as swallows) have started wintering in Britain.

So what are their strategies for dealing with the winter chill in the UK?

Layering on the fat and feathers

Eat to heat

As temperatures cool, birds will increase their energy intake to build up their fat reserves. However, while mammals can build up an excess of fat stores in preparation for a long winter, birds are limited in how much fat they can hold on their bodies.

This is because birds also need to be able to fly so that they can escape predators. To balance their need for warmth with their need for flight, birds will often spend each day building up just enough fat to get them through a few nights at most, or sometimes even just one night at a time.

Birds who don’t manage to build up sufficient fat stores through the day are at risk of perishing overnight. Help your local wild birds prepare for the twilight frost by keeping your bird feeder stocked with energy-dense seed mixes and fat balls.

Fluffy feathers

Just as mammals can thicken up their coats for winter, so too can birds add extra feathers for insulation. These feathers are added next to their body, underneath their exterior feathers. Also known as down feathers, this extra layer is softer and finer than their tougher outer and flight feathers.

The fluffiness of down feathers makes them excellent for trapping plenty of warm air under the stiffer exterior feathers. You might sometimes see birds fluffing up their exterior feathers—this is their strategy for trapping even more warm air amongst their down feathers.

Practical preening

A bird’s strong exterior feathers also play an important role in trapping the warm air held by the down feathers and keeping it from escaping. Birds will preen these tough outer feathers, distributing oil along them to keep them clean, well-lubricated and waterproof in order to protect the soft down underneath.

Specialised scales

Birds lack feathers on their legs and feet, but make up for this with special scales that help minimise heat loss from these areas. They’ll also sometimes tuck one leg up into their feathers or crouch down to cover both legs, protecting them from the chill.

Bird behaviours to get cosy

Huddling and flocking

Like emperor penguins surviving the darkest months in the Antarctic, many birds that winter in the UK will huddle up together for warmth. Sparrows, wrens, swallows, tits and finches are just some of the bird species you may see bundling together on tree branches when temperatures drop, sharing their body heat for survival.

In a similar vein, birds will flock close together to reduce individual exposure to the cold air.

Twilight torpor

At night, birds will sometimes enter a state known as torpor to conserve energy.

Torpor is similar to hibernation. In torpor, birds will temporarily drop their body temperature to a lower level that’s easier to maintain than their ideal body temperature, allowing them to decrease their metabolism and conserve fat stores.

Nesting to escape the night frost

Night-time nests

Birds endeavour to find the warmest spots available to avoid freezing overnight. Preferred hideaways include tree cavities, thick vegetation and roof spaces. These nooks allow birds to get out of the cold, plus they provide protection from hungry predators.

Unfortunately, not all birds survive the winter freeze, due in part to a lack of sufficient shelter. Adding some simple nesting pouches or a stylish nesting box to your garden can make a huge difference and help these exposed little birds make it through the harsh winter months.

Nesting Boxes   Nesting Wool

Don’t forget to add one of our seed mixes to your order to qualify for free delivery!

Short answer: bird seed typically stays fresh for 6 – 12 months when stored in a clean, airtight container. The exact shelf life will depend on what type of seed it is.

Let’s look at how long bird seed lasts in different conditions, what you can do to keep it fresh, and when it’s best to start over with a fresh batch.

How to store bird seed

The best way to maximise the shelf life of your bird seed is to decant the seeds into a suitable airtight container as soon as possible after opening them.

Bird food storage tins protect seeds in several ways:

• Protection from the elements. Depending on where they’re stored, bags of bird feed may be vulnerable to rain and external contaminants, all of which can damage the feed and make it unsuitable for consumption.
  
  
• A cool, dry environment. This is important because it keeps the seed from getting damp and mouldy, which can make the whole batch unsafe for birds to eat.
  
  
• Defence against rodents and insects. If pests like rodents and insects gain access to your bird seed supply, not only will they eat the seeds, they may contaminate whatever is left behind. A sturdy storage container will help to keep them out!

Besides storing your bird food in a dedicated bird food tin, there are a few things you can do to keep your bird feed in tip-top condition while it awaits the feeder:

• Keep the container out of reach of potential pests.
  
  
• Stir the feed occasionally to prevent the seeds from becoming stagnant.
  
  
• Use up the oldest seed first before adding fresh feed to the storage tin.

How long does bird seed last in the feeder?

How long seed will stay fresh in the feeder while waiting for some lucky bird to devour it depends on a number of factors. Rain and pests will speed up deterioration, and feed that’s damp should be replaced immediately to avoid mould growth.

However, assuming the weather’s fine and the food is inaccessible to rodents and insects, bird seed should last up to about a week in a feeder or on the bird table. After this point, any uneaten feed should be replaced with fresh seed mix.

How can you tell when bird seed has gone bad?

• Obvious signs of spoilage (such as mould, damp, a musty smell or an unpleasant odour) mean it’s time to start again with fresh seed.
  
  
• Discolouration may be a less obvious indication of spoilage, but this is another clue that the seed is past its best and should be replaced.
  
  
• If the seeds are showing signs of germination (green growth or shoots are a sure sign they’ve started sprouting!) then they should be removed from the tin or feeder.
  
  
• Any signs of insect activity (for example, any bugs, larvae or webbing amongst the seeds) indicate the feed is potentially dangerous for birds and should be replaced.
  
  
• If the birds themselves show little interest in the feed, this may be a sign they don’t consider it up to snuff and it’s time to give them some fresh food.
  
  
• Finally, it’s not just when food has obviously spoiled that it needs to be replaced. The older the seed, the less nutritional value it has. Seeds lose nutrients over time, so it becomes more like a filler food rather than the nutrient-dense feed you had in mind when you bought it. This shouldn’t be an issue as long as you’re using your bird feed within the recommended 6 – 12 month window.

Here at Really Wild Bird Food we have a variety of bird food storage solutions to suit your needs so you never have to worry about your seeds spoiling before your feathery friends can get their share!

We also offer free delivery on any order that includes at least one of our seed mixes, so don’t forget to pair your food storage tin with something tasty to put in it.

Bird Feed Storage   Bird Seed Mixes

Wildflower meadows—lush fields brimming with colour, busy with bees and butterflies—are essential habitats that form a fundamental feature of our British countryside.