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  Caterpillar of the Brown House-moth (Hofmannophila pseudospretella)Inappropriate food storage may result in parasite infestation. Some parasites may be harmful to your birds. The infestation usually occurs before the grains are sold to shops or dealers. In form of eggs or larvae some parasites invade your household unnoticed. In the worst case, they will multiply uncontrollably and infest anything containing grains or starch.

Many parasites thrive not only in bird seeds, but also in flour, oatmeal and any other whole food. To avoid a (massive) parasitic infestation, you should always store grains and seeds in a way preventing an epidemic spread of parasites.

Recognising parasites
Sticky foodSome are visible to the naked eye. The seeds in the picture on the right are riddled with the capillary threads spun by the larvae of grain moths (see below). The grains stick to one another like beads on a string.

Other parasites cause an odd smell. Still others are big enough to be easily detected, e.g. beetles. But on the other hand, some beetles are very small and therefore it's not easy to find them. But in case you think that the grains may be infested with beetles, you should put the bird food into a transparent food container or an empty jar. Then close the lid and place the food container or jar into direct sunlight. The warth and the brightness will change the behaviour of the beetles. They will come out and climb up the walls. You can easily detect them there and on the lid.

What to do
Throw away infested food, as some parasites may damage your birds' health. Others are harmless to your birds, but could spread into your own food stores. Particularly flightless parasites are very difficult to get rid off. The following paragraphs will give some information on the most common food parasites that occur in Germany or other European countries.

Sawtoothed grain beetleGrain beetles thrive in many different kinds of grains or seeds. As they can fly, they spread quickly and efficiently in food storages, unless the infested grains or seeds are stored in air-tight containers. The picture on the right shows a sawtoothed grain beetle (Oryzaephilus surinamensis) next to a 1-(Euro) cent-coin.

Sawtoothed grain beetle (Oryzaephilus surinamensis)

Mites and flour mites
These parasites are tiny and in most cases they cannot be seen with the naked eye. Infested seeds often have a mouldy smell. Common species that can be found in bird seeds are for example Acarus siro and Tyrophagus putrescentiae, see photos below.

Tyrophagus putrescentiae seen through a microscope  Acarus siro seen through a microscope,  Joel Mills, GNU Free Documentation License
Tyrophagus putrescentiae                      Acarus siro, photo Joel Mills

To check your food for mites, try the following: put seeds in a small cup and make sure they form a mound. Leave it undisturbed over night. If the next morning some seeds are scattered around the cup and the mound in the cup looks "flattened", the seeds are infested with mites. Never feed mite-infested seeds to your birds, it may lead to serious indigestions and allergic reactions, in the worst case with fatal consequences.

Grain moths and Brown House-moths
Grain Moth (Sitotroga cerealella)If you're living in Europe and you detect a winged parasite in your bird food container, it is most probably a Grain Moth (Sitotroga cerealella) or a Brown House-moth (Hofmannophila pseudospretella). Thise insects are about one centimetre (appox. half an inch) long, they have brownishto greyish wings and a wing span of about 2 centimetres. They resemble the webbing clothes moth, but this species is more brownish. The antennas of the Grain Moth or the Brown House-moth are quite long and thin. These moths lay their eggs into the food what may cause problems: The Larvae hatch from the eggs soon. Next, the food is riddled with grubs. These grubs are beige with reddish brown heads and reach a length of approx. one centimetre, see photo below. Their silk threads plaster the food up, before the grubs pupate in the food container to evolve into moths.

Caterpillar of the Brown House-moth
Caterpillar of the Brown House-moth

In theory, food infested with grain moths is edible for birds, if you deep-freeze it for 2 days after detecting the moths or grubs, thus killing the parasites. The birds may even eat the dead moths. Still, it is not very hygienic to stock food containing dead parasites. I therefore recommend to discard parasite-infested grains.

German version of this text: Gaby Schulemann-Maier,
English translation of this chapter: Claudia Neumann.

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